Introduced QQuickCanvas::releaseResources().

This function can be used in certain situations to purge the texture cache
and triggers more lazily to take down the scene graph and GL context

Change-Id: Icd9360ff50fda0e721ba0f1b520cda678e457a35
Reviewed-by: Aaron Kennedy <aaron.kennedy@nokia.com>

6 files changed, 143 insertions, 27 deletions

diff --git a/src/quick/items/qquickcanvas.cpp b/src/quick/items/qquickcanvas.cpp
index 53ff4fd217..cbc5b8e00e 100644
--- a/src/quick/items/qquickcanvas.cpp
+++ b/src/quick/items/qquickcanvas.cpp
@@ -66,6 +66,8 @@
 #include <QtCore/qabstractanimation.h>
 #include <QtDeclarative/qdeclarativeincubator.h>
 
+#include <QtQuick/private/qdeclarativepixmapcache_p.h>
+
 #include <private/qdeclarativeprofilerservice_p.h>
 
 QT_BEGIN_NAMESPACE
@@ -748,6 +750,21 @@ QQuickCanvas::~QQuickCanvas()
     delete d->rootItem; d->rootItem = 0;
 }
 
+
+
+/*!
+    This function tries to release redundant resources currently held by the QML scene.
+ */
+
+void QQuickCanvas::releaseResources()
+{
+    Q_D(QQuickCanvas);
+    d->windowManager->releaseResources();
+    QDeclarativePixmap::purgeCache();
+}
+
+
+
 /*!
   Returns the invisible root item of the scene.
 
diff --git a/src/quick/items/qquickcanvas.h b/src/quick/items/qquickcanvas.h
index 335cbf784d..3246d53a42 100644
--- a/src/quick/items/qquickcanvas.h
+++ b/src/quick/items/qquickcanvas.h
@@ -124,6 +124,9 @@ Q_SIGNALS:
     void afterRendering();
     void clearColorChanged(const QColor &);
 
+public slots:
+    void releaseResources();
+
 protected:
     QQuickCanvas(QQuickCanvasPrivate &dd, QWindow *parent = 0);
 
diff --git a/src/quick/items/qquickwindowmanager.cpp b/src/quick/items/qquickwindowmanager.cpp
index c28b77f63b..916615bdd8 100644
--- a/src/quick/items/qquickwindowmanager.cpp
+++ b/src/quick/items/qquickwindowmanager.cpp
@@ -164,6 +164,7 @@ public:
         , shouldExit(false)
         , hasExited(false)
         , isDeferredUpdatePosted(false)
+        , runToReleaseResources(false)
         , canvasToGrab(0)
     {
         sg->moveToThread(this);
@@ -194,6 +195,8 @@ public:
     void sync(bool guiAlreadyLocked);
 
     void initialize();
+    void releaseResources();
+    void releaseResourcesInThread();
 
     bool *allowMainThreadProcessing() { return &allowMainThreadProcessingFlag; }
 
@@ -249,6 +252,7 @@ private:
     uint shouldExit : 1;
     uint hasExited : 1;
     uint isDeferredUpdatePosted : 1;
+    uint runToReleaseResources : 1;
 
     QQuickCanvas *canvasToGrab;
     QImage grabContent;
@@ -287,6 +291,7 @@ public:
 
     void canvasDestroyed(QQuickCanvas *canvas);
 
+    void releaseResources();
     void initializeGL();
     void renderCanvas(QQuickCanvas *canvas);
     void paint(QQuickCanvas *canvas);
@@ -298,6 +303,7 @@ public:
     bool *allowMainThreadProcessing();
 
     QSGContext *sceneGraphContext() const;
+    QQuickCanvas *masterCanvas() const;
 
     bool event(QEvent *);
 
@@ -548,10 +554,18 @@ void QQuickRenderThreadSingleContextWindowManager::run()
 #ifdef THREAD_DEBUG
     printf("QML Rendering Thread Started\n");
 #endif
-
     lock();
-    Q_ASSERT(!gl);
-    initialize();
+
+    if (runToReleaseResources) {
+        releaseResourcesInThread();
+        runToReleaseResources = false;
+        unlock();
+        return;
+    }
+
+    if (!gl)
+        initialize();
+
     // Wake GUI as it is waiting for the GL context to have appeared, as
     // an indication that the render thread is now running.
     wake();
@@ -748,12 +762,6 @@ void QQuickRenderThreadSingleContextWindowManager::run()
     m_removed_windows << m_rendered_windows.keys();
     handleRemovedWindows();
 
-    sg->invalidate();
-
-    gl->doneCurrent();
-    delete gl;
-    gl = 0;
-
 #ifdef THREAD_DEBUG
     printf("                RenderThread: render loop exited... Good Night!\n");
 #endif
@@ -772,6 +780,60 @@ void QQuickRenderThreadSingleContextWindowManager::run()
 #endif
 }
 
+void QQuickRenderThreadSingleContextWindowManager::releaseResourcesInThread()
+{
+#ifdef THREAD_DEBUG
+    printf("                RenderThread: releasing resources...\n");
+#endif
+
+    QQuickCanvas *canvas = masterCanvas();
+    QWindow *tmpSurface = 0;
+
+    if (canvas) {
+        gl->makeCurrent(canvas);
+    } else {
+        tmpSurface = new QWindow();
+        tmpSurface->setSurfaceType(QSurface::OpenGLSurface);
+        tmpSurface->resize(4, 4);
+        tmpSurface->create();
+        gl->makeCurrent(tmpSurface);
+    }
+
+    sg->invalidate();
+    gl->doneCurrent();
+    delete gl;
+    gl = 0;
+
+    if (tmpSurface)
+        delete tmpSurface;
+
+    wake();
+}
+
+void QQuickRenderThreadSingleContextWindowManager::releaseResources()
+{
+#ifdef THREAD_DEBUG
+    printf("GUI: releasing resources\n");
+#endif
+
+    lockInGui();
+    if (!isRunning() && gl) {
+        runToReleaseResources = true;
+        start();
+
+        while (gl) {
+            wait();
+        }
+    }
+#ifdef THREAD_DEBUG
+    else {
+        printf("GUI: render thread running not releasing resources...\n");
+    }
+#endif
+    unlockInGui();
+
+}
+
 bool QQuickRenderThreadSingleContextWindowManager::event(QEvent *e)
 {
     Q_ASSERT(QThread::currentThread() == qApp->thread());
@@ -1003,7 +1065,6 @@ void QQuickRenderThreadSingleContextWindowManager::startRendering()
         animationTimer = -1;
     }
 
-
 }
 
 
@@ -1146,17 +1207,46 @@ void QQuickTrivialWindowManager::hide(QQuickCanvas *canvas)
     m_windows.remove(canvas);
     QQuickCanvasPrivate *cd = QQuickCanvasPrivate::get(canvas);
     cd->cleanupNodesOnShutdown();
+}
+
+void QQuickTrivialWindowManager::canvasDestroyed(QQuickCanvas *canvas)
+{
+    hide(canvas);
+}
 
+void QQuickTrivialWindowManager::releaseResources()
+{
     if (m_windows.size() == 0) {
+        QQuickCanvas *canvas = masterCanvas();
+        QWindow *tmpSurface = 0;
+
+        if (canvas) {
+            gl->makeCurrent(canvas);
+        } else {
+            tmpSurface = new QWindow();
+            tmpSurface->setSurfaceType(QSurface::OpenGLSurface);
+            tmpSurface->resize(4, 4);
+            tmpSurface->create();
+            gl->makeCurrent(tmpSurface);
+        }
+
         sg->invalidate();
         delete gl;
         gl = 0;
+
+        delete tmpSurface;
     }
 }
 
-void QQuickTrivialWindowManager::canvasDestroyed(QQuickCanvas *canvas)
+QQuickCanvas *QQuickTrivialWindowManager::masterCanvas() const
 {
-    hide(canvas);
+    // Find a "proper surface" to bind...
+    for (QHash<QQuickCanvas *, CanvasData>::const_iterator it = m_windows.constBegin();
+             it != m_windows.constEnd(); ++it) {
+            if (it.key()->visible())
+                return it.key();
+    }
+    return 0;
 }
 
 void QQuickTrivialWindowManager::renderCanvas(QQuickCanvas *canvas)
@@ -1166,30 +1256,20 @@ void QQuickTrivialWindowManager::renderCanvas(QQuickCanvas *canvas)
 
     CanvasData &data = const_cast<CanvasData &>(m_windows[canvas]);
 
-    QQuickCanvas *masterCanvas = 0;
-    if (!canvas->visible()) {
-        // Find a "proper surface" to bind...
-        for (QHash<QQuickCanvas *, CanvasData>::const_iterator it = m_windows.constBegin();
-             it != m_windows.constEnd() && !masterCanvas; ++it) {
-            if (it.key()->visible())
-                masterCanvas = it.key();
-        }
-    } else {
-        masterCanvas = canvas;
-    }
+    QQuickCanvas *window = canvas->visible() ? canvas : masterCanvas();
 
-    if (!masterCanvas)
+    if (!window)
         return;
 
     if (!gl) {
         gl = new QOpenGLContext();
-        gl->setFormat(masterCanvas->requestedFormat());
+        gl->setFormat(window->requestedFormat());
         gl->create();
-        if (!gl->makeCurrent(masterCanvas))
+        if (!gl->makeCurrent(window))
             qWarning("QQuickCanvas: makeCurrent() failed...");
         sg->initialize(gl);
     } else {
-        gl->makeCurrent(masterCanvas);
+        gl->makeCurrent(window);
     }
 
     bool alsoSwap = data.updatePending;
diff --git a/src/quick/items/qquickwindowmanager_p.h b/src/quick/items/qquickwindowmanager_p.h
index 6134204464..014b38132e 100644
--- a/src/quick/items/qquickwindowmanager_p.h
+++ b/src/quick/items/qquickwindowmanager_p.h
@@ -67,6 +67,8 @@ public:
 
     virtual QSGContext *sceneGraphContext() const = 0;
 
+    virtual void releaseResources() = 0;
+
     // ### make this less of a singleton
     static QQuickWindowManager *instance();
 };
diff --git a/src/quick/util/qdeclarativepixmapcache.cpp b/src/quick/util/qdeclarativepixmapcache.cpp
index 43ce3346cb..95cbd361b8 100644
--- a/src/quick/util/qdeclarativepixmapcache.cpp
+++ b/src/quick/util/qdeclarativepixmapcache.cpp
@@ -695,6 +695,8 @@ public:
     void unreferencePixmap(QDeclarativePixmapData *);
     void referencePixmap(QDeclarativePixmapData *);
 
+    void purgeCache();
+
 protected:
     virtual void timerEvent(QTimerEvent *);
 
@@ -827,6 +829,16 @@ void QDeclarativePixmapStore::timerEvent(QTimerEvent *)
     }
 }
 
+void QDeclarativePixmapStore::purgeCache()
+{
+    shrinkCache(m_unreferencedCost);
+}
+
+void QDeclarativePixmap::purgeCache()
+{
+    pixmapStore()->purgeCache();
+}
+
 QDeclarativePixmapReply::QDeclarativePixmapReply(QDeclarativePixmapData *d)
 : data(d), engineForReader(0), requestSize(d->requestSize), url(d->url), loading(false), redirectCount(0)
 {
diff --git a/src/quick/util/qdeclarativepixmapcache_p.h b/src/quick/util/qdeclarativepixmapcache_p.h
index 19c3a5264f..69cd84c465 100644
--- a/src/quick/util/qdeclarativepixmapcache_p.h
+++ b/src/quick/util/qdeclarativepixmapcache_p.h
@@ -126,6 +126,8 @@ public:
     bool connectDownloadProgress(QObject *, const char *);
     bool connectDownloadProgress(QObject *, int);
 
+    static void purgeCache();
+
 private:
     Q_DISABLE_COPY(QDeclarativePixmap)
     QDeclarativePixmapData *d;