How to check if a figure is closed using the big red 'X' mark?

Hi! I am using a gui in my application. There are 'Ok' and 'Cancel' buttons there which upon clicking close the figure and do some additional processing before returning control to the main matlab program.

My query is how do I perform error checking if the user instead of pressing either of the two buttons, chooses to close the gui window using the window close button (big red X in windows)?

I read the documentation about CloseRequestFcn but was unable to figure it out from there.

Answer 1

[Image Analyst]

Do you want them to do the OK button or the Cancel button if they do that? Which ever it is, just call the OK or Cancel callback from the closerequestfcn.

[Udit Gupta]

I think this will set the program to go in an infinite loop of call backs because the Ok and Cancel buttons also close the figure. Please correct me if I am wrong.

[Image Analyst]

No. But if you want, you can also shutdown from that function by deleting the handle. See this example:

% --- Executes when user attempts to close figMainWindow.
function figMainWindow_CloseRequestFcn(hObject, eventdata, handles)
% hObject    handle to figMainWindow (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% Hint: delete(hObject) closes the figure
global vidobj;  % Video camera object.
try    % Save the current settings to our disk file.
    SaveUserSettings(handles, true);
  
  % Shut down the timer.
  StopTimer(handles);  

      % Shut down the camera
    try
      delete(vidobj);
    catch
    end

      % Get rid of variables from the global workspace so that they aren't
      % hanging around the next time we try to run this m-file.
      clear global;
    delete(hObject);
  catch ME
      warningMessage = sprintf('Error in function figMainWindow_CloseRequestFcn.\nError Message:\n%s', ME.message);
      set(handles.txtInfo, 'string', warningMessage);
      WarnUser(warningMessage);
  end
  fprintf(1, '\n=================     Exited figMainWindow_CloseRequestFcn.     =================\n');
  return; % from figMainWindow_CloseRequestFcn()

[Udit Gupta]

OK! Now I see what's happening. Thanks for the info.