Skip paint property update and visual rect update if no geometry change

third_party/WebKit/Source/core/paint/FindPaintOffsetAndVisualRectNeedingUpdate.h

Index: third_party/WebKit/Source/core/paint/FindPaintOffsetAndVisualRectNeedingUpdate.h
diff --git a/third_party/WebKit/Source/core/paint/FindPaintOffsetAndVisualRectNeedingUpdate.h b/third_party/WebKit/Source/core/paint/FindPaintOffsetAndVisualRectNeedingUpdate.h
new file mode 100644
index 0000000000000000000000000000000000000000..292dfe5d6b3376f30dd4a10230dc5203336d021e
--- /dev/null
+++ b/third_party/WebKit/Source/core/paint/FindPaintOffsetAndVisualRectNeedingUpdate.h
@@ -0,0 +1,177 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.

[pdr., 2017/03/27 21:15:02]

Nice file, I like this.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FindPaintOffsetAndVisualRectNeedingUpdate_h
+#define FindPaintOffsetAndVisualRectNeedingUpdate_h
+
+#if DCHECK_IS_ON()
+
+#include "core/layout/LayoutObject.h"
+#include "core/paint/FindPropertiesNeedingUpdate.h"
+#include "core/paint/ObjectPaintInvalidator.h"
+#include "core/paint/PaintInvalidator.h"
+#include "core/paint/PaintPropertyTreeBuilder.h"
+
+namespace blink {
+
+// This file contains scope classes for catching cases where paint offset or
+// visual rect needed an update but were not marked as such. If paint offset or
+// any visual rect (including visual rect of the object itself, scroll controls,
+// caret, selection, etc.) will change, the object must be marked as such by
+// LayoutObject::setNeedsPaintOffsetAndVisualRectUpdate() (which is a private
+// function called by several public paint-invalidation-flag setting functions).
+
+class FindPaintOffsetNeedingUpdateScope {
+ public:
+  FindPaintOffsetNeedingUpdateScope(
+      const LayoutObject& object,
+      const PaintPropertyTreeBuilderContext& context)
+      : m_object(object),
+        m_context(context),
+        m_oldPaintOffset(object.paintOffset()) {
+    if (object.paintProperties() &&
+        object.paintProperties()->paintOffsetTranslation()) {
+      m_oldPaintOffsetTranslation =
+          object.paintProperties()->paintOffsetTranslation()->clone();
+    }
+  }
+
+  ~FindPaintOffsetNeedingUpdateScope() {
+    if (m_context.isActuallyNeeded)
+      return;
+    DCHECK_OBJECT_PROPERTY_EQ(m_object, &m_oldPaintOffset,
+                              &m_object.paintOffset());
+    const auto* paintOffsetTranslation =
+        m_object.paintProperties()
+            ? m_object.paintProperties()->paintOffsetTranslation()
+            : nullptr;
+    DCHECK_OBJECT_PROPERTY_EQ(m_object, m_oldPaintOffsetTranslation.get(),
+                              paintOffsetTranslation);
+  }
+
+ private:
+  const LayoutObject& m_object;
+  const PaintPropertyTreeBuilderContext& m_context;
+  LayoutPoint m_oldPaintOffset;
+  RefPtr<const TransformPaintPropertyNode> m_oldPaintOffsetTranslation;
+};
+
+class FindVisualRectNeedingUpdateScopeBase {
+ protected:
+  FindVisualRectNeedingUpdateScopeBase(const LayoutObject& object,
+                                       const PaintInvalidatorContext& context,
+                                       const LayoutRect& oldVisualRect)
+      : m_object(object),
+        m_context(context),
+        m_oldVisualRect(oldVisualRect),
+        m_neededVisualRectUpdate(context.needsVisualRectUpdate(object)) {
+    if (m_neededVisualRectUpdate) {
+      DCHECK(!RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled() ||
+             (context.m_treeBuilderContext &&
+              context.m_treeBuilderContext->isActuallyNeeded));
+      return;
+    }
+    context.m_forceVisualRectUpdateForChecking = true;
+    DCHECK(context.needsVisualRectUpdate(object));
+  }
+
+  ~FindVisualRectNeedingUpdateScopeBase() {
+    m_context.m_forceVisualRectUpdateForChecking = false;
+    DCHECK_EQ(m_neededVisualRectUpdate,
+              m_context.needsVisualRectUpdate(m_object));
+  }
+
+  static LayoutRect inflatedRect(const LayoutRect& r) {
+    LayoutRect result = r;
+    result.inflate(1);
+    return result;
+  }
+
+  void checkVisualRect(const LayoutRect& newVisualRect) {
+    if (m_neededVisualRectUpdate)
+      return;
+    DCHECK((m_oldVisualRect.isEmpty() && newVisualRect.isEmpty()) ||
+           m_oldVisualRect == newVisualRect ||
+           // The following check is to tolerate the differences caused by
+           // pixel snapping that may happen for one rect but not for another
+           // while we need neither paint invalidation nor raster invalidation
+           // for the change. This may miss some real subpixel changes of visual
+           // rects. TODO(wangxianzhu): Look into whether we can tighten this
+           // for SPv2.
+           inflatedRect(m_oldVisualRect).contains(newVisualRect) ||
+           inflatedRect(newVisualRect).contains(m_oldVisualRect))
+        << "Visual rect changed without needing update"
+        << " object=" << m_object.debugName()
+        << " old=" << m_oldVisualRect.toString()
+        << " new=" << newVisualRect.toString();
+  }
+
+  const LayoutObject& m_object;
+  const PaintInvalidatorContext& m_context;
+  LayoutRect m_oldVisualRect;
+  bool m_neededVisualRectUpdate;
+};
+
+// For updates of visual rects (e.g. of scroll controls, caret, selection,etc.)
+// contained by an object.
+class FindVisualRectNeedingUpdateScope : FindVisualRectNeedingUpdateScopeBase {
+ public:
+  FindVisualRectNeedingUpdateScope(const LayoutObject& object,
+                                   const PaintInvalidatorContext& context,
+                                   const LayoutRect& oldVisualRect,
+                                   // Must be a reference to a rect that
+                                   // outlives this scope.
+                                   const LayoutRect& newVisualRect)
+      : FindVisualRectNeedingUpdateScopeBase(object, context, oldVisualRect),
+        m_newVisualRectRef(newVisualRect) {}
+
+  ~FindVisualRectNeedingUpdateScope() { checkVisualRect(m_newVisualRectRef); }
+
+ private:
+  const LayoutRect& m_newVisualRectRef;
+};
+
+// For updates of object visual rect and location.
+class FindObjectVisualRectNeedingUpdateScope
+    : FindVisualRectNeedingUpdateScopeBase {
+ public:
+  FindObjectVisualRectNeedingUpdateScope(const LayoutObject& object,
+                                         const PaintInvalidatorContext& context)
+      : FindVisualRectNeedingUpdateScopeBase(object,
+                                             context,
+                                             object.visualRect()),
+        m_oldLocation(ObjectPaintInvalidator(object).locationInBacking()) {}
+
+  ~FindObjectVisualRectNeedingUpdateScope() {
+    checkVisualRect(m_object.visualRect());
+    checkLocation();
+  }
+
+  void checkLocation() {
+    if (m_neededVisualRectUpdate)
+      return;
+    LayoutPoint newLocation =
+        ObjectPaintInvalidator(m_object).locationInBacking();
+    // Location of LayoutText and non-root SVG is location of the visual rect
+    // which have been checked above.
+    DCHECK(m_object.isText() || m_object.isSVGChild() ||
+           newLocation == m_oldLocation ||
+           // See checkVisualRect for the issue of approximation.
+           LayoutRect(-1, -1, 2, 2)
+               .contains(LayoutPoint(newLocation - m_oldLocation)))
+        << "Location changed without needing update"
+        << " object=" << m_object.debugName()
+        << " old=" << m_oldLocation.toString()
+        << " new=" << newLocation.toString();
+  }
+
+ private:
+  LayoutPoint m_oldLocation;
+};
+
+}  // namespace blink
+
+#endif  // DCHECK_IS_ON()
+
+#endif  // FindPaintOffsetAndVisualRectNeedingUpdate_h