Ignore auto repeat in X11 applications

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If you press and hold a key in X11 while AutoRepeat is enabled, you continuously receive KeyPress and KeyRelease events. I know that AutoRepeat can be disabled using the function XAutoRepeatOff(), but this changes the setting for the whole X server. Is there a way to either disable AutoRepeat for a single application or to ignore repeated keystrokes?

What I'm looking for is a single KeyPress event when a key is pressed and a single KeyRelease event when a key is released, without interfering with the X server's AutoRepeat setting.

Here's a minimal example to get you going (mostly from the Beginner Xlib Tutorial):

#include <stdio.h>
#include <stdlib.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/Xos.h>
#include <X11/Xatom.h>
#include <X11/keysym.h>

Display *dis;
Window win;
XEvent report;

int main ()
{
  dis = XOpenDisplay (NULL);
  // XAutoRepeatOn(dis);
  win = XCreateSimpleWindow (dis, RootWindow (dis, 0), 1, 1, 500, 500,
        0, BlackPixel (dis, 0), BlackPixel (dis, 0));
  XSelectInput (dis, win, KeyPressMask | KeyReleaseMask);
  XMapWindow (dis, win);
  XFlush (dis);

  while (1)
    {
      XNextEvent (dis, &report);
      switch (report.type)
 {
 case KeyPress:
   fprintf (stdout, "key #%ld was pressed.\n",
     (long) XLookupKeysym (&report.xkey, 0));
   break;
 case KeyRelease:
   fprintf (stdout, "key #%ld was released.\n",
     (long) XLookupKeysym (&report.xkey, 0));
   break;
 }
    }

  return (0);
}
6 Answers

You can use the XkbSetDetectableAutorepeat function to tell the X server to only send KeyRelease events when the user actually releases the key - when you don't want autorepeat events, then you discard any KeyPress without matching KeyRelease.

You could set a timer when a key is pressed or released and ignore KeyPress and KeyRelease events that occur within the repetition interval.

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