App Designer - Pointer update issue

Hello,

I am working on an App Designer app.

I have coded the function below. It is supposed to change the pointer to watch if it is an arrow or to arrow if it is a watch.

methods (Access = public)
        function pointer_change(app)
            if app.UIFigure.Pointer == 'arrow'
                set(app.UIFigure, 'pointer', 'watch');
            else
                set(app.UIFigure, 'pointer', 'arrow');
            end
            
            drawnow()
        end
        end

All my callbacks look like this :

  function callback1(app, event)
    pointer_change(app);
    
    %some code that takes a long time to run so I need to change the cursor 
    %to indicate that matlab is busy running
    
    pointer_change(app);
end

When I change the pointer from 'watch' to 'arrow' (which corresponds to the second call of pointer_change), the pointer is not updated until I move the mouse, as if the drawnow statement was not executed. As soon as I move the mouse, the pointer becomes an arrow.

Does anyone know why ?

Many thanks,

Gwendal

[Geoff Hayes]

@Gwendal Marrec - how or when is your callback1 method called? If I put the code from pointer_change into a button callback, then the mouse pointer changes immediately (without the need even for the drawnow.

[Gwendal Marrec]

@Geoff Hayes, callback1 is called when pushing a button. My app will contain about 100 callbacks so I would like to have a clean code by using a function to change the pointer appearance. At first, I put the code from pointer_change into every callbacks but the problem was the same : the pointer was not updated until I moved the mouse.

it works well to change from 'arrow' to 'watch' but the opposite way does not work properly.

[Geoff Hayes]

@Gwendal Marrec - it isn't clear to me why the pointer doesn't immediately change. I'm using R2021a and the pointer does change without the need to move the mouse pointer

        function ButtonPushed(app, event)
            if app.UIFigure.Pointer == 'arrow'
                set(app.UIFigure, 'pointer','watch');
            else
                set(app.UIFigure, 'pointer','arrow');
            end
            
            for k = 1:30
                pause(1);
            end
            
            if app.UIFigure.Pointer == 'arrow'
                set(app.UIFigure, 'pointer','watch');
            else
                set(app.UIFigure, 'pointer','arrow');
            end
        end

The above automatically changes the mouse pointer after the simulated work (30 seconds) completes.

[Geoff Hayes]

@Gwendal Marrec - can you provide a small working example that exhibits this behaviour?

Answer 1

[Veronica Taurino]

I have the same problem. The pointer does not change until I move the cursor. I am working in the app designer, each callback has something like:

 function callback1(app, event)
    set(app.UIFigure, 'Pointer','watch')
    
    % do stuff...
    
    set(app.UIFigure, 'Pointer','arrow')
end

[Gwendal Marrec]

We have the exact same issue. Have you tried to put drawnow ?

[Veronica Taurino]

Yes I did, but it didn't work

[Geoff Hayes]

Does the same issue occur with the sample code I provided above? Note that I'm using a Macbook...not sure which OS either of you are using.

[Gwendal Marrec]

Your sample code works well for me. Really intriguing.

I'm on Windows 10 20H2.

Answer 2

[Gwendal Marrec]

Up. I've tried a couple of things but none of them worked out. Whenever I call another function to handle the pointer change, it never returns to 'arrow' until I move the mouse.