Correctly position abspos content inside relpos inlines [spv2]

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/PaintPropertyTreeBuilder.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/Settings.h"
+#include "core/layout/LayoutInline.h"
 #include "core/layout/LayoutPart.h"
 #include "core/paint/ObjectPaintProperties.h"
 #include "core/paint/PaintLayer.h"
 #include "platform/graphics/paint/ClipPaintPropertyNode.h"
 #include "platform/graphics/paint/TransformPaintPropertyNode.h"
 #include "platform/transforms/TransformationMatrix.h"
 
 namespace blink {
 
 // The context for layout tree walk.
@@ skipping 307 matching lines @@
     context.currentTransform = scrollTranslation.get();
     object.ensureObjectPaintProperties().setScrollTranslation(scrollTranslation.release());
 }
 
 void PaintPropertyTreeBuilder::updateOutOfFlowContext(LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
     if (object.canContainAbsolutePositionObjects()) {
         context.transformForAbsolutePosition = context.currentTransform;
         context.paintOffsetForAbsolutePosition = context.paintOffset;
         context.clipForAbsolutePosition = context.currentClip;
+
+        // Absolutely positioned content in an inline should be positioned relative to the first
+        // inline box. See: LayoutInline::offsetForInFlowPositionedInline.
+        // FIXME(pdr): There is a special case when the descendant has static position where this
+        // offset should be removed and an offset based on the inline position should be used instead.
+        if (object.isInline() && object.isLayoutInline()) {
+            const LayoutInline& layoutInline = toLayoutInline(object);
+            if (layoutInline.firstLineBox()) {
+                LayoutPoint inlineOffset = layoutInline.firstLineBox()->topLeft();
+                if (!object.styleRef().isHorizontalWritingMode())
+                    inlineOffset = inlineOffset.transposedPoint();
+                context.paintOffsetForAbsolutePosition += inlineOffset;
+            }
+        }

[Xianzhu, 2016/05/26 18:02:27]

It's better to use the same algorithm as in PaintInvalidationState
(https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...)
and LayoutBox::mapToVisualRectInAncestorSpace() about absolute-position under
relative inline.

Why do we need to care about statically-positioned absolute-position? Hasn't it
be already layouted at the proper place?

     }
 
     // TODO(pdr): Remove the !object.isLayoutView() condition when removing FrameView
     // paint properties for rootLayerScrolls.
     if (!object.isLayoutView() && object.canContainFixedPositionObjects()) {
         context.transformForFixedPosition = context.currentTransform;
         context.paintOffsetForFixedPosition = context.paintOffset;
         context.clipForFixedPosition = context.currentClip;
     } else if (object.objectPaintProperties() && object.objectPaintProperties()->cssClip()) {
         // CSS clip applies to all descendants, even if this object is not a containing block
@@ skipping 89 matching lines @@
 
     if (object.isLayoutPart()) {
         Widget* widget = toLayoutPart(object).widget();
         if (widget && widget->isFrameView())
             walk(*toFrameView(widget), localContext);
         // TODO(pdr): Investigate RemoteFrameView (crbug.com/579281).
     }
 }
 
 } // namespace blink