Support semi-transparent surfaces in the OpenVG graphics system

Task-number: QT-2026
Reviewed-by: Jason Barron

3 files changed, 41 insertions, 3 deletions

diff --git a/src/openvg/qpaintengine_vg.cpp b/src/openvg/qpaintengine_vg.cpp
index 75b7fa5..fda4b10 100644
--- a/src/openvg/qpaintengine_vg.cpp
+++ b/src/openvg/qpaintengine_vg.cpp
@@ -3407,6 +3407,34 @@ void QVGPaintEngine::restoreState(QPaintEngine::DirtyFlags dirty)
 #endif
 }
 
+void QVGPaintEngine::fillRegion
+    (const QRegion& region, const QColor& color, const QSize& surfaceSize)
+{
+    Q_D(QVGPaintEngine);
+    if (d->clearColor != color || d->clearOpacity != 1.0f) {
+        VGfloat values[4];
+        values[0] = color.redF();
+        values[1] = color.greenF();
+        values[2] = color.blueF();
+        values[3] = color.alphaF();
+        vgSetfv(VG_CLEAR_COLOR, 4, values);
+        d->clearColor = color;
+        d->clearOpacity = 1.0f;
+    }
+    if (region.rectCount() == 1) {
+        QRect r = region.boundingRect();
+        vgClear(r.x(), surfaceSize.height() - r.y() - r.height(),
+                r.width(), r.height());
+    } else {
+        const QVector<QRect> rects = region.rects();
+        for (int i = 0; i < rects.size(); ++i) {
+            QRect r = rects.at(i);
+            vgClear(r.x(), surfaceSize.height() - r.y() - r.height(),
+                    r.width(), r.height());
+        }
+    }
+}
+
 #if !defined(QVG_NO_SINGLE_CONTEXT) && !defined(QT_NO_EGL)
 
 QVGCompositionHelper::QVGCompositionHelper()
diff --git a/src/openvg/qpaintengine_vg_p.h b/src/openvg/qpaintengine_vg_p.h
index 1202b55..86a522a 100644
--- a/src/openvg/qpaintengine_vg_p.h
+++ b/src/openvg/qpaintengine_vg_p.h
@@ -151,6 +151,8 @@ public:
 
     QVGPaintEnginePrivate *vgPrivate() { Q_D(QVGPaintEngine); return d; }
 
+    void fillRegion(const QRegion& region, const QColor& color, const QSize& surfaceSize);
+
 protected:
     QVGPaintEngine(QVGPaintEnginePrivate &data);
 
diff --git a/src/openvg/qwindowsurface_vg.cpp b/src/openvg/qwindowsurface_vg.cpp
index f8486a6..a1301e3 100644
--- a/src/openvg/qwindowsurface_vg.cpp
+++ b/src/openvg/qwindowsurface_vg.cpp
@@ -48,6 +48,7 @@
 #if !defined(QT_NO_EGL)
 
 #include <QtGui/private/qegl_p.h>
+#include <QtGui/private/qwidget_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -71,7 +72,6 @@ QVGWindowSurface::~QVGWindowSurface()
 
 QPaintDevice *QVGWindowSurface::paintDevice()
 {
-    d_ptr->beginPaint(window());
     return this;
 }
 
@@ -94,8 +94,16 @@ bool QVGWindowSurface::scroll(const QRegion &area, int dx, int dy)
 
 void QVGWindowSurface::beginPaint(const QRegion &region)
 {
-    // Nothing to do here.
-    Q_UNUSED(region);
+    d_ptr->beginPaint(window());
+
+    // If the window is not opaque, then fill the region we are about
+    // to paint with the transparent color.
+    if (!qt_widget_private(window())->isOpaque &&
+            window()->testAttribute(Qt::WA_TranslucentBackground)) {
+        QVGPaintEngine *engine = static_cast<QVGPaintEngine *>
+            (d_ptr->paintEngine());
+        engine->fillRegion(region, Qt::transparent, d_ptr->surfaceSize());
+    }
 }
 
 void QVGWindowSurface::endPaint(const QRegion &region)