Land layer squashing behind a flag

Source/core/rendering/RenderLayerRepainter.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 137 matching lines @@
         if (child->hasCompositedLayerMapping())
             continue;
 
         repaintRect.unite(child->repainter().repaintRectIncludingNonCompositingDescendants());
     }
     return repaintRect;
 }
 
 void RenderLayerRepainter::setBackingNeedsRepaint()
 {
-    ASSERT(m_renderer->hasCompositedLayerMapping());
-    m_renderer->compositedLayerMapping()->setContentsNeedDisplay();
+    ASSERT(m_renderer->compositingState() != NotComposited);
+
+    if (m_renderer->compositingState() == PaintsIntoGroupedBacking) {
+        // FIXME: should probably setNeedsDisplayInRect for this layer's bounds only.
+        m_renderer->groupedMapping()->squashingLayer()->setNeedsDisplay();
+    } else {
+        m_renderer->compositedLayerMapping()->setContentsNeedDisplay();
+    }
 }
 
 void RenderLayerRepainter::setBackingNeedsRepaintInRect(const LayoutRect& r)
 {
     // https://bugs.webkit.org/show_bug.cgi?id=61159 describes an unreproducible crash here,
     // so assert but check that the layer is composited.
-    ASSERT(m_renderer->hasCompositedLayerMapping());
-    if (!m_renderer->hasCompositedLayerMapping()) {
+    ASSERT(m_renderer->compositingState() != NotComposited);
+    if (m_renderer->compositingState() == NotComposited) {
         // If we're trying to repaint the placeholder document layer, propagate the
         // repaint to the native view system.
         LayoutRect absRect(r);
         LayoutPoint delta;
         m_renderer->layer()->convertToLayerCoords(m_renderer->layer()->root(), delta);
         absRect.moveBy(delta);
 
         RenderView* view = m_renderer->view();
         if (view)
             view->repaintViewRectangle(absRect);
     } else {
-        m_renderer->compositedLayerMapping()->setContentsNeedDisplayInRect(pixelSnappedIntRect(r));
+        if (m_renderer->compositingState() == PaintsIntoGroupedBacking) {
+            IntRect offsetRect = pixelSnappedIntRect(r);
+            offsetRect.move(-m_renderer->layer()->offsetFromSquashingLayerOrigin());

[enne (OOO), 2013/11/27 23:20:26]

Should you be storing all of these offsets as LayoutUnits and not IntRects? It
seems like you're losing precision all the way through this squashing pipeline.

Related: https://codereview.chromium.org/20723003/

[shawnsingh, 2013/12/02 01:55:03]

Would you be OK with us moving forward with this version of the patch, and I can
create a crbug report to address the subpixel issue?

For what it's worth, I believe I didn't do any additional rounding in this
patch.  So if there is any subpixel bugs, it would be that i'm using an
already-rounded value that shouldn't be rounded before I use it.

+            m_renderer->groupedMapping()->squashingLayer()->setNeedsDisplayInRect(offsetRect);
+        } else {
+            m_renderer->compositedLayerMapping()->setContentsNeedDisplayInRect(pixelSnappedIntRect(r));
+        }
     }
 }
 
 void RenderLayerRepainter::repaintIncludingDescendants()
 {
     m_renderer->repaint();
     for (RenderLayer* curr = m_renderer->layer()->firstChild(); curr; curr = curr->nextSibling())
         curr->repainter().repaintIncludingDescendants();
 }
 
@@ skipping 44 matching lines @@
 RenderLayer* RenderLayerRepainter::enclosingFilterRepaintLayer() const
 {
     for (const RenderLayer* curr = m_renderer->layer(); curr; curr = curr->parent()) {
         if ((curr != m_renderer->layer() && curr->requiresFullLayerImageForFilters()) || curr->compositingState() == PaintsIntoOwnBacking || curr->isRootLayer())
             return const_cast<RenderLayer*>(curr);
     }
     return 0;
 }
 
 } // Namespace WebCore