tor-browser

The Tor Browser
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APZUtils.cpp (3527B)

      1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
      3 /* This Source Code Form is subject to the terms of the Mozilla Public
      4 * License, v. 2.0. If a copy of the MPL was not distributed with this
      5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
      6 
      7 #include "mozilla/layers/APZUtils.h"
      8 
      9 #include "mozilla/StaticPrefs_apz.h"
     10 #include "mozilla/StaticPrefs_layers.h"
     11 
     12 namespace mozilla {
     13 namespace layers {
     14 
     15 namespace apz {
     16 
     17 bool IsCloseToHorizontal(float aAngle, float aThreshold) {
     18  return (aAngle < aThreshold || aAngle > (M_PI - aThreshold));
     19 }
     20 
     21 bool IsCloseToVertical(float aAngle, float aThreshold) {
     22  return (fabs(aAngle - (M_PI / 2)) < aThreshold);
     23 }
     24 
     25 bool IsStuckAtBottom(gfxFloat aTranslation,
     26                     const LayerRectAbsolute& aInnerRange,
     27                     const LayerRectAbsolute& aOuterRange) {
     28  // The item will be stuck at the bottom if the async scroll delta is in
     29  // the range [aOuterRange.Y(), aInnerRange.Y()]. Since the translation
     30  // is negated with repect to the async scroll delta (i.e. scrolling down
     31  // produces a positive scroll delta and negative translation), we invert it
     32  // and check to see if it falls in the specified range.
     33  return aOuterRange.Y() <= -aTranslation && -aTranslation <= aInnerRange.Y();
     34 }
     35 
     36 bool IsStuckAtTop(gfxFloat aTranslation, const LayerRectAbsolute& aInnerRange,
     37                  const LayerRectAbsolute& aOuterRange) {
     38  // Same as IsStuckAtBottom, except we want to check for the range
     39  // [aInnerRange.YMost(), aOuterRange.YMost()].
     40  return aInnerRange.YMost() <= -aTranslation &&
     41         -aTranslation <= aOuterRange.YMost();
     42 }
     43 
     44 bool AboutToCheckerboard(const FrameMetrics& aPaintedMetrics,
     45                         const FrameMetrics& aCompositorMetrics) {
     46  // The main-thread code to compute the painted area can introduce some
     47  // rounding error due to multiple unit conversions, so we inflate the rect by
     48  // one app unit to account for that.
     49  CSSRect painted = aPaintedMetrics.GetDisplayPort() +
     50                    aPaintedMetrics.GetLayoutScrollOffset();
     51  painted.Inflate(CSSMargin::FromAppUnits(nsMargin(1, 1, 1, 1)));
     52 
     53  // Inflate the rect by the danger zone. See the description of the danger zone
     54  // prefs in AsyncPanZoomController.cpp for an explanation of this.
     55  CSSRect visible =
     56      CSSRect(aCompositorMetrics.GetVisualScrollOffset(),
     57              aCompositorMetrics.CalculateBoundedCompositedSizeInCssPixels());
     58  visible.Inflate(ScreenSize(StaticPrefs::apz_danger_zone_x(),
     59                             StaticPrefs::apz_danger_zone_y()) /
     60                  aCompositorMetrics.DisplayportPixelsPerCSSPixel());
     61 
     62  // Clamp both rects to the scrollable rect, because having either of those
     63  // exceed the scrollable rect doesn't make sense, and could lead to false
     64  // positives.
     65  painted = painted.Intersect(aPaintedMetrics.GetScrollableRect());
     66  visible = visible.Intersect(aPaintedMetrics.GetScrollableRect());
     67 
     68  return !painted.Contains(visible);
     69 }
     70 
     71 SideBits GetOverscrollSideBits(const ParentLayerPoint& aOverscrollAmount) {
     72  SideBits sides = SideBits::eNone;
     73 
     74  if (aOverscrollAmount.x < 0) {
     75    sides |= SideBits::eLeft;
     76  } else if (aOverscrollAmount.x > 0) {
     77    sides |= SideBits::eRight;
     78  }
     79 
     80  if (aOverscrollAmount.y < 0) {
     81    sides |= SideBits::eTop;
     82  } else if (aOverscrollAmount.y > 0) {
     83    sides |= SideBits::eBottom;
     84  }
     85 
     86  return sides;
     87 }
     88 
     89 }  // namespace apz
     90 }  // namespace layers
     91 }  // namespace mozilla