[Transforms] Repaint issue with relative position and transform

[Simon Fraser (smfr)]

The attached testcase shows a problem repainting a relatively positioned element with a transform when innerText changes.

[Simon Fraser (smfr)]

Created attachment 26688 [details]
Testcase

[Simon Fraser (smfr)]

Created attachment 26689 [details]
Another testcase -- same issue?

[Simon Fraser (smfr)]

This is a LayoutState issue. Towards the end of RenderBlock::layoutBlock(), after we've popped the layout state, we're doing a repaintRectangle(). The current element has a transform, so we'd normally have disabled the layout state, but we after the pop, so we think it's ok to use the LayoutState in the repaint.

[Simon Fraser (smfr)]

This seems to be an issue with LayoutState and transforms. This change fixes it but maybe we can do something more subtle.

diff --git a/WebCore/rendering/RenderObject.cpp b/WebCore/rendering/RenderObject.cpp
index 48d6d57..3e7b2de 100644
--- a/WebCore/rendering/RenderObject.cpp
+++ b/WebCore/rendering/RenderObject.cpp
@@ -1170,7 +1170,15 @@ void RenderObject::repaintRectangle(const IntRect& r, bool immediate)
     dirtyRect.move(view->layoutDelta());
 
     RenderBoxModelObject* repaintContainer = containerForRepaint();
+    
+    if (hasTransform())
+        view->disableLayoutState();
+
     computeRectForRepaint(repaintContainer, dirtyRect);
+
+    if (hasTransform())
+        view->enableLayoutState();
+
     repaintUsingContainer(repaintContainer ? repaintContainer : view, dirtyRect, immediate);
 }
 

[Simon Fraser (smfr)]

Created attachment 29219 [details]
Patch, testcase, changelog

This patch fixes both testcases in this bug.

[Simon Fraser (smfr)]

http://trac.webkit.org/changeset/42197