Compress touch events in QQuickWindow.

Instead of sending multiple touch updates per frame, we
store the last one and flush the pending events just before
we enter into the scene graph sync phase.

[ChangeLog][QtQuick] QQuickWindow will compresses touch events
and delivers at most one touch event per frame.

Done-with: Robin Burchell <robin.burchell@jollamobile.com>
Change-Id: Ia0169bc4a3f0da67709b91ca65c326934b55d372
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>

1 files changed, 44 insertions, 17 deletions

diff --git a/src/quick/scenegraph/qsgthreadedrenderloop.cpp b/src/quick/scenegraph/qsgthreadedrenderloop.cpp
index 7b01f64ee0..a5b46b7c75 100644
--- a/src/quick/scenegraph/qsgthreadedrenderloop.cpp
+++ b/src/quick/scenegraph/qsgthreadedrenderloop.cpp
@@ -51,6 +51,8 @@
 #include <QtGui/QScreen>
 #include <QtGui/QOffscreenSurface>
 
+#include <qpa/qwindowsysteminterface.h>
+
 #include <QtQuick/QQuickWindow>
 #include <private/qquickwindow_p.h>
 
@@ -1063,13 +1065,33 @@ void QSGThreadedRenderLoop::polishAndSync(Window *w, bool inExpose)
 {
     QSG_GUI_DEBUG(w->window, "polishAndSync()");
 
-    if (!w->window->isExposed() || !w->window->isVisible() || w->window->size().isEmpty()) {
+    QQuickWindow *window = w->window;
+    if (!window->isExposed() || !window->isVisible() || window->size().isEmpty()) {
         QSG_GUI_DEBUG(w->window, " - not exposed, aborting...");
         killTimer(w->timerId);
         w->timerId = 0;
         return;
     }
 
+    // Flush pending touch events.
+    // First we force flushing of the windowing system events, so that we're
+    // working with the latest possible data. This can trigger event processing
+    // which in turn can stop rendering this window, so verify that before
+    // proceeding. Then we flush the touch event and as that also does event
+    // processing, verify again that we still are active and rendering.
+    QWindowSystemInterface::flushWindowSystemEvents();
+    w = windowFor(m_windows, window);
+    if (w) {
+        QQuickWindowPrivate::get(window)->flushDelayedTouchEvent();
+        w = windowFor(m_windows, window);
+    }
+    if (!w) {
+        QSG_GUI_DEBUG(w->window, " - removed after event flushing..");
+        killTimer(w->timerId);
+        w->timerId = 0;
+        return;
+    }
+
 
 #ifndef QSG_NO_RENDER_TIMING
     QElapsedTimer timer;
@@ -1081,7 +1103,7 @@ void QSGThreadedRenderLoop::polishAndSync(Window *w, bool inExpose)
         timer.start();
 #endif
 
-    QQuickWindowPrivate *d = QQuickWindowPrivate::get(w->window);
+    QQuickWindowPrivate *d = QQuickWindowPrivate::get(window);
     d->polishItems();
 
 #ifndef QSG_NO_RENDER_TIMING
@@ -1091,14 +1113,14 @@ void QSGThreadedRenderLoop::polishAndSync(Window *w, bool inExpose)
 
     w->updateDuringSync = false;
 
-    emit w->window->afterAnimating();
+    emit window->afterAnimating();
 
-    QSG_GUI_DEBUG(w->window, " - lock for sync...");
+    QSG_GUI_DEBUG(window, " - lock for sync...");
     w->thread->mutex.lock();
     m_lockedForSync = true;
-    w->thread->postEvent(new WMSyncEvent(w->window, inExpose));
+    w->thread->postEvent(new WMSyncEvent(window, inExpose));
 
-    QSG_GUI_DEBUG(w->window, " - wait for sync...");
+    QSG_GUI_DEBUG(window, " - wait for sync...");
 #ifndef QSG_NO_RENDER_TIMING
     if (profileFrames)
         waitTime = timer.nsecsElapsed();
@@ -1106,7 +1128,7 @@ void QSGThreadedRenderLoop::polishAndSync(Window *w, bool inExpose)
     w->thread->waitCondition.wait(&w->thread->mutex);
     m_lockedForSync = false;
     w->thread->mutex.unlock();
-    QSG_GUI_DEBUG(w->window, " - unlocked after sync...");
+    QSG_GUI_DEBUG(window, " - unlocked after sync...");
 
 #ifndef QSG_NO_RENDER_TIMING
     if (profileFrames)
@@ -1117,9 +1139,9 @@ void QSGThreadedRenderLoop::polishAndSync(Window *w, bool inExpose)
     w->timerId = 0;
 
     if (m_animation_timer == 0 && m_animation_driver->isRunning()) {
-        QSG_GUI_DEBUG(w->window, " - animations advancing");
+        QSG_GUI_DEBUG(window, " - animations advancing");
         m_animation_driver->advance();
-        QSG_GUI_DEBUG(w->window, " - animations done");
+        QSG_GUI_DEBUG(window, " - animations done");
         // We need to trigger another sync to keep animations running...
         maybePostPolishRequest(w);
         emit timeToIncubate();
@@ -1131,7 +1153,7 @@ void QSGThreadedRenderLoop::polishAndSync(Window *w, bool inExpose)
 #ifndef QSG_NO_RENDER_TIMING
     if (qsg_render_timing)
         qDebug(" - Gui Thread: window=%p, polish=%d, lock=%d, block/sync=%d -- animations=%d",
-               w->window,
+               window,
                int(polishTime/1000000),
                int((waitTime - polishTime)/1000000),
                int((syncTime - waitTime)/1000000),
@@ -1145,6 +1167,17 @@ void QSGThreadedRenderLoop::polishAndSync(Window *w, bool inExpose)
 #endif
 }
 
+QSGThreadedRenderLoop::Window *QSGThreadedRenderLoop::windowForTimer(int timerId) const
+{
+    for (int i=0; i<m_windows.size(); ++i) {
+        if (m_windows.at(i).timerId == timerId) {
+            return const_cast<Window *>(&m_windows.at(i));
+            break;
+        }
+    }
+    return 0;
+}
+
 bool QSGThreadedRenderLoop::event(QEvent *e)
 {
     switch ((int) e->type()) {
@@ -1157,13 +1190,7 @@ bool QSGThreadedRenderLoop::event(QEvent *e)
             emit timeToIncubate();
         } else {
             QSG_GUI_DEBUG((void *) 0, "QEvent::Timer -> Polish & Sync");
-            Window *w = 0;
-            for (int i=0; i<m_windows.size(); ++i) {
-                if (m_windows.at(i).timerId == te->timerId()) {
-                    w = const_cast<Window *>(&m_windows.at(i));
-                    break;
-                }
-            }
+            Window *w = windowForTimer(te->timerId());
             if (w)
                 polishAndSync(w);
         }