Re: Capturing global key press events

[Vikram Noel Ambrose <noel ambrose gmail com>]

Lex Trotman wrote:
> On 2 March 2010 15:29, Vikram Noel Ambrose <noel ambrose gmail com 
> <mailto:noel ambrose gmail com>> wrote:
>
>     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 :)
>
>
> I assume you've looked at accelerator groups and accelerator maps 
> then, what don't they do?

By "global" I meant from any keyboard on a particular X Display. ie, my 
gtk application will not be the focus of input.