I'm writing a pure Xlib app and want to use XInput2 extension for RawMotion events. The problem appears if I use XISelectEvents
when I set the mask with any XI2 event higher than XI_PropertyEvent
. So, for example, if I use XISetMask(mask, XI_Motion);
it works normally unlike with XISetMask(mask, XI_RawMotion);
. Also the error appears regardless of the deviceid passed and regardless of other event types set to mask. Why could it happen?
The code example:
#include <X11/Xlib.h>
#include <X11/extensions/XInput2.h>
int main() {
Display* display = XOpenDisplay(nullptr);
int screen_num = DefaultScreen(display);
Window window = XCreateSimpleWindow(
display,
RootWindow(display, screen_num),
0, 0,
640, 480,
4,
16711680,
WhitePixel(display, screen_num)
);
XSelectInput(display, window, KeyPressMask);
int major_opcode, first_event, first_error;
XQueryExtension(display, "XInputExtension", &major_opcode, &first_event, &first_error);
unsigned char mask[XIMaskLen(XI_LASTEVENT)] = {0, };
XISetMask(mask, XI_RawMotion);
XIEventMask event_mask;
event_mask.deviceid = XIAllDevices;
event_mask.mask_len = sizeof(mask);
event_mask.mask = mask;
XISelectEvents(display, window, &event_mask, 1);
XMapWindow(display, window);
XFlush(display);
while (true) {
XEvent ev;
XNextEvent(display, &ev);
if (ev.type == KeyPress && ev.xkey.keycode == 9) {
break;
}
}
XUnmapWindow(display, window);
XFlush(display);
XDestroyWindow(display, window);
XCloseDisplay(display);
return 0;
}
The error:
X Error of failed request: BadValue (integer parameter out of range for operation)
Major opcode of failed request: 131 (XInputExtension)
Minor opcode of failed request: 46 ()
Value in failed request: 0xd
Serial number of failed request: 16
Current serial number in output stream: 17
The problem is that XInput2 call XISelectEvents
with raw events works only if the root window passed. So the solution is to use XISelectEvents(display, DefaultRootWindow(display), &event_mask, 1);