Automatically destroy VG pixmaps when the last window surface goes away

Under S60, Qt will destroy the window surfaces of an application that
goes into the background, which frees up EGL surface objects.  But the
VGImage's for pixmaps, and the EGLContext, were still using GPU memory.

This change keeps track of the number of widgets / window surfaces that
are in use and then calls hibernate() on all QVGPixmapData objects when
it goes to zero.  Once all the VGImage's are destroyed, the EGLContext
should also be destroyed.

Task-number: QT-2555
Reviewed-by: Sarah Smith

4 files changed, 169 insertions, 29 deletions

diff --git a/src/openvg/qpixmapdata_vg.cpp b/src/openvg/qpixmapdata_vg.cpp
index 19c90ed..5d5fcbf 100644
--- a/src/openvg/qpixmapdata_vg.cpp
+++ b/src/openvg/qpixmapdata_vg.cpp
@@ -65,12 +65,21 @@ QVGPixmapData::QVGPixmapData(PixelType type)
     recreate = true;
 #if !defined(QT_NO_EGL)
     context = 0;
+    qt_vg_register_pixmap(this);
 #endif
     setSerialNumber(++qt_vg_pixmap_serial);
 }
 
 QVGPixmapData::~QVGPixmapData()
 {
+    destroyImageAndContext();
+#if !defined(QT_NO_EGL)
+    qt_vg_unregister_pixmap(this);
+#endif
+}
+
+void QVGPixmapData::destroyImageAndContext()
+{
     if (vgImage != VG_INVALID_HANDLE) {
         // We need to have a context current to destroy the image.
 #if !defined(QT_NO_EGL)
@@ -93,11 +102,16 @@ QVGPixmapData::~QVGPixmapData()
         if (vgImageOpacity != VG_INVALID_HANDLE)
             vgDestroyImage(vgImageOpacity);
 #endif
+        vgImage = VG_INVALID_HANDLE;
+        vgImageOpacity = VG_INVALID_HANDLE;
     }
 #if !defined(QT_NO_EGL)
-    if (context)
-        qt_vg_destroy_context(context);
+    if (context) {
+        qt_vg_destroy_context(context, QInternal::Pixmap);
+        context = 0;
+    }
 #endif
+    recreate = true;
 }
 
 QPixmapData *QVGPixmapData::createCompatiblePixmapData() const
@@ -217,7 +231,7 @@ VGImage QVGPixmapData::toVGImage()
 #if !defined(QT_NO_EGL)
     // Increase the reference count on the shared context.
     if (!context)
-        context = qt_vg_create_context(0);
+        context = qt_vg_create_context(0, QInternal::Pixmap);
 #endif
 
     if (recreate && prevSize != QSize(w, h)) {
@@ -286,6 +300,17 @@ VGImage QVGPixmapData::toVGImage(qreal opacity)
 #endif
 }
 
+void QVGPixmapData::hibernate()
+{
+    // If the image was imported (e.g, from an SgImage under Symbian),
+    // then we cannot copy it back to main memory for storage.
+    if (vgImage != VG_INVALID_HANDLE && source.isNull())
+        return;
+
+    forceToImage();
+    destroyImageAndContext();
+}
+
 extern int qt_defaultDpiX();
 extern int qt_defaultDpiY();
 
@@ -376,7 +401,7 @@ void QVGPixmapData::fromNativeType(void* pixmap, NativeType type)
         // when "0" used as argument then
         // default display, context are used
         if (!context)
-            context = qt_vg_create_context(0);
+            context = qt_vg_create_context(0, QInternal::Pixmap);
 
         if (vgImage != VG_INVALID_HANDLE) {
             vgDestroyImage(vgImage);
diff --git a/src/openvg/qpixmapdata_vg_p.h b/src/openvg/qpixmapdata_vg_p.h
index fe19f35..c0bb098 100644
--- a/src/openvg/qpixmapdata_vg_p.h
+++ b/src/openvg/qpixmapdata_vg_p.h
@@ -55,8 +55,6 @@
 
 #include <QtGui/private/qpixmap_raster_p.h>
 #include <private/qvg_p.h>
-#if !defined(QT_NO_EGL)
-#endif
 
 #if defined(Q_OS_SYMBIAN)
 class RSGImage;
@@ -66,6 +64,15 @@ QT_BEGIN_NAMESPACE
 
 class QEglContext;
 
+#if !defined(QT_NO_EGL)
+class QVGPixmapData;
+class QVGSharedContext;
+
+void qt_vg_register_pixmap(QVGPixmapData *pd);
+void qt_vg_unregister_pixmap(QVGPixmapData *pd);
+void qt_vg_hibernate_pixmaps(QVGSharedContext *context);
+#endif
+
 class Q_OPENVG_EXPORT QVGPixmapData : public QPixmapData
 {
 public:
@@ -94,6 +101,14 @@ public:
     // Return the VGImage form for a specific opacity setting.
     virtual VGImage toVGImage(qreal opacity);
 
+    // Release the VG resources associated with this pixmap and copy
+    // the pixmap's contents out of the GPU back into main memory.
+    // The VG resource will be automatically recreated the next time
+    // toVGImage() is called.  Does nothing if the pixmap cannot be
+    // hibernated for some reason (e.g. VGImage is shared with another
+    // process via a SgImage).
+    virtual void hibernate();
+
     QSize size() const { return QSize(w, h); }
 
 #if defined(Q_OS_SYMBIAN)
@@ -108,6 +123,16 @@ protected:
     void cleanup();
 #endif
 
+#if !defined(QT_NO_EGL)
+private:
+    QVGPixmapData *next;
+    QVGPixmapData *prev;
+
+    friend void qt_vg_register_pixmap(QVGPixmapData *pd);
+    friend void qt_vg_unregister_pixmap(QVGPixmapData *pd);
+    friend void qt_vg_hibernate_pixmaps(QVGSharedContext *context);
+#endif
+
 protected:
     QSize prevSize;
     VGImage vgImage;
@@ -121,6 +146,8 @@ protected:
 
     void forceToImage();
     QImage::Format sourceFormat() const;
+
+    void destroyImageAndContext();
 };
 
 QT_END_NAMESPACE
diff --git a/src/openvg/qvg_p.h b/src/openvg/qvg_p.h
index 04e2bab..3577013 100644
--- a/src/openvg/qvg_p.h
+++ b/src/openvg/qvg_p.h
@@ -71,11 +71,17 @@ class QEglContext;
 
 // Create an EGL context, but don't bind it to a surface.  If single-context
 // mode is enabled, this will return the previously-created context.
-Q_OPENVG_EXPORT QEglContext *qt_vg_create_context(QPaintDevice *device);
+// "devType" indicates the type of device using the context, usually
+// QInternal::Widget or QInternal::Pixmap.
+Q_OPENVG_EXPORT QEglContext *qt_vg_create_context
+    (QPaintDevice *device, int devType);
 
 // Destroy an EGL context that was created by qt_vg_create_context().
 // If single-context mode is enabled, this will decrease the reference count.
-Q_OPENVG_EXPORT void qt_vg_destroy_context(QEglContext *context);
+// "devType" indicates the type of device destroying the context, usually
+// QInternal::Widget or QInternal::Pixmap.
+Q_OPENVG_EXPORT void qt_vg_destroy_context
+    (QEglContext *context, int devType);
 
 // Return the shared pbuffer surface that can be made current to
 // destroy VGImage objects when there is no other surface available.
diff --git a/src/openvg/qwindowsurface_vgegl.cpp b/src/openvg/qwindowsurface_vgegl.cpp
index 62871cf..1571083 100644
--- a/src/openvg/qwindowsurface_vgegl.cpp
+++ b/src/openvg/qwindowsurface_vgegl.cpp
@@ -111,15 +111,19 @@ public:
 
     QEglContext *context;
     int refCount;
+    int widgetRefCount;
     QVGPaintEngine *engine;
     EGLSurface surface;
+    QVGPixmapData *firstPixmap;
 };
 
 QVGSharedContext::QVGSharedContext()
     : context(0)
     , refCount(0)
+    , widgetRefCount(0)
     , engine(0)
     , surface(EGL_NO_SURFACE)
+    , firstPixmap(0)
 {
 }
 
@@ -154,6 +158,28 @@ void qt_vg_destroy_paint_engine(QVGPaintEngine *engine)
     Q_UNUSED(engine);
 }
 
+void qt_vg_register_pixmap(QVGPixmapData *pd)
+{
+    QVGSharedContext *shared = sharedContext();
+    pd->next = shared->firstPixmap;
+    pd->prev = 0;
+    if (shared->firstPixmap)
+        shared->firstPixmap->prev = pd;
+    shared->firstPixmap = pd;
+}
+
+void qt_vg_unregister_pixmap(QVGPixmapData *pd)
+{
+    if (pd->next)
+        pd->next->prev = pd->prev;
+    if (pd->prev) {
+        pd->prev->next = pd->next;
+    } else {
+        QVGSharedContext *shared = sharedContext();
+        shared->firstPixmap = pd->next;
+    }
+}
+
 #else
 
 QVGPaintEngine *qt_vg_create_paint_engine(void)
@@ -166,6 +192,16 @@ void qt_vg_destroy_paint_engine(QVGPaintEngine *engine)
     delete engine;
 }
 
+void qt_vg_register_pixmap(QVGPixmapData *pd)
+{
+    Q_UNUSED(pd);
+}
+
+void qt_vg_unregister_pixmap(QVGPixmapData *pd)
+{
+    Q_UNUSED(pd);
+}
+
 #endif
 
 #ifdef EGL_VG_ALPHA_FORMAT_PRE_BIT
@@ -278,9 +314,11 @@ static QEglContext *createContext(QPaintDevice *device)
 
 #if !defined(QVG_NO_SINGLE_CONTEXT)
 
-QEglContext *qt_vg_create_context(QPaintDevice *device)
+QEglContext *qt_vg_create_context(QPaintDevice *device, int devType)
 {
     QVGSharedContext *shared = sharedContext();
+    if (devType == QInternal::Widget)
+        ++(shared->widgetRefCount);
     if (shared->context) {
         ++(shared->refCount);
         return shared->context;
@@ -291,23 +329,65 @@ QEglContext *qt_vg_create_context(QPaintDevice *device)
     }
 }
 
-void qt_vg_destroy_context(QEglContext *context)
+static void qt_vg_destroy_shared_context(QVGSharedContext *shared)
+{
+    shared->context->makeCurrent(qt_vg_shared_surface());
+    delete shared->engine;
+    shared->engine = 0;
+    shared->context->doneCurrent();
+    if (shared->surface != EGL_NO_SURFACE) {
+        eglDestroySurface(shared->context->display(), shared->surface);
+        shared->surface = EGL_NO_SURFACE;
+    }
+    delete shared->context;
+    shared->context = 0;
+}
+
+void qt_vg_hibernate_pixmaps(QVGSharedContext *shared)
+{
+    // Artificially increase the reference count to prevent the
+    // context from being destroyed until after we have finished
+    // the hibernation process.
+    ++(shared->refCount);
+
+    // We need a context current to hibernate the VGImage objects.
+    shared->context->makeCurrent(qt_vg_shared_surface());
+
+    // Scan all QVGPixmapData objects in the system and hibernate them.
+    QVGPixmapData *pd = shared->firstPixmap;
+    while (pd != 0) {
+        pd->hibernate();
+        pd = pd->next;
+    }
+
+    // Don't need the current context any more.
+    shared->context->lazyDoneCurrent();
+
+    // Decrease the reference count and destroy the context if necessary.
+    if (--(shared->refCount) <= 0)
+        qt_vg_destroy_shared_context(shared);
+}
+
+void qt_vg_destroy_context(QEglContext *context, int devType)
 {
     QVGSharedContext *shared = sharedContext();
     if (shared->context != context) {
         // This is not the shared context.  Shouldn't happen!
         delete context;
-    } else if (--(shared->refCount) <= 0) {
-        shared->context->makeCurrent(qt_vg_shared_surface());
-        delete shared->engine;
-        shared->engine = 0;
-        shared->context->doneCurrent();
-        if (shared->surface != EGL_NO_SURFACE) {
-            eglDestroySurface(shared->context->display(), shared->surface);
-            shared->surface = EGL_NO_SURFACE;
-        }
-        delete shared->context;
-        shared->context = 0;
+        return;
+    }
+    if (devType == QInternal::Widget)
+        --(shared->widgetRefCount);
+    if (--(shared->refCount) <= 0) {
+        qt_vg_destroy_shared_context(shared);
+    } else if (shared->widgetRefCount <= 0 && devType == QInternal::Widget) {
+        // All of the widget window surfaces have been destroyed
+        // but we still have VG pixmaps active.  Ask them to hibernate
+        // to free up GPU resources until a widget is shown again.
+        // This may eventually cause the EGLContext to be destroyed
+        // because nothing in the system needs a context, which will
+        // free up even more GPU resources.
+        qt_vg_hibernate_pixmaps(shared);
     }
 }
 
@@ -338,13 +418,15 @@ EGLSurface qt_vg_shared_surface(void)
 
 #else
 
-QEglContext *qt_vg_create_context(QPaintDevice *device)
+QEglContext *qt_vg_create_context(QPaintDevice *device, int devType)
 {
+    Q_UNUSED(devType);
     return createContext(device);
 }
 
-void qt_vg_destroy_context(QEglContext *context)
+void qt_vg_destroy_context(QEglContext *context, int devType)
 {
+    Q_UNUSED(devType);
     delete context;
 }
 
@@ -434,7 +516,7 @@ QVGEGLWindowSurfaceVGImage::~QVGEGLWindowSurfaceVGImage()
         }
         if (windowSurface != EGL_NO_SURFACE)
             context->destroySurface(windowSurface);
-        qt_vg_destroy_context(context);
+        qt_vg_destroy_context(context, QInternal::Widget);
     }
 }
 
@@ -453,7 +535,7 @@ QEglContext *QVGEGLWindowSurfaceVGImage::ensureContext(QWidget *widget)
     if (!context) {
         // Create a new EGL context.  We create the surface in beginPaint().
         size = newSize;
-        context = qt_vg_create_context(widget);
+        context = qt_vg_create_context(widget, QInternal::Widget);
         if (!context)
             return 0;
         isPaintingActive = false;
@@ -548,7 +630,7 @@ QVGEGLWindowSurfaceDirect::~QVGEGLWindowSurfaceDirect()
     if (context) {
         if (windowSurface != EGL_NO_SURFACE)
             context->destroySurface(windowSurface);
-        qt_vg_destroy_context(context);
+        qt_vg_destroy_context(context, QInternal::Widget);
     }
 }
 
@@ -587,7 +669,7 @@ QEglContext *QVGEGLWindowSurfaceDirect::ensureContext(QWidget *widget)
         qt_vg_destroy_paint_engine(engine);
         engine = 0;
         context->destroySurface(windowSurface);
-        qt_vg_destroy_context(context);
+        qt_vg_destroy_context(context, QInternal::Widget);
         context = 0;
         windowSurface = EGL_NO_SURFACE;
     }
@@ -596,7 +678,7 @@ QEglContext *QVGEGLWindowSurfaceDirect::ensureContext(QWidget *widget)
     if (!context) {
         // Create a new EGL context and bind it to the widget surface.
         size = newSize;
-        context = qt_vg_create_context(widget);
+        context = qt_vg_create_context(widget, QInternal::Widget);
         if (!context)
             return 0;
         // We want a direct to window rendering surface if possible.
@@ -613,7 +695,7 @@ QEglContext *QVGEGLWindowSurfaceDirect::ensureContext(QWidget *widget)
 #endif
         EGLSurface surface = context->createSurface(widget, &surfaceProps);
         if (surface == EGL_NO_SURFACE) {
-            qt_vg_destroy_context(context);
+            qt_vg_destroy_context(context, QInternal::Widget);
             context = 0;
             return 0;
         }