Capturing global key press events

[Vikram Noel Ambrose <noel ambrose gmail com>]

I'd like to capture global key press events to enable a "Global 
Shortcuts" feature in my application.

I've looked at a few other projects that have such capabilities and they 
all seem to hook straight into xlib. Is there a more GTK way of doing it?

At the moment I'm using,
XKeysymToKeycode($DISPLAY,XStringToKeysym("some key in here"));

And then passing the resulting key code to XGrabKey,
XGrabKey($DISPLAY,key,Mod4Mask|ShiftMask,$WINDOW,True,GrabModeAsync,GrabModeAsync);

Then I call XSync($DISPLAY,0); I dont know why, but if I dont, gtk 
segfaults.
I then wait for events with XNextEvent($DISPLAY,&event); inside a 
pthread and when an event comes by, i call a signal callback surrounded 
with gdk_threads_enter and _leave.

Now all this worked nicely for a while, but somehow I've managed to 
break it :(

It doesnt seem to pick up the events from the keys I passed to XGrabKeys 
anymore. If I switch to AnyModifier, it picks things up, but obviously 
the keyboard becomes unusable for other applications then.

I believe XGrabKeys will alert me with a BadAccess error if i try to use 
a key that is already being grabbed by another x client, but I dont know 
how well this mechanism works.

Mod4Mask seems to refer to the Super Key, aka, "Windows Key". So in my 
example I have modifiers Shift+Super and keycode "key".

When it worked, I had Shift+Super+{z,x,c,v,b} setup. Now nothing works 
and for the best of me, I can't seem to understand what I've changed.

A little background information: My app is heavily threaded, there are 
about 12+ threads at any given time. They are all created with 
pthread_create, and use gdk_threads_enter/leave before touching anything 
gdk/gtk/glib related.

In main() I call g_thread_init( NULL ); and gdk_threads_init(); before 
gtk_init(argc,argv);

I've read in some places one should surround gtk_main() with 
gdk_threads_enter/leave, but this absolutely doesnt make any sense to 
me.  If I try to do that, the app locks in gtk_main and doesnt startup.

My assumption is that gdk_threads_enter() "acts" like sem_wait() and 
gdk_threads_leave() acts like sem_post(), where gdk_threads_init() sets 
the value of the semaphore to 1.

With this assumption I've used gdk_threads_enter/leave throughout my app 
and it definitely works.

I'm guessing there is some sort of conflict between the key-press-event 
for the top level GtkWindow and my xlib key grabbing, but I don't know 
how to debug the situation further. Any ideas whats going on?

thanks,


Vikram.
PS: GTK docs are much better than X11 docs :)