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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
#ifndef ScrollbarActivity_h___
#define ScrollbarActivity_h___
#include "mozilla/Assertions.h"
#include "nsCOMPtr.h"
#include "nsIDOMEventListener.h"
class nsIContent;
class nsIScrollbarMediator;
class nsITimer;
namespace mozilla {
namespace dom {
class Element;
class EventTarget;
} // namespace dom
namespace layout {
* ScrollbarActivity
* This class manages scrollbar behavior that imitates the native Mac OS X
* Lion overlay scrollbar behavior: Scrollbars are only shown while "scrollbar
* activity" occurs, and they're hidden with a fade animation after a short
* delay.
* Scrollbar activity has these states:
* - inactive:
* Scrollbars are hidden.
* - ongoing activity:
* Scrollbars are visible and being operated on in some way, for example
* because they're hovered or pressed.
* - active, but waiting for fade out
* Scrollbars are still completely visible but are about to fade away.
* - fading out
* Scrollbars are subject to a fade-out animation.
* Initial scrollbar activity needs to be reported by the scrollbar holder that
* owns the ScrollbarActivity instance. This needs to happen via a call to
* ActivityOccurred(), for example when the current scroll position or the size
* of the scroll area changes.
* As soon as scrollbars are visible, the ScrollbarActivity class manages the
* rest of the activity behavior: It ensures that mouse motions inside the
* scroll area keep the scrollbars visible, and that scrollbars don't fade away
* while they're being hovered / dragged. It also sets a sticky hover attribute
* on the most recently hovered scrollbar.
* ScrollbarActivity falls into hibernation after the scrollbars have faded
* out. It only starts acting after the next call to ActivityOccurred() /
* ActivityStarted().
class ScrollbarActivity final : public nsIDOMEventListener {
explicit ScrollbarActivity(nsIScrollbarMediator* aScrollableFrame)
: mScrollableFrame(aScrollableFrame) {
void Destroy();
void ActivityOccurred();
void ActivityStarted();
void ActivityStopped();
bool IsActive() const { return mNestedActivityCounter; }
virtual ~ScrollbarActivity() = default;
void StartFadeTimer();
void CancelFadeTimer();
void BeginFade();
void HandleEventForScrollbar(const nsAString& aType, nsIContent* aTarget,
dom::Element* aScrollbar,
bool* aStoredHoverState);
void StartListeningForScrollbarEvents();
void StartListeningForScrollAreaEvents();
void StopListeningForScrollbarEvents();
void StopListeningForScrollAreaEvents();
void AddScrollbarEventListeners(dom::EventTarget* aScrollbar);
void RemoveScrollbarEventListeners(dom::EventTarget* aScrollbar);
void HoveredScrollbar(dom::Element* aScrollbar);
dom::Element* GetScrollbarContent(bool aVertical);
dom::Element* GetHorizontalScrollbar() { return GetScrollbarContent(false); }
dom::Element* GetVerticalScrollbar() { return GetScrollbarContent(true); }
nsIScrollbarMediator* const mScrollableFrame;
nsCOMPtr<dom::EventTarget> mHorizontalScrollbar; // null while inactive
nsCOMPtr<dom::EventTarget> mVerticalScrollbar; // null while inactive
nsCOMPtr<nsITimer> mFadeTimer;
uint32_t mNestedActivityCounter = 0;
// This boolean is true from the point activity starts to the point BeginFade
// runs, and effectively reflects the "active" attribute of the scrollbar.
bool mScrollbarEffectivelyVisible = false;
bool mListeningForScrollbarEvents = false;
bool mListeningForScrollAreaEvents = false;
bool mHScrollbarHovered = false;
bool mVScrollbarHovered = false;
} // namespace layout
} // namespace mozilla
#endif /* ScrollbarActivity_h___ */