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, 3 insertions, 1 deletions

diff --git a/src/opengl/qgl_p.h b/src/opengl/qgl_p.h
index 03532c8..e86b843 100644
--- a/src/opengl/qgl_p.h
+++ b/src/opengl/qgl_p.h
@@ -175,6 +175,7 @@ class QGLWidgetPrivate : public QWidgetPrivate
     Q_DECLARE_PUBLIC(QGLWidget)
 public:
     QGLWidgetPrivate() : QWidgetPrivate()
+                       , disable_clear_on_painter_begin(false)
 #ifdef Q_WS_QWS
                        , wsurf(0)
 #endif
@@ -197,6 +198,8 @@ public:
     QGLColormap cmap;
     QMap<QString, int> displayListCache;
 
+    bool disable_clear_on_painter_begin;
+
 #if defined(Q_WS_WIN)
     void updateColormap();
     QGLContext *olcx;
@@ -295,7 +298,6 @@ public:
     uint sharing : 1;
     uint initDone : 1;
     uint crWin : 1;
-    uint clear_on_painter_begin : 1;
     uint internal_context : 1;
     uint version_flags_cached : 1;
     QPaintDevice *paintDevice;