Avoid flicker when invalidate is propagated in a widget/layout hierarchy

* Do not call invalidate from activateRecursive().
  This resulted in that a layout was invalidated as many times as there
  were items in the layout.

* Several improvements. Do not call resize(size()) too often.
  Calling resize() from the widgetEvent() is not very nice though...

* Remove commented out code

* make sure layout is activated even if the widget does not change size

* activate the layout if the resize is same as size()

* In order to not break existing apps, make this an opt-in feature
  with QGraphicsLayout::setInstantInvalidatePropagation(true);

Reviewed-by: Frederik Gladhorn
Reviewed-by: John Tapsell

1 files changed, 2 insertions, 0 deletions

diff --git a/src/gui/graphicsview/qgraphicslayout.h b/src/gui/graphicsview/qgraphicslayout.h
index c622fb881e..60311744a2 100644
--- a/src/gui/graphicsview/qgraphicslayout.h
+++ b/src/gui/graphicsview/qgraphicslayout.h
@@ -76,6 +76,8 @@ public:
     virtual QGraphicsLayoutItem *itemAt(int i) const = 0;
     virtual void removeAt(int index) = 0;
 
+    static void setInstantInvalidatePropagation(bool enable);
+    static bool instantInvalidatePropagation();
 protected:
     QGraphicsLayout(QGraphicsLayoutPrivate &, QGraphicsLayoutItem *);
     void addChildLayoutItem(QGraphicsLayoutItem *layoutItem);