greatly speed up QTransform::mapRect() for projective transforms

The code so far was converting the rect to a painterpath, mapping
that one and then taking the bounding rect. It is actually sufficient
to simply map the four corners of the rectangle and take the bounding
rect of these four points even in the projective case.

Reviewed-by: Andreas

1 files changed, 2 insertions, 10 deletions

diff --git a/src/gui/painting/qtransform.cpp b/src/gui/painting/qtransform.cpp
index c00012a..86e594c 100644
--- a/src/gui/painting/qtransform.cpp
+++ b/src/gui/painting/qtransform.cpp
@@ -1788,7 +1788,7 @@ QRect QTransform::mapRect(const QRect &rect) const
             y -= h;
         }
         return QRect(x, y, w, h);
-    } else if (t < TxProject) {
+    } else {
         // see mapToPolygon for explanations of the algorithm.
         qreal x = 0, y = 0;
         MAP(rect.left(), rect.top(), x, y);
@@ -1812,10 +1812,6 @@ QRect QTransform::mapRect(const QRect &rect) const
         xmax = qMax(xmax, x);
         ymax = qMax(ymax, y);
         return QRect(qRound(xmin), qRound(ymin), qRound(xmax)-qRound(xmin), qRound(ymax)-qRound(ymin));
-    } else {
-        QPainterPath path;
-        path.addRect(rect);
-        return map(path).boundingRect().toRect();
     }
 }
 
@@ -1858,7 +1854,7 @@ QRectF QTransform::mapRect(const QRectF &rect) const
             y -= h;
         }
         return QRectF(x, y, w, h);
-    } else if (t < TxProject) {
+    } else {
         qreal x = 0, y = 0;
         MAP(rect.x(), rect.y(), x, y);
         qreal xmin = x;
@@ -1881,10 +1877,6 @@ QRectF QTransform::mapRect(const QRectF &rect) const
         xmax = qMax(xmax, x);
         ymax = qMax(ymax, y);
         return QRectF(xmin, ymin, xmax-xmin, ymax - ymin);
-    } else {
-        QPainterPath path;
-        path.addRect(rect);
-        return map(path).boundingRect();
     }
 }