Re: GDB does not stop in breakpoint!

[tomas]

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On Thu, Jan 14, 2010 at 09:49:31AM +0100, A. Soare wrote:
> 
> >     I put a breakpoint in Fx_create_frame. When I start emacs using "r" , 
> > the
> >     breakpoint is never reached, and the X windows stops responding.
> > 
> > There are times, when the screen is grabbed, that stopping the program
> > would cause X not to respond.  If you have put the breakpoint at a
> > line which is in the middle of a grab, that would explain this.
> > 
> 
> What means that the screen to be grabbed? How does this happen?

That's when the program tells the X server "now give me all events until
I tell you". If the program doesn't react to events (e.g. in a tight
loop) and doesn't release the screen grab, the X sever seems to hang.

Grabs are useful whenwaiting for example for a menu choice to finish
(when the user clicks on the menu, it "opens" and then the program
usually grabs the screen until a choice is made or the menu click is
cancelled).

See, for example the manual pages of XGrabServer, XGrabPointer,
XGrabKeyboard and so on.

Grabs are often used for those all-horrible modal windows which seem to
be becoming en-vogue these days. But I disgress.

Regards
- -- tomás
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