Old(ish) regression in widgets

[jtappin]

Somewhere between bc3197a (about 2 Sep) and 6c1d6bc (about 19 Sep), there seems to have been a change in the handling of widget events and the event_func seems to be ignored.

Essentially in graffer in order to allow pop-up menus to work modularly even though the main event loop is non-blocking, I use a home-brew event loop for these, e.g.:

  widget_control, base, event_func = 'grf_tlz_event', set_uvalue = $
                  uvs, /no_copy

  repeat begin
     ev = widget_event(base)
  endrep until ev.exited ne 0

and the final part of the handler routine is:

  return, {id:event.handler, $
           top:event.top, $
           handler:0l, $
           exited:iexit}

I only noticed this today when I got errors about the structure not having an EXITED tag. A little further investigation shows that the call to widget_event is returning the original widget events and is not calling the handler routine.

I need to dig a little deeper to check exactly what conditions trigger the problem. Clearly event_pro settings in groups that are handled within xmanager are not affected (otherwise I'd never have reached the pop-ups in the first place).

P.S. Sorry about the initial blank post

[GillesDuvert]

Certainly #1882
Will have to digest this one.

[jtappin]

I've now managed to generate a "distilled" code that illustrates the problem.
handlers.pro

In IDL, clicking on the "Continue" button in the sub-menu gives:

SUB_EVENT
** Structure WIDGET_BUTTON, 4 tags, length=16, data length=16:
   ID              LONG                 8
   TOP             LONG                 7
   HANDLER         LONG                 7
   SELECT          LONG                 1
SUB_MENU
** Structure <38d7b08>, 4 tags, length=16, data length=13, refs=1:
   ID              LONG                 7
   TOP             LONG                 7
   HANDLER         LONG                 0
   EXIT            BYTE         0

whereas in GDL I only see:

 SUB_MENU
** Structure WIDGET_BUTTON, 4 tags,memsize =16, data length=16/16:
   ID              LONG                54
   TOP             LONG                53
   HANDLER         LONG                 0
   SELECT          LONG                 1

Similarly, clicking on "Exit" in IDL gives:

SUB_EVENT
** Structure WIDGET_BUTTON, 4 tags, length=16, data length=16:
   ID              LONG                 9
   TOP             LONG                 7
   HANDLER         LONG                 7
   SELECT          LONG                 1
SUB_MENU
** Structure <38b6dd8>, 4 tags, length=16, data length=13, refs=1:
   ID              LONG                 7
   TOP             LONG                 7
   HANDLER         LONG                 0
   EXIT            BYTE         1
Done
IDL> 

and the sub menu is destroyed. Whereas in GDL, only:

SUB_MENU
** Structure WIDGET_BUTTON, 4 tags,memsize =16, data length=16/16:
   ID              LONG                55
   TOP             LONG                53
   HANDLER         LONG                 0
   SELECT          LONG                 1

is displayed and the sub-menu is not destroyed.

It appears to me that GDL's implementation of widget_event misses out (at least) clause 4 from the description of the behaviour of widget_event in the IDL documentation.

It does look as though it is possible to achieve the desired behaviour using xmanager (I'm guessing that either handling a mixture of blocking and non-blocking widgets didn't work in the early days (ca. 1995-7) or else the documentation was even less clear than it now is.)

[GillesDuvert]

Rats! I've spent days checking the conformance to this accursed documentation when doing #1882. Will have to review that again!
Thanks for handler.pro

[jtappin]

Possibly more serious is that it seems to break some compound widgets (cw_bgroup), I only spotted that last night while trying to update the handling in graffer and found that a radio button menu failed.

Will update once I've checked properly.

[jtappin]

Possibly more serious is that it seems to break some compound widgets (cw_bgroup), I only spotted that last night while trying to update the handling in graffer and found that a radio button menu failed.

Will update once I've checked properly.

OK. Problem resolved (patch attached).
cw_bgroup.pro.diff

Radio button menus were only returning the release event. It turns out that this was a result of GDL returning the press event before the release event, (whereas IDL returns release then press) so to be able to get a reasonable behaviour for user event handlers I put in a line that threw away the second event received. Now GDL is returning the events in the sensible order, so the throwaway line can now be removed.