plot inside a callback

1. I started a blank GUIDE app
2. Created an axes.
3. Created a callback on ButtonDownFcn.
4. Just added plot([0 rand], [0 rand])

function axes1_ButtonDownFcn(hObject, eventdata, handles)
  plot([0 rand], [0 rand])

Then the callback is actually called only the first time I click on the axes. This happened only with plot.

Is plot hiding the axes away?

I tried also with:

plot(handles.axes1, [0 rand], [0 rand])

or with

axes(handles.axes1)
plot(handles.axes1, [0 rand], [0 rand])

but this didn't solve the problem

Answer 1

[David Barry]

I think you need to reset the callback if you plot into the axes. Try adding the line below after your plot command.

hObject.ButtonDownFcn = {@axes1_ButtonDownFcn, handles};

[Walter Roberson]

No, this is not needed.

[David Barry]

I believe it is needed. See example below where callback is reset in 2nd section. It's nothing to do with HitTest. The alternative is to set the NextPlot property on the axes to 'replacechildren' instead of default 'replace'

%%all good
a = gca;
plot(a, 1:10);
a.ButtonDownFcn = @(~,~) disp('You clicked');
a.ButtonDownFcn

%%now plot some new data and see callback is empty
plot(a, 1:20);
a.ButtonDownFcn

[Walter Roberson]

Ah, I see what you mean. But instead,

a.NextPlot = 'replacechildren';

Answer 2

[Walter Roberson]

Once the axes has something in it, then your clicks are potentially being absorbed by what is plotted in the axes rather than getting through to the axes itself.

If you are using R2014b or later, see https://www.mathworks.com/help/matlab/creating_plots/capturing-mouse-clicks.html with regards to pickableparts and hittest .

In R2014a and earlier you can still look at that, but only the hittest part existed then.

[David Barry]

Incorrect. Issue is that callback is getting reset because default value for the NextPlot property on the axes is 'replace'.

[Walter Roberson]

Both issues are important when you are dealing with axes callbacks.