Try using pure scissor clip in GL 2 engine for rotations.

As long as the final clip area is rectangular and axis aligned we can
use a scissor clip. This prevents performance problems when doing
90-degree rotated rectangle clips.

Reviewed-by: Bjørn Erik Nilsen

1 files changed, 5 insertions, 1 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index ac41c04..7045fe9 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -2141,7 +2141,11 @@ void QGL2PaintEngineEx::clip(const QVectorPath &path, Qt::ClipOperation op)
         const QPointF* const points = reinterpret_cast<const QPointF*>(path.points());
         QRectF rect(points[0], points[2]);
 
-        if (state()->matrix.type() <= QTransform::TxScale) {
+        if (state()->matrix.type() <= QTransform::TxScale
+            || (state()->matrix.type() == QTransform::TxRotate
+                && qFuzzyIsNull(state()->matrix.m11())
+                && qFuzzyIsNull(state()->matrix.m22())))
+        {
             state()->rectangleClip = state()->rectangleClip.intersected(state()->matrix.mapRect(rect).toRect());
             d->updateClipScissorTest();
             return;