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/DefineEnum.h"
   9 #include "mozilla/TypedEnumBits.h"
  10
  11 // Types used in main-thread scrolling interfaces such as ScrollContainerFrame.
  12
  13 namespace mozilla {
  14
  15 /**
  16  * Scroll modes for main-thread scroll operations. These are mostly used
  17  * by ScrollContainerFrame methods.
  18  *
  19  * When a scroll operation is requested, we ask for instant, smooth,
  20  * smooth msd, or normal scrolling.
  21  *
  22  * |Smooth| scrolls have a symmetrical acceleration and deceleration curve
  23  * modeled with a set of splines that guarantee that the destination will be
  24  * reached over a fixed time interval.  |Smooth| will only be smooth if smooth
  25  * scrolling is actually enabled.  This behavior is utilized by keyboard and
  26  * mouse wheel scrolling events.
  27  *
  28  * |SmoothMsd| implements a physically based model that approximates the
  29  * behavior of a mass-spring-damper system.  |SmoothMsd| scrolls have a
  30  * non-symmetrical acceleration and deceleration curve, can potentially
  31  * overshoot the destination on intermediate frames, and complete over a
  32  * variable time interval.  |SmoothMsd| will only be smooth if cssom-view
  33  * smooth-scrolling is enabled.
  34  *
  35  * |Instant| is always synchronous, |Normal| can be asynchronous.
  36  *
  37  * If an |Instant| scroll request happens while a |Smooth| or async scroll is
  38  * already in progress, the async scroll is interrupted and we instantly
  39  * scroll to the destination.
  40  *
  41  * If an |Instant| or |Smooth| scroll request happens while a |SmoothMsd|
  42  * scroll is already in progress, the |SmoothMsd| scroll is interrupted without
  43  * first scrolling to the destination.
  44  */
  45 MOZ_DEFINE_ENUM_CLASS_WITH_BASE_AND_TOSTRING(ScrollMode, uint8_t,
  46                                              (Instant, Smooth, SmoothMsd,
  47                                               Normal));
  48
  49 /**
  50  * When scrolling by a relative amount, we can choose various units.
  51  */
  52 enum class ScrollUnit { DEVICE_PIXELS, LINES, PAGES, WHOLE };
  53
  54 /**
  55  * Representing whether there's an on-going animation in APZC and it was
  56  * triggered by script or by user input.
  57  */
  58 enum class APZScrollAnimationType {
  59   No,                   // No animation.
  60   TriggeredByScript,    // Animation triggered by script.
  61   TriggeredByUserInput  // Animation triggered by user input.
  62 };
  63
  64 enum class ScrollSnapFlags : uint8_t {
  65   Disabled = 0,
  66   // https://drafts.csswg.org/css-scroll-snap/#intended-end-position
  67   IntendedEndPosition = 1 << 0,
  68   // https://drafts.csswg.org/css-scroll-snap/#intended-direction
  69   IntendedDirection = 1 << 1
  70 };
  71
  72 MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(ScrollSnapFlags);
  73
  74 }  // namespace mozilla
  75
  76 #endif  // mozilla_ScrollTypes_h