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

1 files changed, 103 insertions, 21 deletions

diff --git a/src/openvg/qwindowsurface_vgegl.cpp b/src/openvg/qwindowsurface_vgegl.cpp
index 62871cf38e..15710830f6 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;
         }