[lmi] EVT_UPDATE_UI occurring when !wxTheApp->IsActive()

[Greg Chicares]

Vadim--I've "fixed" a problem, but I'd like to ask you to take a look
at it and tell me whether I've done it in the best way.

* Observable symptom

Using lmi just before the change committed Mar 13 16:45:09 2006 UTC,
or apparently any version since Fri Dec 2 05:18:38 2005 UTC, under msw:
 - do 'File | New | Illustration'
 - focus any control other than the first control on the notebook page
 - switch to any other application with alt-Tab
 - switch back to lmi
Now, the control you had focused has lost focus, and the first control
on the notebook page is focused instead.

* Proximate cause

In 'xml_notebook.cpp', XmlNotebook::EnsureOptimalFocus() is called by
XmlNotebook::UponUpdateGUI(), the EVT_UPDATE_UI handler. When a task
switch occurred, XmlNotebook::EnsureOptimalFocus() called FindFocus(),
which returned null. Treating this as a problem it needed to fix,
XmlNotebook::EnsureOptimalFocus() focused the first control on the
notebook page.

Experimentally adding
  if(!wxTheApp->IsActive()) return;
at the top of XmlNotebook::EnsureOptimalFocus() prevented the symptom.
However, that is not the change I committed.

* Ultimate cause

I believe the underlying problem is that XmlNotebook::UponUpdateGUI()
was called when the application wasn't active. Shouldn't that ideally
be prevented?

I added code equivalent to
  if(!wxTheApp->IsActive()) return;
at the top of XmlNotebook::UponUpdateGUI(): that's the change I
committed on Mar 13 16:45:09 2006 UTC. This prevents the observable
symptom described above. I conjecture that this is the best way to
address the problem: I see no reason why EVT_UPDATE_UI events should
be sent while the application is not active, and I suppose that those
events might have other deleterious consequences that we just haven't
noticed yet.