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, 26 insertions, 0 deletions

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;
+    }
+}