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	grabkeys: Avoid missing events when a keysym maps to multiple keycodes - dwm - …
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	---
	commit 89f9905714c1c1b2e8b09986dfbeca15b68d8af8
	parent ba56fe9fea0a28d8184a727a987836a0903e2682
	Author: Chris Down <[email protected]>
	Date: Wed, 7 Dec 2022 14:55:08 +0000

	grabkeys: Avoid missing events when a keysym maps to multiple keycodes

	It's not uncommon for one keysym to map to multiple keycodes. For
	example, the "play" button on my keyboard sends keycode 172, but my
	bluetooth headphones send keycode 208, both of which map back to
	XF86AudioPlay:

	% xmodmap -pke \| grep XF86AudioPlay
	keycode 172 = XF86AudioPlay XF86AudioPause XF86AudioPlay XF86AudioPause
	keycode 208 = XF86AudioPlay NoSymbol XF86AudioPlay
	keycode 215 = XF86AudioPlay NoSymbol XF86AudioPlay

	This is a problem because the current code only grabs a single one of
	these keycodes, which means that events for any other keycode also
	mapping to the bound keysym will not be handled by dwm. In my case, this
	means that binding XF86AudioPlay does the right thing and correctly
	handles my keyboard's keys, but does nothing on my headphones. I'm not
	the only person affected by this, there are other reports[0].

	In order to fix this, we look at the mappings between keycodes and
	keysyms at grabkeys() time and pick out all matching keycodes rather
	than just the first one. The keypress() side of this doesn't need any
	changes because the keycode gets converted back to a canonical keysym
	before any action is taken.

	0: https://github.com/cdown/dwm/issues/11

	Diffstat:
	M dwm.c \| 24 +++++++++++++++++-------

	1 file changed, 17 insertions(+), 7 deletions(-)
	---
	diff --git a/dwm.c b/dwm.c
	@@ -955,16 +955,26 @@ grabkeys(void)
	{
	updatenumlockmask();
	{
	- unsigned int i, j;
	+ unsigned int i, j, k;
	unsigned int modifiers[] = { 0, LockMask, numlockmask, numlock…
	- KeyCode code;
	+ int start, end, skip;
	+ KeySym *syms;

	XUngrabKey(dpy, AnyKey, AnyModifier, root);
	- for (i = 0; i < LENGTH(keys); i++)
	- if ((code = XKeysymToKeycode(dpy, keys[i].keysym)))
	- for (j = 0; j < LENGTH(modifiers); j++)
	- XGrabKey(dpy, code, keys[i].mod \| modi…
	- True, GrabModeAsync, GrabModeA…
	+ XDisplayKeycodes(dpy, &start, &end);
	+ syms = XGetKeyboardMapping(dpy, start, end - start + 1, &skip);
	+ if (!syms)
	+ return;
	+ for (k = start; k <= end; k++)
	+ for (i = 0; i < LENGTH(keys); i++)
	+ /* skip modifier codes, we do that ourselves */
	+ if (keys[i].keysym == syms[(k - start) * skip])
	+ for (j = 0; j < LENGTH(modifiers); j++)
	+ XGrabKey(dpy, k,
	+ keys[i].mod \| modifie…
	+ root, True,
	+ GrabModeAsync, GrabMo…
	+ XFree(syms);
	}
	}