Add support for calculating the position of the top controls in the cc layer.

cc/top_controls_manager.h

+// Copyright 2012 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 CC_TOP_CONTROLS_MANAGER_H_
+#define CC_TOP_CONTROLS_MANAGER_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "cc/layer_impl.h"
+#include "ui/gfx/size.h"
+#include "ui/gfx/vector2d_f.h"
+
+namespace base {
+class TimeTicks;
+}
+
+namespace cc {
+
+class LayerTreeImpl;
+class TopControlsAnimation;
+
+class TopControlsDelegate {

[jamesr, 2012/12/19 22:56:29]

this should have a protected destructor since it wouldn't make any sense for
someone to delete this class via a pointer to one of these.

our naming convention is that this is a "...Client", not Delegate.

can you put this in its own header? then layer_tree_host_impl.h wouldn't have to
#include this file

[Ted C, 2012/12/20 00:42:39]

Done.

+ public:
+  virtual void setNeedsRedraw() = 0;
+  virtual void setNeedsUpdateDrawProperties() = 0;
+  virtual LayerTreeImpl* activeTree() = 0;
+};
+
+// Manages the position of the top controls.
+class TopControlsManager {
+ public:
+  static scoped_ptr<TopControlsManager> Create(TopControlsDelegate* delegate,
+                                               float top_controls_height);
+  virtual ~TopControlsManager();
+
+  float controls_top_offset() { return controls_top_offset_; }
+  float content_top_offset() { return content_top_offset_; }
+  float is_overlay_mode() { return is_overlay_mode_; }
+  TopControlsAnimation* animation() { return top_controls_animation_.get(); }
+
+  void UpdateDrawPositions();
+
+  void ScrollBegin();
+  gfx::Vector2dF ScrollBy(const gfx::Vector2dF pending_delta);
+  void ScrollEnd();
+
+  void Animate(base::TimeTicks monotonic_time);
+
+ protected:
+  TopControlsManager(TopControlsDelegate* delegate, float top_controls_height);
+
+ private:
+  gfx::Vector2dF ScrollInternal(const gfx::Vector2dF pending_delta);
+  void ResetAnimations();
+  LayerImpl* RootScrollLayer();
+  float RootScrollLayerTotalScrollY();
+  void StartAnimationIfNecessary();
+  void StartAutoHideAnimation(int64 triggered_time);
+
+  base::WeakPtrFactory<TopControlsManager> weak_ptr_factory_;
+
+  TopControlsDelegate* delegate_;  // owned by this.
+

[jamesr, 2012/12/19 22:56:29]

I don't think this comment can be right - we never delete the delegate with this
pointer, nor would it make a lot of sense to do so

[Ted C, 2012/12/20 00:42:39]

Yeah...poorly worded.  I meant the delegate is the owner of "this" being the
TopControlsManager.

+  scoped_ptr<TopControlsAnimation> top_controls_animation_;
+  bool is_overlay_mode_;
+  float controls_top_offset_;
+  float content_top_offset_;
+  float top_controls_height_;
+  int64 top_controls_auto_hide_trigger_time_;
+  bool scroll_readjustment_enabled_;
+  float previous_root_scroll_offset_;
+
+  DISALLOW_COPY_AND_ASSIGN(TopControlsManager);
+};
+
+}  // namespace cc
+
+#endif  // CC_TOP_CONTROLS_MANAGER_H_