No, no, not again!

[steinhh(at)ulrik.uio.no (Stein Vidar Hagfors Haugan)]

<Rant mode on>

As John Krist mentioned, one particularly painful aspect of new IDL
version releases is the way they almost invariably break some
existing, well-functioning code (even when written in the most kosher
way for previous versions), especially widgets.

Sadly, I just discovered (yet) another one of these instances.  The
"new and improved" handling of modal widgets is the culprit in this
case.

Modality used to be the method of choice whenever a widget program
needed to return something - this made sure the widget program didn't
"fall through" the XMANAGER call and return before the answer was
finished - no matter how complex the task. 

(Note that for such applications, it's not very meaningful to switch
modality on or off through a keyword - if you're returning data
through return values or output parameters, you *should never*
return to the caller before you're finished).

With the old system (xmanager,....,/modal), modal widgets could have
any level of complexity - no questions asked.  With the "new and
improved" system (widget_base(...,/modal)), RSI has changed the
meaning of modality!

Modality is now apparently meant exclusively to make braindead
*dialogs*. When I say braindead, I mean braindead as in "less than an
application".  Indeed, more like just an "Abort/Retry/Fail?" question
than an application!

Let's say I have application A, which may call application B in order
to massage some of the data "owned" by A. Naturally, I want to be
able to shut off application A until B is finished, since the state of
the data in A may be "undefined" while B is working on them. So,
application B should be modal. Fine.

The problem is that if application B needs to have "auxiliary"
widgets, those widgets now have to be modal! (Since their group leader
is modal - check the doc's for widget_base/group_leader keyword).

But I don't *want* those to be modal! I want to have my analysis program
work, *and* have the auxiliary widget launched from it work at the
same time. I want my auxiliary widget to exist in peace and harmony
with application B, letting the user control the state of the color
scaling method continuously while using application B!

I can't see any way of doing this the new way, and it's a serious flaw
in the "new and improved" modal method (widget_base(...,/modal))!

But the *worst* thing is that this could be done in version 4 with the
old modality (xmanager,...,/modal), and now it's ^%#^%# broken!  If I
start a non-modal widget alongside a modal application, the non-modal
widget doesn't register any events. It can't even use the window
manager to close the window! This is on { alpha OSF unix 5.1.1 Jul 20
1998}.

(Though through some *weird* mechanism, clicking and dragging the
mouse in a draw window in the non-modal widget a few times somehow
manages to "wake" it up for a while, but I guess this is a bug
somewhere, not a feature!)

Below is an example program. To demonstrate the effect, start it with
"IDL> test", press "Push to start new (modal)", then press "Push to
start new (nonmodal)" on the new widget. The last widget appearing
(#3) is all "dead" on my machine, while #2 is alive. #3 does disappear
though, when I exit #2. One funny thing is that #3 dies with #2, even
when I do *not* propagate the information about the group leader from
the caller (#2)...??

I do hope that RSI will give the old functionality of the
xmanager,....,/modal call back (5.2 ??? I guess I'm too late).  It's
just too silly not to be able to write modal widgets of any level of
complexity. I know that it's *possible* to write workarounds for this
(like doing manually the things xmanager used to do when I want
widgets to be modal in the now unsupported way), but that's too 
silly as well. My programs used to work, and now they don't!

<Rant mode off>

Regards,

Stein Vidar

Test program: --------------------------------------------

PRO test_event,ev
  widget_control,ev.id,get_uvalue=uval
  CASE uval OF 
     'NEWN': test,group=ev.top
     'NEWM': test,/modal,group=ev.top
     'QUIT': widget_control,ev.top,/destroy
  END
END

PRO test,modal=modal,group=group

  IF n_elements(group) NE 1 THEN  b = widget_base(/column) $
  ELSE                            b = widget_base(/column,group_leader=group)
  
  bb = widget_button(b,value='Push to start new (modal)',uvalue='NEWM')
  bb = widget_button(b,value='Push to start new (nonmodal)',uvalue='NEWN')
  bb = widget_button(b,value='Push to exit',uvalue='QUIT')
  
  widget_control,b,/realize
  
  IF keyword_set(modal) THEN xmanager,'test',b,/modal $
  ELSE                       xmanager,'test',b
END