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// Copyright 2020 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 THIRD_PARTY_BLINK_RENDERER_PLATFORM_WIDGET_INPUT_OVERSCROLL_BOUNCE_CONTROLLER_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_WIDGET_INPUT_OVERSCROLL_BOUNCE_CONTROLLER_H_
#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "cc/input/input_handler.h"
#include "cc/input/overscroll_behavior.h"
#include "cc/input/scroll_elasticity_helper.h"
#include "third_party/blink/public/common/input/web_gesture_event.h"
#include "third_party/blink/public/platform/input/elastic_overscroll_controller.h"
namespace blink {
// The overbounce version of elastic overscrolling mimics Windows style
// overscroll animations.
class BLINK_PLATFORM_EXPORT OverscrollBounceController
: public ElasticOverscrollController {
public:
explicit OverscrollBounceController(cc::ScrollElasticityHelper* helper);
~OverscrollBounceController() override;
base::WeakPtr<ElasticOverscrollController> GetWeakPtr() override;
void ObserveGestureEventAndResult(
const blink::WebGestureEvent& gesture_event,
const cc::InputHandlerScrollResult& scroll_result) override;
void Animate(base::TimeTicks time) override;
void ReconcileStretchAndScroll() override;
gfx::Vector2d OverscrollBounceDistance(
const gfx::Vector2dF& distance_overscrolled,
const gfx::Size& scroller_bounds) const;
private:
void ObserveRealScrollBegin(const blink::WebGestureEvent& gesture_event);
void ObserveRealScrollEnd();
gfx::Vector2dF OverscrollBoundary(const gfx::Size& scroller_bounds) const;
void EnterStateActiveScroll();
void OverscrollIfNecessary(const gfx::Vector2dF& overscroll_delta);
void ObserveScrollUpdate(const gfx::Vector2dF& unused_scroll_delta);
enum State {
// The initial state, during which the overscroll amount is zero.
kStateInactive,
// ActiveScroll indicates that this controller is listening to future GSU
// events, and those events may or may not update the overscroll amount.
// This occurs when the user is actively panning either via a touchscreen or
// touchpad, or is an active fling that has not triggered an overscroll.
kStateActiveScroll,
};
State state_;
cc::ScrollElasticityHelper* helper_;
// This is the accumulated raw delta in pixels that's been overscrolled. It
// will be fed into a tanh function (ranging [0, 2]) that decides the stretch
// bounds.
gfx::Vector2dF accumulated_scroll_delta_;
base::WeakPtrFactory<OverscrollBounceController> weak_factory_;
DISALLOW_COPY_AND_ASSIGN(OverscrollBounceController);
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_WIDGET_INPUT_OVERSCROLL_BOUNCE_CONTROLLER_H_
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