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// Copyright 2018 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.
#include <memory>
#include "base/time/time.h"
#include "cc/cc_export.h"
#include "ui/gfx/geometry/vector2d_f.h"
namespace cc {
namespace test {
class SnapFlingControllerTest;
class SnapFlingCurve;
// A client that provides information to the controller. It also executes the
// scroll operations and requests animation frames. All the inputs and outputs
// are in the same coordinate space.
class SnapFlingClient {
virtual bool GetSnapFlingInfo(const gfx::Vector2dF& natural_displacement,
gfx::Vector2dF* initial_offset,
gfx::Vector2dF* target_offset) const = 0;
virtual gfx::Vector2dF ScrollByForSnapFling(const gfx::Vector2dF& delta) = 0;
virtual void ScrollEndForSnapFling() = 0;
virtual void RequestAnimationForSnapFling() = 0;
// SnapFlingController ensures that an incoming fling event (or inertial-phase
// scroll event) would land on a snap position if there is a valid one nearby.
// It takes an input event, filters it if it conflicts with the current fling,
// or generates a curve if the SnapFlingClient finds a valid snap position.
// It also animates the curve by notifying the client to scroll when clock
// ticks.
class CC_EXPORT SnapFlingController {
enum class GestureScrollType { kBegin, kUpdate, kEnd };
struct GestureScrollUpdateInfo {
gfx::Vector2dF delta;
bool is_in_inertial_phase;
base::TimeTicks event_time;
explicit SnapFlingController(SnapFlingClient* client);
static std::unique_ptr<SnapFlingController> CreateForTests(
SnapFlingClient* client,
std::unique_ptr<SnapFlingCurve> curve);
// Returns true if the event should be consumed for snapping and should not be
// processed further.
bool FilterEventForSnap(GestureScrollType gesture_scroll_type);
// Creates the snap fling curve from the first inertial GSU. Returns true if
// the event if a snap fling curve has been created and the event should not
// be processed further.
bool HandleGestureScrollUpdate(const GestureScrollUpdateInfo& info);
// Notifies the snap fling controller to update or end the scroll animation.
void Animate(base::TimeTicks time);
friend class test::SnapFlingControllerTest;
enum class State {
// We haven't received an inertial GSU in this scroll sequence.
// We have received an inertial GSU but decided not to snap for this scroll
// sequence.
// We have received an inertial GSU and decided to snap and animate it for
// this scroll sequence. So subsequent GSUs and GSE in the scroll sequence
// are consumed for snapping.
// The animation of the snap fling has finished for this scroll sequence.
// Subsequent GSUs and GSE in the scroll sequence are ignored.
SnapFlingController(SnapFlingClient* client,
std::unique_ptr<SnapFlingCurve> curve);
void ClearSnapFling();
// Sets the |curve_| to |curve| and the |state| to |kActive|.
void SetCurveForTest(std::unique_ptr<SnapFlingCurve> curve);
void SetActiveStateForTest() { state_ = State::kActive; }
SnapFlingClient* client_;
State state_ = State::kIdle;
std::unique_ptr<SnapFlingCurve> curve_;
} // namespace cc