Linux hotkey can not be canceled correctly

[data-niklas]

Description

The Linux C code event loop only returns after the hotkey was pressed. The hotkey can not be canceled while waitHotkey waits for a new hotkey. hk.Unregister() can be successfully called, but the hotkey is only unregistered after it was triggered.

Steps to reproduce

1. Register a simple hotkey on Linux
2. Unregister the hotkey

Notes

hk := h.New([]h.Modifier{h.ModCtrl}, h.KeyM)
hk.Register()
go func() {
  time.Sleep(time.Second * 1)
  fmt.Println("Hotkey will be unregistered")
  hk.Unregister()
  fmt.Println("Hotkey unregistered")
  hk.Register()
  fmt.Println("Registered again")
}()
<-hk.Keydown()

This code blocks. I would expect the chan to be closed and the program to exit.

hotkey/hotkey_linux.c

Lines 64 to 77 in a5dde31

	while(1) {
	XNextEvent(d, &ev);
	switch(ev.type) {
	case KeyPress:
	hotkeyDown(hkhandle);
	continue;
	case KeyRelease:
	hotkeyUp(hkhandle);
	XUngrabKey(d, keycode, mod, DefaultRootWindow(d));
	XCloseDisplay(d);
	return 0;
	}
	}
	}

I would expect that the above loop checks, if the hotkey was unregistered. XNextEvent also blocks until the next event, but that should be fine as long as a lot of events are triggered. Else something like XPending could be used to check, if new events can be processed.

[changkun]

This is a bit tricky. Semantically, the hotkey is unregistered, not triggered. That's why the Keydown is not triggered and blocks forever.

[data-niklas]

Updated the example code. I tested a bit. The Unregister itself also blocks.