Toolstrips can be a bit complex to develop so I’m proceeding slowly, with each post in the miniseries building on the previous posts. I encourage you to review the earlier posts in the Toolstrip miniseries before reading this post.

Also, remember to add the following code snippet at the beginning of your code so that the relevant toolstrip classes will be recognized by Matlab:

import matlab.ui.internal.toolstrip.*

Main steps and usage example

To attach a figure popup to a toolstrip control, follow these steps:

1. Create a new figure, using GUIDE or the figure function. The figure should typically be created modal and non-visible, unless there’s a good reason to avoid this. Note that the figure needs to be a legacy (Java-based) figure, created with GUIDE or the figure function — web-based uifigure (created with AppDesigner or the uifigure function) is not [currently] supported.
2. Create a callback function that opens and initializes this figure, and then moves it to the expected screen location using the following syntax: hToolGroup.showFigureDialog(hFig,hAnchor), where hFig is the figure’s handle, and hAnchor is the handle for the triggering toolstrip control.
3. Attach the callback function to the triggering toolstrip control.

Here’s a simple usage example, in which I present a file-selector popup:

% Create a toolstrip section, column & push-button
hSection = hTab.addSection('Popup');
hColumn = hSection.addColumn();
hButton = Button('Open',Icon.OPEN_24);
hButton.ButtonPushedFcn = {@popupFigure,hButton};  % attach popup callback to the button
hColumn.add(hButton);
 
% Callback function invoked when the toolstrip button is clicked
function popupFigure(hAction, hEventData, hButton)
    % Create a new non-visible modal figure
    hFig = figure('MenuBar','none', 'ToolBar','none', 'WindowStyle','modal', ...
                  'Visible','off', 'NumberTitle','off', 'Name','Select file:');
 
    % Add interactive control(s) to the figure (in this case, a file chooser initialized to current folder)
    jFileChooser = handle(javaObjectEDT(javax.swing.JFileChooser(pwd)), 'CallbackProperties');
    [jhFileChooser, hComponent] = javacomponent(jFileChooser, [0,0,200,200], hFig);
    set(hComponent, 'Units','normalized', 'Position',[0,0,1,1]);  % resize component within containing figure
 
    % Set popup control's callback (in this case, display the selected file and close the popup)
    jhFileChooser.ActionPerformedCallback = @popupActionPerformedCallback;
    function popupActionPerformedCallback(jFileChooser, jEventData)
        fprintf('Selected file: %s\n', char(jFileChooser.getSelectedFile));
        delete(hFig);
    end
 
    % Display the popup figure onscreen, just beneath the triggering button
    showFigureDialog(hToolGroup,hFig,hButton);
 
    % Wait for the modal popup figure to close before resuming GUI interactivity
    waitfor(hFig);
end

This leads to the popup figure as shown in the screenshot above.

The popup figure initially appears directly beneath the triggering button. The figure can then be moved away from that position, by dragging its title bar or border frame.

Note how the popup is an independent heavy-weight figure window, having a border frame, title bar and a separate task-bar icon. Removing the border frame and title-bar of Matlab figures can be done using an undocumented visual illusion – this can make the popup less obtrusive, but also prevent its moving/resizing. An entirely different and probably better approach is to present a light-weight popup panel using the Toolpack framework, which I plan to discuss in the following post(s). The PopupPanel container that I discussed in another post cannot be used, because it is displayed as a sub-component of a Matlab figure, and in this case the popup is not attached to any figure (the toolstrip and ToolGroup are not Matlab figures, as explained here).

The astute reader may wonder why I bothered going to all the trouble of displaying a modal popup with a JFileChooser, when I could have simply used the built-in uigetfile or uiputfile functions in the button’s callback. The answer is that (a) this mechanism displays the popup directly beneath the triggering button using hToolGroup.showFigureDialog(), and also (b) enables complex popups (dialogs) that have no direct builtin Matlab function (for example, a file-selector with preview, or a multi-component input form).

Compatibility considerations for R2018a or older

In Matlab releases R2018a or older that do not have the hToolGroup.showFigureDialog() function, you can create it yourself in a separate showFigureDialog.m file, as follows:

function showFigureDialog(hToolGroup, hFig, hAnchor)
    %   showFigureDialog - Display a figure-based dialog below a toolstrip control.
    %
    %   Usage example:
    %       showFigureDialog(hToolGroup, hFig, hAnchor);
    %   where: 
    %       "hToolGroup" must be a "matlab.ui.internal.desktop.ToolGroup" handle
    %       "hFig" must be a "figure" handle, not a "uifigure"
    %       "hAnchor" must be a "matlab.ui.internal.toolstrip.***" handle
 
    %hWarn = ctrlMsgUtils.SuspendWarnings('MATLAB:HandleGraphics:ObsoletedProperty:JavaFrame'); %#ok<NASGU>
    hWarn = warning('off','MATLAB:HandleGraphics:ObsoletedProperty:JavaFrame');
    jf = get(hFig, 'JavaFrame');
    if isempty(jf)
        error('UI figure cannot be added to "ToolGroup". Use a regular figure instead.')
    else
        screen_size = get(0,'ScreenSize');
        old_pos = get(hFig,'OuterPosition');
        dpi_ratio = com.mathworks.util.ResolutionUtils.scaleSize(100)/100;
        jAnchor = hToolGroup.ToolstripSwingService.Registry.getWidgetById(hAnchor.getId());
        pt = javaMethodEDT('getLocationOnScreen',jAnchor); % pt is anchor top left
        pt.y = pt.y + jAnchor.getVisibleRect().height;     % pt is anchor bottom left
        new_x = pt.getX()/dpi_ratio-5;                           % figure outer left
        new_y = screen_size(end)-(pt.getY/dpi_ratio+old_pos(4)); % figure outer bottom
        hFig.OuterPosition = [new_x new_y old_pos(3) old_pos(4)];
        hFig.Visible = 'on';
    end
    warning(hWarn);
end

Under the hood of showFigureDialog()

How does showFigureDialog() know where to place the figure, directly beneath the triggering toolstrip anchor?

The answer is really quite simple, if you look at this method’s source-code in %matlabroot%/toolbox/matlab/toolstrip/+matlab/+ui/+internal/+desktop/ToolGroup.m (around line 500, depending on the Matlab release).

The function first checks whether the input hFig handle belongs to a figure or uifigure, and issues an error message in case it’s a uifigures (only legacy figures are currently supported).
Then the function fetches the toolstrip control’s underlying Java control handle using the following code (slightly modified for clarity), as explained here:

jAnchor = hToolGroup.ToolstripSwingService.Registry.getWidgetById(hAnchor.getId());

Next, it uses the Java control’s getLocationOnScreen() to get the control’s onscreen position, accounting for monitor DPI variation that affects the X location.
The figure’s OuterPosition property is then set so that the figure’s top-left corner is exactly next to the control’s bottom-left corner.
Finally, the figure’s Visible property is set to ‘on’ to make the figure visible in its new position.

The popup figure’s location is recomputed by showFigureDialog() whenever the toolstrip control is clicked, so the popup figure is presented in the expected position even when you move or resize the tool-group window.

Toolstrip miniseries roadmap

The following post(s) will present the Toolpack framework. Non-figure (lightweight) popup toolpack panels can be created, which appear more polished/stylish than the popup figures that I presented today. The drawdown is that toolpack panels may be somewhat more complex to program than figures, and IMHO are more likely to change across Matlab releases. In addition to the benefit of popup toolpack panels, toolpack presents an alternative way for toolstrip creation and customization, enabling programmers to choose between using the toolstrip framework (that I discussed so far), and the new toolpack framework.

In a succeeding post, I’ll discuss toolstrip collapsibility, i.e. what happens when the user resizes the window, reducing the toolstrip width. Certain toolstrip controls will drop their labels, and toolstrip sections shrink into a drop-down. The priority of control/section collapsibility can be controlled, so that less-important controls will collapse before more-important ones.

In future posts, I plan to discuss docking layout, DataBrowser panel, QAB (Quick Access Bar), underlying Java controls, and adding toolstrips to figures – not necessarily in this order.
Matlab toolstrips can be a bit complex, so I plan to proceed in small steps, each post building on top of its predecessors.

If you would like me to assist you in building a custom toolstrip or GUI for your Matlab program, please let me know.

Toolstrip example (basic controls)

Component icons

Many toolstrip controls (such as buttons, but not checkboxes for example) have a settable Icon property. The standard practice is to use a 16×16 icon for a component within a multi-component toolstrip column (i.e., when 2 or 3 components are displayed on top of each other), and a 24×24 icon for a component that spans the entire column height (i.e., when the column contains only a single component).

We can use one of the following methods to specify the icon. Note that you need to import matlab.ui.internal.toolstrip.* if you wish to use the Icon class without the preceding package name.

• The Icon property value is typically empty ([]) by default, meaning that no icon is displayed.
   
• We can use one of ~150 standard icons using the format Icon.<icon-name>. For example: icon = Icon.REFRESH_24. These icons typically come in 2 sizes: 16×16 pixels (e.g. Icon.REFRESH_16) that we can use with the small-size components (which are displayed when the column has 2-3 controls), and 24×24 pixels (e.g. REFRESH_24) that we can use with the large-size components (which are displayed when the column contains only a single control). You can see the list of the standard icons by running

  matlab.ui.internal.toolstrip.Icon.showStandardIcons

  
• We can use the Icon constructor by specifying the full filepath for any PNG or JPG image file. Note that other file type (such as GIF) are not supported by this method. For example:

  icon = Icon(fullfile(matlabroot,'toolbox','matlab','icons','tool_colorbar.png')); % PNG/JPG image file (not GIF!)

  In fact, the ~150 standard icons above use this mechanism under the hood: Icon.REFRESH_24 is basically a public static method of the Icon class, which simply calls Icon('REFRESH_24','Refresh_24') (note the undocumented use of a 2-input Icon constructor). This method in turn uses the Refresh_24.png file in Matlab’s standard toolstrip resources folder: %matlabroot%/toolbox/shared/controllib/general/resources/toolstrip_icons/Refresh_24.png.

• We can also use the Icon constructor by specifying a PNG or JPG file contained within a JAR file, using the standard jar:file:...jar!/ notation. There are numerous icons included in Matlab’s JAR files – simply open these files in WinZip or WinRar and browse. In addition, you can include images included in any external JAR file. For example:

  icon = Icon(['jar:file:/' matlabroot '/java/jar/mlwidgets.jar!/com/mathworks/mlwidgets/actionbrowser/resources/uparrow.png']);

• We can also use the Icon constructor by specifying a Java javax.swing.ImageIcon object. Fortunately we can create such objects from a variety of image formats (including GIFs). For example:

  iconFilename = fullfile(matlabroot,'toolbox','matlab','icons','boardicon.gif');
  jIcon = javax.swing.ImageIcon(iconFilename);  % Java ImageIcon from file (inc. GIF)
  icon = Icon(jIcon);

  If we need to resize the Java image (for example, from 16×16 to 24×24 or vise versa), we can use the following method:

  % Resize icon to 24x24 pixels
  jIcon = javax.swing.ImageIcon(iconFilename);  % get Java ImageIcon from file (inc. GIF)
  jIcon = javax.swing.ImageIcon(jIcon.getImage.getScaledInstance(24,24,jIcon.getImage.SCALE_SMOOTH))  % resize to 24x24
  icon = Icon(jIcon);

• We can apparently also use a CSS class-name to load images. This is only relevant for the JavaScript-based uifigures, not legacy Java-based figures that I discussed so far. Perhaps I will explore this in some later post that will discuss toolstrip integration in uifigures.

App window icon

The app window’s icon can also be set. By default, the window uses the standard Matlab membrane icon (%matlabroot%/toolbox/matlab/icons/matlabicon.gif). This can be modified using the hToolGroup.setIcon method, which currently [R2018b] expects a Java ImageIcon object as input. For example:

iconFilename = fullfile(matlabroot,'toolbox','matlab','icons','reficon.gif');
jIcon = javax.swing.ImageIcon(iconFilename);
hToolGroup.setIcon(jIcon)

This icon should be set before the toolgroup window is shown (hToolGroup.open).

Custom app window icon

An odd caveat here is that the icon size needs to be 16×16 – setting a larger icon results in the icon being ignored and the default Matlab membrane icon used. For example, if we try to set ‘boardicon.gif’ (16×17) instead of ‘reficon.gif’ (16×16) we’d get the default icon instead. If our icon is too large, we can resize it to 16×16, as shown above:

% Resize icon to 16x16 pixels
jIcon = javax.swing.ImageIcon(iconFilename);  % get Java ImageIcon from file (inc. GIF)
jIcon = javax.swing.ImageIcon(jIcon.getImage.getScaledInstance(16,16,jIcon.getImage.SCALE_SMOOTH))  % resize to 16x16
hToolGroup.setIcon(jIcon)

It’s natural to expect that hToolGroup, which is a pure-Matlab MCOS wrapper class, would have an Icon property that accepts Icon objects, just like for controls as described above. For some reason, this is not the case. It’s very easy to fix it though – after all, the Icon class is little more than an MCOS wrapper class for the underlying Java ImageIcon (not exactly, but close enough). Adapting ToolGroup‘s code to accept an Icon is quite easy, and I hope that MathWorks will indeed implement this in a near-term future release. I also hope that MathWorks will remove the 16×16 limitation, or automatically resize icons to 16×16, or at the very least issue a console warning when a larger icon is specified by the user. Until then, we can use the setIcon(jImageIcon) method and take care to send it the 16×16 ImageIcon object that it expects.

Toolstrip miniseries roadmap

The next post will discuss complex components, including button-group, drop-down, listbox, split-button, slider, popup form, gallery etc.

Following that, my plan is to discuss toolstrip collapsibility, the ToolPack framework, docking layout, DataBrowser panel, QAB (Quick Access Bar), underlying Java controls, and adding toolstrips to figures – not necessarily in this order. Matlab toolstrips can be a bit complex, so I plan to proceed in small steps, each post building on top of its predecessors.

If you would like me to assist you in building a custom toolstrip or GUI for your Matlab program, please let me know.

We can add a Matlab toolstrip to 3 types of Matlab GUI windows:

1. To a Java-based Matlab figure (so-called “legacy” figures, created using GUIDE or the figure function)
2. To a container window of docked Java-based figures, typically called an “App” (marketing name) or “Tool Group” (internal technical name)
3. To a JavaScript/HTML-based Matlab figure (so called “web” figures, created using App Designer or the uifigure function)

Today I will show how to add a basic dynamic toolstrip to a ToolGroup (App, window type #2):

ToolGroup with clients and dynamic toolstrip

Figure containers (“Tool Groups”)

Most Matlab users are familiar with window types #1 and #3 (legacy and web-based figures), but type #2 may seem strange. In fact, it shouldn’t be: All the Matlab “Apps” and Desktop components use such a container of docked clients. For example, both the Matlab Editor and Desktop are containers of individual client windows (individual files in the Editor; Command Window, Workspace etc. in the desktop).

Similarly, when we dock figures, they dock as client windows into a container called “Figures” (this can be controlled programmatically: see my setFigDockGroup utility on the File Exchange). This is the basis for all Matlab “Apps”, as far as I am aware (some Apps may possibly use a different GUI container, after all there are ~100 Matlab Apps and I’m not familiar with all of them). Such Apps are basically stand-alone Tool Groups (client container windows) that contain one or more docked figures, a toolstrip, and a side-panel with controls (so-called “Data Browser”).

Note: MathWorks uses confusing terminology here, using the same term “App” for both MathWorks-created GUIs containers (that have toolstrips, Data Browser and docked figures) and also user-created utilities on the File Exchange (that do not have these). Unfortunately, MathWorks has chosen not [yet] to release to the general public its set of tools that enable creating true “Apps”, i.e. those that have a toolstrip, Data Browser and docked figures.

Today’s post will attempt to fill this gap, by showing how we can create user Apps that have a toolstrip and docked figures. I will ignore the Data Browser today, and will describe it in a future post. Since docking figures into a standalone user-created container is a solved problem (using my setFigDockGroup utility), this post will focus on adding a toolstrip to such a container.

A ToolGroup object (matlab.ui.internal.desktop.ToolGroup) is created either implicitly (by docking a figure into a group that has a new name), or explicitly (by invoking its constructor):

% Create a new non-visible empty App (Tool Group)
hToolGroup = matlab.ui.internal.desktop.ToolGroup('Toolstrip example on UndocumentedMatlab.com');

Some things only work properly after the app is displayed, so let’s display the ToolGroup (however, note that for improved performance it is better to do whatever customizations and GUI updates that you can before the app is made visible):

% Display the ToolGroup window
hToolGroup.open();

Basic empty ToolGroup (without toolstrip or clients)

An annoying quirk with ToolGroups is that they automatically close when their reference handle is deleted from Matlab memory. The specific behavior changes depending on the contents of the container and the Matlab release, but in general it’s safest to preserve the hToolGroup variable, to prevent the window from closing, when this variable goes out of scope, when the function (in which we create the ToolGroup) returns. There are many ways to persist this variable. Here’s one alternative, in which we persist it in itself (or rather, attached to its internal Java peer control):

% Store toolgroup reference handle so that app will stay in memory
jToolGroup = hToolGroup.Peer;
internal.setJavaCustomData(jToolGroup, hToolGroup);

internal.setJavaCustomData is an undocumented Matlab function that adds a new custom property to a Java reference handle. In our case, it adds a CustomData property to the jToolGroup handle and sets its value to the Matlab hToolGroup handle. The source code for internal.setJavaCustomData is available in %matlabroot%/toolbox/shared/controllib/general/+internal/setJavaCustomData.m and is very simple: it essentially uses the old schema-based schema.prop method for adding new properties to handles. Schema is an old deprecated mechanism that is mostly replaced by the newer MCOS (Matlab Class Object System), but for some specific cases such as this it’s still very useful (the standard addprop function can add new properties to Matlab GUI handles, but not to Java reference handles).

Finally, let’s discard the Data Browser side panel (I’ll discuss it in a separate future post):

% Discard the Data-browser left panel
hToolGroup.disableDataBrowser();

Adding a toolstrip to the ToolGroup

Now that we have the basic container ready, let’s add a toolstrip. To simplify matters in this introductory post (after all, I have still not described the internal packages and classes that make up a toolstrip), we’ll use some of the tabs used in the showcaseToolGroup example that I discussed in my previous post. You can see the relevant source code in %matlabroot%/toolbox/matlab/toolstrip/+matlab/+ui/+internal/+desktop/*.m, in case you want to jump ahead and customize your own toolstrip tabs, groups and buttons. In the code snippet below, we first create an empty TabGroup, then add toolstrip tabs into it, and finally add this TabGroup into our ToolGroup using its addTabGroup(hTabGroup) method:

% Create a new tab group
%hTabGroup = matlab.ui.internal.desktop.showcaseBuildTabGroup('swing');
hTabGroup = matlab.ui.internal.toolstrip.TabGroup();
hTab1 = matlab.ui.internal.desktop.showcaseBuildTab_Buttons('swing');
hTabGroup.add(hTab1);
%hTabGroup.add(matlab.ui.internal.desktop.showcaseBuildTab_Gallery());
hTabGroup.add(matlab.ui.internal.desktop.showcaseBuildTab_Layout('swing'));
 
% Select tab #1 (common)
hTabGroup.SelectedTab = hTab1;
 
% Add the tab group to the built-in toolstrip
hToolGroup.addTabGroup(hTabGroup);

We now have an “App” that has a toolstrip, but no clients (yet), and a hidden Data Browser side-panel:

Now let’s add some clients (docked figures):

Adding clients (docked figures) to the ToolGroup

There are two easy variants for adding docked figures in a ToolGroup: The easiest is to use the ToolGroup’s addFigure(hFigure) method:

% Create a figure and dock it into the tool-group
hFig1 = figure('Name','3D');
surf(peaks);
hToolGroup.addFigure(hFig1);

The second variant enables to dock a figure that has a specific set of toolstrip tabs attached to it. These tabs will only display in the toolstrip when that particular figure has focus. We do this by creating a new TabGroup (just as we have done above), and then add the figure and TabGroup to the container using the ToolGroup’s addClientTabGroup(hFigure,hTabGroup) method:

% Create the 2nd figure
hFig2 = figure('Name','2D');
plot(rand(5)); drawnow
 
% Add a few tabs that are only relevant to this specific figure
hTabGroup2 = matlab.ui.internal.toolstrip.TabGroup();
hTab2 = matlab.ui.internal.desktop.showcaseBuildTab_Selections();
hTabGroup2.add(hTab2);
hTabGroup2.add(matlab.ui.internal.desktop.showcaseBuildTab_EditValue());
 
% Add the figure and tabs to the ToolGroup
hToolGroup.addClientTabGroup(hFig2, hTabGroup2);

ToolGroup with clients and dynamic toolstrip

In this example, the “Selection” and “Values” toolstrip tabs only appear when the 2nd figure (“2D”) has focus. A similar behavior exists in the Matlab Desktop and Editor, where some tabs are only shown when certain clients have focus.

Removing the View tab

Note that the “View” toolstrip tab (which enables setting the appearance of the docked figures: layout, tab positions (top/bottom/left/right), ordering etc.) is automatically added to the toolstrip and always appears last. We can remove this View tab using the ToolGroup’s hideViewTab() method. The tab will not immediately be removed, only when the toolstrip is repainted, for example, when we switch focus between the docked figures:

hToolGroup.hideViewTab;  % toolstrip View tab is still visible at this point
figure(hFig1);  % change focus to hFig1 - toolstrip is repainted without View tab

Conclusion

It’s relatively easy to dock figures into a standalone “App” window that has a custom toolstrip, which can even be dynamically modified based on the figure which is currently in focus. Naturally, this has little benefit if we cannot customize the toolstrip components: labels, icons, control type, grouping and most importantly – callbacks. This topic deserves a dedicated post, which I plan to be the next in this miniseries. Stay tuned – hopefully the next post will not take me as long to publish as this post (I was quite busy recently)…

Scrollable Matlab GUI panel

Technical description

The basic idea is that in HG2 (Matlab release R2014b onward), uipanels are implemented using standard Java JPanel components. This enables all sorts of interesting customizations. For the purposes of today’s discussion, the important thing to note is that the underlying JPanel object can be re-parented to reside inside a Java JScrollPanel.

So, the idea is to get the Matlab panel’s underlying JPanel object reference, then embed it within a new JScrollPanel object that is placed at the exact same GUI coordinates as the original panel. The essential Matlab code snippet is this:

% Create the Matlab uipanel in the GUI
hPanel = uipanel(...); drawnow
 
% Get the panel's underlying JPanel object reference
jPanel = hPanel.JavaFrame.getGUIDEView.getParent;
 
% Embed the JPanel within a new JScrollPanel object
jScrollPanel = javaObjectEDT(javax.swing.JScrollPane(jPanel));
 
% Remove the JScrollPane border-line
jScrollPanel.setBorder([]);
 
% Place the JScrollPanel in same GUI location as the original panel
pixelpos = getpixelposition(hPanel);
hParent = hPanel.Parent;
[hjScrollPanel, hScrollPanel] = javacomponent(jScrollPanel, pixelpos, hParent);
hScrollPanel.Units = 'norm';
 
% Ensure that the scroll-panel and contained panel have linked visibility
hLink = linkprop([hPanel,hScrollPanel],'Visible');
setappdata(hPanel,'ScrollPanelVisibilityLink',hLink);

Note that this code will only work with panels created in legacy figures, not web-based uifigures (as I mentioned above, a similar solution for uifigures will be presented here next week).

Also note that the new scroll-panel is created with javaObjectEDT, in order to avoid EDT synchronization problems

We also want to link the visibility of the scroll-panel and its contained Matlab panel (hPanel), so that when the panel is set to be non-visible (hPanel.Visible='off'), the entire scroll-panel (scrollbars included) will become invisible, and vice-versa. We can do this by linking the Visible property of the Matlab panel and the scroll-panel container (hScrollPanel) using the linkprop function at the bottom of the script above. Note that we must persist the resulting hLink otherwise it becomes defunct – this is done by using setappdata to store the link in the panel (this way, when the panel is deleted, so does the link).

Resizing the container

The scroll-panel is created with a specific pixelpos location and size, and then its container is made to have normalized units. This ensures that when the container (hParent) grows, the scroll-panel grows as well, and no scrollbars appear (since they are not needed). But when the container shrinks in the X and/or Y direction, corresponding scrollbars appear as-needed. It sounds complicated, but it’s actually very intuitive, as the animated image above shows.

When the container resizes, the displayed viewport image may “jump” sideways. To fix this we can attach a simple repaint callback function to the scroll-panel’s SizeChangedFcn property:

% Attach a repaint callback function
hScrollPanel.SizeChangedFcn = @repaintScrollPane;
 
% Define the callback function:
function repaintScrollPane(hScrollPanel, varargin)
    drawnow
    jScrollPanel = hScrollPanel.JavaPeer;
    offsetX = 0; %or: jScrollPanel.getHorizontalScrollBar.getValue;
    offsetY = 0; %or: jScrollPanel.getVerticalScrollBar.getValue;
    jOffsetPoint = java.awt.Point(offsetX, offsetY);
    jViewport = jScrollPanel.getViewport;
    jViewport.setViewPosition(jOffsetPoint);
    jScrollPanel.repaint;
end

Scrollbars automatically appear as-needed during resize

Viewport position/offset

It would be convenient to have an easy-to-use ViewOffset property in the hScrollPanel object, in order to be able to programmatically query and set the current viewport position (i.e., scrollbars offset). We can add this property via the addprop function:

% Add a new Viewoffset property to hSCrollPanel object
hProp = addprop(hScrollPanel, 'ViewOffset');
hProp.GetMethod = @getViewOffset;  %viewOffset = getViewOffset(hScrollPanel)
hProp.SetMethod = @setViewOffset;  %setViewOffset(hScrollPanel, viewOffset)
 
% Getter method for the dynamic ViewOffset property
function viewOffset = getViewOffset(hScrollPanel, varargin)
    jScrollPanel = hScrollPanel.JavaPeer;
    jPoint = jScrollPanel.getViewport.getViewPosition;
    viewOffset = [jPoint.getX, jPoint.getY];
end
 
% Setter method for the dynamic ViewOffset property
function setViewOffset(hScrollPanel, viewOffset)
    jPoint = java.awt.Point(viewOffset(1), viewOffset(2));
    jScrollPanel = hScrollPanel.JavaPeer;
    jScrollPanel.getViewport.setViewPosition(jPoint);
    jScrollPanel.repaint;
end

This enables us to both query and update the scroll-panel’s view position – [0,0] means top-left corner (i.e., no scroll); [12,34] mean scrolling 12 to the right and 34 down:

>> offset = hScrollPanel.ViewOffset   % or: get(hScrollPanel,'ViewOffset')
offset = 
     0     0
 
>> offset = hScrollPanel.ViewOffset   % or: get(hScrollPanel,'ViewOffset')
offset = 
    12    34
 
% Scroll 30 pixels right, 50 pixels down
>> hScrollPanel.ViewOffset = [30,50];   % or: set(hScrollPanel,'ViewOffset',[30,50])

attachScrollPanelTo utility

I have prepared a utility called attachScrollPanelTo (downloadable from the Matlab File Exchange), which encapsulates all of the above, plus a few other features: inputs validation, Viewport property in the output scroll-pane object, automatic encasing in a new panel for input object that are not already a panel, etc. Feel free to download the utility, use it in your program, and modify the source-code to fit your needs. Here are some usage examples:

attachScrollPanelTo();  % display the demo
 
attachScrollPanelTo(hPanel) % place the specified hPanel in a scroll-panel
 
hScroll = attachScrollPanelTo(hPanel);
hScroll.ViewOffset = [30,50];  % set viewport offset (30px right, 50px down)
set(hScroll, 'ViewOffset',[30,50]);  % equivalent alternative

If you’d like me to add flare to your Matlab GUI, don’t hesitate to contact me on my Consulting page.

• Streaming (asynchronous, non-blocking) – incoming server data is processed by internal callback functions in the background, and is made available for the user to query at any later time.
• Blocking (synchronously waiting for data) – in this case, the main Matlab processing flows waits until the data arrives, or until the specified timeout period has passed – whichever comes first.

Implementing streaming mode is relatively simple in general – all we need to do is ensure that the underlying connector object passes the incoming server messages to the relevant Matlab function for processing, and ensure that the user has some external way to access this processed data in Matlab memory (in practice making the connector object pass incoming data messages as Matlab callback events may be non-trivial, but that’s a separate matter – read here for details).

In today’s article I’ll explain how we can implement a blocking mode in Matlab. It may sound difficult but it turns out to be relatively simple.

I had several requirements/criteria for my blocked-wait implementation:

1. Compatibility – It had to work on all Matlab platforms, and all Matlab releases in the past decade (which rules out using Microsoft Dot-NET objects)
2. Ease-of-use – It had to work out-of-the-box, with no additional installation/configuration (which ruled out using Perl/Python objects), and had to use a simple interface function
3. Timeout – It had to implement a timed-wait, and had to be able to tell whether the program proceeded due to a timeout, or because the expected event has arrived
4. Performance – It had to have minimal performance overhead

The basic idea

The basic idea is to use Matlab’s builtin waitfor, as I explained in another post back in 2012. If our underlying connector object has some settable boolean property (e.g., Done) then we can set this property in our event callback, and then waitfor(object,'Done'). The timeout mechanism is implemented using a dedicated timer object, as follows:

% Wait for data updates to complete (isDone = false if timeout, true if event has arrived)
function isDone = waitForDone(object, timeout)
    % Initialize: timeout flag = false
    object.setDone(false);
 
    % Create and start the separate timeout timer thread
    hTimer = timer('TimerFcn',@(h,e)object.setDone(true), 'StartDelay',timeout);
    start(hTimer);
 
    % Wait for the object property to change or for timeout, whichever comes first
    waitfor(object,'Done');
 
    % waitfor is over - either because of timeout or because the data changed
    % To determine which, check whether the timer callback was activated
    isDone = isvalid(hTimer) && hTimer.TasksExecuted == 0;
 
    % Delete the timer object
    try stop(hTimer);   catch, end
    try delete(hTimer); catch, end
 
    % Return the flag indicating whether or not timeout was reached
end  % waitForDone

where the event callback is responsible for invoking object.setDone(true) when the server data arrives. The usage would then be similar to this:

requestDataFromServer();
 
if isBlockingMode
   % Blocking mode - wait for data or timeout (whichever comes first)
   isDone = waitForDone(object, 10.0);  % wait up to 10 secs for data to arrive
   if ~isDone  % indicates a timeout
      fprintf(2, 'No server data has arrived within the specified timeout period!\n')
   end
else
   % Non-blocking (streaming) mode - continue with regular processing
end

Using a stand-alone generic signaling object

But what can we do if we don’t have such a Done property in our underlying object, or if we do not have programmatic access to it?

We could create a new non-visible figure and then waitfor one of its properties (e.g. Resize). The property would be initialized to 'off', and within both the event and timer callbacks we would set it to 'on', and then waitfor(hFigure,'Resize','on'). However, figures, even if non-visible, are quite heavy objects in terms of both memory, UI resources, and performance.

It would be preferable to use a much lighter-weight object, as long as it abides by the other criteria above. Luckily, there are numerous such objects in Java, which is bundled in every Matlab since 2000, on every Matlab platform. As long as we choose a small Java object that has existed forever, we should be fine. For example, we could use a simple javax.swing.JButton and its boolean property Enabled:

hSemaphore = handle(javax.swing.JButton);  % waitfor() expects a handle() object, not a "naked" Java reference
 
% Wait for data updates to complete (isDone = false if timeout, true if event has arrived)
function isDone = waitForDone(hSemaphore, timeout)
    % Initialize: timeout flag = false
    hSemaphore.setEnabled(false);
 
    % Create and start the separate timeout timer thread
    hTimer = timer('TimerFcn',@(h,e)hSemaphore.setEnabled(true), 'StartDelay',timeout);
    start(hTimer);
 
    % Wait for the object property to change or for timeout, whichever comes first
    waitfor(hSemaphore,'Enabled');
 
    % waitfor is over - either because of timeout or because the data changed
    % To determine which, check whether the timer callback was activated
    isDone = isvalid(hTimer) && hTimer.TasksExecuted == 0;
 
    % Delete the timer object
    try stop(hTimer);   catch, end
    try delete(hTimer); catch, end
 
    % Return the flag indicating whether or not timeout was reached
end  % waitForDone

In this implementation, we would need to pass the hSemaphore object handle to the event callback, so that it would be able to invoke hSemaphore.setEnabled(true) when the server data has arrived.

Under the hood, note that Enabled is not a true “property” of javax.swing.JButton, but rather exposes two simple public getter/setter methods (setEnabled() and isEnabled()), which Matlab interprets as a “property”. For all intents and purposes, in our Matlab code we can treat Enabled as a property of javax.swing.JButton, including its use by Matlab’s builtin waitfor function.

There is a light overhead to this: on my laptop the waitfor function returns ~20 mSecs after the invocation of hSemaphore.setEnabled(true) in the timer or event callback – in many cases this overhead is negligible compared to the networking latencies for the blocked data request. When event reactivity is of utmost importance, users can always use streaming (non-blocking) mode, and process the incoming data events immediately in a callback.

Of course, it would have been best if MathWorks would add a timeout option and return value to Matlab’s builtin waitfor function, similar to my waitForDone function – this would significantly simplify the code above. But until this happens, you can use waitForDone pretty-much as-is. I have used similar combinations of blocking and streaming modes with multiple other connectors that I implemented over the years (Interactive Brokers, CQG, Bloomberg and Reuters for example), and the bottom line is that it actually works well in practice.

Let me know if you’d like me to assist with your own Matlab project or data connector, either developing it from scratch or improving your existing code. I will be visiting Boston and New York in early June and would be happy to meet you in person to discuss your specific needs.

Note: I will be traveling to the USA in June, and to Spain in August. If you would like me to visit your location for onsite consulting or training, then please let me know.

Happy Easter/Passover!

Overview

Editor-plugin's cool logo

The default Keyboard shortcuts listed below for the features can be customized. Most variables can be customized as well (I will point out which variables are not [yet] customizable).

Most GUIs have a search field. Within this search field you can move the list or the tree up and down using arrow keys, or hit <escape> to return to editor. These search fields allow you to enter regular expressions to limit results shown in list or tree. Also, most GUIs are dockable.

The Editor-Plugin utility is open-source. It is available on GitHub and also mirrored on the Matlab File Exchange. A detailed setup guide is provided on the utility’s wiki section in GitHub.

If you discover any problem or have any suggestion for improvement, please visit the utility’s Issues section on GitHub, where all open/closed issues can be tracked and discussed.

A brief overview of some of the features is presented below. For a detailed explanation of these and other features (which are not listed below), please review the Features section of the utility’s wiki (you guessed it: on GitHub…).

Editing

• Delete / duplicate lines – CTRL + SHIFT + Y or D allows you to delete or duplicate current line.
  
• Move lines up or down – CTRL + ALT + UP or DOWN allows you to move selected lines up or down.
  
• Live (auto-replace) templates – Live Templates are editor commands you can design to insert predefined code. Here’s an example for the command %this% (delivered within the package). When you type a command into the editor the string will get replaced by the predefined text. This predefined text may include variables depending on what you want to achieve. %this% was designed to insert the fully qualified name of the current class you’re in (or function, or script).
  
• Clipboard Stack – CTRL + SHIFT + V opens the Clipboard Stack, where the last 10 copied/cut text are stored and can be directly inserted into the current editor position. The Clipboard Stack only stores text copied from editor.

Navigation

• Auto switch current folder and detail viewer – Switching editor tabs will update the Desktop’s current folder and detail viewer. This behavior can be directly changed in the detail viewer bar.
  Use the new icons in the Desktop’s Current Folder panel: to toggle detail viewer and to toggle following the current editor file.
  
• File Structure – I personally use this one the most: CTRL + F12 will show a GUI that let you search methods and properties including inherited ones.
  
• Navigation History – Every editor file that is opened is stored in the navigation history. Up to 50 editor file paths are stored. If you have a 5-Button Mouse, you can navigate through previous location (backward and forward).
• Recently Closed – CTRL + SHIFT + T will show a GUI that allows you to reopen closed editors this or last session.
• Bookmarks – CTRL + SHIFT + F2 will show a GUI that allows you to name, search and delete bookmarks. Matlab has this nice feature to delete bookmarks after closing the editor. This feature will store all bookmarks. If an editor or Matlab is closed and opened later. All Bookmarks will be restored.
  This feature has some issues though. The most obvious first: if the source file has been changed outside of Matlab, the bookmark does not get updated, and may point to the wrong line, or gets deleted. Also on some Systems the default shortcut does not work. But there are workarounds.

Other useful features

• Dockable Windows – As mentioned before, most GUIs are dockable.
  
• Preferences – Preferences panel integrated in Matlab’s main Preferences window.
  
• Execute current line – SHIFT + F9 allows you to execute the current line. This is equivalent to selecting the entire line, then clicking F9, and is similar in concept to the editor’s built-in ability to execute the current cell-block.
  
• VarDiff – Select two variables in the workspace and compare them using Matlab’s internal comparison feature (adding a custom hook to the Workspace context-menu was discussed by Yair back in 2010).
  
• KeyPressListener – Allows you to create custom keyboard shortcuts for your own functions. A similar functionality was discussed by Yair back in 2009.

As noted above, a detailed explanation of these and other features is provided in the Features section of the utility’s wiki. If you discover any problem or have any suggestion for improvement, please visit the utility’s Issues section on GitHub, where issues can be tracked and discussed.

An undocumented way to attach actual new user-defined properties to objects such as GUI handles or Java references has historically (in HG1, up to R2014a) been to use the undocumented schema.prop function, as I explained here. As I wrote in that post, in HG2 (R2014b onward), we can use the fully-documented addprop function to add new custom properties (and methods) to such objects. What is still NOT documented, as far as I could tell, is that all of Matlab’s builtin handle graphics objects indirectly inherit the dynamicprops class, which allows this. The bottom line is that we can dynamically add custom properties in run-time to any HG object, without affecting any other object. In other words, the new properties will only be added to the handles that we specifically request, and not to any others.

All this is important, because for some unexplained reason that escapes my understanding, MathWorks chose to seal its classes, thus preventing users to extend them with sub-classes that contain the new properties. So much frustration could have been solved if MathWorks would simply remove the Sealed class meta-property from its classes. Then again, I’d have less to blog about in that case…

Anyway, why am I rehashing old news that I have already reported a few years ago?

Well, first, because my experience has been that this little tidbit is [still] fairly unknown by Matlab developers. Secondly, I happened to run into a perfect usage example a short while ago that called for this solution: a StackExchange user asked whether it is possible to tell a GUI figure’s age, in other words the elapsed time since the figure was created. The simple answer would be to use setappdata with the creation date whenever we create a figure. However, a “cleaner” approach seems to be to create new read-only properties for the figure’s CreationTime and Age:

First, create a small Matlab function as follows, that attaches the CreationTime property to a figure:

function setCreationTime(hFig,varargin)
   hProp = addprop(hFig,'CreationTime');
   hFig.CreationTime = now;
   hProp.SetAccess = 'private';  % make property read-only after setting its initial value
 
   hProp = addprop(hFig,'Age');
   hProp.GetMethod = @(h,e) etime(datevec(hFig.CreationTime), clock);  % compute on-the-fly
   hProp.SetAccess = 'private';  % make property read-only
end

Now assign this function as the default CreateFcn callback function for all new figures from now on:

set(0,'DefaultFigureCreateFcn',@setCreationTime)

That’s it – you’re done! Whenever a new figure will be created from now on, it will have two custom read-only properties: CreationTime and Age.

For example:

>> newFig = figure;
>> newFig.CreationTime
ans =
      737096.613706748
 
>> ageInDays = now - newFig.CreationTime
ageInDays = 
       0.0162507836846635
>> ageDuration = duration(ageInDays*24,0,0)
ageDuration = 
  duration
   00:23:24
>> ageString = datestr(ageInDays, 'HH:MM:SS.FFF')
ageString = 
    '00:23:24.068'
 
>> ageInSecs = newFig.Age
ageInSecs =
       1404.06771035492

Note that an alternative way to set the computed property Age would have been to set its value to be an anonymous function, but this would have necessitated invoking it with parenthesis (as in: ageInSecs = newFig.Age()). By setting the property’s GetMethod meta-property we avoid this need.

Keen readers will have noticed that the mechanism that I outlined above for the Age property/method can also be used to add custom user methods. For example, we can create a new custom property named refresh that would be read-only and have a GetMethod which is the function handle of the function that refreshes the object in some way.

Do you have any special uses for custom user-defined properties/methods in your program? or perhaps you have a use-case that might show MathWorks why sub-classing the built-in classes might improve your work? if so, then please place a comment about it below. If enough users show MathWorks why this is important, then maybe it will be fixed in some future release.

The solution is based on the fact that Matlab comes with a huge set of professional Java-based controls by JideSoft, bundled in various JAR libraries within the %matlabroot%/java/jarext/jide Matlab installation folder. For our specific purposes (an IP-address entry/display control), we are interested in the com.jidesoft.field.IPTextField control (online documentation), which is part of the JIDE Grids library (%matlabroot%/java/jarext/jide/jide-grids.jar). We can use it as follows:

jIPField = com.jidesoft.field.IPTextField('255.255.255.0');  % set default IP
[jIPField, hContainer] = javacomponent(jIPField, [10,10,120,20], hParent);  % hParent: panel/figure handle

IPTextField control in a Matlab GUI

You can modify the position/size of the text-field in the javacomponent call above, or by modifying the Position / Units properties of the returned hContainer.

We can retrieve the IP text/numeric values using:

vals = jIPField.getValue';         % 1x4 uint32 array => [255,255,255,0]
vals = cell(jIPField.getRawText)'; % 1x4 string cells => {'255','255','255','0'} 
ip   = char(jIPField.getText);     % entire IP string => '255.255.255.0'

The IPTextField component auto-validates the IP values, ensuring that the displayed IP is always valid (for example, IP components cannot be negative or larger than 255). The component has many other features, including the ability to enable/disable, color or format the IP components etc.

We can set a callback function to process user changes, by setting the component’s *StateChangedCallback* property, for example:

jIPField.StateChangedCallback = @(jComponent,jEventData) disp(jComponent.getValue');

The JIDE libraries that come with Matlab contain numerous other similarly-useful components, including date/time/font/color/file/folder selectors, calendars in various formats, credit-card fields, and many more.

For more information about using the javacomponent function and handling Java components in Matlab GUI, see other posts on this website – particularly those marked with the “JIDE” tag.

Additional discussion of JIDE’s combo-boxes, and JIDE controls in general, is available in Chapter 5 of my Matlab-Java Programming book.

If you need to integrate professional-looking controls such as these in your Matlab GUI, consider hiring my consulting services.

Caution

Remember that JIDE evolves with Matlab, and so JIDE’s online documentation, which refers to the latest JIDE version, may be partially inapplicable if you use an old Matlab version. In any case, Matlab releases always lag the latest JIDE release by at least a year (e.g., Matlab R2017b still uses JIDE v3.4.1 that was released in June 2012 – MathWorks used to update the bundled JIDE libraries to newer versions, but for some reason has stopped doing that in 2013). The older your Matlab, the more such inconsistencies that you may find. For example, I believe that DateSpinnerComboBox only became available around R2010b; similarly, some control properties behave differently (or are missing altogether) in different releases. To determine the version of JIDE that you are currently using in Matlab, run the following (the result can then be compared to JIDE’s official change-log history):

>> com.jidesoft.utils.Lm.getProductVersion
ans =
3.4.1

Note that JIDE is a commercial product. We may not use it without JIDESoft’s permission outside the Matlab environment. It is my understanding however, that we can freely use it within Matlab. Note that this is not legal advise as I am an engineer, not a lawyer. If you have any licensing questions, contact sales@jidesoft.com.

Also note that all of JIDE’s controls use the Java-based figures (that are created using GUIDE or the figure function), and will not work on the new web-based uifigures (created using App Designer or the uifigure function). There is currently no corresponding IP entry/display control for web-based GUIs, and since there is [still] no way to integrate external Javascript/CSS libraries in uifigures, the only resort is to use a plain-vanilla edit-box. If MathWorks would simply open a hook to integrate external JS/CSS libraries, that would enable users to use 3rd-party libraries that have such custom controls and MathWorks would then not need to spend a huge amount of effort to develop multiple UI control variants.

Well, not so fast it seems:

hToolbar = findall(hFig, 'tag','FigureToolBar');  % get the figure's toolbar handle
uipushtool(hToolbar, 'String','1');               % add a pushbutton to the toolbar
Error using uipushtool
There is no String property on the PushTool class. 

Apparently, for some unknown reason, standard Matlab only enables us to set the icon (CData) of a toolbar control, but not a text label.

Once again, Java to the rescue:

We first get the Java toolbar reference handle, then add the button in standard Matlab (using uipushtool, uitoggletool and their kin). We can now access the Java toolbar’s last component, relying on the fact that Matlab always adds new buttons at the end of the toolbar. Note that we need to use a short drawnow to ensure that the toolbar is fully re-rendered, otherwise we’d get an invalid Java handle. Finally, once we have this reference handle to the underlying Java button component, we can set and customize its label text and appearance (font face, border, size, alignment etc.):

hToolbar = findall(hFig, 'tag','FigureToolBar');     % get the figure's toolbar handle
jToolbar = hToolbar.JavaContainer.getComponentPeer;  % get the toolbar's Java handle
for buttonIdx = 1 : 4
    % First create the toolbar button using standard Matlab code
    label = num2str(buttonIdx);  % create a string label
    uipushtool(hToolbar, 'ClickedCallback',{@myCallback,analysisIdx}, 'TooltipString',['Run analysis #' label]);
 
    % Get the Java reference handle to the newly-created button
    drawnow; pause(0.01);  % allow the GUI time to re-render the toolbar
    jButton = jToolbar.getComponent(jToolbar.getComponentCount-1);
 
    % Set the button's label
    jButton.setText(label)
end

The standard Matlab toolbar button size (23×23 pixels) is too small to display more than a few characters. To display a longer label, we need to widen the button:

% Make the button wider than the standard 23 pixels
newSize = java.awt.Dimension(50, jButton.getHeight);
jButton.setMaximumSize(newSize)
jButton.setPreferredSize(newSize)
jButton.setSize(newSize)

Using a text label does not prevent us from also displaying an icon: In addition to the text label, we can also display a standard icon (by setting the button’s CData property in standard Matlab). This icon will be displayed to the left of the text label. You can widen the button, as shown in the code snippet above, to make space for both the icon and the label. If you want to move the label to a different location relative to the icon, simply modify the Java component’s HorizontalTextPosition property:

jButton.setHorizontalTextPosition(jButton.RIGHT);   % label right of icon (=default)
jButton.setHorizontalTextPosition(jButton.CENTER);  % label on top of icon
jButton.setHorizontalTextPosition(jButton.LEFT);    % label left of icon

In summary, here’s the code snippet that generated the screenshot above:

% Get the Matlab & Java handles to the figure's toolbar
hToolbar = findall(hFig, 'tag','FigureToolBar');     % get the figure's toolbar handle
jToolbar = hToolbar.JavaContainer.getComponentPeer;  % get the toolbar's Java handle
 
% Button #1: label only, no icon, 23x23 pixels
h1 = uipushtool(hToolbar);
drawnow; pause(0.01);
jButton = jToolbar.getComponent(jToolbar.getComponentCount-1);
jButton.setText('1')
 
% Create the icon CData from an icon file
graphIcon = fullfile(matlabroot,'/toolbox/matlab/icons/plotpicker-plot.gif');
[graphImg,map] = imread(graphIcon);
map(map(:,1)+map(:,2)+map(:,3)==3) = NaN;  % Convert white pixels => transparent background
cdata = ind2rgb(graphImg,map);
 
% Button #2: label centered on top of icon, 23x23 pixels
h2 = uipushtool(hToolbar, 'CData',cdata);
drawnow; pause(0.01);
jButton = jToolbar.getComponent(jToolbar.getComponentCount-1);
jButton.setText('2')
jButton.setHorizontalTextPosition(jButton.CENTER)
 
% Button #3: label on right of icon, 50x23 pixels
h3 = uipushtool(hToolbar, 'CData',cdata);
drawnow; pause(0.01);
jButton = jToolbar.getComponent(jToolbar.getComponentCount-1);
jButton.setText('3...')
d = java.awt.Dimension(50, jButton.getHeight);
jButton.setMaximumSize(d); jButton.setPreferredSize(d); jButton.setSize(d)
 
% Button #4: label on left of icon, 70x23 pixels
h4 = uipushtool(hToolbar, 'CData',cdata);
drawnow; pause(0.01);
jButton = jToolbar.getComponent(jToolbar.getComponentCount-1);
jButton.setText('and 4:')
jButton.setHorizontalTextPosition(jButton.LEFT)
d = java.awt.Dimension(70, jButton.getHeight);
jButton.setMaximumSize(d); jButton.setPreferredSize(d); jButton.setSize(d)

Many additional toolbar customizations can be found here and in my book “Undocumented Secrets of MATLAB-Java Programming“. If you’d like me to design a professional-looking GUI for you, please contact me.

Caveat emptor: all this only works with the regular Java-based GUI figures, not web-based (“App-Designer”) uifigures.

In today’s post I will discuss several possible mechanisms to integrate SQLite in Matlab code, and you can take your pick among them. Except for the Database Toolbox, all the alternatives are free (open-source) libraries (even the commercial Database Toolbox relies on one of the open-source libraries, by the way).

sqlite4java

sqlite4java is a Java package by ALM Works that is bundled with Matlab for the past several years (in the %matlabroot%/java/jarext/sqlite4java/ folder). This is a lightweight open-source package that provides a minimalist and fast (although not very convenient) interface to SQLite. You can either use the package that comes with your Matlab installation, or download and use the latest version from the project repository, where you can also find documentation.

Mark Mikofski exposed this hidden nugget back in 2015, and you are welcome to view his post for additional details. Here’s a sample usage:

% Open the DB data file
db = com.almworks.sqlite4java.SQLiteConnection(java.io.File('C:\Yair\Data\IGdb 2017-11-13.sqlite'));
db.open;
 
% Prepare an SQL query statement
stmt = db.prepare(['select * from data_table where ' conditionStr]);
 
% Step through the result set rows
row = 1;
while stmt.step
   numericValues(row) = stmt.columnInt(0);    % column #0
   stringValues{row}  = stmt.columnString(1); % column #1
end
 
% Cleanup
stmt.dispose
db.dispose

Note that since sqlite4java uses a proprietary interface (similar, but not identical, to JDBC), it can take a bit of time to get used to it. I am generally a big fan of preferring built-in components over externally-installed ones, but in this particular case I prefer other alternatives.

JDBC

JDBC (Java Database Connectivity) is the industry standard for connectivity to databases. Practically all databases nowadays have at least one JDBC connector, and many DBs have multiple JDBC drivers created by different groups. As long as they all adhere to the JDBC interface standard, these drivers are all equivalent and you can choose between them based on availability, cost, support, license, performance and other similar factors. SQLite is no exception to this rule, and has several JDBC driver implementations, including xerial’s sqlite-jdbc (also discussed by Mark Mikofski) and sqlitejdbc. If you ask me,
sqlite-jdbc is better as it is being maintained with new versions released periodically.

The example above would look something like this with sqlite-jdbc:

% Add the downloaded JAR library file to the dynamic Java classpath
javaaddpath('C:\path\to\sqlite\sqlite-jdbc-3.21.0.jar')
 
% Open the DB file
jdbc = org.sqlite.JDBC;
props = java.util.Properties;
conn = jdbc.createConnection('jdbc:sqlite:C:\Yair\Data\IGdb 2017-11-13.sqlite',props);  % org.sqlite.SQLiteConnection object
 
% Prepare and run an SQL query statement
sqlStr = ['select * from data_table where ' conditionStr];
stmt = conn.createStatement;     % org.sqlite.jdbc4.JDBC4Statement object
rs = stmt.executeQuery(sqlStr);  % org.sqlite.jdbc4.JDBC4ResultSet object
 
% Step through the result set rows
rows = 1;
while rs.next
   numericValues(row) = rs.getLong('ID');
   stringValues{row}  = rs.getString('Name');
end
 
% Cleanup
rs.close
stmt.close
conn.close

Database toolbox

In addition to all the above, MathWorks sells the Database Toolbox which has an integral SQLite connector, in two flavors – native and JDBC (the JDBC connector is simply sqlite-jdbc that I mentioned above, see a short discussion here).

I assume that the availability of this feature in the DB toolbox is the reason why MathWorks has never created a documented wrapper function for the bundled sqlite4java. I could certainly understand this from a business perspective. Still, with so many free alternatives available as discussed in this post, I see not reason to purchase the toolbox merely for its SQLite connector. Then again, if you need to connect to several different database types, not just SQLite, then getting the toolbox might make sense.

mksqlite

My personal favorite is actually none of these Java-based connectors (surprise, surprise), but rather the open-source mksqlite connector by Martin Kortmann and Andreas Martin. This is a native (Mex-file) connector that acts as a direct Matlab function. The syntax is pretty straight-forward and supports SQL queries. IMHO, its usage is a much simpler than with any of the other alternatives:

% Open the DB file
mksqlite('open', 'C:\Yair\Data\IGdb 2017-11-13.sqlite');
 
% Query the database
results = mksqlite(['select * from data_table where ' conditionStr]);
numericValues = [results.ID];
stringValues  = {results.Name};
 
% Cleanup
mksqlite('close');

Can it be any simpler than this!?

However, the main benefit of mksqlite over the other connectors is not its simplicity but the connector’s speed. This speed is due to the fact that the query is vectorized and we do not need to loop over all the separate data rows and fields. With the other connectors, it is actually not the loop that takes so long in Matlab, but rather the overheads and inefficiencies of numerous library calls to fetch one single value at a time from the result-set – this is avoided in mksqlite where there is only a single call. This results in lightning speed: A couple of years ago I consulted to a client who used a JDBC connector to an SQLite database; by switching from a JDBC connector to mksqlite, I reduced the execution time from 7 secs to 70 msecs – a 100x speedup! In that specific case, this made the difference between an unusable program and a highly interactive/responsive one.

Other alternatives

In addition to all the above, we can also use a .NET-based connector or a Python one – I leave these as an exercise for the reader…

Have I forgotten some important alternative? Or perhaps you have have some related tip you’d like to share? If so, then please leave a comment below.

Happy New Year everybody!

Customized plot-edit context-menu

A few workarounds were suggested to the original poster and you are most welcome to review them. There is also some discussion about the technical reasons that none of the “standard” ways of finding and modifying menu items fail in this case.

In today’s post I wish to repost my solution, in the hope that it might help other users in similar cases.

My solution is basically this:

1. First, enter plot-edit mode programmatically using the plotedit function
2. Next, move the mouse to the screen location of the relevant figure component (e.g. axes). This can be done in several different ways (the root object’s PointerLocation property, the moveptr function, or java.awt.Robot.mouseMove() method).
3. Next, automate a mouse right-click using the built in java.awt.Robot class (as discussed in this blog back in 2010)
4. Next, locate the relevant context-menu item and modify its label, callback or any of its other properties
5. Next, dismiss the context-menu by simulating a follow-on right-click using the same Robot object
6. Finally, exit plot-edit mode and return the mouse pointer to its original location

% Create an initial figure / axes for demostration purpose
fig = figure('MenuBar','none','Toolbar','figure');
plot(1:5); drawnow; 
 
% Enter plot-edit mode temporarily
plotedit(fig,'on'); drawnow
 
% Preserve the current mouse pointer location
oldPos = get(0,'PointerLocation');
 
% Move the mouse pointer to within the axes boundary
% ref: https://undocumentedmatlab.com/blog/undocumented-mouse-pointer-functions
figPos = getpixelposition(fig);   % figure position
axPos  = getpixelposition(gca,1); % axes position
figure(fig);  % ensure that the figure is in focus
newPos = figPos(1:2) + axPos(1:2) + axPos(3:4)/4;  % new pointer position
set(0,'PointerLocation',newPos);  % alternatives: moveptr(), java.awt.Robot.mouseMove()
 
% Simulate a right-click using Java robot
% ref: https://undocumentedmatlab.com/blog/gui-automation-robot
robot = java.awt.Robot;
robot.mousePress  (java.awt.event.InputEvent.BUTTON3_MASK); pause(0.1)
robot.mouseRelease(java.awt.event.InputEvent.BUTTON3_MASK); pause(0.1)
 
% Modify the <clear-axes> menu item
hMenuItem = findall(fig,'Label','Clear Axes');
if ~isempty(hMenuItem)
   label = '<html><b><i><font color="blue">Undocumented Matlab';
   callback = 'web(''https://undocumentedmatlab.com'',''-browser'');';
   set(hMenuItem, 'Label',label, 'Callback',callback);
end
 
% Hide the context menu by simulating a left-click slightly offset
set(0,'PointerLocation',newPos+[-2,2]);  % 2 pixels up-and-left
pause(0.1)
robot.mousePress  (java.awt.event.InputEvent.BUTTON1_MASK); pause(0.1)
robot.mouseRelease(java.awt.event.InputEvent.BUTTON1_MASK); pause(0.1)
 
% Exit plot-edit mode
plotedit(fig,'off'); drawnow
 
% Restore the mouse pointer to its previous location
set(0,'PointerLocation',oldPos);

In this code, I sprinkled a few pauses at several locations, to ensure that everything has time to fully render. Different pause values, or perhaps no pause at all, may be needed on your specific system.

Modifying the default context-menu shown in plot-edit mode may perhaps be an uncommon use-case. But the technique that I demonstrated above – of using a combination of Matlab and Java Robot commands to automate a certain animation – can well be used in many other use-cases where we cannot easily access the underlying code. For example, when the internal code is encoded/encrypted, or when a certain functionality (such as the plot-edit context-menu) is created on-the-fly.

If you have encountered a similar use-case where such automated animations can be used effectively, please add a comment below.

Matlab's builtin PopupPanel widget

As you can see, this popup-panel displays richly-formatted contents, having either an opaque or transparent background, with vertical scrollbars being applied automatically. The popup pane is not limited to displaying text messages – in fact, it can display any Java GUI container (e.g. a settings panel). This popup-panel is similar in concept to the HelpPopup widget, and yet much more powerful in several aspects.

Creating the popup panel

Creating a PopupPanel is very simple:

% Create the popup-panel in the specified figure
hPopupPanel = ctrluis.PopupPanel(gcf);  % use gcf or any figure handle
hPopupPanel.setPosition([.1,.1,.8,.8]);  % set panel position (normalized units)
 
% Alternative #1: set popup-panel's contents to some HTML-formatted message
% note: createMessageTextPane() has optional input args FontName (arg #2), FontSize (#3)
jPanel = ctrluis.PopupPanel.createMessageTextPane('testing <b><i>123</i></b> ...')
hPopupPanel.setPanel(jPanel);
 
% Alternative #2: set popup-panel's contents to a webpage URL
url = 'https://undocumentedmatlab.com/files/sample-webpage.html';
jPanel = javaObjectEDT(javax.swing.JEditorPane(url));
hPopupPanel.setPanel(jPanel);

The entire contents are embedded within a scroll-box (which is a com.mathworks.widgets.LightScrollPane object) whose scrollbars automatically appear as-needed, so we don’t need to worry about the contents fitting the allocated space.

To display custom GUI controls in the popup, we can simply contain those GUI controls in a Java container (e.g., a JPanel) and then do hPopupPanel.setPanel(jPanel). This functionality can be used to create unobtrusive settings panels, input dialogs etc.

The nice thing about the popup widget is that it is attached to the figure, and yet is not assigned a heavyweight window (so it does not appear in the OS task-bar). The popup moves along with the figure when the figure is moved, and is automatically disposed when the figure is closed.

A few caveats about the ctrluis.PopupPanel control:

• The widget’s parent is expected to be a figure that has pixel units. If it doesn’t, the internal computations of ctrluis.PopupPanel croak.
• The widget’s position is specified in normalized units (default: [0,0,1,1]). This normalized position is only used during widget creation: after creation, if you resize the figure the popup-panel’s position remains unchanged. To modify/update the position of the popup-panel programmatically, use hPopupPanel.setPosition(newPosition). Alternatively, update the control’s Position property and then call hPopupPanel.layout() (there is no need to call layout when you use setPosition).
• This functionality is only available for Java-based figures, not the new web-based (AppDesigner) uifigures.

Popup panel customizations

We can open/close the popup panel by clicking on its icon, as shown in the screenshots above, or programmatically using the control’s methods:

% Programmatically open/close the popup-panel
hPopupPanel.showPanel;
hPopupPanel.hidePanel;
 
% Show/hide entire popup-panel widget (including its icon)
hPopupPanel.setVisible(true);   % or .setVisible(1) or .Visible=1
hPopupPanel.setVisible(false);  % or .setVisible(0) or .Visible=0

To set a transparent background to the popup-panel (as shown in the screenshots above), we need to unset the opacity of the displayed panel and several of its direct parents:

% Set a transparent popup-panel background
for idx = 1 : 6
   jPanel.setOpaque(false);  % true=opaque, false=transparent
   jPanel = jPanel.getParent;
end
jPanel.repaint

Note that in the screenshots above, the panel’s background is made transparent, but the contained text and image remain opaque. Your displayed images can of course contain transparency and animation, if this is supported by the image format (for example, GIF).

iptui.internal.utilities.addMessagePane

ctrluis.PopupPanel is used internally by iptui.internal.utilities.addMessagePane(hFig,message) in order to display a minimizable single-line message panel at the top of a specified figure:

hPopupPanel = iptui.internal.utilities.addMessagePane(gcf, 'testing <b>123</b> ...');  % note the HTML formatting

The function updates the message panel’s position whenever the figure’s size is modified (by trapping the figure’s SizeChangedFcn), to ensure that the panel is always attached to the top of the figure and spans the full figure width. This is a simple function so I encourage you to take a look at its code (%matlabroot%/toolbox/images/imuitools/+iptui/+internal/+utilities/addMessagePane.m) – note that this might require the Image Processing Toolbox (I’m not sure).

Matlab's builtin iptui.internal.utilities.addMessagePane

Professional assistance anyone?

As shown by this and many other posts on this site, a polished interface and functionality is often composed of small professional touches, many of which are not exposed in the official Matlab documentation for various reasons. So if you need top-quality professional appearance/functionality in your Matlab program, or maybe just a Matlab program that is dependable, robust and highly-performant, consider employing my consulting services.

A quick recap: Matlab’s sendmail function uses Java (specifically, the standard javax.mail package) to prepare and send emails. The Java classes are extremely powerful and so there is no wonder that Mathworks chose to use them rather than reinventing the wheel. However, Matlab’s sendmail function only uses part of the functionality exposed by these classes (admittedly, the most important parts that deal with the basic mail-sending mechanism), and does not expose external hooks or input args that would enable the user to take full advantage of the more advanced features, HTML formatting included.

Only two small changes are needed in sendmail.m to support HTML formatting:

1. HTML formatting required calling the message-object’s setContent() method, rather than setText().
2. We need to specify 'text/html' as part of the message’s encoding

To implement these features, change the following (lines #119-130 in the original sendmail.m file of R2017a, changed lines highlighted):

% Construct the body of the message and attachments.
body = formatText(theMessage);
if numel(attachments) == 0    if ~isempty(charset)        msg.setText(body, charset);
    else
        msg.setText(body);
    end
else
    % Add body text.
    messageBodyPart = MimeBodyPart;
    if ~isempty(charset)        messageBodyPart.setText(body, charset);
    ...

to this (changed lines highlighted):

% Construct the body of the message and attachments.
body = formatText(theMessage);
isHtml = ~isempty(body) && body(1) == '<';  % msg starting with '<' indicates HTMLif isHtml    if isempty(charset)        charset = 'text/html; charset=utf-8';    else        charset = ['text/html; charset=' charset];    endendif numel(attachments) == 0  && ~isHtml    if isHtml        msg.setContent(body, charset);    elseif ~isempty(charset)        msg.setText(body, charset);
    else
        msg.setText(body);
    end
    else
        % Add body text.
        messageBodyPart = MimeBodyPart;
        if isHtml            messageBodyPart.setContent(body, charset);        elseif ~isempty(charset)            messageBodyPart.setText(body, charset);
        ...

In addition, I also found it useful to remove the hard-coded 75-character line-wrapping in text messages. This can be done by changing the following (line #291 in the original sendmail.m file of R2017a):

maxLineLength = 75;

to this:

maxLineLength = inf;  % or some other large numeric value

Deployment

It’s useful to note two alternatives for making these fixes:

• Making the changes directly in %matlabroot%/toolbox/matlab/iofun/sendmail.m. You will need administrator rights to edit this file. You will also need to redo the fix whenever you install Matlab, either installation on a different machine, or installing a new Matlab release. In general, I discourage changing Matlab’s internal files because it is simply not very maintainable.
• Copying %matlabroot%/toolbox/matlab/iofun/sendmail.m into a dedicated wrapper function (e.g., sendEmail.m) that has a similar function signature and exists on the Matlab path. This has the benefit of working on multiple Matlab releases, and being copied along with the rest of our m-files when we install our Matlab program on a different computer. The downside is that our wrapper function will be stuck with the version of sendmail.m that we copied into it, and we’d lose any possible improvements that Mathworks may implement in future Matlab releases.

The basic idea for the second alternative, the sendEmail.m wrapper, is something like this (the top highlighted lines are the additions made to the original sendmail.m, with everything placed in sendEmail.m on the Matlab path):

function sendEmail(to,subject,theMessage,attachments)%SENDEMAIL Send e-mail wrapper (with HTML formatting)   sendmail(to,subject,theMessage,attachments); 
% The rest of this file is copied from %matlabroot%/toolbox/matlab/iofun/sendmail.m (with the modifications mentioned above):
function sendmail(to,subject,theMessage,attachments)
%SENDMAIL Send e-mail.
%   SENDMAIL(TO,SUBJECT,MESSAGE,ATTACHMENTS) sends an e-mail.  TO is either a
%   character vector specifying a single address, or a cell array of character vector
...

We would then call the wrapper function as follows:

sendEmail('abc@gmail.com', 'email subject', 'regular text message');     % will send a regular text message
sendEmail('abc@gmail.com', 'email subject', '<b><font color="blue">HTML-formatted</font> <i>message');  % HTML-formatted message

In this case, the code automatically infers HTML formatting based on whether the first character in the message body is a ‘<‘ character. Instead, we could just as easily have passed an additional input argument (isHtml) to our sendEmail wrapper function.

Hopefully, in some future Matlab release Mathworks will be kind enough to enable sending 21^st-century HTML-formatted emails without needing such hacks. Until then, note that sendmail.m relies on standard non-GUI Java networking classes, which are expected to be supported far into the future, well after Java-based GUI may cease to be supported in Matlab. For this reason I believe that while it seems a bit tricky, the changes that I outlined in today’s post actually have a low risk of breaking in a future Matlab release.

Do you have some other advanced email feature that you use in your Matlab program by some crafty customization to sendmail? If so, please share it in a comment below.

• Survey regarding usage of the javacomponent function: http://www.mathworks.com/javacomponent
• Survey regarding usage of the JavaFrame property: http://www.mathworks.com/javaframe

In MathWorks’ words:

In order to extend your ability to build MATLAB apps, we understand you sometimes need to make use of undocumented Java UI technologies, such as the JavaFrame property. In response to your needs, we are working to develop documented alternatives that address gaps in our app building offerings.

To help inform our work and plans, we would like to understand how you are using the JavaFrame property. Based on your understanding of how it is being used within your app, please take a moment to fill out the following survey. The survey will take approximately 1-2 minutes to finish.

I urge anyone who uses one or both of these features to let MathWorks know how you’re using them, so that they could incorporate that functionality into the core (documented) Matlab. The surveys are really short and to the point. If you wish to send additional information, please email George.Caia at mathworks.com.

The more feedback responses that MathWorks will get, the better it will be able to prioritize its R&D efforts for the benefit of all users, and the more likely are certain features to get a documented solution at some future release. If you don’t take the time now to tell MathWorks how you use these features in your code, don’t complain if and when they break in the future…

My personal uses of these features

• Functionality:
  • Figure: maximize/minimize/restore, enable/disable, always-on-top, toolbar controls, menu customizations (icons, tooltips, font, shortcuts, colors)
  • Table: sorting, filtering, grouping, column auto-sizing, cell-specific behavior (tooltip, context menu, context-sensitive editor, merging cells)
  • Tree control
  • Listbox: cell-specific behavior (tooltip, context menu)
  • Tri-state checkbox
  • uicontrols in general: various event callbacks (e.g. mouse hover/unhover, focus gained/lost)
  • Ability to add Java controls e.g. color/font/date/file selector panel or dropdown, spinner, slider, search box, password field
  • Ability to add 3rd-party components e.g. JFreeCharts, JIDE controls/panels

• Appearance:
  • Figure: undecorated (frameless), other figure frame aspects
  • Table: column/cell-specific rendering (alignment, icons, font, fg/bg color, string formatting)
  • Listbox: auto-hide vertical scrollbar as needed, cell-specific renderer (icon, font, alignment, fg/bg color)
  • Button/checkbox/radio: icons, text alignment, border customization, Look & Feel
  • Right-aligned checkbox (button to the right of label)
  • Panel: border customization (rounded/matte/…)

You can find descriptions/explanations of many of these in posts I made on this website over the years.

Matlab GUI configuration panel including password and spinner controls (click to zoom-in)

Password fields are basically editboxes that hide the typed text with some generic echo character (such as * or a bullet); spinners are editboxes that only enable typing certain preconfigured values (e.g., numbers in a certain range). Both controls are part of the standard Java Swing package, on which the current (non-web-based) Matlab GUIs relies. In both cases, we can use the javacomponent function to place the built-in Swing component in our Matlab GUI.

Password field

The relevant Java Swing control for password fields is javax.swing.JPasswordField. JPasswordField is basically an editbox that hides any typed key with a * or bullet character.

Here’s a basic code snippet showing how to display a simple password field:

jPasswordField = javax.swing.JPasswordField('defaultPassword');  % default password arg is optional
jPasswordField = javaObjectEDT(jPasswordField);  % javaObjectEDT is optional but recommended to avoid timing-related GUI issues
jhPasswordField = javacomponent(jPasswordField, [10,10,70,20], gcf);

Password control

We can set/get the password string programmatically via the Text property; the displayed (echo) character can be set/get using the EchoChar property.

To attach a data-change callback, set jhPasswordField’s ActionPerformedCallback property.

Spinner control

detailed post on using spinners in Matlab GUI

The relevant Java Swing control for spinners is javax.swing.JSpinner. JSpinner is basically an editbox with two tiny adjacent up/down buttons that visually emulate a small round spinning knob. Spinners are similar in functionality to a combo-box (a.k.a. drop-down or pop-up menu), where a user can switch between several pre-selected values. They are often used when the list of possible values is too large to display in a combo-box menu. Like combo-boxes, spinners too can be editable (meaning that the user can type a value in the editbox) or not (the user can only “spin” the value using the up/down buttons).

JSpinner uses an internal data model. The default model is SpinnerNumberModel, which defines a min/max value (unlimited=[] by default) and step-size (1 by default). Additional predefined models are SpinnerListModel (which accepts a cell array of possible string values) and SpinnerDateModel (which defines a date range and step unit).

Here’s a basic code snippet showing how to display a simple numeric spinner for numbers between 20 and 35, with an initial value of 24 and increments of 0.1:

jModel = javax.swing.SpinnerNumberModel(24,20,35,0.1);
jSpinner = javax.swing.JSpinner(jModel);
jSpinner = javaObjectEDT(jSpinner);  % javaObjectEDT is optional but recommended to avoid timing-related GUI issues
jhSpinner = javacomponent(jSpinner, [10,10,70,20], gcf);

The spinner value can be set using the edit-box or by clicking on one of the tiny arrow buttons, or programmatically by setting the Value property. The spinner object also has related read-only properties NextValue and PreviousValue. The spinner’s model object has the corresponding Value (settable), NextValue (read-only) and PreviousValue (read-only) properties. In addition, the various models have specific properties. For example, SpinnerNumberModel has the settable Maximum, Minimum and StepSize properties.

To attach a data-change callback, set jhSpinner’s StateChangedCallback property.

I have created a small Matlab demo, SpinnerDemo, which demonstrates usage of JSpinner in Matlab figures. Each of the three predefined models (number, list, and date) is presented, and the spinner values are inter-connected via their callbacks. The Matlab code is modeled after the Java code that is used to document JSpinner in the official Java documentation. Readers are welcome to download this demo from the Matlab File Exchange and reuse its source code.

Matlab SpinnerDemo

The nice thing about spinners is that you can set a custom display format without affecting the underlying data model. For example, the following code snippet update the spinner’s display format without affecting its underlying numeric data model:

formatStr = '$ #,##0.0 Bn';
jEditor = javaObject('javax.swing.JSpinner$NumberEditor', jhSpinner, formatStr);
jhSpinner.setEditor(jEditor);

Formatted spinner control

For more information, refer to my detailed post on using spinners in Matlab GUI.

Caveat emptor

MathWorks’ new web-based GUI paradigm will most probably not directly support the Java components presented in today’s post, or more specifically the javacomponent function that enables placing them in Matlab GUIs. The new web-based GUI-building application (AppDesigner, aka AD) does contain a spinner, although it is [currently] limited to displaying numeric values (not dates/lists as in my SpinnerDemo). Password fields are not currently supported by AppDesigner at all, and it is unknown whether they will ever be.

All this means that users of Java controls who wish to transition to the new web-based GUIs will need to develop programmatic workarounds, that would presumably appear and behave less professional. It’s a tradeoff: AppDesigner does include features that improve GUI usability, not to mention the presumed future ability to post Matlab GUIs online (hopefully without requiring a monstrous Matlab Production Server license/installation).

In the past, MathWorks has posted a dedicated webpage to solicit user feedback on how they are using the figure’s JavaFrame property. MathWorks will presumably prepare a similar webpage to solicit user feedback on uses of the javacomponent function, so they could add the top items to AppDesigner, making the transition to web-based GUIs less painful. When such a survey page becomes live, I will post about it on this website so that you could tell MathWorks about your specific use-cases and help them prioritize their R&D efforts.

In any case, regardless of whether the functionality eventually makes it into AppDesigner, my hope is that when the time comes MathWorks will not pull the plug from non-web GUIs, and will still enable running them on desktops for backward compatibility (“legacy mode”). Users of existing GUIs will then not need to choose between upgrading their Matlab (and redeveloping their GUI as a web-based app) and running their existing programs. Instead, users will face the much less painful choice between keeping the existing Java-based programs and developing a web-based variant at some later time, separate from the choice of whether or not to upgrade Matlab. The increased revenue from license upgrades and SMS (maintenance plan) renewals might well offset the R&D effort that would be needed to keep supporting the old Java-based figures. The traumatic^* release of HG2 in R2014b, where a less-than-perfect version was released with no legacy mode, resulting in significant user backlash/disappointment, is hopefully still fresh in the memory of decision makers and would hopefully not be repeated.

^*well, traumatic for some at least. I really don’t wish to make this a debate on HG2’s release; I’d rather focus on making the transition to web-based GUIs as seamless as possible.

None of the information I’ll present today is really new – it was all there already if you just knew what to search for online. But hopefully today’s post will concentrate all these loose ends in a single place, so it may have some value:

• Using a secure mail server
• Emailing multiple recipients
• Sending text messages
• User configuration panel

Using a secure mail server

All modern mail servers use end-to-end TLS/SSL encryption. The sendmail function needs extra configuration to handle such connections, since it is configured for a non-encrypted connection by default. Here’s the code that does this for gmail, using SMTP server smtp.gmail.com and default port #465 (for other SMTP servers, see here):

setpref('Internet', 'E_mail', from_address);  % sender "from" address, typically same as username, e.g. 'xyz@gmail.com'
setpref('Internet', 'SMTP_Username', username);
setpref('Internet', 'SMTP_Password', password);
setpref('Internet', 'SMTP_Server',   'smtp.gmail.com');
 
props = java.lang.System.getProperties;
props.setProperty('mail.smtp.auth',                'true');  % Note: 'true' as a string, not a logical value!
props.setProperty('mail.smtp.starttls.enable',     'true');  % Note: 'true' as a string, not a logical value!
props.setProperty('mail.smtp.socketFactory.port',  '465');   % Note: '465'  as a string, not a numeric value!
props.setProperty('mail.smtp.socketFactory.class', 'javax.net.ssl.SSLSocketFactory');
 
sendmail(recipient, title, body, attachments);  % e.g., sendmail('recipient@gmail.com', 'Hello world', 'What a nice day!', 'C:\images\sun.jpg')

All this is not enough to enable Matlab to connect to gmail’s SMTP servers. In addition, we need to set the Google account to allow access from “less secure apps” (details, direct link). Without this, Google will not allow Matlab to relay emails. Other mail servers may require similar server-side account configurations to enable Matlab’s access.

Note: This code snippet uses a bit of Java as you can see. Under the hood, all networking code in Matlab relies on Java, and sendmail is no exception. For some reason that I don’t fully understand, MathWorks chose to label the feature of using sendmail with secure mail servers as a feature that relies on “undocumented commands” and is therefore not listed in sendmail‘s documentation. Considering the fact that all modern mail servers are secure, this seems to make sendmail rather useless without the undocumented extension. I assume that TMW are well aware of this, which is the reason they posted a partial documentation in the form of an official tech-support answer. I hope that one day MathWorks will incorporate it into sendmail as optional input args, so that using sendmail with secure servers would become fully documented and officially supported.

Emailing multiple recipients

To specify multiple email recipients, it is not enough to set sendmail‘s recipient input arg to a string with , or ; delimiters. Instead, we need to provide a cell array of individual recipient strings. For example:

sendmail({'recipient1@gmail.com','recipient2@gmail.com'}, 'Hello world', 'What a nice day!')

Note: this feature is actually fully documented in sendmail‘s doc-page, but for some reason I see that some users are not aware of it (to which it might be said: RTFM!).

Sending phone text (SMS) messages

With modern smartphones, text (SMS) messages have become rather outdated, as most users get push notifications of incoming emails. Still, for some users text messages may still be a useful. To send such messages, all we need is to determine our mobile carrier’s email gateway for SMS messages, and send a simple text message to that email address. For example, to send a text message to T-Mobile number 123-456-7890 in the US, simply email the message to 1234567890@tmomail.net (details).

Ke Feng posted a nice Matlab File Exchange utility that wraps this messaging for a wide variety of US carriers.

User configuration panel

Many GUI programs contain configuration panels/tabs/windows. Enabling the user to set up their own email provider is a typical use-case for such a configuration. Naturally, you’d want your config panel not to display plain-text password, nor non-integer port numbers. You’d also want the user to be able to test the email connection.

Here’s a sample implementation for such a panel that I implemented for a recent project – I plan to discuss the implementation details of the password and port (spinner) controls in my next post, so stay tuned:

User configuration of emails in Matlab GUI (click to zoom-in)

% Load the appropriate JDBC driver class into Matlab's memory
% (but not directly, to bypass JIT pre-processing - we must do it in run-time!)
driver = eval('com.mysql.jdbc.Driver');  % or com.microsoft.sqlserver.jdbc.SQLServerDriver or whatever
 
% Connect to DB
dbPort = '3306'; % mySQL=3306; SQLServer=1433; Oracle=...
connectionStr = ['jdbc:mysql://' dbURL ':' dbPort '/' schemaName];  % or ['jdbc:sqlserver://' dbURL ':' dbPort ';database=' schemaName ';'] or whatever
dbConnObj = java.sql.DriverManager.getConnection(connectionStr, username, password);
 
% Send an SQL query statement to the DB and get the ResultSet
stmt = dbConnObj.createStatement(java.sql.ResultSet.TYPE_SCROLL_INSENSITIVE, java.sql.ResultSet.CONCUR_READ_ONLY);
try stmt.setFetchSize(1000); catch, end  % the default fetch size is ridiculously small in many DBs
rs = stmt.executeQuery(sqlQueryStr);
 
% Get the column names and data-types from the ResultSet's meta-data
MetaData = rs.getMetaData;
numCols = MetaData.getColumnCount;
data = cell(0,numCols);  % initialize
for colIdx = numCols : -1 : 1
    ColumnNames{colIdx} = char(MetaData.getColumnLabel(colIdx));
    ColumnType{colIdx}  = char(MetaData.getColumnClassName(colIdx));  % http://docs.oracle.com/javase/7/docs/api/java/sql/Types.html
end
ColumnType = regexprep(ColumnType,'.*\.','');
 
% Get the data from the ResultSet into a Matlab cell array
rowIdx = 1;
while rs.next  % loop over all ResultSet rows (records)
    for colIdx = 1 : numCols  % loop over all columns in the row
        switch ColumnType{colIdx}
            case {'Float','Double'}
                data{rowIdx,colIdx} = rs.getDouble(colIdx);
            case {'Long','Integer','Short','BigDecimal'}
                data{rowIdx,colIdx} = double(rs.getDouble(colIdx));
            case 'Boolean'
                data{rowIdx,colIdx} = logical(rs.getBoolean(colIdx));
            otherwise %case {'String','Date','Time','Timestamp'}
                data{rowIdx,colIdx} = char(rs.getString(colIdx));
        end
    end
    rowIdx = rowIdx + 1;
end
 
% Close the connection and clear resources
try rs.close();   catch, end
try stmt.close(); catch, end
try dbConnObj.closeAllStatements(); catch, end
try dbConnObj.close(); catch, end  % comment this to keep the dbConnObj open and reuse it for subsequent queries

Naturally, in a real-world implementation you also need to handle database timeouts and various other errors, handle data-manipulation queries (not just SELECTs), etc.

Anyway, this works well in general, but when you try to fetch a ResultSet that has many thousands of records you start to feel the pain – The SQL statement may execute much faster on the DB server (the time it takes for the stmt.executeQuery call), yet the subsequent double-loop processing to fetch the data from the Java ResultSet object into a Matlab cell array takes much longer.

In one of my recent projects, performance was of paramount importance, and the DB query speed from the code above was simply not good enough. You might think that this was due to the fact that the data cell array is not pre-allocated, but this turns out to be incorrect: the speed remains nearly unaffected when you pre-allocate data properly. It turns out that the main problem is due to Matlab’s non-negligible overhead in calling methods of Java objects. Since the JDBC interface only enables retrieving a single data item at a time (in other words, bulk retrieval is not possible), we have a double loop over all the data’s rows and columns, in each case calling the appropriate Java method to retrieve the data based on the column’s type. The Java methods themselves are extremely efficient, but when you add Matlab’s invocation overheads the total processing time is much much slower.

So what can be done? As Andrew Janke explained in much detail, we basically need to push our double loop down into the Java level, so that Matlab receives arrays of primitive values, which can then be processed in a vectorized manner in Matlab.

So let’s create a simple Java class to do this:

// Copyright (c) Yair Altman UndocumentedMatlab.com
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Types;
 
public class JDBC_Fetch {
 
	public static int DEFAULT_MAX_ROWS = 100000;   // default cache size = 100K rows (if DB does not support non-forward-only ResultSets)
 
	public static Object[] getData(ResultSet rs) throws SQLException {
		try {
			if (rs.last()) {  // data is available
				int numRows = rs.getRow();    // row # of the last row
				rs.beforeFirst();             // get back to the top of the ResultSet
				return getData(rs, numRows);  // fetch the data
			} else {  // no data in the ResultSet
				return null;
			}
		} catch (Exception e) {
			return getData(rs, DEFAULT_MAX_ROWS);
		}
	}
 
	public static Object[] getData(ResultSet rs, int maxRows) throws SQLException {
		// Read column number and types from the ResultSet's meta-data
		ResultSetMetaData metaData = rs.getMetaData();
		int numCols = metaData.getColumnCount();
		int[] colTypes = new int[numCols+1];
		int numDoubleCols = 0;
		int numBooleanCols = 0;
		int numStringCols = 0;
		for (int colIdx = 1; colIdx <= numCols; colIdx++) {
			int colType = metaData.getColumnType(colIdx);
			switch (colType) {
				case Types.FLOAT:
				case Types.DOUBLE:
				case Types.REAL:
					colTypes[colIdx] = 1;  // double
					numDoubleCols++;
					break;
				case Types.DECIMAL:
				case Types.INTEGER:
				case Types.TINYINT:
				case Types.SMALLINT:
				case Types.BIGINT:
					colTypes[colIdx] = 1;  // double
					numDoubleCols++;
					break;
				case Types.BIT:
				case Types.BOOLEAN:
					colTypes[colIdx] = 2;  // boolean
					numBooleanCols++;
					break;
				default: // 'String','Date','Time','Timestamp',...
					colTypes[colIdx] = 3;  // string
					numStringCols++;
			}
		}
 
		// Loop over all ResultSet rows, reading the data into the 2D matrix caches
		int rowIdx = 0;
		double [][] dataCacheDouble  = new double [numDoubleCols] [maxRows];
		boolean[][] dataCacheBoolean = new boolean[numBooleanCols][maxRows];
		String [][] dataCacheString  = new String [numStringCols] [maxRows];
		while (rs.next() && rowIdx < maxRows) {
			int doubleColIdx = 0;
			int booleanColIdx = 0;
			int stringColIdx = 0;
			for (int colIdx = 1; colIdx <= numCols; colIdx++) {
				try {
					switch (colTypes[colIdx]) {
						case 1:  dataCacheDouble[doubleColIdx++][rowIdx]   = rs.getDouble(colIdx);   break;  // numeric
						case 2:  dataCacheBoolean[booleanColIdx++][rowIdx] = rs.getBoolean(colIdx);  break;  // boolean
						default: dataCacheString[stringColIdx++][rowIdx]   = rs.getString(colIdx);   break;  // string
					}
				} catch (Exception e) {
					System.out.println(e);
					System.out.println(" in row #" + rowIdx + ", col #" + colIdx);
				}
			}
			rowIdx++;
		}
 
		// Return only the actual data in the ResultSet
		int doubleColIdx = 0;
		int booleanColIdx = 0;
		int stringColIdx = 0;
		Object[] data = new Object[numCols];
		for (int colIdx = 1; colIdx <= numCols; colIdx++) {
			switch (colTypes[colIdx]) {
				case 1:   data[colIdx-1] = dataCacheDouble[doubleColIdx++];    break;  // numeric
				case 2:   data[colIdx-1] = dataCacheBoolean[booleanColIdx++];  break;  // boolean
				default:  data[colIdx-1] = dataCacheString[stringColIdx++];            // string
			}
		}
		return data;
	}
}

So now we have a JDBC_Fetch class that we can use in our Matlab code, replacing the slow double loop with a single call to JDBC_Fetch.getData(), followed by vectorized conversion into a Matlab cell array (matrix):

% Get the data from the ResultSet using the JDBC_Fetch wrapper
data = cell(JDBC_Fetch.getData(rs));
for colIdx = 1 : numCols
   switch ColumnType{colIdx}
      case {'Float','Double'}
          data{colIdx} = num2cell(data{colIdx});
      case {'Long','Integer','Short','BigDecimal'}
          data{colIdx} = num2cell(data{colIdx});
      case 'Boolean'
          data{colIdx} = num2cell(data{colIdx});
      otherwise %case {'String','Date','Time','Timestamp'}
          %data{colIdx} = cell(data{colIdx});  % no need to do anything here!
   end
end
data = [data{:}];

On my specific program the resulting speedup was 15x (this is not a typo: 15 times faster). My fetches are no longer limited by the Matlab post-processing, but rather by the DB’s processing of the SQL statement (where DB indexes, clustering, SQL tuning etc. come into play).

Additional speedups can be achieved by parsing dates at the Java level (rather than returning strings), as well as several other tweaks in the Java and Matlab code (refer to Andrew Janke’s post for some ideas). But certainly the main benefit (the 80% of the gain that was achieved in 20% of the worktime) is due to the above push of the main double processing loop down into the Java level, leaving Matlab with just a single Java call to JDBC_Fetch.

Many additional ideas of speeding up database queries and Matlab programs in general can be found in my second book, Accelerating Matlab Performance.

If you’d like me to help you speed up your Matlab program, please email me (altmany at gmail), or fill out the query form on my consulting page.

>> get(0,'ScreenSize')   % with 100% DPI (unscaled standard)
ans =
        1       1      1366       768
 
>> get(0,'ScreenSize')   % with 125% DPI (scaled)
ans =
        1       1      1092.8     614.4

The same phenomenon also affects other related properties, for example MonitorPositions.

Raimund Schlüßler, a reader on this blog, was kind enough to point me to this problem and its workaround, which I thought worthy to share here: To get the physical screen-size, use the following builtin Java command:

>> jScreenSize = java.awt.Toolkit.getDefaultToolkit.getScreenSize
jScreenSize =
java.awt.Dimension[width=1366,height=768]
 
>> width = jScreenSize.getWidth
width =
        1366
 
>> height = jScreenSize.getHeight
height =
        768

Also see the related recent article on an issue with the DPI-aware feature starting with R2015b.

Upcoming travels – London/Belfast, Zürich & Geneva

I will shortly be traveling to consult some clients in Belfast (via London), Zürich and Geneva. If you are in the area and wish to meet me to discuss how I could bring value to your work, then please email me (altmany at gmail):

• Belfast: Nov 28 – Dec 1 (flying via London)
• Zürich: Dec 11-12
• Geneva: Dec 13-15

It is often useful to have an integrated preview panel to display the contents of a file in a file-selection dialog. Clicking the various files in the tree-view would display a user-defined preview in the panel below, based on the file’s contents. An integrated panel avoids the need to manage multiple figure windows, one for the selector dialog and another for the preview. It also reduces the screen real-estate used by the dialog (also see the related resizing customization below).

I call the end-result uigetfile_with_preview; you can download it from the Matlab File Exchange:

filename = uigetfile_with_preview(filterSpec, prompt, folder, callbackFunction, multiSelectFlag)

As you can see from the function signature, the user can specify the file-type filter, prompt and initial folder (quite similar to uigetfile, uiputfile), as well as a custom callback function for updating the preview of a selected file, and a flag to enable selecting multiple files (not just one).

uigetfile_with_preview.m only has ~120 lines of code and plenty of comments, so feel free to download and review the code. It uses the following undocumented aspects:

1. I used a com.mathworks.hg.util.dFileChooser component for the main file selector. This is a builtin Matlab control that extends the standard javax.swing.JFileChooser with a few properties and methods. I don’t really need the extra features, so you can safely replace the component with a JFileChooser if you wish (lines 54-55). Various properties of the file selector are then set, such as the folder that is initially displayed, the multi-selection flag, the component background color, and the data-type filter options.
2. I used the javacomponent function to place the file-selector component within the dialog window.
3. I set a callback on the component’s PropertyChangeCallback that is invoked whenever the user interactively selects a new file. This callback clears the preview panel and then calls the user-defined callback function (if available).
4. I set a callback on the component’s ActionPerformedCallback that is invoked whenever the user closes the figure or clicks the “Open” button. The selected filename(s) is/are then returned to the caller and the dialog window is closed.
5. I set a callback on the component’s file-name editbox’s KeyTypedCallback that is invoked whenever the user types in the file-name editbox. The callback checks whether the entered text looks like a valid folder path and if so then it automatically updates the displayed folder as-you-type.

If you want to convert the code to a uiputfile variant, add the following code lines before the uiwait in line 111:

hjFileChooser.setShowOverwriteDialog(true);  % default: false (true will display a popup alert if you select an existing file)
hjFileChooser.setDialogType(hjFileChooser.java.SAVE_DIALOG);  % default: OPEN_DIALOG
hjFileChooser.setApproveButtonText('Save');  % or any other string. Default for SAVE_DIALOG: 'Save'
hjFileChooser.setApproveButtonToolTipText('Save file');  % or any other string. Default for SAVE_DIALOG: 'Save selected file'

In memory of my dear father.

>> hListbox = uicontrol('Style','list', 'String',{'item #1','item #2','item #3','item #4','item #5','item #6'});
>> set(hListbox,'Value',[]);
Warning: Single-selection 'listbox' control requires a scalar Value.
Control will not be rendered until all of its parameter values are valid
(Type "warning off MATLAB:hg:uicontrol:ValueMustBeScalar" to suppress this warning.)

The reader’s question was whether there is a way to bypass this limitation so that no listbox item will be selected. The answer to this question was provided by MathWorker Steve(n) Lord. Steve is a very long-time benefactor of the Matlab community with endless, tireless, and patient advise to queries small and large (way beyond the point that would have frustrated mere mortals). Steve pointed out that by default, Matlab listboxes only enable a single selection – not more and not less. However, when the listbox’s Max value is set to be >1, the listbox enables multiple-items selection, meaning that Value accepts and reports an array of item indices, and there is nothing that prevents this array from being empty (meaning no items selected):

>> hListbox = uicontrol('Style','list', 'Max',2, 'String',{'item #1','item #2','item #3','item #4','item #5','item #6'});
>> set(hListbox,'Value',[]);  % this is ok - listbox appears with no items selected

Note: actually, the listbox checks the value of Max–Min, but by default Min=0 and there is really no reason to modify this default value, just Max.

While this makes sense if you think about it, the existing documentation makes no mention of this fact:

The Max property value helps determine whether the user can select multiple items in the list box simultaneously. If Max – Min > 1, then the user can select multiple items simultaneously. Otherwise, the user cannot select multiple items simultaneously. If you set the Max and Min properties to allow multiple selections, then the Value property value can be a vector of indices.

Some readers might think that this feature is not really undocumented, since it does not directly conflict with the documentation text, but then so are many other undocumented aspects and features on this blog, which are not mentioned anywhere in the official documentation. I contend that if this feature is officially supported, then it deserves an explicit sentence in the official documentation.

However, the original CSSM reader wanted to preserve Matlab’s single-selection model while enabling deselection of an item. Basically, the reader wanted a selection model that enables 0 or 1 selections, but not 2 or more. This requires some tweaking using the listbox’s selection callback:

set(hListbox,'Callback',@myCallbackFunc);
 
...
function test(hListbox, eventData)
   value = get(hListbox, 'Value');
   if numel(value) > 1
       set(hListbox, 'Value', value(1));
   end
end

…or a callback-function version that is a bit better because it takes the previous selection into account and tries to set the new selection to the latest-selected item (this works in most cases, but not with shift-clicks as explained below):

function myCallbackFunc(hListbox, eventData)
   lastValue = getappdata(hListbox, 'lastValue');
   value = get(hListbox, 'Value');
   if ~isequal(value, lastValue)
      value2 = setdiff(value, lastValue);
      if isempty(value2)
         setappdata(hListbox, 'lastValue', value);
      else
         value = value2(1);  % see quirk below
         setappdata(hListbox, 'lastValue', value);
         set(hListbox, 'Value', value);
      end
   end
end

This does the job of enabling only a single selection at the same time as allowing the user to interactively deselect that item (by ctrl-clicking it).

There’s just a few quirks: If the user selects a block of items (using shift-click), then only the second-from-top item in the block is selected, rather than the expected last-selected item. This is due to line #9 in the callback code which selects the first value. Matlab does not provide us with information about which item was clicked, so this cannot be helped using pure Matlab. Another quirk that cannot easily be solved using pure Matlab is the flicker that occurs when the selection changes and is then corrected by the callback.

We can solve both of these problems using the listbox’s underlying Java component, which we can retrieve using my findjobj utility:

% No need for the standard Matlab callback now
set(hListbox,'Callback',[]);
 
% Get the underlying Java component peer
jScrollPane = findjobj(h);
jListbox = jScrollPane.getViewport.getView;
jListbox = handle(jListbox,'CallbackProperties');  % enable callbacks
 
% Attach our callback to the listbox's Java peer
jListbox.ValueChangedCallback = {@myCallbackFunc, hListbox};
 
...
function myCallbackFunc(jListbox, eventData, hListbox)
   if numel(jListbox.getSelectedIndices) > 1
      set(hListbox, 'Value', jListbox.getLeadSelectionIndex+1);  % +1 because Java indices start at 0
   end
end

We can use a similar mechanism to control other aspects of selection, for example to enable only up to 3 selections but no more etc.

We can use this underlying Java component peer for a few other useful selection-related hacks: First, we can use the peer’s RightSelectionEnabled property or setRightSelectionEnabled() method to enable the user to select by right-clicking listbox items (this is disabled by default):

jListbox.setRightSelectionEnabled(true);  % false by default
set(jListbox,'RightSelectionEnabled',true);  % equivalent alternative

A similarly useful property is DragSelectionEnabled (or the corresponding setDragSelectionEnabled() method), which is true by default, and controls whether the selection is extended to other items when the mouse drags an item up or down the listbox.

Finally, we can control whether in multi-selection mode we enable the user to only select a single contiguous block of items, or not (which is Matlab’s default behavior). This is set via the SelectionMode property (or associated setSelectionMode() method), as follows:

jListbox.setSelectionMode(javax.swing.ListSelectionModel.SINGLE_INTERVAL_SELECTION);
jListbox.setSelectionMode(1);  % equivalent alternative (less maintainable/readable, but simpler)

SINGLE_SELECTION =0	SINGLE_INTERVAL_SELECTION =1	MULTIPLE_INTERVAL_SELECTION =2
(Matlab default for Max=1)	(only possible with Java)	(Matlab default for Max>1)

Additional listbox customizations can be found in related posts on this blog (see links below), or in section 6.6 of my Matlab-Java Programming Secrets book (which is still selling nicely almost five years after its publication, to the pleasant surprise of my publisher…).