Go ahead and push it.  The ui* series of functions need a lot of work and it would be nice if we could update them with bug fixes, rather than have to wait until 4.2 because we don't want to break ABI compatibility.

Good point.  We don't want to break ABI compatibility.

@Panxto: Maybe hold off until after the 4.0.0 release.  We're anticipating that there will be a very quick 4.0.1 release 6-8 weeks after 4.0.0 to deal with whatever is uncovered by wide scale testing.  Maybe it can go in then.

Also works for me.

I have attached a more general fix which includes BIST tests:

• setting "uicontextmenu" to [] only resets the value
• deleting  a uicontextmenu object will also reset the "uicontextmenu" property of all the objects that have it as current.

(file #33639)

I have attached a simple patch that fixes the issue for me. However it does only handle the case of deleting a uicontextmenu and reseting its parent "uicontextmenu" property.
I am working on a more general solution that uses Rik's suggestion to do the cleanup in the uicontextmenu destructor. uicontextmenu objects will store a list of objects that may depend on them, and reset their "uicontextmenu" property at destruction if needed.

(file #33637)

I am working on a simple solution that doesn't involve making use of the deletefcn (which we should keep available for the user).

The problem appears to be that the C++ graphics code assumes that whenever an object is deleted it should be removed from it's parent's "children" property.  In this case, the graphics handle for the menu is under the "uicontextmenu" rather than "children.

You can hack around this for now, or dive into the source if it is really bothersome.

First, delete() is the correct thing to do to remove a handle so

delete (c)

will rid Octave of the uicontextmenu.  The 'uicontextmenu' property expects a graphics_handle to be entered.  This is a double value, where NaN has the special meaning of invalid.  At some point, libinterp/corefcn/graphics.in.h should be modified to accept an empty matrix input ([]).  For now, this will safely rid the figure of the now deleted uicontextmenu.

set (F, 'uicontextmenu', NaN)

As a workaround that combines these two things you could write a special deletefcn to be called whenever a uicontextmenu is deleted.

function cb_delete_uicontextmenu (h)
  p = get (h, "parent");
  set (p, "uicontextmenu", NaN);
  delete (h);
endfunction

Now you can write

% By default, uicontextmenu is []
F = figure;
get(F,'uicontextmenu')

% add a uicontextmenu
c = uicontextmenu;
set (c, "deletefcn", @cb_delete_uicontextmenu);
m = uimenu('parent',c,'label','menu');
set(F,'uicontextmenu',c);

% Now delete and check that object is gone
delete (c)
get (c)
get(F,'uicontextmenu')

Since uicontextmenu is an m-file in scripts/gui this could be made a default part of Octave.  Or the C++ deletion code in graphics.in.h could be improved.  The destructor ~uicontextmenu is currently empty.  Maybe that is the place to check the parent and see if there is a 'uicontextmenu' property and delete it, rather than in an m-file callback.