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// Copyright 2014 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 "base/macros.h"
#include "ui/android/ui_android_export.h"
#include "ui/gfx/geometry/size_f.h"
#include "ui/gfx/geometry/vector2d_f.h"
// A Java counterpart will be generated for this enum.
enum OverscrollAction { NONE = 0, PULL_TO_REFRESH = 1, HISTORY_NAVIGATION = 2 };
namespace cc {
struct OverscrollBehavior;
namespace ui {
class OverscrollRefreshHandler;
// Simple pull-to-refresh styled effect. Listens to scroll events, conditionally
// activating when:
// 1) The scroll begins when the page's root layer 1) has no vertical scroll
// offset and 2) lacks the overflow-y:hidden property.
// 2) The page doesn't consume the initial scroll events.
// 3) The initial scroll direction is upward.
// The actuall pull response, animation and action are delegated to the
// provided refresh handler.
class UI_ANDROID_EXPORT OverscrollRefresh {
// Minmum number of overscrolling pull events required to activate the effect.
// Useful for avoiding accidental triggering when a scroll janks (is delayed),
// capping the impulse per event.
enum { kMinPullsToActivate = 3 };
explicit OverscrollRefresh(OverscrollRefreshHandler* handler);
virtual ~OverscrollRefresh();
// Scroll event stream listening methods.
void OnScrollBegin();
// Returns whether the refresh was activated.
void OnScrollEnd(const gfx::Vector2dF& velocity);
// Scroll ack listener. The effect will only be activated if |can_navigate|
// is true which happens when the scroll update is not consumed and the
// overscroll_behavior on y axis is 'auto'.
// This method is made virtual for mocking.
virtual void OnOverscrolled(
const cc::OverscrollBehavior& overscroll_behavior);
// Returns true if the effect has consumed the |scroll_delta|.
bool WillHandleScrollUpdate(const gfx::Vector2dF& scroll_delta);
// Release the effect (if active), preventing any associated refresh action.
void ReleaseWithoutActivation();
// Notify the effect of the latest scroll offset and overflow properties.
// The effect will be disabled when the offset is non-zero or overflow is
// hidden. Note: All dimensions are in device pixels.
void OnFrameUpdated(const gfx::Vector2dF& content_scroll_offset,
bool root_overflow_y_hidden);
// Reset the effect to its inactive state, immediately detaching and
// disabling any active effects.
// This method is made virtual for mocking.
virtual void Reset();
// Returns true if the refresh effect is either being manipulated or animated.
// This method is made virtual for mocking.
virtual bool IsActive() const;
// Returns true if the effect is waiting for an unconsumed scroll to start.
// This method is made virtual for mocking.
virtual bool IsAwaitingScrollUpdateAck() const;
// This constructor is for mocking only.
void Release(bool allow_refresh);
bool scrolled_to_top_;
// True if the content y offset was zero before scroll began. Overscroll
// should not be triggered for the scroll that started from non-zero offset.
bool top_at_scroll_start_;
bool overflow_y_hidden_;
enum ScrollConsumptionState {
} scroll_consumption_state_;
gfx::Vector2dF cumulative_scroll_;
OverscrollRefreshHandler* const handler_;
} // namespace ui