Move buffer clear out of the paint engine and into the QGLPaintDevices

Previously, the paint engine cleared the surface's buffers in begin.
This logic really belongs in QGLPaintDevice::beginPaint as not all paint
devices will want this behaviour (in fact most don't). This also makes
QGLPaintDevice API much simpler as the virtual getters for the clear
color, etc. can be removed. It's much cleaner this way. The only
possible problem is with the GL1 engine, which also cleared the
accumulation & depth buffers in begin. However, the engine will also
clear the depth buffer later as part of it's clipping logic. It also
doesn't use the accumulation buffer, so clearing it seems unnessisary.

1 files changed, 40 insertions, 24 deletions

diff --git a/src/opengl/qglpaintdevice.cpp b/src/opengl/qglpaintdevice.cpp
index 51f9627..4f000ba 100644
--- a/src/opengl/qglpaintdevice.cpp
+++ b/src/opengl/qglpaintdevice.cpp
@@ -86,20 +86,20 @@ void QGLPaintDevice::endPaint()
     }
 }
 
-QColor QGLPaintDevice::backgroundColor() const
-{
-    return QApplication::palette().brush(QPalette::Background).color();
-}
+//QColor QGLPaintDevice::backgroundColor() const
+//{
+//    return QApplication::palette().brush(QPalette::Background).color();
+//}
 
-bool QGLPaintDevice::autoFillBackground() const
-{
-    return false;
-}
+//bool QGLPaintDevice::autoFillBackground() const
+//{
+//    return false;
+//}
 
-bool QGLPaintDevice::hasTransparentBackground() const
-{
-    return false;
-}
+//bool QGLPaintDevice::hasTransparentBackground() const
+//{
+//    return false;
+//}
 
 QGLFormat QGLPaintDevice::format() const
 {
@@ -112,6 +112,7 @@ QSize QGLPaintDevice::size() const
 }
 
 
+
 QGLWidgetGLPaintDevice::QGLWidgetGLPaintDevice()
 {
 }
@@ -121,26 +122,41 @@ QPaintEngine* QGLWidgetGLPaintDevice::paintEngine() const
     return glWidget->paintEngine();
 }
 
-QColor QGLWidgetGLPaintDevice::backgroundColor() const
-{
-    return glWidget->palette().brush(glWidget->backgroundRole()).color();
-}
+//QColor QGLWidgetGLPaintDevice::backgroundColor() const
+//{
+//    return glWidget->palette().brush(glWidget->backgroundRole()).color();
+//}
 
-bool QGLWidgetGLPaintDevice::autoFillBackground() const
-{
-    return glWidget->autoFillBackground();
-}
+//bool QGLWidgetGLPaintDevice::autoFillBackground() const
+//{
+//    return glWidget->autoFillBackground();
+//}
 
-bool QGLWidgetGLPaintDevice::hasTransparentBackground() const
-{
-    return glWidget->testAttribute(Qt::WA_TranslucentBackground);
-}
+//bool QGLWidgetGLPaintDevice::hasTransparentBackground() const
+//{
+//    return glWidget->testAttribute(Qt::WA_TranslucentBackground);
+//}
 
 void QGLWidgetGLPaintDevice::setWidget(QGLWidget* w)
 {
     glWidget = w;
 }
 
+void QGLWidgetGLPaintDevice::beginPaint()
+{
+    QGLPaintDevice::beginPaint();
+    if (!glWidget->d_func()->disable_clear_on_painter_begin && glWidget->autoFillBackground()) {
+        if (glWidget->testAttribute(Qt::WA_TranslucentBackground))
+            glClearColor(0.0, 0.0, 0.0, 0.0);
+        else {
+            const QColor &c = glWidget->palette().brush(glWidget->backgroundRole()).color();
+            float alpha = c.alphaF();
+            glClearColor(c.redF() * alpha, c.greenF() * alpha, c.blueF() * alpha, alpha);
+        }
+        glClear(GL_COLOR_BUFFER_BIT);
+    }
+}
+
 void QGLWidgetGLPaintDevice::endPaint()
 {
     if (glWidget->autoBufferSwap())