[PATCH] Xi: don't copy the modifier key count when copying device classes (#25480)

[Peter Hutterer]

The modifier key count is maintained by the XKB layer and
increased/decreased for all modifiers that set state.

Test case, MD/SD modifier key count in comment:
1. keyboard 1: press and hold Shift_L    # SD:1     MD:1
2. keyboard 2: press and release Shift_L # SD:1,0   MD:1,0
<class copy happens>                     # SD:1     MD:1
3. keyboard 1: release Shift_L           # SD:0     MD:1
4. keyboard 1: press and release Shift_L # SD:1,0   MD:2,1

The modifier is now logically down on the MD but not on keyboard 1 or
keyboard 2.

XKB is layered in before the DIX, it increases/decreases the modifier key
count accordingly. In the above example, during (2), the MD gets the key
release and thus clears the modifier bit. (3) doesn't forward the release to
the MD because it is already cleared. The copy of modifierKeysDown when the
lastSlave changes however increases the counter for the held key. On (4),
the press and release are both forwarded to the MD, causing a offset by 1
and thus do not clear the logical modifier state.

X.Org Bug 25480 <http://bugs.freedesktop.org/show_bug.cgi?id=25480>

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 Xi/exevents.c |    4 ----
 1 files changed, 0 insertions(+), 4 deletions(-)

diff --git a/Xi/exevents.c b/Xi/exevents.c
index e680f6f..566b0ef 100644
--- a/Xi/exevents.c
+++ b/Xi/exevents.c
@@ -196,16 +196,12 @@ void
 CopyKeyClass(DeviceIntPtr device, DeviceIntPtr master)
 {
     KeyClassPtr mk = master->key;
-    KeyClassPtr dk = device->key;
-    int i;
 
     if (device == master)
         return;
 
     mk->sourceid = device->id;
 
-    for (i = 0; i < 8; i++)
-        mk->modifierKeyCount[i] = dk->modifierKeyCount[i];
 
     if (!XkbCopyDeviceKeymap(master, device))
         FatalError("Couldn't pivot keymap from device to core!\n");
-- 
1.6.5.2