Fix gradient background invalidation when HTML size changes

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

+// Copyright 2017 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/ViewPaintInvalidator.h"
+
+#include "core/layout/LayoutView.h"
+#include "core/paint/BoxPaintInvalidator.h"
+#include "platform/geometry/LayoutSize.h"
+
+namespace blink {
+
+PaintInvalidationReason ViewPaintInvalidator::invalidatePaintIfNeeded() {

[chrishtr, 2017/02/16 23:11:25]

Indentation nit:

if (m_view.styleRef().hasEntirelyFixedBackground())
  return;
...

[Xianzhu, 2017/02/16 23:39:35]

Done.

+  if (!m_view.styleRef().hasEntirelyFixedBackground()) {
+    // LayoutView's non-fixed-attachment background is positioned in the
+    // document element.

[chrishtr, 2017/02/16 23:11:25]

Please link to the spec here, for reference.

[Xianzhu, 2017/02/16 23:39:35]

Done.

+    if (Element* documentElement = m_view.document().documentElement()) {
+      const LayoutObject* backgroundObject = documentElement->layoutObject();
+      if (backgroundObject && backgroundObject->isBox()) {
+        const LayoutBox& backgroundBox = toLayoutBox(*backgroundObject);
+        LayoutSize oldSize =
+            BoxPaintInvalidator::previousBorderBoxSize(backgroundBox);
+        LayoutSize newSize = backgroundBox.size();
+        const auto& backgroundLayers = m_view.styleRef().backgroundLayers();
+        if ((oldSize.width() != newSize.width() &&
+             LayoutBox::mustInvalidateFillLayersPaintOnWidthChange(

[chrishtr, 2017/02/16 23:11:25]

This looks like mostly the same code as
LayoutView::setShouldDoFullPaintInvalidationOnResizeIfNeeded. Re-use/
refactor to re-use?

[Xianzhu, 2017/02/16 23:39:35]

Currently we can only reuse 4 lines of code because other conditions are
different. Now we still need the fixed-attachment code in LayoutView because we
don't have the previous view size here. Will move the fixed-attachment code here
when we enable rootLayerScrolling permanently (when we can use
previousBorderBoxSize as the viewport size).

+                 backgroundLayers)) ||
+            (oldSize.height() != newSize.height() &&
+             LayoutBox::mustInvalidateFillLayersPaintOnHeightChange(
+                 backgroundLayers))) {
+          m_view.getMutableForPainting().setShouldDoFullPaintInvalidation(
+              PaintInvalidationViewBackground);
+        }
+      }
+    }
+  }
+
+  return BoxPaintInvalidator(m_view, m_context).invalidatePaintIfNeeded();
+}
+
+}  // namespace blink