Working with non-standard DPI displays

November 9, 2016 6 Comments

With high-density displays becoming increasingly popular, some users set their display’s DPI to a higher-than-standard (i.e., >100%) value, in order to compensate for the increased pixel density to achieve readable interfaces. This OS setting tells the running applications that there are fewer visible screen pixels, and these are spread over a larger number of physical pixels. This works well for most cases (at least on recent OSes, it was a bit buggy in non-recet ones). Unfortunately, in some cases we might actually want to know the screen size in physical, rather than logical, pixels. Apparently, Matlab root’s ScreenSize property only reports the logical (scaled) pixel size, not the physical (unscaled) one:

>> 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

6 Responses

Thomas Pieper November 17, 2016 at 14:17 Reply

If you feel more as a Microsoft family member you might want to use .NET commands. Try

NET.addAssembly('System.Windows.Forms');
System.Windows.Forms.Screen.PrimaryScreen.Bounds

System.Windows.Forms.SystemInformation.PrimaryMonitorSize

and you get something like

ans = 
 
  System.Drawing.Rectangle
  Package: System.Drawing
 
  Properties:
    Location: [1x1 System.Drawing.Point]
        Size: [1x1 System.Drawing.Size]
           X: 0
           Y: 0
       Width: 1920
      Height: 1080
        Left: 0
         Top: 0
       Right: 1920
      Bottom: 1080
     IsEmpty: 0
       Empty: [1x1 System.Drawing.Rectangle]

Greetings,

Thomas

Yair Altman November 17, 2016 at 14:47 Reply

@Thomas – the problem with your .NET solution is that it only works on Windows; the Java-based solution in my post works on all Matlab platforms, including Mac and Linux.

Matthias Kirchhoff November 24, 2016 at 16:09 Reply

As for me the solution using java.awt.Toolkit.getDefaultToolkit.getScreenSize does not work correctly when using more than one monitor.
Better use:

ge = javaObjectEDT(java.awt.GraphicsEnvironment.getLocalGraphicsEnvironment());
gs = ge.getScreenDevices();
jmonitorposition = [];
if ~isempty(gs)
  for iRun_ = 1:size(gs,1)
     dm = gs(iRun_).getDisplayMode();
     jmonitorposition(iRun_,:) = [1 1 dm.getWidth dm.getHeight];
  end
end

Best regards
Matthias

Yaroslav November 28, 2016 at 10:59 Reply
Hi Yair,

Suppose I have two monitors. How can I tell a figure to appear on the secondary one, if it exists? I can do something like
hFig = figure('Units','normalized','Position',[1.10 0.10 0.80 0.70]);
hFig = figure('Units','normalized','Position',[1.10 0.10 0.80 0.70]);
but it doesn’t tell me whether the second screen exists or not (if not, it will effectively hide the figure).

Best regards

marco November 29, 2016 at 16:12 Reply
Hi,
maybe this can be helpful:
>> monitorPos = get(0,'MonitorPositions') monitorPos = 1 1 1600 900 1601 1 3200 900
>> monitorPos = get(0,'MonitorPositions') monitorPos = 1 1 1600 900 1601 1 3200 900
then you can play with ‘pixels’ positions

Yaroslav November 29, 2016 at 21:28 Reply

Hi @Marco,

Thank you for your comment. Unfortunately, your solution tells me only how many monitors I can have. What I need is to know how many monitors I currently have.

To be more precise, MonitorPositions tells me how many monitors I had at the time of Matlab’s startup. It does not change if I attach a monitor after startup. This is the behaviour in my Windows 8.1 laptop.

I can do a little trick to circumvent this problem. By using the PointerLocation, I can check on which monitor the pointer is. For example

% get root handle
hRoot = groot;
% check if (a) there are at least two monitors
%          (b) pointer's x location is larger than 2nd monitor's x0 position
if     size(hRoot.MonitorPositions,1) >= 2 ...
    && hRoot.PointerLocation(1) > hRoot.MonitorPositions(2,1)
    % put figure on the second monitor
else
    % put figure on the first monitor
end

However, as you can see, it assumes you have control over the cursor’s position during execution. I wish there was an option to tell how many active monitors are there.

HTML tags such as <b> or <i> are accepted.
Wrap code fragments inside <pre lang="matlab"> tags, like this:

<pre lang="matlab">
a = magic(3);
disp(sum(a))
</pre>

I reserve the right to edit/delete comments (read the site policies).
Not all comments will be answered. You can always email me (altmany at gmail) for private consulting.

Click here to cancel reply.

JCFL (23 hours 42 minutes ago): I was trying the above trick to change the transparency of contour lines and wondering why not all the lines have changed — then I found your post. Thanks and your post saved me.
Patrick Fitzgerald (3 days 3 hours ago): Just a heads up to anyone else digging around for help related to this: if you assign BackrgoundColor to a pushbutton-style uicontrol, it seems to prevent you from...
Vasiliy (18 days 22 hours ago): Hi Yair, i’m trying to use the MonthChooserPanel class. com.mathworks.mwswing.MJUtilit ies.initJIDE; handles.jPanel = com.jidesoft.combobox.MonthCho oserPanel;...
DM (18 days 22 hours ago): Hi Yair, I’m trying to use the MonthChooserPanel class. com.mathworks.mwswing.MJUtilit ies.initJIDE; handles.jPanel = com.jidesoft.combobox.MonthCho oserPanel; [handles.hPanel,...
Yair Altman (22 days 15 hours ago): @Alex – thanks, but keep in mind that new functions will only work on the recent Matlab releases. If your code needs to work on older Matlab releases, you could revert to...
Alex Churchill (22 days 15 hours ago): I was looking up how to do this exact task today. I was about to hold my nose and use the internal controllib function, when I happened to chance across a slightly newer...
Sebastian Hölz (28 days 21 hours ago): I have not investigated this in detail, but I think one way to go in new versions of Matlab (>2019b) might be to use listeners to suitable figure properties, e.g. fig =...
Prathep (29 days 0 hours ago): Hi Yair, Thanks for your introduction on Matlab Toostrip. Is there any way to add Matlab toolstrip for uifigures as you have done already for figure?
Josh (35 days 7 hours ago): Dear Yair, Small typo; you wrote >>Move lines up or down – CTRL + ALT + UP or DOWN allows you to move selected lines up or down but it’s actually ALT+SHIFT then UP/DOWN...
Yair Altman (42 days 1 hour ago): You can try to increase the Java heap memory size in the Matlab preferences (General => Java Heap Memory). Any changes to the settings will only take effect after restarting...
Thomas (42 days 3 hours ago): Hello, thanks for sharing! I currently receive the following memory error message when using savezip with a big object (Matlab R2020b, Windows 10). Error using...
Yair Altman (45 days 10 hours ago): Yerlan – either use menuItem1.setEnabled(0) or set(menuItem1,'Enabled',0)
Manzn (45 days 13 hours ago): Thank you man! you saved me, when there was no more light 😀
Yerlan (46 days 18 hours ago): Hello Mr. Altman, how can I disable menu items in the context menu? E.g. when I am trying to do this: menuItems = jmenu.getSubElements; menuItem1 = menuItems(1);...
Yair Altman (47 days 10 hours ago): Thanks for the note Eric – you forgot the crucial call to jTable.setLabelTable(labelTabl e) – I added it into your code snippet above.

Upcoming travels – London/Belfast, Zürich & Geneva

Related posts:

6 Responses

Leave a Reply