[wx-dev] wxGTK: wxDropSource::DoDragDrop problem

[Robin Dunn]

Robin Dunn wrote:
> I've run into a problem in wxGTK's wxDropSource::DoDragDrop.  The call 
> to gtk_drag_begin returns NULL, which is later causing this message:
> 
> Gtk-CRITICAL **: gtk_drag_set_icon_widget: assertion 
> `GDK_IS_DRAG_CONTEXT (context)' failed
> 
> and then it gets stuck in the loop calling gtk_main_iteration().  I 
> assume that the NULL return from gtk_drag_begin indicates an error, but 
> I can't find anything to help me diagnose what the cause of the problem 
> could be.  Any suggestions?
> 
> If it makes any difference this DnD operation is being launched from a 
> wxGrid's EVT_GRID_CELL_BEGIN_DRAG event handler.
> 

FYI, I got setup to trace into gtk code and found that launching the DnD 
  from the EVT_GRID_CELL_BEGIN_DRAG handler *is* relevant to this 
problem.  The wxGrid code captures the mouse before where it decides to 
send this event, and GTK's gtk_drag_begin() will fail if its call to 
gdk_pointer_grab() fails.  Just adding a call to ReleaseMouse in my 
event handler doesn't work either because apparently it doesn't get 
immediately released in gtk.  So I rearranged the code in wxGrid a bit 
and it seems to be working fine now.  I will check in my changes after a 
bit more testing.


-- 
Robin Dunn
Software Craftsman
http://wxPython.org  Java give you jitters?  Relax with wxPython!