Archive for December, 2009

GUI integrated HTML panel

Tuesday, December 15th, 2009

Last week, I explained how a browser control can be integrated in Matlab GUI applications. Sometimes we only need to display simple HTML, for which a full browser seems like overkill. Moreover, we may wish to edit the displayed contents, which cannot be done using the browser control. The solution is to use a standard Java Swing JEditorPane control, which is an editable HTML-aware control.

Oddly enough, it was only yesterday that Mikhail, a known Matlab Java specialist on the CSSM newsgroup, posted an example for this as answer to a question on the StackOverflow forum (slightly edited for clarity):

mytext = ['<html><body><table border="1">' ...
          '<tr><th>Month</th><th>Savings</th></tr>' ...
          '<tr><td>January</td><td>$100</td></tr>' ...
          '</table></body></html>'];
 
% Create a figure with a scrollable JEditorPane
hfig = figure();
je = javax.swing.JEditorPane('text/html', mytext);
jp = javax.swing.JScrollPane(je);
[hcomponent, hcontainer] = javacomponent(jp, [], hfig);
set(hcontainer, 'units', 'normalized', 'position', [0,0,1,1]);
 
% Turn anti-aliasing on (R2006a, Java 5.0)
java.lang.System.setProperty('awt.useSystemAAFontSettings', 'on');
je.setFont(java.awt.Font('Arial', java.awt.Font.PLAIN, 13));
je.putClientProperty(javax.swing.JEditorPane.HONOR_DISPLAY_PROPERTIES, true);
 
% This only works on Java 1.5 (Matlab R14SP2 to R2007a):
je.putClientProperty(com.sun.java.swing.SwingUtilities2.AA_TEXT_PROPERTY_KEY, true);

Editable HTML-aware JEditorPane

Editable HTML-aware JEditorPane

Mikhail’s code included setting SwingUtilities2’s AA_TEXT_PROPERTY_KEY property for anti-aliased fonts. Unfortunately, SwingUtilities2 was an unsupported and undocumented internal class in Java 1.5 (undocumented/unsupported by Sun, not MathWorks for a change…) and completely disappeared in Java 1.6 (which is bundled with Matlab R2007b onward). Therefore, SwingUtilities2 and its antialias property can only be used on Matlab releases R14SP2 (7.0.4) through R2007a (7.4) – other Matlab versions will throw an error.

Alternately, use JIDE’s AA_TEXT_PROPERTY_KEY (JIDE is bundled with Matlab and this is supported even on new Matlab releases – I will present JIDE in future articles).

property = com.jidesoft.swing.JideSwingUtilities.AA_TEXT_PROPERTY_KEY;
je.putClientProperty(property, true);

Or, simply add the following switch to your java.opt file:

-Dswing.aatext=true

With this switch, you no longer need to set anti-aliasing separately for each component. It is entirely harmless to set this switch even on Matlab/Java versions that do not support it (the switch is simply ignored in these cases).

Note that while JEditorPane’s support for HTML is extensive, it is incomplete. It also does not contain a JavaScript engine or other web-related features we have come to expect in a browser. For the more complex stuff we can use the browser control as explained in last week’s article.

Matlab’s own multi-line editbox uicontrol uses JEditorPane (or actually its derived-class JTextPane) as an underlying component. This means that the simple-looking Matlab editbox is actually a powerful HTML-aware component. In order to use these hidden undocumented features we need the editbox’s underlying JTextPane handle. This is done using the FindJObj utility, which will be described in my next article. Following that, I will show how to customize Matlab’s dull-looking editbox into something much more powerful. Here’s a sample, to help you stay tuned:

HTML contents in a regular Matlab editbox

HTML contents in a regular Matlab editbox

GUI integrated browser control

Wednesday, December 9th, 2009

Last week, I described the built-in PopupPanel object, and showed how it can be used to present popup messages with HTML content and even entire webpages. I explained that PopupPanel uses an internal browser object to achieve this. In fact, Matlab’s browser object predates PopupPanel by many years and quite a few releases. This browser object can be used as a stand-alone component that we can easily embed in our Matlab GUI applications.

Here is a simple example in which a Matlab Listbox uicontrol is used to select the contents of an adjacent browser component:

% Create a blank figure window
f=figure('Name','Browser GUI demo','Num','off','Units','norm');
 
% Add the browser object on the right
jObject = com.mathworks.mlwidgets.html.HTMLBrowserPanel;
[browser,container] = javacomponent(jObject, [], f);
set(container, 'Units','norm', 'Pos',[0.3,0.05,0.65,0.9]);
 
% Add the URLs listbox on the left
urls = {'www.cnn.com','www.bbc.co.uk','myLocalwebpage.html',...
        'www.Mathworks.com', 'UndocumentedMatlab.com'};
hListbox = uicontrol('style','listbox', 'string',urls, ...
        'units','norm', 'pos',[0.05,0.05,0.2,0.9], ...
        'userdata',browser);
 
% Set the listbox's callback to update the browser contents
cbStr=['strs = get(gcbo,''string''); ' ...
      'url = strs{get(gcbo,''value'')};' ...
      'browser = get(gcbo,''userdata''); ' ...
      'msg=[''<html><h2>Loading '' url '' - please wait''];'...
      'browser.setHtmlText(msg); pause(0.1); drawnow;'...
      'browser.setCurrentLocation(url);'];
set(hListbox,'Callback',cbStr);

Browser object integrated in Matlab GUI (click for large image)

Browser object integrated in Matlab GUI

In this simple example, we can see how the Java browser object can easily be controlled by Matlab. Specifically, we use two modes of the browser: first we present an HTML message (‘Loading www.cnn.com – please wait‘) and then replacing this content with the actual webpage, if accessible. If the webpage is not accessible, an error message is displayed:

Browser message when webpage is missing (click for large image)

Browser message when webpage is missing

We can easily expand this simple example to display any HTML message or webpage, in a seamless integration within our GUI.

Now, who ever said that Matlab GUI looks static or boring???

In an unrelated note, I would like to extend good wishes to Ken Orr, who has left the Mathworks Desktop development team to join Apple a few days ago. You probably know Ken from his good work on the Desktop and the official Matlab Desktop blog. Hopefully, in his new position Ken will be able to influence Mac Java in a way that will reduce the numerous recurring issues that afflict Matlab Mac releases.