Fix test failure & optimize matrix operations in QGraphicsItem.

This fixes failures in tst_QGraphicsItem::setTransformProperties().

Change 9e8ff32d introduced QMatrix4x4 as an internal matrix for
QGraphicsItem. Problem is, QMatrix4x4 is float-based whereas QTransform
is double-based. This change readds the use of QTransform in the case
where there are no QGraphicsTransforms in the list. This by itself also
makes this common case a bit faster.

The workaround is moot if somebody adds any QGraphicsTransform,
including one that doesn't do anything (like rotate by 0 degrees). So
we might have to find a better fix.

Reviewed-by: Olivier

1 files changed, 13 insertions, 0 deletions

diff --git a/src/gui/graphicsview/qgraphicsitem_p.h b/src/gui/graphicsview/qgraphicsitem_p.h
index 49361cf..55ed62e 100644
--- a/src/gui/graphicsview/qgraphicsitem_p.h
+++ b/src/gui/graphicsview/qgraphicsitem_p.h
@@ -517,6 +517,19 @@ struct QGraphicsItemPrivate::TransformData
             return transform * *postmultiplyTransform;
         }
 
+        if (graphicsTransforms.isEmpty()) {
+            // Faster, and higher precision if there are no graphics
+            // transforms.
+            QTransform x(transform);
+            x.translate(xOrigin, yOrigin);
+            x.rotate(rotation);
+            x.scale(scale, scale);
+            x.translate(-xOrigin, -yOrigin);
+            if (postmultiplyTransform)
+                x *= *postmultiplyTransform;
+            return x;
+        }
+
         QMatrix4x4 x(transform);
         for (int i = 0; i < graphicsTransforms.size(); ++i)
             graphicsTransforms.at(i)->applyTo(&x);