determine if the mouse is pressed in a given moment

I’m wondering if the Figure class has some (probably hidden) property that expresses if the mouse is pressed (and which button) in the moment that the moment that the property is read. If the figure had an event for button up and down events that would also solve my problem.

I know I could set WindowButtonDownFcn and WindowButtonUpFcn to inform a global variable to keep track on when the mouse is used, but that's deeply unpractical (in my code WindowButtonDownFcn gets changed frequently depending on the actions of the user)

Answer 1

[Jan]

It would be easy, if you do not change the WindowButtonDownFcn frequently, but keep it statically and use a persistent variable for branching. Then you had to insert the code to store the button state at one location only.

If you check the button state, you have to consider the currently active window also. You do not want to react to clicks in the task bar or the desktop.

What about https://www.mathworks.com/matlabcentral/fileexchange/61976-check-if-mouse-button-is-pressed under Windows?

[EDITED] The FEX submission is not working out of the box. Try this:

% !!! UNTESTED !!!
function [L, R, M] = GetMouseKeyStatus()
if ~ispc
  error('Running under Windows only.');
end

if ~libisloaded('user32')
   loadlibrary('user32.dll', 'user32.h');
end

L = calllib('user32', 'GetAsyncKeyState', int32(1)) ~= 0;
R = calllib('user32', 'GetAsyncKeyState', int32(2)) ~= 0;
M = calllib('user32', 'GetAsyncKeyState', int32(4)) ~= 0;
end

[Arabarra]

Thanks Jan... hm, a pity this option is only available in Windows. I'll try it, anyway.

[Walter Roberson]

Possibly some of the routines from PsychToolbox might help? See https://www.mathworks.com/matlabcentral/answers/310311-how-to-get-psychtoolbox-to-wait-for-keypress-but-move-on-if-it-hasn-t-recieved-one-in-a-set-time

[Bruno Luong]

It seems LOADLIBRARY is not working on my system (Windows 10, 20H2)

K>> loadlibrary('user32.dll', 'user32.h')
Error using loadlibrary
Could not find file user32.h.

Error in loadlibrary

user32.dll still exists however.

Here is my workaround. I create an h-file called WinMouse.h and place it together with ismousedpressed.m

function keypressed = ismousedpressed()
% keypressed = ismousedpressed()
% returns
%   0 no button is pressed
%   1 is left button
%   2 is right button
%   3 is scroll button push (not scrolling)
% Restriction: Windows only
% TIP: call ismousedpressed() once when your app start
%      so that when really needed; ismousedpressed() returns result faster.
%
% Author: Mbvalentin
% https://www.mathworks.com/matlabcentral/fileexchange/61976-check-if-mouse-button-is-pressed
% Modified by Bruno Luong


if ~libisloaded('user32')
    try
        loadlibrary('C:\WINDOWS\system32\user32.dll', 'user32.h');
    catch
        % user.h is removed on certain recent version of Windows
        % We replace with a simple customized header file 
        here = fileparts(mfilename('fullpath'));
        loadlibrary('C:\WINDOWS\system32\user32.dll', [here '\WinMouse.h']);
    end
end
left    = calllib('user32','GetAsyncKeyState',int32(1)) ~= 0;
right   = calllib('user32','GetAsyncKeyState',int32(2)) ~= 0;
scroll  = calllib('user32','GetAsyncKeyState',int32(4)) ~= 0;
keypressed = max([1 2 3].*double([left right scroll]));

end % ismousedpressed

File WinMouse.h, this suppose the GetAsyncKeyState signature won't change on Windows OS (which likely the case)

/* WinMouse.h
 * Replacement of user32.h if it's not available 
   see ismousedpressed.m 
   This file must be located at the same place as ismousedpressed */

short GetAsyncKeyState(
  int vKey
);

Answer 2

[Ankit Bhardwaj]

You can use ButtonDownFcn callback for your figure. This callback executes whenever the user clicks a mouse button while the pointer is in the figure window, but not over a child object such as a uicontrol, uipanel, axes, or axes child. Moreover, mouse selection type returns 'normal', 'extend' , 'alt' , or 'open'. MATLAB maintains this property to provide information about the last mouse-button press that occurred within the figure window. This information indicates the type of selection made. Please go through the following documentation to learn about callback properties of figure object.

https://www.mathworks.com/help/matlab/ref/figure-properties.html#zmw57dd0e274973

[Arabarra]

Hi Ankit,

thanks for your suggestion. This would be rather unpractical in my case, as in my GUI I define a large number of "modus" (similar to the zoom, rotation, etc of a regular matlab figure). This means, a lot of ButtonDownFcns that change during runtime. To implement your solution, I would be forced to make certain that every ButtonDownFcn triggers an event that tells some listener that the button was pressed, and that every ButtonUpFcn broadcasts the release of the button. That'd be a titanic effort, specially because I rely on a large library of code that I didn't develop specifically for this application (and which I don't wish to modify, as they are used by other applications).

cheers, Daniel

[Walter Roberson]

I wonder if iptaddcallback() would help ?