How to fire a button/callback in a code generated figure

I want to mimic a click event on a pushbutton in a code generated figure. The code for the button is as followed

u(4) = uicontrol('Parent',figh, ...
  'Units', 'normalized', ...
  'Position',posbut(4,:), ...
  'Tag','Pushbutton4',...
  'string','>>',...
  'Callback',['global in_callback;', ...
                'if isempty(in_callback);in_callback=1;', ...
                '    try eegplot(''drawp'',4);', ...
                '        clear global in_callback;', ...
                '    catch error_struct;', ...
                '        clear global in_callback;', ...
                '        error(error_struct);', ...
                '    end;', ...
                'else;return;end;']);%James Desjardins 2013/Jan/22

This is from a toolbox I use. To fire i would need to call the callback, but I can't figure it out.

The way I find this button and its callback is like this:

forwardButton = findall(groot,'Tag','Pushbutton4');
callbackCell= get(forwardButton,'Callback');

from here on I'm quite stuck. I tried thing like str2func, or calling the function in a way like this: callbackCell(callbackCell,[])

Does anyone have an idea on what approach would be more valid to achieve this button click mimic.

Answer 1

[Walter Roberson]

evalin('base', callbackCell)

... but really that code should be re-written to invoke a real function. And the toolbox should probably be rewritten to avoid global variables.

[Tybault Hollanders]

using that method still gives me errors of not being a char vector: (I checked the class in the first debug line)

Class of callbackCell: char
Error using error
The message must be specified as either a character vector or a message structure.

I then looked into the workspace where a new variable was generated called struct_error where it seems to be this problem:

MATLAB:structRefFromNonStruct

originating from the toolbox's .m file. I started putting in debugging lines in that code and compared the difference between a actual push of the button and the scripted evalin. It seems that calling callback through evalin, it cannot seem to find objects anymore using findobj('tag',...) not findall(groot,Tag,...).

Excuse me for these abstract problems I'm having. I am a beginner at matlab

Concerning the rewrite: I think it is a valid point, especially for a relatively large usergroup EEGLab has

[Walter Roberson]

It sounds to me as if some graphics objects are set to have handlevisibility 'callback'. Such objects would be found by findall() at any time, but would be found by findobj() only if a callback (any callback) was executing. That was good debugging effort on your part to localize it down to that point.

You can either change the findobj to findall, or you can change the object handlevisibility to 'on', or you could temporarily set the root property ShowHiddenHandles

[Tybault Hollanders]

Yes it was something in that trend. Thank you for the advise, the way it looked for the figure was with the gcf command. This figure was used as a Parent variable in the findobj method. I now find the parent figure with a findobj/findall method and works fine (but a bit slow). Thanks for the advise