6 files changed, 52 insertions, 2 deletions

diff --git a/doc/src/howtos/openvg.qdoc b/doc/src/howtos/openvg.qdoc
index 9c805bb..f70ed54 100644
--- a/doc/src/howtos/openvg.qdoc
+++ b/doc/src/howtos/openvg.qdoc
@@ -295,6 +295,16 @@
     Convolution, colorize, drop shadow, and blur filters are accelerated
     using OpenVG operations.
 
+    \section2 Scrolling
+
+    By default, accelerated scrolling is not enabled because the impact on
+    performance is very much tied to the hardware platform. To enable
+    accelerated scrolling, you should ensure that QVG_BUFFER_SCROLLING is
+    defined when compiling the QtOpenVG module.
+
+    You should only enable this feature if vgCopyPixels() is known to be
+    efficient on your hardware platform.
+
     \section1 Known issues
 
     Performance of copying the contents of an OpenVG-rendered window to the
diff --git a/doc/src/platforms/emb-openvg.qdocinc b/doc/src/platforms/emb-openvg.qdocinc
index 37ccb9c..2f9cc21 100644
--- a/doc/src/platforms/emb-openvg.qdocinc
+++ b/doc/src/platforms/emb-openvg.qdocinc
@@ -259,6 +259,12 @@ at present.
         \o Convolution, colorize, drop shadow, and blur filters are
 accelerated using OpenVG operations.
 
+    \row
+        \o Scrolling
+        \o Accelerated scrolling is implemented but disabled by default
+unless QVG_BUFFER_SCROLLING is defined. This should only be enabled on
+OpenVG engines where vgCopyPixels() is known to be efficient.
+
 \endtable
 
 \section2 Known issues
diff --git a/src/openvg/openvg.pro b/src/openvg/openvg.pro
index 3790492..883f0f3 100644
--- a/src/openvg/openvg.pro
+++ b/src/openvg/openvg.pro
@@ -33,7 +33,7 @@ contains(QT_CONFIG, egl) {
         qwindowsurface_vgegl.cpp
 }
 
-symbian: DEFINES += QVG_RECREATE_ON_SIZE_CHANGE
+symbian: DEFINES += QVG_RECREATE_ON_SIZE_CHANGE QVG_BUFFER_SCROLLING
 
 include(../qbase.pri)
 
diff --git a/src/openvg/qwindowsurface_vg.cpp b/src/openvg/qwindowsurface_vg.cpp
index 83b0764..c19d5d1 100644
--- a/src/openvg/qwindowsurface_vg.cpp
+++ b/src/openvg/qwindowsurface_vg.cpp
@@ -57,6 +57,7 @@ QVGWindowSurface::QVGWindowSurface(QWidget *window)
 {
     // Create the default type of EGL window surface for windows.
     d_ptr = new QVGEGLWindowSurfaceDirect(this);
+    setStaticContentsSupport(d_ptr->supportsStaticContents());
 }
 
 QVGWindowSurface::QVGWindowSurface
@@ -89,7 +90,9 @@ void QVGWindowSurface::setGeometry(const QRect &rect)
 
 bool QVGWindowSurface::scroll(const QRegion &area, int dx, int dy)
 {
-    return QWindowSurface::scroll(area, dx, dy);
+    if (!d_ptr->scroll(window(), area, dx, dy))
+        return QWindowSurface::scroll(area, dx, dy);
+    return true;
 }
 
 void QVGWindowSurface::beginPaint(const QRegion &region)
diff --git a/src/openvg/qwindowsurface_vgegl.cpp b/src/openvg/qwindowsurface_vgegl.cpp
index 46a905f..99b614b 100644
--- a/src/openvg/qwindowsurface_vgegl.cpp
+++ b/src/openvg/qwindowsurface_vgegl.cpp
@@ -758,6 +758,33 @@ void QVGEGLWindowSurfaceDirect::endPaint
     }
 }
 
+bool QVGEGLWindowSurfaceDirect::supportsStaticContents() const
+{
+#if defined(QVG_BUFFER_SCROLLING) && !defined(QVG_NO_PRESERVED_SWAP)
+    return true;
+#else
+    return QVGEGLWindowSurfacePrivate::supportsStaticContents();
+#endif
+}
+
+bool QVGEGLWindowSurfaceDirect::scroll(QWidget *widget, const QRegion& area, int dx, int dy)
+{
+#ifdef QVG_BUFFER_SCROLLING
+    QEglContext *context = ensureContext(widget);
+    if (context) {
+        context->makeCurrent(windowSurface);
+        QRect scrollRect = area.boundingRect();
+        int sx = scrollRect.x();
+        int sy = size.height() - scrollRect.y() - scrollRect.height();
+        vgSeti(VG_SCISSORING, VG_FALSE);
+        vgCopyPixels(sx + dx, sy - dy, sx, sy, scrollRect.width(), scrollRect.height());
+        context->lazyDoneCurrent();
+        return true;
+    }
+#endif
+    return false;
+}
+
 QT_END_NAMESPACE
 
 #endif
diff --git a/src/openvg/qwindowsurface_vgegl_p.h b/src/openvg/qwindowsurface_vgegl_p.h
index aa0c648..892fd9d 100644
--- a/src/openvg/qwindowsurface_vgegl_p.h
+++ b/src/openvg/qwindowsurface_vgegl_p.h
@@ -77,6 +77,8 @@ public:
         (QWidget *widget, const QRegion& region, QImage *image = 0) = 0;
     virtual VGImage surfaceImage() const;
     virtual QSize surfaceSize() const = 0;
+    virtual bool supportsStaticContents() const { return false; }
+    virtual bool scroll(QWidget *, const QRegion&, int, int) { return false; }
 
 private:
     QVGPaintEngine *engine;
@@ -128,6 +130,8 @@ public:
     void beginPaint(QWidget *widget);
     void endPaint(QWidget *widget, const QRegion& region, QImage *image);
     QSize surfaceSize() const { return size; }
+    bool supportsStaticContents() const;
+    bool scroll(QWidget *widget, const QRegion& area, int dx, int dy);
 
 protected:
     QEglContext *context;