How to properly use XGrabKey to get a program hotkey
cheshirekow at gmail.com
Wed Oct 27 11:56:13 PDT 2010
My goal is to have a program that sleeps in the background but can be
activated by the user via some "hotkey". From digging around the Xlib
manual and the Xlib O'reilly manual, I gather that the correct way to to
this is with XGrabKey. However my understanding of the process is
incorrect as a simple proof of concept does not work.
My understanding is that if I call XGrabKey with the root window as the
grab_window, and owner_events false, then whenever my hotkey is pressed
the event will be sent *only* to the root window. If I then select
KeyPress events from the root window, and then listen for X events, I
should get a key press event when the hotkey is pressed. I've pasted a
minimal example below.
What I expect is that when the program is run, regardless of what window
has focus, if Ctrl+Shift+K is pressed, my program should output "Hot key
pressed!" in the console, and then terminate.
Furthermore, it is my understanding that if the XGrabKey fails, the
default error handler will display a message, and since it does not I am
assuming that the call succeeds.
Obviously, my understanding is flawed somehow. Can anyone point me in
the right direction?
using namespace std;
Display* dpy = XOpenDisplay(0);
Window root = DefaultRootWindow(dpy);
unsigned int modifiers = ControlMask | ShiftMask;
int keycode = XKeysymToKeycode(dpy,XK_K);
Window grab_window = root;
Bool owner_events = False;
int pointer_mode = GrabModeAsync;
int keyboard_mode = GrabModeAsync;
XGrabKey(dpy, keycode, modifiers, grab_window, owner_events,
XSelectInput(dpy, root, KeyPressMask);
bool shouldQuit = false;
cout << "Hot key pressed!" << endl;
shouldQuit = true;
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