Re: pointer grabs and drawing areas

[Owen Taylor <otaylor redhat com>]

Paul Davis <pbd op net> writes:

> i have a drawing area set up to receive both button press+release
> events. my understanding is that X/GDK automatically does a pointer
> grab when a GdkWindow has these events set for itself. i also receive
> motion events, via motion hints.
> 
> if i press and then move the pointer outside the drawing area, i
> continue to get motion events. however, this is only true if i don't
> move the pointer into the canvas that is packed above the drawing area
> in a table. 
> 
> how could this be? can the canvas grab the pointer away somehow?

Sounds like this is with GTK+-1.2. 

Read the description of owner_events in the XGrabPointer() man page;
GTK+-1.2 always put OwnerGrabButtonMask in the event mask so the
automatic grab was like a grab with owner_events = TRUE. GTK+-2.0
doesn't add OwnerGrabButtonMask.

For GTK+-1.2, the way that people got around this problem was
by doing a gtk_grab_add() on button press, and a gtk_grab_remove
on button release.

Regards,
                                        Owen