Fix effects for highdpi graphical items

Create a highdpi pixmap as a source for graphical effects.

Fixes: QTBUG-74963
Change-Id: Ie144df3dbe61421fb28e639e640857aca6e6320f
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

3 files changed, 9 insertions, 6 deletions

diff --git a/src/widgets/graphicsview/qgraphicsitem.cpp b/src/widgets/graphicsview/qgraphicsitem.cpp
index 86f3d6a2f0..30b35ad92f 100644
--- a/src/widgets/graphicsview/qgraphicsitem.cpp
+++ b/src/widgets/graphicsview/qgraphicsitem.cpp
@@ -11334,7 +11334,7 @@ void QGraphicsItemEffectSourcePrivate::draw(QPainter *painter)
 }
 
 // sourceRect must be in the given coordinate system
-QRect QGraphicsItemEffectSourcePrivate::paddedEffectRect(Qt::CoordinateSystem system, QGraphicsEffect::PixmapPadMode mode, const QRectF &sourceRect, bool *unpadded) const
+QRectF QGraphicsItemEffectSourcePrivate::paddedEffectRect(Qt::CoordinateSystem system, QGraphicsEffect::PixmapPadMode mode, const QRectF &sourceRect, bool *unpadded) const
 {
     QRectF effectRectF;
 
@@ -11362,7 +11362,7 @@ QRect QGraphicsItemEffectSourcePrivate::paddedEffectRect(Qt::CoordinateSystem sy
             *unpadded = true;
     }
 
-    return effectRectF.toAlignedRect();
+    return effectRectF;
 }
 
 QPixmap QGraphicsItemEffectSourcePrivate::pixmap(Qt::CoordinateSystem system, QPoint *offset,
@@ -11380,7 +11380,8 @@ QPixmap QGraphicsItemEffectSourcePrivate::pixmap(Qt::CoordinateSystem system, QP
 
     bool unpadded;
     const QRectF sourceRect = boundingRect(system);
-    QRect effectRect = paddedEffectRect(system, mode, sourceRect, &unpadded);
+    QRectF effectRectF = paddedEffectRect(system, mode, sourceRect, &unpadded);
+    QRect effectRect = effectRectF.toAlignedRect();
 
     if (offset)
         *offset = effectRect.topLeft();
@@ -11396,7 +11397,9 @@ QPixmap QGraphicsItemEffectSourcePrivate::pixmap(Qt::CoordinateSystem system, QP
     if (effectRect.isEmpty())
         return QPixmap();
 
-    QPixmap pixmap(effectRect.size());
+    const auto dpr = info ? info->painter->device()->devicePixelRatioF() : 1.0;
+    QPixmap pixmap(QRectF(effectRectF.topLeft(), effectRectF.size() * dpr).toAlignedRect().size());
+    pixmap.setDevicePixelRatio(dpr);
     pixmap.fill(Qt::transparent);
     QPainter pixmapPainter(&pixmap);
     pixmapPainter.setRenderHints(info ? info->painter->renderHints() : QPainter::TextAntialiasing);
diff --git a/src/widgets/graphicsview/qgraphicsitem_p.h b/src/widgets/graphicsview/qgraphicsitem_p.h
index d586a22544..54c25bf6e1 100644
--- a/src/widgets/graphicsview/qgraphicsitem_p.h
+++ b/src/widgets/graphicsview/qgraphicsitem_p.h
@@ -644,7 +644,7 @@ public:
     QPixmap pixmap(Qt::CoordinateSystem system,
                    QPoint *offset,
                    QGraphicsEffect::PixmapPadMode mode) const override;
-    QRect paddedEffectRect(Qt::CoordinateSystem system, QGraphicsEffect::PixmapPadMode mode, const QRectF &sourceRect, bool *unpadded = 0) const;
+    QRectF paddedEffectRect(Qt::CoordinateSystem system, QGraphicsEffect::PixmapPadMode mode, const QRectF &sourceRect, bool *unpadded = 0) const;
 
     QGraphicsItem *item;
     QGraphicsItemPaintInfo *info;
diff --git a/src/widgets/graphicsview/qgraphicsscene.cpp b/src/widgets/graphicsview/qgraphicsscene.cpp
index bba992144d..3dce958b08 100644
--- a/src/widgets/graphicsview/qgraphicsscene.cpp
+++ b/src/widgets/graphicsview/qgraphicsscene.cpp
@@ -4847,7 +4847,7 @@ void QGraphicsScenePrivate::drawSubtreeRecursive(QGraphicsItem *item, QPainter *
                 && painter->worldTransform().type() <= QTransform::TxTranslate)
             {
                 QRectF sourceRect = sourced->boundingRect(Qt::DeviceCoordinates);
-                QRect effectRect = sourced->paddedEffectRect(Qt::DeviceCoordinates, sourced->currentCachedMode(), sourceRect);
+                QRect effectRect = sourced->paddedEffectRect(Qt::DeviceCoordinates, sourced->currentCachedMode(), sourceRect).toAlignedRect();
 
                 sourced->setCachedOffset(effectRect.topLeft());
             } else {