Create a new dix touch record for an emulated touch with no listeners

As a special case, if a still physically active pointer emulated touch
has no listeners and the device is explicitly grabbed for pointer
events, create a new dix touch record for the grab only.

This allows for clients to "hand off" grabs. For example, when dragging
a window under compiz the window decorator sees the button press and
then ungrabs the implicit grab. It then tells compiz to grab the device,
and compiz then moves the window with the pointer motion. This is racy,
but is allowed by the input protocol for pointer events when there are
no other clients with a grab on the device.

Signed-off-by: Chase Douglas <chase.douglas@canonical.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>

1 files changed, 28 insertions, 0 deletions

diff --git a/Xi/exevents.c b/Xi/exevents.c
index ae3652b68..c8bd222e9 100644
--- a/Xi/exevents.c
+++ b/Xi/exevents.c
@@ -1610,6 +1610,34 @@ ProcessTouchEvent(InternalEvent *ev, DeviceIntPtr dev)
     else
         ti = TouchFindByClientID(dev, touchid);
 
+    /* Under the following circumstances we create a new touch record for an
+     * existing touch:
+     *
+     * - The touch may be pointer emulated
+     * - An explicit grab is active on the device
+     * - The grab is a pointer grab
+     *
+     * This allows for an explicit grab to receive pointer events for an already
+     * active touch.
+     */
+    if (!ti && type != ET_TouchBegin && emulate_pointer &&
+        dev->deviceGrab.grab && !dev->deviceGrab.fromPassiveGrab &&
+        (dev->deviceGrab.grab->grabtype == CORE ||
+         dev->deviceGrab.grab->grabtype == XI ||
+         !xi2mask_isset(dev->deviceGrab.grab->xi2mask, dev, XI_TouchBegin))) {
+        ti = TouchBeginTouch(dev, ev->device_event.sourceid, touchid,
+                             emulate_pointer);
+        if (!ti) {
+            DebugF("[Xi] %s: Failed to create new dix record for explicitly "
+                   "grabbed touchpoint %d\n",
+                   dev->name, type, touchid);
+            return;
+        }
+
+        TouchBuildSprite(dev, ti, ev);
+        TouchSetupListeners(dev, ti, ev);
+    }
+
     if (!ti) {
         DebugF("[Xi] %s: Failed to get event %d for touchpoint %d\n",
                dev->name, type, touchid);