Invalidate row/section for backgrounds when cell's geometry changes

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

+// 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.
+
+#ifndef TableCellPaintInvalidator_h
+#define TableCellPaintInvalidator_h
+
+#include "platform/graphics/PaintInvalidationReason.h"
+#include "platform/wtf/Allocator.h"
+
+namespace blink {
+
+class LayoutTableCell;
+struct PaintInvalidatorContext;
+
+class TableCellPaintInvalidator {

[wkorman, 2017/04/27 22:30:23]

Add class header doc noting why we need a table cell specific paint invalidator.

[Xianzhu, 2017/04/28 00:31:06]

I tried to add header doc but all would be implementation details that the
callers don't care about. This is like a private/protected overriding method
whose reason is explained by the implementation. Actually if we didn't want to
separate paint invalidation code from layout code, this would be just in
LayoutTableCell::invalidatePaintIfNeeded().

[wkorman, 2017/04/28 02:24:54]

Yeah, this makes sense. Could add a brief header comment essentially just
stating that then, but am ok either way.

We did similar for PropertyTreeManager which is basically a private class used
by PaintArtifactCompositor:

https://cs.chromium.org/chromium/src/third_party/WebKit/Source/platform/graph...

+  STACK_ALLOCATED();
+
+ public:
+  TableCellPaintInvalidator(const LayoutTableCell& cell,
+                            const PaintInvalidatorContext& context)
+      : cell_(cell), context_(context) {}
+
+  PaintInvalidationReason InvalidatePaintIfNeeded();
+
+ private:
+  const LayoutTableCell& cell_;
+  const PaintInvalidatorContext& context_;
+};
+
+}  // namespace blink
+
+#endif