Fix gradient background invalidation when HTML size changes

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

 // Copyright 2016 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/BoxPaintInvalidator.h"
 
 #include "core/frame/Settings.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/compositing/CompositedLayerMapping.h"
 #include "core/paint/ObjectPaintInvalidator.h"
@@ skipping 294 matching lines @@
     area->invalidatePaintOfScrollControlsIfNeeded(m_context);
 
   // This is for the next invalidatePaintIfNeeded so must be at the end.
   savePreviousBoxGeometriesIfNeeded();
 
   return reason;
 }
 
 bool BoxPaintInvalidator::needsToSavePreviousBoxGeometries() {
   LayoutSize paintInvalidationSize = m_context.newVisualRect.size();
-  // Don't save old box Geometries if the paint rect is empty because we'll
-  // full invalidate once the paint rect becomes non-empty.
-  if (paintInvalidationSize.isEmpty())
-    return false;
 
-  if (m_box.paintedOutputOfObjectHasNoEffectRegardlessOfSize())
-    return false;
+  // The shortcuts doesn't apply to HTML element. ViewPaintInvalidator needs to
+  // know its previous border box size even if it has visibility:hidden (causing
+  // empty paintInvalidationSize) or has no painted output.
+  if (!m_box.node() || !m_box.node()->isHTMLElement()) {
+    // Don't save old box geometries if the paint rect is empty because we'll
+    // fully invalidate once the paint rect becomes non-empty.
+    if (paintInvalidationSize.isEmpty())
+      return false;
+
+    if (m_box.paintedOutputOfObjectHasNoEffectRegardlessOfSize())
+      return false;
+  }
 
   const ComputedStyle& style = m_box.styleRef();
 
   // If we use border-box sizing we need to track changes in the size of the
   // content box.
   if (style.boxSizing() == EBoxSizing::kBorderBox)
     return true;
 
   // No need to save old border box size if we can use size of the old paint
   // rect as the old border box size in the next invalidation.
@@ skipping 21 matching lines @@
     }
     return;
   }
 
   PreviousBoxGeometries geometries = {m_box.size(), m_box.contentBoxRect(),
                                       m_box.layoutOverflowRect()};
   previousBoxGeometriesMap().set(&m_box, geometries);
   m_box.getMutableForPainting().setHasPreviousBoxGeometries(true);
 }
 
+static LayoutSize previousBorderBoxSizeInternal(const LayoutBox& box,
+                                                const LayoutSize& defaultSize) {
+  DCHECK(box.hasPreviousBoxGeometries() ==
+         previousBoxGeometriesMap().contains(&box));
+  if (box.hasPreviousBoxGeometries())
+    return previousBoxGeometriesMap().get(&box).borderBoxSize;
+  return defaultSize;
+}
+
+// This is used by ViewPaintInvalidator to get the previous border box size
+// of the HTML element, before the HTML element is paint invalidated.
+LayoutSize BoxPaintInvalidator::previousBorderBoxSize(const LayoutBox& box) {

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

It's weird that there are two methods with the same name that use a different
implicit rect. How about just removing these non-static methods and making
everyone pass two args to previousBorderBoxSizeInternal? (which would be
renamed).

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

Done.

+  return previousBorderBoxSizeInternal(box, box.visualRect().size());
+}
+
+// This is used during paint invalidation of the m_box. PaintInvalidator has
+// already updated m_box.visualRect() to the current value, so we need to use
+// context.oldVisualRect as the default value.
 LayoutSize BoxPaintInvalidator::previousBorderBoxSize() {
-  DCHECK(m_box.hasPreviousBoxGeometries() ==
-         previousBoxGeometriesMap().contains(&m_box));
-  if (m_box.hasPreviousBoxGeometries())
-    return previousBoxGeometriesMap().get(&m_box).borderBoxSize;
-
-  // We didn't save the old border box size because it was the same as the size
-  // of oldVisualRect.
-  return m_context.oldVisualRect.size();
+  return previousBorderBoxSizeInternal(m_box, m_context.oldVisualRect.size());
 }
 
 LayoutRect BoxPaintInvalidator::previousContentBoxRect() {
   DCHECK(m_box.hasPreviousBoxGeometries() ==
          previousBoxGeometriesMap().contains(&m_box));
   return m_box.hasPreviousBoxGeometries()
              ? previousBoxGeometriesMap().get(&m_box).contentBoxRect
              : LayoutRect();
 }
 
 LayoutRect BoxPaintInvalidator::previousLayoutOverflowRect() {
   DCHECK(m_box.hasPreviousBoxGeometries() ==
          previousBoxGeometriesMap().contains(&m_box));
   return m_box.hasPreviousBoxGeometries()
              ? previousBoxGeometriesMap().get(&m_box).layoutOverflowRect
              : LayoutRect();
 }
 
 }  // namespace blink