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/* 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 mozilla_ScrollTypes_h
#define mozilla_ScrollTypes_h
// Types used in main-thread scrolling interfaces such as nsIScrollableFrame.
namespace mozilla {
/**
* Scroll modes for main-thread scroll operations. These are mostly used
* by nsIScrollableFrame methods.
*
* When a scroll operation is requested, we ask for instant, smooth,
* smooth msd, or normal scrolling.
*
* |eSmooth| scrolls have a symmetrical acceleration and deceleration curve
* modeled with a set of splines that guarantee that the destination will be
* reached over a fixed time interval. |eSmooth| will only be smooth if smooth
* scrolling is actually enabled. This behavior is utilized by keyboard and
* mouse wheel scrolling events.
*
* |eSmoothMsd| implements a physically based model that approximates the
* behavior of a mass-spring-damper system. |eSmoothMsd| scrolls have a
* non-symmetrical acceleration and deceleration curve, can potentially
* overshoot the destination on intermediate frames, and complete over a
* variable time interval. |eSmoothMsd| will only be smooth if cssom-view
* smooth-scrolling is enabled.
*
* |eInstant| is always synchronous, |eNormal| can be asynchronous.
*
* If an |eInstant| scroll request happens while a |eSmooth| or async scroll is
* already in progress, the async scroll is interrupted and we instantly
* scroll to the destination.
*
* If an |eInstant| or |eSmooth| scroll request happens while a |eSmoothMsd|
* scroll is already in progress, the |eSmoothMsd| scroll is interrupted without
* first scrolling to the destination.
*/
enum class ScrollMode { Instant, Smooth, SmoothMsd, Normal };
/**
* When scrolling by a relative amount, we can choose various units.
*/
enum class ScrollUnit { DEVICE_PIXELS, LINES, PAGES, WHOLE };
} // namespace mozilla
#endif // mozilla_ScrollTypes_h