glib dispatcher: rework userEventSourcePrepare() event source

This is a better solution for fbb485d4f6985643b27da3cc6c5b5f960c32e74d.

The existing solution was working fine, but it was exposing logic that is
internal to QWindowSystemInterface and platform plugin interaction. Some
platform plugins do event filtering at native event level - those that
support QAbstractEventDispatcher::filterNativeEvent(). Other plugins rely
on QWindowSystemInterface to do the filtering. Dispatchers should not care
about this.

The new logic rely on the fact that QWindowSystemInterfacePrivate::handleWindowSystemEvent
calls QAbstractEventDispatcher::wakeUp(). The same way postEventSourcePrepare()
rely on QCoreApplication::postEvent() to call QAbstractEventDispatcher::wakeUp().

Event sources run in the order they are attached, postEventSourcePrepare runs
before userEventSourcePrepare(). We rely on that order to pass wakeUpCalled
value.

Change-Id: I0327f4f2398fd863fb2421b8033bb1df8d65f5af
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

2 files changed, 3 insertions, 2 deletions

diff --git a/src/corelib/kernel/qeventdispatcher_glib.cpp b/src/corelib/kernel/qeventdispatcher_glib.cpp
index 4c780a9294..45c6e29e4b 100644
--- a/src/corelib/kernel/qeventdispatcher_glib.cpp
+++ b/src/corelib/kernel/qeventdispatcher_glib.cpp
@@ -260,8 +260,8 @@ static gboolean postEventSourcePrepare(GSource *s, gint *timeout)
     *timeout = canWait ? -1 : 0;
 
     GPostEventSource *source = reinterpret_cast<GPostEventSource *>(s);
-    return (!canWait
-            || (source->serialNumber.load() != source->lastSerialNumber));
+    source->d->wakeUpCalled = source->serialNumber.load() != source->lastSerialNumber;
+    return !canWait || source->d->wakeUpCalled;
 }
 
 static gboolean postEventSourceCheck(GSource *source)
diff --git a/src/corelib/kernel/qeventdispatcher_glib_p.h b/src/corelib/kernel/qeventdispatcher_glib_p.h
index 799f23b14a..88ff316ee5 100644
--- a/src/corelib/kernel/qeventdispatcher_glib_p.h
+++ b/src/corelib/kernel/qeventdispatcher_glib_p.h
@@ -108,6 +108,7 @@ public:
     GSocketNotifierSource *socketNotifierSource;
     GTimerSource *timerSource;
     GIdleTimerSource *idleTimerSource;
+    bool wakeUpCalled = true;
 
     void runTimersOnceWithNormalPriority();
 };