/* 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_ScrollOrigin_h_
#define mozilla_ScrollOrigin_h_

#include "mozilla/DefineEnum.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.
MOZ_DEFINE_ENUM_CLASS_WITH_BASE_AND_TOSTRING(
    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.
        None,

        // This is a default value that we use when we don't know of a more
        // specific value that we can use.
        NotSpecified,
        // The scroll came from APZ code.
        Apz,
        // The scroll came from an attempt at restoring a scroll position saved
        // in the bfcache or history.
        Restore,
        // 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.
        Relative,
        // The scroll came from an attempt by the main thread to re-clamp the
        // scroll position after a reflow.
        Clamp,

        // 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.
        Other,
        // The scroll was originated by pixel-scrolling input device (e.g.
        // precision mouse wheel).
        Pixels,
        // The scroll was originated by a line-scrolling input device (e.g.
        // up/down keyboard buttons).
        Lines,
        // The scroll was originated by a page-scrolling input device (e.g.
        // pgup/ pgdn keyboard buttons).
        Pages,
        // The scroll was originated by a mousewheel that scrolls by lines.
        MouseWheel,
        // The scroll was originated by moving the scrollbars.
        Scrollbars));

}  // namespace mozilla

#endif  // mozilla_ScrollOrigin_h_
