gecko/layout/generic/ScrollbarActivity.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 http://mozilla.org/MPL/2.0/. */
#ifndef ScrollbarActivity_h___
#define ScrollbarActivity_h___
#include "nsCOMPtr.h"
#include "mozilla/TimeStamp.h"
class nsIContent;
class nsITimer;
class nsIAtom;
class nsIScrollableFrame;
namespace mozilla {
/**
* ScrollbarActivity
*
* This class manages scrollbar active state. When some activity occured
* the 'active' attribute of the both the horizontal scrollbar and vertical
* scrollbar is set.
* After a small amount of time of inactivity this attribute is unset from
* both scrollbars.
* Some css specific rules can affect the scrollbar, like showing/hiding it
* with a fade transition.
*
* Initial scrollbar activity needs to be reported by the scrollbar frame 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.
*
* ScrollbarActivity then wait until a timeout has expired or a new call to
* ActivityOccured() has been made. When the timeout expires ActivityFinished()
* is call and reset the active state.
*/
class ScrollbarActivity {
public:
ScrollbarActivity(nsIScrollableFrame* aScrollableFrame)
: mIsActive(false)
, mScrollableFrame(aScrollableFrame)
{}
void ActivityOccurred();
void ActivityFinished();
~ScrollbarActivity();
protected:
/*
* mIsActive is true once any type of activity occurent on the scrollable
* frame and until kScrollbarActivityFinishedDelay has expired.
* This does not reflect the value of the 'active' attributes on scrollbars.
*/
bool mIsActive;
/*
* Hold a reference to the scrollable frame in order to retrieve the
* horizontal and vertical scrollbar boxes where to set the 'active'
* attribute.
*/
nsIScrollableFrame* mScrollableFrame;
nsCOMPtr<nsITimer> mActivityFinishedTimer;
void SetIsActive(bool aNewActive);
enum { kScrollbarActivityFinishedDelay = 450 }; // milliseconds
static void ActivityFinishedTimerFired(nsITimer* aTimer, void* aSelf) {
reinterpret_cast<ScrollbarActivity*>(aSelf)->ActivityFinished();
}
void StartActivityFinishedTimer();
void CancelActivityFinishedTimer();
nsIContent* GetScrollbarContent(bool aVertical);
nsIContent* GetHorizontalScrollbar() {
return GetScrollbarContent(false);
}
nsIContent* GetVerticalScrollbar() {
return GetScrollbarContent(true);
}
};
} // namespace mozilla
#endif /* ScrollbarActivity_h___ */