xkb: merge lockedPtrButtons state from all attached SDs.

Problem:
lockedPtrButtons keeps the state of the buttons locked by a PointerKeys button
press. Unconditionally clearing the bits may cause stuck buttons in this
sequence of events:

1. type Shift + NumLock to enable PointerKeys
2. type 0/Ins on keypad to emulate Button 1 press
        → button1 press event to client
3. press and release button 1 on physical mouse
        → button1 release event to client

Button 1 on the MD is now stuck and cannot be released.

Cause:
XKB PointerKeys button events are posted through the XTEST pointer device.
Once a press is generated, the XTEST device's button is down. The DIX merges
the button state of all attached SDs, hence the MD will have a button down
while the XTEST device has a button down.

PointerKey button events are only generated on the master device to avoid
duplicate events (see XkbFakeDeviceButton()). If the MD has the
lockedPtrButtons bit cleared by a release event on a physical device, no
such event is generated when a keyboard device triggers the PointerKey
ButtonRelease trigger. Since the event - if generated - is posted through
the XTEST pointer device, lack of a generated ButtonRelease event on the
XTEST pointer device means the button is never released, resulting in the
stuck button observed above.

Solution:
This patch merges the MD's lockedPtrButtons with the one of all attached
slave devices on release events. Thus, as long as one attached keyboard has
a lockedPtrButtons bit set, this bit is kept in the MD. Once a PointerKey
button is released on all keyboards, the matching release event is emulated
from the MD through the XTEST pointer device, thus also releasing the button
in the DIX.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

1 files changed, 8 insertions, 0 deletions

diff --git a/xkb/xkbActions.c b/xkb/xkbActions.c
index d1149a196..b4b839558 100644
--- a/xkb/xkbActions.c
+++ b/xkb/xkbActions.c
@@ -634,6 +634,14 @@ _XkbFilterPointerBtn(	XkbSrvInfoPtr	xkbi,
 		}
 		xkbi->lockedPtrButtons&= ~(1<<button);
 
+		if (IsMaster(xkbi->device))
+		{
+		    XkbMergeLockedPtrBtns(xkbi->device);
+                    /* One SD still has lock set, don't post event */
+		    if ((xkbi->lockedPtrButtons & (1 << button)) != 0)
+			break;
+		}
+
 		/* fallthrough */
 	    case XkbSA_PtrBtn:
 		XkbFakeDeviceButton(xkbi->device, 0, button);