Branching a WindowButtonDown function

Hi. I have written a windowsButtonDown function (in App Designer) to report back the coordinates of a plot on a UIAxes component.

                    function figure1WindowButtonDown(app, event)
                    %Remove any previous drawn "roi point object" that is used to indicate the position clicked on the UIAXes
                    delete(findobj(app.UIAxes,'type','images.roi.Point'));
                    z=app.UIAxes.CurrentPoint;
                    x=z(1,1);  y=z(1,2);               
                    %Determine if user clicked on UIAxes
                    if x >= app.UIAxes.XLim(1) & x <= app.UIAxes.XLim(2) & y >= app.UIAxes.YLim(1) & y <= app.UIAxes.YLim(2)              
                         app.xyAX1=[x,y];  %Save for later use
                         drawpoint(app.UIAxes,'Position',[x y]);
                    end

Whilst this works, I also want to use a button down function on a seperate UIAxes4 which holds a greyscale Image (16 bit). (The idea is read back the value on the image at the location as the useful impixelinfo tool (for GUIDE) doesn't work with appdesigner yet.

So I put another if statement in:

                    %See if user selects the Image (UIAxes 4)
                    if x >= app.UIAxes4.XLim(1) & x <= app.UIAxes4.XLim(2) & y >= app.UIAxes4.YLim(1) & y <= app.UIAxes4.YLim(2)
                        delete(findobj(app.UIAxes4,'Marker','+'));   %Remove any previously drawn '+'
                        z=app.UIAxes4.CurrentPoint;
                        x=round(z(1,1));  y=round(z(1,2));                           
                        hold(app.UIAxes4,'on');
                        plot(app.UIAxes4,x,y,'r+')  %Visualise positon on image
                        % TODO....Then will get value from image at this location
                    end
                    

But it doesnt seem to be branching correctly, when I click on UIAxes not only does it draw the point (via drawpoint) on the UIAxes, it also does on the UIAxes4 (and resizes the image weirdly!)

Answer 1

[J. Alex Lee]

If you don't mind using undocumented features, I have had success using the standard axes() object instead of uiaxes(), because it still supports the axes's own buttondownfcn. You can make a placeholder uipanel in app designer, then in a startupfcn create an axes in the panel (be sure to declare a custom property to hold that axes object) with the appropriate buttondownfcn.

I think this is the cleaner way within current matlab limitations, to avoid branching on the figures windowbuttondownfcn.

At least with 2019b, I can confirm this doesn't break when creating a web app.