xkb: release XTEST pointer buttons on physical releases. (#28808)

If a button release event is posted for the MD pointer, post a release event
through the matching XTEST device. This way, a client who posts a button
press through the XTEST extension cannot inadvertedly lock the button.

This behaviour is required for historical reasons, until server 1.7 the core
pointer would release a button press on physical events, regardless of the
XTEST state. Clients seem to rely on this behaviour, causing seemingly stuck
grabs.

The merged behaviour is kept for multiple keyboard PointerKey events, if two
physical keyboards hold the button down as a result of PointerKey actions,
the button is not released until the last keyboard releases the button.

X.Org Bug 28808 <http://bugs.freedesktop.org/show_bug.cgi?id=28808>

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

3 files changed, 18 insertions, 15 deletions

diff --git a/include/xkbsrv.h b/include/xkbsrv.h
index 956b2249b..9f1507e8e 100644
--- a/include/xkbsrv.h
+++ b/include/xkbsrv.h
@@ -927,6 +927,12 @@ extern int XkbGetEffectiveGroup(
 extern void XkbMergeLockedPtrBtns(
         DeviceIntPtr            /* master */);
 
+extern void XkbFakeDeviceButton(
+        DeviceIntPtr            /* dev */,
+        int                     /* press */,
+        int                     /* button */);
+
+
 #include "xkbfile.h"
 #include "xkbrules.h"
 
diff --git a/xkb/xkbAccessX.c b/xkb/xkbAccessX.c
index 81f959677..10c38ca47 100644
--- a/xkb/xkbAccessX.c
+++ b/xkb/xkbAccessX.c
@@ -710,19 +710,16 @@ DeviceEvent     *event = &ev->device_event;
 	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);
+            if (IsMaster(dev))
+            {
+                DeviceIntPtr source;
+                int rc;
+                rc = dixLookupDevice(&source, event->sourceid, serverClient, DixWriteAccess);
+                if (rc != Success)
+                    ErrorF("[xkb] bad sourceid '%d' on button release event.\n", event->sourceid);
+                else if (!IsXTestDevice(source, GetMaster(dev, MASTER_POINTER)))
+                    XkbFakeDeviceButton(dev, FALSE, event->detail.key);
+            }
 	}
 
 	changed |= XkbPointerButtonMask;
diff --git a/xkb/xkbActions.c b/xkb/xkbActions.c
index 49d7b3d53..96d3847b9 100644
--- a/xkb/xkbActions.c
+++ b/xkb/xkbActions.c
@@ -45,7 +45,7 @@ THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
 DevPrivateKeyRec xkbDevicePrivateKeyRec;
 
-static void XkbFakeDeviceButton(DeviceIntPtr dev,Bool press,int button);
+void XkbFakeDeviceButton(DeviceIntPtr dev,Bool press,int button);
 static void XkbFakePointerMotion(DeviceIntPtr dev, unsigned flags,int x,int y);
 
 void
@@ -1364,7 +1364,7 @@ XkbFakePointerMotion(DeviceIntPtr dev, unsigned flags,int x,int y)
     FreeEventList(events, GetMaximumEventsNum());
 }
 
-static void
+void
 XkbFakeDeviceButton(DeviceIntPtr dev,Bool press,int button)
 {
     EventListPtr        events;