From 5969625334270892e39b6b43f4da735b830abdbe Mon Sep 17 00:00:00 2001
From: Bjoern Erik Nilsen <bjorn.nilsen@nokia.com>
Date: Wed, 29 Apr 2009 17:33:10 +0200
Subject: Speed-up QPainter::clipRegion().

We can speed up the calculation by using rect intersections
if possible, i.e. QRegion &= QRect instead of QRegion &= QRegion.
Then we'll get rid of one QRegion construction and the intersection
itself is slightly faster.

Reviewed-by: Samuel
---
 src/gui/painting/qpainter.cpp | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/src/gui/painting/qpainter.cpp b/src/gui/painting/qpainter.cpp
index 65d87fa..759bd7e 100644
--- a/src/gui/painting/qpainter.cpp
+++ b/src/gui/painting/qpainter.cpp
@@ -2398,7 +2398,6 @@ QRegion QPainter::clipRegion() const
     // ### Falcon: Use QPainterPath
     for (int i=0; i<d->state->clipInfo.size(); ++i) {
         const QPainterClipInfo &info = d->state->clipInfo.at(i);
-        QRegion other;
         switch (info.clipType) {
 
         case QPainterClipInfo::RegionClip: {
@@ -2451,15 +2450,20 @@ QRegion QPainter::clipRegion() const
                 lastWasNothing = false;
                 continue;
             }
-            if (info.operation == Qt::IntersectClip)
-                region &= QRegion(info.rect) * matrix;
-            else if (info.operation == Qt::UniteClip)
+            if (info.operation == Qt::IntersectClip) {
+                // Use rect intersection if possible.
+                if (matrix.type() <= QTransform::TxScale)
+                    region &= matrix.mapRect(info.rect);
+                else
+                    region &= matrix.map(QRegion(info.rect));
+            } else if (info.operation == Qt::UniteClip) {
                 region |= QRegion(info.rect) * matrix;
-            else if (info.operation == Qt::NoClip) {
+            } else if (info.operation == Qt::NoClip) {
                 lastWasNothing = true;
                 region = QRegion();
-            } else
+            } else {
                 region = QRegion(info.rect) * matrix;
+            }
             break;
         }
 
@@ -2470,15 +2474,20 @@ QRegion QPainter::clipRegion() const
                 lastWasNothing = false;
                 continue;
             }
-            if (info.operation == Qt::IntersectClip)
-                region &= QRegion(info.rectf.toRect()) * matrix;
-            else if (info.operation == Qt::UniteClip)
+            if (info.operation == Qt::IntersectClip) {
+                // Use rect intersection if possible.
+                if (matrix.type() <= QTransform::TxScale)
+                    region &= matrix.mapRect(info.rectf.toRect());
+                else
+                    region &= matrix.map(QRegion(info.rectf.toRect()));
+            } else if (info.operation == Qt::UniteClip) {
                 region |= QRegion(info.rectf.toRect()) * matrix;
-            else if (info.operation == Qt::NoClip) {
+            } else if (info.operation == Qt::NoClip) {
                 lastWasNothing = true;
                 region = QRegion();
-            } else
+            } else {
                 region = QRegion(info.rectf.toRect()) * matrix;
+            }
             break;
         }
         }
-- 
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