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authorMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
committerMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
commit5f8de423f190bbb79a62f804151bc24824fa32d8 (patch)
tree10027f336435511475e392454359edea8e25895d /layout/generic/ScrollSnap.cpp
parent49ee0794b5d912db1f95dce6eb52d781dc210db5 (diff)
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Add m-esr52 at 52.6.0
Diffstat (limited to 'layout/generic/ScrollSnap.cpp')
-rw-r--r--layout/generic/ScrollSnap.cpp311
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diff --git a/layout/generic/ScrollSnap.cpp b/layout/generic/ScrollSnap.cpp
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+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#include "FrameMetrics.h"
+#include "ScrollSnap.h"
+#include "gfxPrefs.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Preferences.h"
+#include "nsLineLayout.h"
+
+namespace mozilla {
+
+using layers::ScrollSnapInfo;
+
+/**
+ * Stores candidate snapping edges.
+ */
+class SnappingEdgeCallback {
+public:
+ virtual void AddHorizontalEdge(nscoord aEdge) = 0;
+ virtual void AddVerticalEdge(nscoord aEdge) = 0;
+ virtual void AddHorizontalEdgeInterval(const nsRect &aScrollRange,
+ nscoord aInterval,
+ nscoord aOffset) = 0;
+ virtual void AddVerticalEdgeInterval(const nsRect &aScrollRange,
+ nscoord aInterval,
+ nscoord aOffset) = 0;
+};
+
+/**
+ * Keeps track of the current best edge to snap to. The criteria for
+ * adding an edge depends on the scrolling unit.
+ */
+class CalcSnapPoints : public SnappingEdgeCallback {
+public:
+ CalcSnapPoints(nsIScrollableFrame::ScrollUnit aUnit,
+ const nsPoint& aDestination,
+ const nsPoint& aStartPos);
+ virtual void AddHorizontalEdge(nscoord aEdge) override;
+ virtual void AddVerticalEdge(nscoord aEdge) override;
+ virtual void AddHorizontalEdgeInterval(const nsRect &aScrollRange,
+ nscoord aInterval, nscoord aOffset)
+ override;
+ virtual void AddVerticalEdgeInterval(const nsRect &aScrollRange,
+ nscoord aInterval, nscoord aOffset)
+ override;
+ void AddEdge(nscoord aEdge,
+ nscoord aDestination,
+ nscoord aStartPos,
+ nscoord aScrollingDirection,
+ nscoord* aBestEdge,
+ bool* aEdgeFound);
+ void AddEdgeInterval(nscoord aInterval,
+ nscoord aMinPos,
+ nscoord aMaxPos,
+ nscoord aOffset,
+ nscoord aDestination,
+ nscoord aStartPos,
+ nscoord aScrollingDirection,
+ nscoord* aBestEdge,
+ bool* aEdgeFound);
+ nsPoint GetBestEdge() const;
+protected:
+ nsIScrollableFrame::ScrollUnit mUnit;
+ nsPoint mDestination; // gives the position after scrolling but before snapping
+ nsPoint mStartPos; // gives the position before scrolling
+ nsIntPoint mScrollingDirection; // always -1, 0, or 1
+ nsPoint mBestEdge; // keeps track of the position of the current best edge
+ bool mHorizontalEdgeFound; // true if mBestEdge.x is storing a valid horizontal edge
+ bool mVerticalEdgeFound; // true if mBestEdge.y is storing a valid vertical edge
+};
+
+CalcSnapPoints::CalcSnapPoints(nsIScrollableFrame::ScrollUnit aUnit,
+ const nsPoint& aDestination,
+ const nsPoint& aStartPos)
+{
+ mUnit = aUnit;
+ mDestination = aDestination;
+ mStartPos = aStartPos;
+
+ nsPoint direction = aDestination - aStartPos;
+ mScrollingDirection = nsIntPoint(0,0);
+ if (direction.x < 0) {
+ mScrollingDirection.x = -1;
+ }
+ if (direction.x > 0) {
+ mScrollingDirection.x = 1;
+ }
+ if (direction.y < 0) {
+ mScrollingDirection.y = -1;
+ }
+ if (direction.y > 0) {
+ mScrollingDirection.y = 1;
+ }
+ mBestEdge = aDestination;
+ mHorizontalEdgeFound = false;
+ mVerticalEdgeFound = false;
+}
+
+nsPoint
+CalcSnapPoints::GetBestEdge() const
+{
+ return nsPoint(mVerticalEdgeFound ? mBestEdge.x : mStartPos.x,
+ mHorizontalEdgeFound ? mBestEdge.y : mStartPos.y);
+}
+
+void
+CalcSnapPoints::AddHorizontalEdge(nscoord aEdge)
+{
+ AddEdge(aEdge, mDestination.y, mStartPos.y, mScrollingDirection.y, &mBestEdge.y,
+ &mHorizontalEdgeFound);
+}
+
+void
+CalcSnapPoints::AddVerticalEdge(nscoord aEdge)
+{
+ AddEdge(aEdge, mDestination.x, mStartPos.x, mScrollingDirection.x, &mBestEdge.x,
+ &mVerticalEdgeFound);
+}
+
+void
+CalcSnapPoints::AddHorizontalEdgeInterval(const nsRect &aScrollRange,
+ nscoord aInterval, nscoord aOffset)
+{
+ AddEdgeInterval(aInterval, aScrollRange.y, aScrollRange.YMost(), aOffset,
+ mDestination.y, mStartPos.y, mScrollingDirection.y,
+ &mBestEdge.y, &mHorizontalEdgeFound);
+}
+
+void
+CalcSnapPoints::AddVerticalEdgeInterval(const nsRect &aScrollRange,
+ nscoord aInterval, nscoord aOffset)
+{
+ AddEdgeInterval(aInterval, aScrollRange.x, aScrollRange.XMost(), aOffset,
+ mDestination.x, mStartPos.x, mScrollingDirection.x,
+ &mBestEdge.x, &mVerticalEdgeFound);
+}
+
+void
+CalcSnapPoints::AddEdge(nscoord aEdge, nscoord aDestination, nscoord aStartPos,
+ nscoord aScrollingDirection, nscoord* aBestEdge,
+ bool *aEdgeFound)
+{
+ // nsIScrollableFrame::DEVICE_PIXELS indicates that we are releasing a drag
+ // gesture or any other user input event that sets an absolute scroll
+ // position. In this case, scroll snapping is expected to travel in any
+ // direction. Otherwise, we will restrict the direction of the scroll
+ // snapping movement based on aScrollingDirection.
+ if (mUnit != nsIScrollableFrame::DEVICE_PIXELS) {
+ // Unless DEVICE_PIXELS, we only want to snap to points ahead of the
+ // direction we are scrolling
+ if (aScrollingDirection == 0) {
+ // The scroll direction is neutral - will not hit a snap point.
+ return;
+ }
+ // nsIScrollableFrame::WHOLE indicates that we are navigating to "home" or
+ // "end". In this case, we will always select the first or last snap point
+ // regardless of the direction of the scroll. Otherwise, we will select
+ // scroll snapping points only in the direction specified by
+ // aScrollingDirection.
+ if (mUnit != nsIScrollableFrame::WHOLE) {
+ // Direction of the edge from the current position (before scrolling) in
+ // the direction of scrolling
+ nscoord direction = (aEdge - aStartPos) * aScrollingDirection;
+ if (direction <= 0) {
+ // The edge is not in the direction we are scrolling, skip it.
+ return;
+ }
+ }
+ }
+ if (!*aEdgeFound) {
+ *aBestEdge = aEdge;
+ *aEdgeFound = true;
+ return;
+ }
+ if (mUnit == nsIScrollableFrame::DEVICE_PIXELS ||
+ mUnit == nsIScrollableFrame::LINES) {
+ if (std::abs(aEdge - aDestination) < std::abs(*aBestEdge - aDestination)) {
+ *aBestEdge = aEdge;
+ }
+ } else if (mUnit == nsIScrollableFrame::PAGES) {
+ // distance to the edge from the scrolling destination in the direction of scrolling
+ nscoord overshoot = (aEdge - aDestination) * aScrollingDirection;
+ // distance to the current best edge from the scrolling destination in the direction of scrolling
+ nscoord curOvershoot = (*aBestEdge - aDestination) * aScrollingDirection;
+
+ // edges between the current position and the scrolling destination are favoured
+ // to preserve context
+ if (overshoot < 0 && (overshoot > curOvershoot || curOvershoot >= 0)) {
+ *aBestEdge = aEdge;
+ }
+ // if there are no edges between the current position and the scrolling destination
+ // the closest edge beyond the destination is used
+ if (overshoot > 0 && overshoot < curOvershoot) {
+ *aBestEdge = aEdge;
+ }
+ } else if (mUnit == nsIScrollableFrame::WHOLE) {
+ // the edge closest to the top/bottom/left/right is used, depending on scrolling direction
+ if (aScrollingDirection > 0 && aEdge > *aBestEdge) {
+ *aBestEdge = aEdge;
+ } else if (aScrollingDirection < 0 && aEdge < *aBestEdge) {
+ *aBestEdge = aEdge;
+ }
+ } else {
+ NS_ERROR("Invalid scroll mode");
+ return;
+ }
+}
+
+void
+CalcSnapPoints::AddEdgeInterval(nscoord aInterval, nscoord aMinPos,
+ nscoord aMaxPos, nscoord aOffset,
+ nscoord aDestination, nscoord aStartPos,
+ nscoord aScrollingDirection,
+ nscoord* aBestEdge, bool *aEdgeFound)
+{
+ if (aInterval == 0) {
+ // When interval is 0, there are no scroll snap points.
+ // Avoid division by zero and bail.
+ return;
+ }
+
+ // The only possible candidate interval snap points are the edges immediately
+ // surrounding aDestination.
+
+ // aDestination must be clamped to the scroll
+ // range in order to handle cases where the best matching snap point would
+ // result in scrolling out of bounds. This clamping must be prior to
+ // selecting the two interval edges.
+ nscoord clamped = std::max(std::min(aDestination, aMaxPos), aMinPos);
+
+ // Add each edge in the interval immediately before aTarget and after aTarget
+ // Do not add edges that are out of range.
+ nscoord r = (clamped + aOffset) % aInterval;
+ if (r < aMinPos) {
+ r += aInterval;
+ }
+ nscoord edge = clamped - r;
+ if (edge >= aMinPos && edge <= aMaxPos) {
+ AddEdge(edge, aDestination, aStartPos, aScrollingDirection, aBestEdge,
+ aEdgeFound);
+ }
+ edge += aInterval;
+ if (edge >= aMinPos && edge <= aMaxPos) {
+ AddEdge(edge, aDestination, aStartPos, aScrollingDirection, aBestEdge,
+ aEdgeFound);
+ }
+}
+
+static void
+ProcessScrollSnapCoordinates(SnappingEdgeCallback& aCallback,
+ const nsTArray<nsPoint>& aScrollSnapCoordinates,
+ const nsPoint& aScrollSnapDestination) {
+ for (nsPoint snapCoords : aScrollSnapCoordinates) {
+ // Make them relative to the scroll snap destination.
+ snapCoords -= aScrollSnapDestination;
+
+ aCallback.AddVerticalEdge(snapCoords.x);
+ aCallback.AddHorizontalEdge(snapCoords.y);
+ }
+}
+
+Maybe<nsPoint> ScrollSnapUtils::GetSnapPointForDestination(
+ const ScrollSnapInfo& aSnapInfo,
+ nsIScrollableFrame::ScrollUnit aUnit,
+ const nsSize& aScrollPortSize,
+ const nsRect& aScrollRange,
+ const nsPoint& aStartPos,
+ const nsPoint& aDestination)
+{
+ if (aSnapInfo.mScrollSnapTypeY == NS_STYLE_SCROLL_SNAP_TYPE_NONE &&
+ aSnapInfo.mScrollSnapTypeX == NS_STYLE_SCROLL_SNAP_TYPE_NONE) {
+ return Nothing();
+ }
+
+ nsPoint destPos = aSnapInfo.mScrollSnapDestination;
+
+ CalcSnapPoints calcSnapPoints(aUnit, aDestination, aStartPos);
+
+ if (aSnapInfo.mScrollSnapIntervalX.isSome()) {
+ nscoord interval = aSnapInfo.mScrollSnapIntervalX.value();
+ calcSnapPoints.AddVerticalEdgeInterval(aScrollRange, interval, destPos.x);
+ }
+ if (aSnapInfo.mScrollSnapIntervalY.isSome()) {
+ nscoord interval = aSnapInfo.mScrollSnapIntervalY.value();
+ calcSnapPoints.AddHorizontalEdgeInterval(aScrollRange, interval, destPos.y);
+ }
+
+ ProcessScrollSnapCoordinates(calcSnapPoints, aSnapInfo.mScrollSnapCoordinates, destPos);
+ bool snapped = false;
+ nsPoint finalPos = calcSnapPoints.GetBestEdge();
+ nscoord proximityThreshold = gfxPrefs::ScrollSnapProximityThreshold();
+ proximityThreshold = nsPresContext::CSSPixelsToAppUnits(proximityThreshold);
+ if (aSnapInfo.mScrollSnapTypeY == NS_STYLE_SCROLL_SNAP_TYPE_PROXIMITY &&
+ std::abs(aDestination.y - finalPos.y) > proximityThreshold) {
+ finalPos.y = aDestination.y;
+ } else {
+ snapped = true;
+ }
+ if (aSnapInfo.mScrollSnapTypeX == NS_STYLE_SCROLL_SNAP_TYPE_PROXIMITY &&
+ std::abs(aDestination.x - finalPos.x) > proximityThreshold) {
+ finalPos.x = aDestination.x;
+ } else {
+ snapped = true;
+ }
+ return snapped ? Some(finalPos) : Nothing();
+}
+
+} // namespace mozilla