Get CurrentPoint gives me wrong values after deploying as web app

I am using appdesigner to develop an application. In the app, I have an axes that plots one image. Once the user clicks the image, it triggers a callback function, as shown below.

him = imagesc(wafermap, 'parent', app.Ax1);
him.ButtonDownFcn = @app.imClicked;

Inside, the callback function, I want to get the X and Y position of the click for some further processing. For convinience, I have output the value to a label.

The codes to get the click position is shown below.

cpt = get(app.Ax1, 'CurrentPointGet ');
pt  = cpt(1, 1:2);
x   = round(pt(1));
y   = round(pt(2));
app.StatusOutput.Text = sprintf('Row: %d,  Column: %d', y, x);

The app works very well on my desktop. The problem comes when being deployed as a web app. The returned x and y values can be 0 or minus sometimes. After palying with the web app for a while, I find that the returned x and y values can change when I change the size of the browser. When I use the maximize button on the bottom left corner, the x values are correct while the y value is always minus 1 from the expected value, that's showing 0 if it is actually 1.

By the way, I am using Matlab 2019a on Windows 10 64bit system.

Any thoughts on how to sort out the problem or any workaround?

Thanks a lot.

Answer 1

[Georgi Nalbantov]

Hi, I noticed that (R2019a) when deployed in a browser, the y-axis coordinates are returned vis-a-vis the bottom of the browser window, and not the bottom of the axes. Similar issue exists with the x-axis. This may lead to current point coordinates offsets of 200+ pixels (!), say if you reduce the height of the browser a lot. As you put it, the returned x and y values change when you change the size of the browser. To get around this, what worked for me was:

To get the current point coordinates, use:

cpt = event.IntersectionPoint;

instead of:

cpt = app.UIAxes.CurrentPoint; % this is the same as: get(app.UIAxes, 'CurrentPoint') .

For example, you can have a mouse-move function like this:

% Window button motion function: UIFigure

function UIFigureWindowButtonMotion(app, event)

C = app.UIAxes.CurrentPoint; % C = get(app.UIAxes, 'CurrentPoint');

D = event.IntersectionPoint;

app.xEditField_CP.Value = num2str(round(1000*C(1,1))/1000);

app.yEditField_CP.Value = num2str(round(1000*C(1,2))/1000);

app.xEditField_EI.Value = num2str(round(1000*D(1))/1000);

app.yEditField_EI.Value = num2str(round(1000*D(2))/1000);

app.UIAxes.Toolbar.Visible = 'off';

end

I got inspired by this topic: https://www.mathworks.com/matlabcentral/answers/674218-drawrectangle-not-working-consistently-help

Hope this helps. See attached file app_get_coordinates.mlapp for a complete example.