Geoaxes zoom not working after adding ButtonDownFcn.

I have an app built in AppDesigner with a map plotted in geoaxes. I need to zoom in and out but I also need to do some action when I click on the map. The problem is that:

• zoom works perfectly when no buttondownfcn is added

f = uifigure;
gx = geoaxes();
geoscatter(gx,10,10)

• zoom does not work at all when buttondownfcn is added.

f = uifigure;
gx = geoaxes(f);
geoscatter(gx,10,10)
gx.ButtonDownFcn = 'disp(''hello'')';

I need to use both functionalities. What should I do?

Answer 1

[Adam Danz]

I'm not sure why assigning the button down function affects the zooming but it can be fixed by resetting the default interactivity of the axes.

gx = geoaxes;
geoscatter(gx,10,10)
enableDefaultInteractivity(gx) % * <-- must be before assigning ButtonDownFcn
gx.ButtonDownFcn = 'disp(''hello'')';

* See Jan Studnicka's comment below.

[Peter Valent]

Thank you Adam. Your code works and answers my question. However it does not work for UIFIGURE which is actually what I need as the app is built in AppDesigner. Try this code:

f = uifigure;
gx = geoaxes(f);
geoscatter(gx,10,10)
gx.ButtonDownFcn = 'disp(''hello'')';
enableDefaultInteractivity(gx)

Does not even work when the geoaxes ButtonDownFcn is substituted by uifigure WindowButtonDownFcn!!!

[Adam Danz]

This has got to be a bug - in both regular figures and uifigures. It just so happens that enableDefaultInteractivity patches the bug with regular figures. None of this is mentioned in the documentation.

Even without the ButtonDownFcn, if I zoom in and out quickly in R2021a I iteratively get this warning,

Warning: A value of class "double" was indexed with no subscripts specified. Currently the result of this operation is the indexed value itself, but in a
future release, it will be an error. 
> In matlab.internal.asynchttpsave/AsyncHTTPContentFileWriter/handleThreadIsFinishedEvent
In matlab.internal.asynchttpsave.AsyncHTTPContentFileWriter
In asyncio/Channel/onPropertyChanged (line 471)
In asyncio.Channel>@(source,data)obj.onPropertyChanged(data.Name,data.Value) (line 401)

You should report this as a bug and feel free to point to this thread. Let us know what they say.

Contact Us - MATLAB & Simulink

[Adam Danz]

Fortunately the zoom buttons on the axes toobar still function.

[Jan Studnicka]

I have just found out, that enableDefaultInteractivity works for uifigure too, however you need to call it before you add ButtonDownFcn callback:

f = uifigure;
gx = geoaxes(f);
geoscatter(gx,10,10)
enableDefaultInteractivity(gx)
gx.ButtonDownFcn = 'disp(''hello'')';

[Adam Danz]

Thanks for the update!

[Malte Nagel]

Has someone already reported this bug? It appears to still be there and it is causing a lot of trouble for me.

[Adam Danz]

> Has someone already reported this bug?

Yes.

Does the workaround in my answer now work for you?

Answer 2

[Jan Studnicka]

As mentioned here in the documentation:

"Sometimes MATLAB® automatically disables the built-in interactions. For example, they might be disabled for charts that have special features, or when you implement certain callbacks such as a WindowScrollWheelFcn."

However, with geoaxes you can easily implement zooming in / out by using WindowScrollWheelFcn callback of the uifigure. This is an example created from the documentation's example on "how to use WindowScrollWheelFcn":

function scroll_wheel
% Shows how to use WindowScrollWheelFcn in combination with geoaxes and
% ButtonDownFcn callback.

   f = uifigure('WindowScrollWheelFcn',@figScroll,'Name','Scroll Wheel Demo');
   gx = geoaxes(f);
   geoscatter(gx,10,10)
   gx.ButtonDownFcn = 'disp(''hello'')';
   title(gx,'Rotate the scroll wheel')

   function figScroll(~,event)
      if event.VerticalScrollCount > 0 
        gx.ZoomLevel = gx.ZoomLevel-0.1;
      elseif event.VerticalScrollCount < 0 
        gx.ZoomLevel = gx.ZoomLevel+0.1;
      end
   end
end

[Adam Danz]

+1 Good idea, Jan. Note that this zooms into the center of the axes rather than zooming into the location of the cursor within the axes.

It's still not clear to me why a ButtonDownFcn would prevent zoom interaction since that callback function does not respond to the scroll wheel. I also find it odd that adding the ButtonDownFcn disables zoom interaction but calling enableDefaultInteractivity can turn it back on in regular figures - that sounds buggy to me. Lastly, I wonder why applying enableDefaultInteractivity doesn't fix the problem with uifigures.

BTW, I also get the same interative warning when zooming in/out using this method (r2021a)

Warning: A value of class "double" was indexed with no subscripts specified. Currently the result of this operation is the indexed value itself, but in a
future release, it will be an error. 
> In matlab.internal.asynchttpsave/AsyncHTTPContentFileWriter/handleThreadIsFinishedEvent
In matlab.internal.asynchttpsave.AsyncHTTPContentFileWriter
In asyncio/Channel/onPropertyChanged (line 471)
In asyncio.Channel>@(source,data)obj.onPropertyChanged(data.Name,data.Value) (line 401) 

There's clearly some cleaning up to do by MW.