Invalidate first line display item clients when first line style changes

third_party/WebKit/Source/core/layout/LayoutInline.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 1406 matching lines @@
 void LayoutInline::invalidateDisplayItemClients(const LayoutBoxModelObject& paintInvalidationContainer, PaintInvalidationReason invalidationReason, const LayoutRect* paintInvalidationRect) const
 {
     LayoutBoxModelObject::invalidateDisplayItemClients(paintInvalidationContainer, invalidationReason, paintInvalidationRect);
 
     // Use the paintInvalidationRect of LayoutInline for inline boxes, which saves the cost to calculate paint invalidation rect
     // for every inline box. This won't cause more rasterization invalidations because the whole LayoutInline is being invalidated.
     for (InlineFlowBox* box = firstLineBox(); box; box = box->nextLineBox())
         paintInvalidationContainer.invalidateDisplayItemClientOnBacking(*box, invalidationReason, paintInvalidationRect);
 }
 
+void LayoutInline::invalidateDisplayItemClientsOfFirstLine()
+{
+    if (alwaysCreateLineBoxes()) {
+        for (InlineFlowBox* box = firstLineBox(); box; box = box->nextLineBox()) {
+            if (!box->isFirstLineStyle())
+                break;
+            box->invalidateDisplayItemClientsOfFirstLine();
+        }
+        return;
+    }
+
+    for (LayoutObject* child = firstChild(); child; child = child->nextSibling()) {

[mstensho (USE GERRIT), 2015/12/01 12:29:49]

Looks like there's nothing that stops at the end of the first line here.

<div>
    <span>[lots of text, creating hundreds of lines]</span>
</div>

You'd end up invalidating the entire block in that case, wouldn't you?

Conversely, there doesn't seem to be any check whether this inline occurs on a
first line at all.

I don't think I understand why we want this part of the method at all. I think
it would be better if the code above tried harder to locate line boxes (in case
of !alwaysCreateLineBoxes()). If that's to much work, how about locating the
containing block and call invalidateDisplayItemClientsOfFirstLine() on it
instead? But I think we should ask a line layout expert.

[Xianzhu, 2015/12/01 20:06:25]

I think invalidating the first line of containing block is a good idea. It may
invalidate more but code is much simpler and the over-invalidation doesn't seem
a big issue.

+        child->setShouldDoFullPaintInvalidation();

[chrishtr, 2015/12/01 01:43:11]

Why this line?

+        if (child->isLayoutInline())
+            toLayoutInline(child)->invalidateDisplayItemClientsOfFirstLine();
+        else if (child->isText())
+            toLayoutText(child)->invalidateDisplayItemClientsOfFirstLine();
+    }
+}
+
 } // namespace blink