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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 */
#ifndef mozilla_ScrollOrigin_h_
#define mozilla_ScrollOrigin_h_
namespace mozilla {
// A scroll origin is a bit of a combination of "what part of the code caused
// this scroll" and "what special properties does this scroll have, in the
// context of what caused it". See specific comments below.
enum class ScrollOrigin : uint8_t {
// This is used as an initial value for the "LastScrollOrigin" property on
// scrollable frames. It is not intended to be an actual scroll origin, but
// a sentinel value that indicates that there was no "last scroll". It is
// used similarly for the "LastSmoothScrollOrigin" property, to indicate
// no smooth scroll is in progress.
// This is a default value that we use when we don't know of a more specific
// value that we can use.
// The scroll came from APZ code.
// The scroll came from an attempt at restoring a scroll position saved in
// the bfcache or history.
// The scroll came from a "relative" scroll method like ScrollBy, where the
// scroll destination is indicated by a delta from the current position
// instead of an absolute value.
// The scroll came from an attempt by the main thread to re-clamp the scroll
// position after a reflow.
// The following scroll origins also are associated with prefs of the form
// general.smoothScroll.<origin>(.*)
// e.g. general.smoothScroll.lines indicates whether or not a scroll with
// origin Lines will be animated smoothly, and e.g. subprefs like
// general.smoothScroll.lines.durationMinMS control some of the animation
// timing behavior.
// The scroll came from some sort of input that's not one of the above or
// below values. Generally this means it came from a content-exposed API,
// like window.scrollTo, but may also be from other sources that don't need
// any particular special handling.
// The scroll was originated by pixel-scrolling input device (e.g. precision
// mouse wheel).
// The scroll was originated by a line-scrolling input device (e.g. up/down
// keyboard buttons).
// The scroll was originated by a page-scrolling input device (e.g. pgup/
// pgdn keyboard buttons).
// The scroll was originated by a mousewheel that scrolls by lines.
// The scroll was originated by moving the scrollbars.
} // namespace mozilla
#endif // mozilla_ScrollOrigin_h_