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>
Reviewed-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

4 files changed, 56 insertions, 1 deletions

diff --git a/include/xkbsrv.h b/include/xkbsrv.h
index 5847e6395..956b2249b 100644
--- a/include/xkbsrv.h
+++ b/include/xkbsrv.h
@@ -924,6 +924,9 @@ extern int XkbGetEffectiveGroup(
         XkbStatePtr             /* xkbstate */,
         CARD8                   /* keycode */);
 
+extern void XkbMergeLockedPtrBtns(
+        DeviceIntPtr            /* master */);
+
 #include "xkbfile.h"
 #include "xkbrules.h"
 
diff --git a/xkb/xkbAccessX.c b/xkb/xkbAccessX.c
index b5486b73b..451c7979f 100644
--- a/xkb/xkbAccessX.c
+++ b/xkb/xkbAccessX.c
@@ -707,8 +707,24 @@ DeviceEvent     *event = &ev->device_event;
 	    changed |= XkbPointerButtonMask;
     }
     else if (event->type == ET_ButtonRelease) {
-	if (xkbi)
+	if (xkbi) {
 	    xkbi->lockedPtrButtons&= ~(1 << (event->detail.key & 0x7));
+
+            /* Merge this MD's lockedPtrButtons with the one of all
+             * attached slave devices.
+             * The DIX uses a merged button state for MDs, not
+             * releasing buttons until the last SD has released
+             * thenm. If we unconditionally clear the
+             * lockedPtrButtons bit on the MD, a PointerKeys button
+             * release on the SD keyboard won't generate the required fake button
+             * event on the XTEST pointer, thus never processing the
+             * button event in the DIX and the XTEST pointer's
+             * buttons stay down - result is a stuck button.
+             */
+	    if (IsMaster(dev))
+                XkbMergeLockedPtrBtns(dev);
+	}
+
 	changed |= XkbPointerButtonMask;
     }
 
diff --git a/xkb/xkbActions.c b/xkb/xkbActions.c
index c5030d04d..b4b839558 100644
--- a/xkb/xkbActions.c
+++ b/xkb/xkbActions.c
@@ -633,6 +633,16 @@ _XkbFilterPointerBtn(	XkbSrvInfoPtr	xkbi,
 		    break;
 		}
 		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);
 		break;
diff --git a/xkb/xkbUtils.c b/xkb/xkbUtils.c
index 3344e5088..14dc784b8 100644
--- a/xkb/xkbUtils.c
+++ b/xkb/xkbUtils.c
@@ -2094,3 +2094,29 @@ XkbGetEffectiveGroup(XkbSrvInfoPtr xkbi, XkbStatePtr xkbState, CARD8 keycode)
 
     return effectiveGroup;
 }
+
+/* Merge the lockedPtrButtons from all attached SDs for the given master
+ * device into the MD's state.
+ */
+void
+XkbMergeLockedPtrBtns(DeviceIntPtr master)
+{
+    DeviceIntPtr d = inputInfo.devices;
+    XkbSrvInfoPtr xkbi = NULL;
+
+    if (!IsMaster(master))
+        return;
+
+    if (!master->key)
+        return;
+
+    xkbi = master->key->xkbInfo;
+    xkbi->lockedPtrButtons = 0;
+
+    for (; d; d = d->next) {
+        if (IsMaster(d) || GetMaster(d, MASTER_KEYBOARD) != master || !d->key)
+            continue;
+
+        xkbi->lockedPtrButtons |= d->key->xkbInfo->lockedPtrButtons;
+    }
+}