如何从Octave图中删除GUI元素？

Question

Relatively new to Octave, and I'm creating a straightforward figure window with a plot in an axis object and some uicontrol objects that can manipulate the plot. All very straightforward up to this point, I make the figure, axes, and uicontrols

figure(1, 'position', ...
h.ax = axes(...
h.button = uicontrol('style', 'pushbutton', 'string', 'press me', 'callback', @func)
h.label = uicontrol(...
guidata(gcf, h)

The problem comes from one of my button callbacks. When the button is pressed, not only is the plot altered, but I need to remove one of the elements from the gui, for instance a uicontrol label. The only method I've found for taking a gui element from a figure window is to delete the uicontrol object, so my callback looks something like

function func (obj)
  h = guidata(obj);

  delete(h.label);
  ...

  guidata(obj, h);
endfunction

This yields "error: guidata: H must be a valid object handle execution error in graphics callback function".

I suspect my mistake will be obvious to someone with a grasp of how graphics handles work in Octave / Matlab. It'd be a huge help to understand what's going wrong.

Answer 1

Instead of deleting the uicontrol object, you could just set its visible property to off . That way, the uicontrol still exist, you just can't see it.

From https://octave.org/doc/v4.2.0/Uicontrol-Properties.html :

visible : " off " | {" on "}

If visible is " off ", the uicontrol is not rendered on screen.

Answer 2

Your code isn't complete, so I cannot comment on a specific bug ... however, this code works for me (in octave):

function testo()
  figure(1, 'position', [10, 10, 400, 400]);
  h.ax = axes('position', [0,0,1,1]);
  h.button = uicontrol('style', 'pushbutton', 'string', 'press me', 'position', [10, 50, 100, 50], 'callback', @func);
  h.label1 = uicontrol('style', 'text', 'string', 'label1', 'position', [120, 50, 100, 50]);
  h.label2 = uicontrol('style', 'text', 'string', 'label2', 'position', [230, 50, 100, 50]);
  guidata(gcf, h)
endfunction

function func (obj,evnt)
  h = guidata(obj);
  delete(h.label1);
  guidata(obj, h);
endfunction

Note that if you press the button again, you get the error you see. So perhaps the problem isn't deleting the label per se, but you deleting something else that doesn't actually exist.