layout/base/ScrollTypes.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_ScrollTypes_h
   6 #define mozilla_ScrollTypes_h
   7
   8 #include "mozilla/TypedEnumBits.h"
   9
  10 // Types used in main-thread scrolling interfaces such as nsIScrollableFrame.
  11
  12 namespace mozilla {
  13
  14 /**
  15  * Scroll modes for main-thread scroll operations. These are mostly used
  16  * by nsIScrollableFrame methods.
  17  *
  18  * When a scroll operation is requested, we ask for instant, smooth,
  19  * smooth msd, or normal scrolling.
  20  *
  21  * |Smooth| scrolls have a symmetrical acceleration and deceleration curve
  22  * modeled with a set of splines that guarantee that the destination will be
  23  * reached over a fixed time interval.  |Smooth| will only be smooth if smooth
  24  * scrolling is actually enabled.  This behavior is utilized by keyboard and
  25  * mouse wheel scrolling events.
  26  *
  27  * |SmoothMsd| implements a physically based model that approximates the
  28  * behavior of a mass-spring-damper system.  |SmoothMsd| scrolls have a
  29  * non-symmetrical acceleration and deceleration curve, can potentially
  30  * overshoot the destination on intermediate frames, and complete over a
  31  * variable time interval.  |SmoothMsd| will only be smooth if cssom-view
  32  * smooth-scrolling is enabled.
  33  *
  34  * |Instant| is always synchronous, |Normal| can be asynchronous.
  35  *
  36  * If an |Instant| scroll request happens while a |Smooth| or async scroll is
  37  * already in progress, the async scroll is interrupted and we instantly
  38  * scroll to the destination.
  39  *
  40  * If an |Instant| or |Smooth| scroll request happens while a |SmoothMsd|
  41  * scroll is already in progress, the |SmoothMsd| scroll is interrupted without
  42  * first scrolling to the destination.
  43  */
  44 enum class ScrollMode { Instant, Smooth, SmoothMsd, Normal };
  45
  46 /**
  47  * When scrolling by a relative amount, we can choose various units.
  48  */
  49 enum class ScrollUnit { DEVICE_PIXELS, LINES, PAGES, WHOLE };
  50
  51 /**
  52  * Representing whether there's an on-going animation in APZC and it was
  53  * triggered by script or by user input.
  54  */
  55 enum class APZScrollAnimationType {
  56   No,                   // No animation.
  57   TriggeredByScript,    // Animation triggered by script.
  58   TriggeredByUserInput  // Animation triggered by user input.
  59 };
  60
  61 enum class ScrollSnapFlags : uint8_t {
  62   Disabled = 0,
  63   // https://drafts.csswg.org/css-scroll-snap/#intended-end-position
  64   IntendedEndPosition = 1 << 0,
  65   // https://drafts.csswg.org/css-scroll-snap/#intended-direction
  66   IntendedDirection = 1 << 1
  67 };
  68
  69 MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(ScrollSnapFlags);
  70
  71 }  // namespace mozilla
  72
  73 #endif  // mozilla_ScrollTypes_h