layout/generic/ScrollOrigin.h

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #ifndef mozilla_ScrollOrigin_h_
   6 #define mozilla_ScrollOrigin_h_
   7
   8 namespace mozilla {
   9
  10 // A scroll origin is a bit of a combination of "what part of the code caused
  11 // this scroll" and "what special properties does this scroll have, in the
  12 // context of what caused it". See specific comments below.
  13 enum class ScrollOrigin : uint8_t {
  14   // This is used as an initial value for the "LastScrollOrigin" property on
  15   // scrollable frames. It is not intended to be an actual scroll origin, but
  16   // a sentinel value that indicates that there was no "last scroll". It is
  17   // used similarly for the "LastSmoothScrollOrigin" property, to indicate
  18   // no smooth scroll is in progress.
  19   None,
  20
  21   // This is a default value that we use when we don't know of a more specific
  22   // value that we can use.
  23   NotSpecified,
  24   // The scroll came from APZ code.
  25   Apz,
  26   // The scroll came from an attempt at restoring a scroll position saved in
  27   // the bfcache or history.
  28   Restore,
  29   // The scroll came from a "relative" scroll method like ScrollBy, where the
  30   // scroll destination is indicated by a delta from the current position
  31   // instead of an absolute value.
  32   Relative,
  33   // The scroll came from an attempt by the main thread to re-clamp the scroll
  34   // position after a reflow.
  35   Clamp,
  36
  37   // The following scroll origins also are associated with prefs of the form
  38   //   general.smoothScroll.<origin>(.*)
  39   // e.g. general.smoothScroll.lines indicates whether or not a scroll with
  40   // origin Lines will be animated smoothly, and e.g. subprefs like
  41   // general.smoothScroll.lines.durationMinMS control some of the animation
  42   // timing behavior.
  43
  44   // The scroll came from some sort of input that's not one of the above or
  45   // below values. Generally this means it came from a content-exposed API,
  46   // like window.scrollTo, but may also be from other sources that don't need
  47   // any particular special handling.
  48   Other,
  49   // The scroll was originated by pixel-scrolling input device (e.g. precision
  50   // mouse wheel).
  51   Pixels,
  52   // The scroll was originated by a line-scrolling input device (e.g. up/down
  53   // keyboard buttons).
  54   Lines,
  55   // The scroll was originated by a page-scrolling input device (e.g. pgup/
  56   // pgdn keyboard buttons).
  57   Pages,
  58   // The scroll was originated by a mousewheel that scrolls by lines.
  59   MouseWheel,
  60   // The scroll was originated by moving the scrollbars.
  61   Scrollbars,
  62 };
  63
  64 }  // namespace mozilla
  65
  66 #endif  // mozilla_ScrollOrigin_h_