Improved performance of translating device coordinate graphics effects.

Don't invalidate the cache if we're only translating and the effect rect
is fully contained within the device rect of the painter.

Task-number: QTBUG-6901
Reviewed-by: Bjørn Erik Nilsen

3 files changed, 52 insertions, 18 deletions

diff --git a/src/gui/graphicsview/qgraphicsitem.cpp b/src/gui/graphicsview/qgraphicsitem.cpp
index 168a9a303b..cae96608de 100644
--- a/src/gui/graphicsview/qgraphicsitem.cpp
+++ b/src/gui/graphicsview/qgraphicsitem.cpp
@@ -10715,27 +10715,18 @@ void QGraphicsItemEffectSourcePrivate::draw(QPainter *painter)
     }
 }
 
-QPixmap QGraphicsItemEffectSourcePrivate::pixmap(Qt::CoordinateSystem system, QPoint *offset,
-                                                 QGraphicsEffect::PixmapPadMode mode) const
+QRect QGraphicsItemEffectSourcePrivate::paddedEffectRect(Qt::CoordinateSystem system, QGraphicsEffect::PixmapPadMode mode, const QRectF &sourceRect, bool *unpadded) const
 {
-    const bool deviceCoordinates = (system == Qt::DeviceCoordinates);
-    if (!info && deviceCoordinates) {
-        // Device coordinates without info not yet supported.
-        qWarning("QGraphicsEffectSource::pixmap: Not yet implemented, lacking device context");
-        return QPixmap();
-    }
-    if (!item->d_ptr->scene)
-        return QPixmap();
-    QGraphicsScenePrivate *scened = item->d_ptr->scene->d_func();
-
-    const QRectF sourceRect = boundingRect(system);
     QRectF effectRectF;
 
-    bool unpadded = false;
+    if (unpadded)
+        *unpadded = false;
+
     if (mode == QGraphicsEffect::PadToEffectiveBoundingRect) {
         if (info) {
             effectRectF = item->graphicsEffect()->boundingRectFor(boundingRect(Qt::DeviceCoordinates));
-            unpadded = (effectRectF.size() == sourceRect.size());
+            if (unpadded)
+                *unpadded = (effectRectF.size() == sourceRect.size());
             if (info && system == Qt::LogicalCoordinates)
                 effectRectF = info->painter->worldTransform().inverted().mapRect(effectRectF);
         } else {
@@ -10747,10 +10738,29 @@ QPixmap QGraphicsItemEffectSourcePrivate::pixmap(Qt::CoordinateSystem system, QP
         effectRectF = sourceRect.adjusted(-1.5, -1.5, 1.5, 1.5);
     } else {
         effectRectF = sourceRect;
-        unpadded = true;
+        if (unpadded)
+            *unpadded = true;
+    }
+
+    return effectRectF.toAlignedRect();
+}
+
+QPixmap QGraphicsItemEffectSourcePrivate::pixmap(Qt::CoordinateSystem system, QPoint *offset,
+                                                 QGraphicsEffect::PixmapPadMode mode) const
+{
+    const bool deviceCoordinates = (system == Qt::DeviceCoordinates);
+    if (!info && deviceCoordinates) {
+        // Device coordinates without info not yet supported.
+        qWarning("QGraphicsEffectSource::pixmap: Not yet implemented, lacking device context");
+        return QPixmap();
     }
+    if (!item->d_ptr->scene)
+        return QPixmap();
+    QGraphicsScenePrivate *scened = item->d_ptr->scene->d_func();
 
-    QRect effectRect = effectRectF.toAlignedRect();
+    bool unpadded;
+    const QRectF sourceRect = boundingRect(system);
+    QRect effectRect = paddedEffectRect(system, mode, sourceRect, &unpadded);
 
     if (offset)
         *offset = effectRect.topLeft();
diff --git a/src/gui/graphicsview/qgraphicsitem_p.h b/src/gui/graphicsview/qgraphicsitem_p.h
index c8d2061003..2d34b80070 100644
--- a/src/gui/graphicsview/qgraphicsitem_p.h
+++ b/src/gui/graphicsview/qgraphicsitem_p.h
@@ -609,6 +609,7 @@ public:
     QPixmap pixmap(Qt::CoordinateSystem system,
                    QPoint *offset,
                    QGraphicsEffect::PixmapPadMode mode) const;
+    QRect paddedEffectRect(Qt::CoordinateSystem system, QGraphicsEffect::PixmapPadMode mode, const QRectF &sourceRect, bool *unpadded = 0) const;
 
     QGraphicsItem *item;
     QGraphicsItemPaintInfo *info;
diff --git a/src/gui/graphicsview/qgraphicsscene.cpp b/src/gui/graphicsview/qgraphicsscene.cpp
index 5c6a8aeb08..cea723c424 100644
--- a/src/gui/graphicsview/qgraphicsscene.cpp
+++ b/src/gui/graphicsview/qgraphicsscene.cpp
@@ -4686,8 +4686,31 @@ void QGraphicsScenePrivate::drawSubtreeRecursive(QGraphicsItem *item, QPainter *
         if (sourced->currentCachedSystem() != Qt::LogicalCoordinates
             && sourced->lastEffectTransform != painter->worldTransform())
         {
+            bool unclipped = false;
+            if (sourced->lastEffectTransform.type() <= QTransform::TxTranslate
+                && painter->worldTransform().type() <= QTransform::TxTranslate)
+            {
+                QRectF itemRect = item->boundingRect();
+                if (!item->d_ptr->children.isEmpty())
+                    itemRect |= item->childrenBoundingRect();
+
+                QRectF oldSourceRect = sourced->lastEffectTransform.mapRect(itemRect);
+                QRectF newSourceRect = painter->worldTransform().mapRect(itemRect);
+
+                QRect oldEffectRect = sourced->paddedEffectRect(sourced->currentCachedSystem(), sourced->currentCachedMode(), oldSourceRect);
+                QRect newEffectRect = sourced->paddedEffectRect(sourced->currentCachedSystem(), sourced->currentCachedMode(), newSourceRect);
+
+                QRect deviceRect(0, 0, painter->device()->width(), painter->device()->height());
+                if (deviceRect.contains(oldEffectRect) && deviceRect.contains(newEffectRect)) {
+                    sourced->setCachedOffset(newEffectRect.topLeft());
+                    unclipped = true;
+                }
+            }
+
             sourced->lastEffectTransform = painter->worldTransform();
-            sourced->invalidateCache(QGraphicsEffectSourcePrivate::TransformChanged);
+
+            if (!unclipped)
+                sourced->invalidateCache(QGraphicsEffectSourcePrivate::TransformChanged);
         }
 
         item->d_ptr->graphicsEffect->draw(painter);