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// 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 RenderWidgetHostViewAuraOverscrollTest;
class OverscrollControllerDelegate;
// 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
};
// 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:
OverscrollController();
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 was handled, in which case
// further processing should cease.
bool WillHandleEvent(const blink::WebInputEvent& event);
// This must be called when the ACK for any event comes in. This updates the
// overscroll gesture status as appropriate.
void ReceivedEventACK(const blink::WebInputEvent& event, bool processed);
// This must be called when a gesture event is filtered out and not sent to
// the renderer.
void DiscardingGestureEvent(const blink::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 RenderWidgetHostViewAuraOverscrollTest;
// 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 blink::WebInputEvent& event) const;
// Returns true to indicate that dispatching the event should reset the
// overscroll gesture status.
bool DispatchEventResetsState(const blink::WebInputEvent& event) const;
// Processes an event to update the internal state for overscroll. Returns
// true if the state is updated, false otherwise.
bool ProcessEventForOverscroll(const blink::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_|). Returns true if overscroll was handled by the
// delegate.
bool ProcessOverscroll(float delta_x,
float delta_y,
blink::WebInputEvent::Type event_type);
// 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);
// 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_
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