1 files changed, 138 insertions, 0 deletions
diff --git a/chromium/content/browser/renderer_host/overscroll_controller.h b/chromium/content/browser/renderer_host/overscroll_controller.h
new file mode 100644
index 00000000000..fc1fc5eb47f
--- /dev/null
+++ b/chromium/content/browser/renderer_host/overscroll_controller.h
@@ -0,0 +1,138 @@
+// Copyright (c) 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 CONTENT_BROWSER_RENDERER_HOST_OVERSCROLL_CONTROLLER_H_
+#define CONTENT_BROWSER_RENDERER_HOST_OVERSCROLL_CONTROLLER_H_
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "third_party/WebKit/public/web/WebInputEvent.h"
+
+namespace ui {
+struct LatencyInfo;
+}
+
+namespace content {
+
+class MockRenderWidgetHost;
+class OverscrollControllerDelegate;
+class RenderWidgetHostImpl;
+
+// Indicates the direction that the scroll is heading in relative to the screen,
+// with the top being NORTH.
+enum OverscrollMode {
+  OVERSCROLL_NONE,
+  OVERSCROLL_NORTH,
+  OVERSCROLL_SOUTH,
+  OVERSCROLL_WEST,
+  OVERSCROLL_EAST,
+  OVERSCROLL_COUNT
+};
+
+// When a page is scrolled beyond the scrollable region, it will trigger an
+// overscroll gesture. This controller receives the events that are dispatched
+// to the renderer, and the ACKs of events, and updates the overscroll gesture
+// status accordingly.
+class OverscrollController {
+ public:
+  // Creates an overscroll controller for the specified RenderWidgetHost.
+  // The RenderWidgetHost owns this overscroll controller.
+  explicit OverscrollController(RenderWidgetHostImpl* widget_host);
+  virtual ~OverscrollController();
+
+  // This must be called when dispatching any event from the
+  // RenderWidgetHostView so that the state of the overscroll gesture can be
+  // updated properly.
+  // Returns true if the event should be dispatched, false otherwise.
+  bool WillDispatchEvent(const WebKit::WebInputEvent& event,
+                         const ui::LatencyInfo& latency_info);
+
+  // This must be called when the ACK for any event comes in. This updates the
+  // overscroll gesture status as appropriate.
+  void ReceivedEventACK(const WebKit::WebInputEvent& event, bool processed);
+
+  // This must be called when a gesture event is filtered out and not sent to
+  // the renderer.
+  void DiscardingGestureEvent(const WebKit::WebGestureEvent& event);
+
+  OverscrollMode overscroll_mode() const { return overscroll_mode_; }
+
+  void set_delegate(OverscrollControllerDelegate* delegate) {
+    delegate_ = delegate;
+  }
+
+  // Resets internal states.
+  void Reset();
+
+  // Cancels any in-progress overscroll (and calls OnOverscrollModeChange on the
+  // delegate if necessary), and resets internal states.
+  void Cancel();
+
+ private:
+  friend class MockRenderWidgetHost;
+
+  // Different scrolling states.
+  enum ScrollState {
+    STATE_UNKNOWN,
+    STATE_PENDING,
+    STATE_CONTENT_SCROLLING,
+    STATE_OVERSCROLLING,
+  };
+
+  // Returns true if the event indicates that the in-progress overscroll gesture
+  // can now be completed.
+  bool DispatchEventCompletesAction(
+      const WebKit::WebInputEvent& event) const;
+
+  // Returns true to indicate that dispatching the event should reset the
+  // overscroll gesture status.
+  bool DispatchEventResetsState(const WebKit::WebInputEvent& event) const;
+
+  // Processes an event and updates internal state for overscroll.
+  void ProcessEventForOverscroll(const WebKit::WebInputEvent& event);
+
+  // Processes horizontal overscroll. This can update both the overscroll mode
+  // and the over scroll amount (i.e. |overscroll_mode_|, |overscroll_delta_x_|
+  // and |overscroll_delta_y_|).
+  void ProcessOverscroll(float delta_x, float delta_y);
+
+  // Completes the desired action from the current gesture.
+  void CompleteAction();
+
+  // Sets the overscroll mode (and triggers callback in the delegate when
+  // appropriate).
+  void SetOverscrollMode(OverscrollMode new_mode);
+
+  // Returns whether the input event should be forwarded to the
+  // RenderWidgetHost.
+  bool ShouldForwardToHost(const WebKit::WebInputEvent& event) const;
+
+  // The RenderWidgetHost that owns this overscroll controller.
+  RenderWidgetHostImpl* render_widget_host_;
+
+  // The current state of overscroll gesture.
+  OverscrollMode overscroll_mode_;
+
+  // Used to keep track of the scrolling state.
+  // If scrolling starts, and some scroll events are consumed at the beginning
+  // of the scroll (i.e. some content on the web-page was scrolled), then do not
+  // process any of the subsequent scroll events for generating overscroll
+  // gestures.
+  ScrollState scroll_state_;
+
+  // The amount of overscroll in progress. These values are invalid when
+  // |overscroll_mode_| is set to OVERSCROLL_NONE.
+  float overscroll_delta_x_;
+  float overscroll_delta_y_;
+
+  // The delegate that receives the overscroll updates. The delegate is not
+  // owned by this controller.
+  OverscrollControllerDelegate* delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(OverscrollController);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_OVERSCROLL_CONTROLLER_H_