Make View::Paint use ui::PaintRecorder to access PaintContext's canvas

ui/compositor/paint_context.h

Index: ui/compositor/paint_context.h
diff --git a/ui/compositor/paint_context.h b/ui/compositor/paint_context.h
new file mode 100644
index 0000000000000000000000000000000000000000..fd3ecd4f4a5926e619f6f714905fd485176edfab
--- /dev/null
+++ b/ui/compositor/paint_context.h
@@ -0,0 +1,104 @@
+// Copyright 2015 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 UI_COMPOSITOR_PAINT_CONTEXT_H_
+#define UI_COMPOSITOR_PAINT_CONTEXT_H_
+
+#include "base/logging.h"
+#include "ui/compositor/compositor_export.h"
+#include "ui/gfx/geometry/rect.h"
+
+namespace gfx {
+class Canvas;
+}
+
+namespace ui {
+class PaintRecorder;
+
+class COMPOSITOR_EXPORT PaintContext {
+ public:
+  // Construct a PaintContext that can only re-paint the area in the
+  // |invalidation|.
+  PaintContext(gfx::Canvas* canvas, const gfx::Rect& invalidation)
+      : canvas_(canvas), invalidation_(invalidation) {
+#if DCHECK_IS_ON()
+    root_visited_ = nullptr;
+#endif
+  }
+
+  // Construct a PaintContext that will re-paint everything (no consideration
+  // for invalidation).
+  explicit PaintContext(gfx::Canvas* canvas)
+      : PaintContext(canvas, gfx::Rect()) {}
+
+  ~PaintContext() {}
+
+  // Clone a PaintContext with an additional |offset|.
+  PaintContext CloneWithPaintOffset(const gfx::Vector2d& offset) const {
+    return PaintContext(*this, offset);
+  }
+
+  // Clone a PaintContext that has no consideration for invalidation.
+  PaintContext CloneWithoutInvalidation() const {
+    return PaintContext(canvas_);
+  }
+
+  // TODO(danakj): Remove this once everything is painting to display lists.
+  gfx::Canvas* canvas() const { return canvas_; }
+
+  // When true, IsRectInvalidated() can be called, otherwise its result would be
+  // invalid.
+  bool CanCheckInvalidated() const { return !invalidation_.IsEmpty(); }
+
+  // When true, the |bounds| touches an invalidated area, so should be
+  // re-painted. When false, re-painting can be skipped. Bounds should be in
+  // the local space with offsets up to the painting root in the PaintContext.
+  bool IsRectInvalidated(const gfx::Rect& bounds) const {
+    DCHECK(CanCheckInvalidated());
+    return invalidation_.Intersects(bounds + offset_);
+  }
+
+#if DCHECK_IS_ON()
+  void Visited(void* visited) const {
+    if (!root_visited_)
+      root_visited_ = visited;
+  }
+  void* RootVisited() const { return root_visited_; }
+  const gfx::Vector2d& PaintOffset() const { return offset_; }
+#endif
+
+ private:
+  // The PaintRecorder needs access to the internal canvas and friends, but we
+  // don't want to expose them on this class so that people must go through the
+  // recorder to access them.
+  friend class PaintRecorder;
+
+  // Clone a PaintContext with an additional |offset|.
+  PaintContext(const PaintContext& other, const gfx::Vector2d& offset)
+      : canvas_(other.canvas_),
+        invalidation_(other.invalidation_),
+        offset_(other.offset_ + offset) {
+#if DCHECK_IS_ON()
+    root_visited_ = other.root_visited_;
+#endif
+  }
+
+  gfx::Canvas* canvas_;
+  // Invalidation in the space of the paint root (ie the space of the layer
+  // backing the paint taking place).
+  gfx::Rect invalidation_;
+  // Offset from the PaintContext to the space of the paint root and the
+  // |invalidation_|.
+  gfx::Vector2d offset_;
+
+#if DCHECK_IS_ON()
+  // Used to verify that the |invalidation_| is only used to compare against
+  // rects in the same space.
+  mutable void* root_visited_;
+#endif
+};
+
+}  // namespace ui
+
+#endif  // UI_COMPOSITOR_PAINT_CONTEXT_H_