370 lines
14 KiB
C++
370 lines
14 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "TiledRegion.h"
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#include <algorithm>
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#include "mozilla/fallible.h"
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namespace mozilla {
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namespace gfx {
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static const int32_t kTileSize = 256;
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static const size_t kMaxTiles = 1000;
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/**
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* TiledRegionImpl stores an array of non-empty rectangles (pixman_box32_ts) to
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* represent the region. Each rectangle is contained in a single tile;
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* rectangles never cross tile boundaries. The rectangles are sorted by their
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* tile's origin in top-to-bottom, left-to-right order.
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* (Note that this can mean that a rectangle r1 can come before another
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* rectangle r2 even if r2.y1 < r1.y1, as long as the two rects are in the same
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* row of tiles and r1.x1 < r2.x1.)
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* Empty tiles take up no space in the array - there is no rectangle stored for
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* them. As a result, any algorithm that needs to deal with empty tiles will
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* iterate through the mRects array and compare the positions of two
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* consecutive rects to figure out whether there are any empty tiles between
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* them.
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*/
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static pixman_box32_t
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IntersectionOfNonEmptyBoxes(const pixman_box32_t& aBox1,
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const pixman_box32_t& aBox2)
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{
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return pixman_box32_t {
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std::max(aBox1.x1, aBox2.x1),
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std::max(aBox1.y1, aBox2.y1),
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std::min(aBox1.x2, aBox2.x2),
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std::min(aBox1.y2, aBox2.y2)
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};
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}
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// A TileIterator points to a specific tile inside a certain tile range, or to
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// the end of the tile range. Advancing a TileIterator will move to the next
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// tile inside the range (or to the range end). The next tile is either the
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// tile to the right of the current one, or the first tile of the next tile
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// row if the current tile is already the last tile in the row.
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class TileIterator {
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public:
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TileIterator(const pixman_box32_t& aTileBounds, const IntPoint& aPosition)
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: mTileBounds(aTileBounds)
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, mPos(aPosition)
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{}
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bool operator!=(const TileIterator& aOther) { return mPos != aOther.mPos; }
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bool operator==(const TileIterator& aOther) { return mPos == aOther.mPos; }
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IntPoint operator*() const { return mPos; }
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const TileIterator& operator++() {
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mPos.x += kTileSize;
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if (mPos.x >= mTileBounds.x2) {
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mPos.x = mTileBounds.x1;
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mPos.y += kTileSize;
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}
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return *this;
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}
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TileIterator& operator=(const IntPoint& aPosition)
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{
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mPos = aPosition;
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return *this;
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}
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bool IsBeforeTileContainingPoint(const IntPoint& aPoint) const
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{
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return (mPos.y + kTileSize) <= aPoint.y ||
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(mPos.y <= aPoint.y && (mPos.x + kTileSize) <= aPoint.x);
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}
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bool IsAtTileContainingPoint(const IntPoint& aPoint) const
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{
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return mPos.y <= aPoint.y && aPoint.y < (mPos.y + kTileSize) &&
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mPos.x <= aPoint.x && aPoint.x < (mPos.x + kTileSize);
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}
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pixman_box32_t IntersectionWith(const pixman_box32_t& aRect) const
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{
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pixman_box32_t tile = { mPos.x, mPos.y,
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mPos.x + kTileSize, mPos.y + kTileSize };
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return IntersectionOfNonEmptyBoxes(tile, aRect);
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}
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private:
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const pixman_box32_t& mTileBounds;
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IntPoint mPos;
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};
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// A TileRange describes a range of tiles contained inside a certain tile
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// bounds (which is a rectangle that includes all tiles that you're
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// interested in). The tile range can start and end at any point inside a
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// tile row.
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// The tile range end is described by the tile that starts at the bottom
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// left corner of the tile bounds, i.e. the first tile under the tile
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// bounds.
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class TileRange {
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public:
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// aTileBounds, aStart and aEnd need to be aligned with the tile grid.
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TileRange(const pixman_box32_t& aTileBounds,
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const IntPoint& aStart, const IntPoint& aEnd)
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: mTileBounds(aTileBounds)
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, mStart(aStart)
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, mEnd(aEnd)
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{}
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// aTileBounds needs to be aligned with the tile grid.
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explicit TileRange(const pixman_box32_t& aTileBounds)
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: mTileBounds(aTileBounds)
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, mStart(mTileBounds.x1, mTileBounds.y1)
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, mEnd(mTileBounds.x1, mTileBounds.y2)
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{}
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TileIterator Begin() const { return TileIterator(mTileBounds, mStart); }
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TileIterator End() const { return TileIterator(mTileBounds, mEnd); }
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// The number of tiles in this tile range.
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size_t Length() const
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{
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if (mEnd.y == mStart.y) {
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return (mEnd.x - mStart.x) / kTileSize;
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}
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int64_t numberOfFullRows = (((int64_t)mEnd.y - (int64_t)mStart.y) / kTileSize) - 1;
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int64_t tilesInFirstRow = ((int64_t)mTileBounds.x2 - (int64_t)mStart.x) / kTileSize;
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int64_t tilesInLastRow = ((int64_t)mEnd.x - (int64_t)mTileBounds.x1) / kTileSize;
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int64_t tilesInFullRow = ((int64_t)mTileBounds.x2 - (int64_t)mTileBounds.x1) / kTileSize;
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int64_t total = tilesInFirstRow + (tilesInFullRow * numberOfFullRows) + tilesInLastRow;
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MOZ_ASSERT(total > 0);
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// The total may be larger than what fits in a size_t, so clamp it to
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// SIZE_MAX in that case.
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return ((uint64_t)total > (uint64_t)SIZE_MAX) ? SIZE_MAX : (size_t)total;
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}
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// If aTileOrigin does not describe a tile inside our tile bounds, move it
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// to the next tile that you'd encounter by "advancing" a tile iterator
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// inside these tile bounds. If aTileOrigin is after the last tile inside
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// our tile bounds, move it to the range end tile.
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// The result of this method is a valid end tile for a tile range with our
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// tile bounds.
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IntPoint MoveIntoBounds(const IntPoint& aTileOrigin) const
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{
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IntPoint p = aTileOrigin;
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if (p.x < mTileBounds.x1) {
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p.x = mTileBounds.x1;
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} else if (p.x >= mTileBounds.x2) {
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p.x = mTileBounds.x1;
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p.y += kTileSize;
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}
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if (p.y < mTileBounds.y1) {
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p.y = mTileBounds.y1;
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p.x = mTileBounds.x1;
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} else if (p.y >= mTileBounds.y2) {
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// There's only one valid state after the end of the tile range, and that's
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// the bottom left point of the tile bounds.
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p.x = mTileBounds.x1;
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p.y = mTileBounds.y2;
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}
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return p;
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}
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private:
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const pixman_box32_t& mTileBounds;
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const IntPoint mStart;
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const IntPoint mEnd;
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};
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static IntPoint
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TileContainingPoint(const IntPoint& aPoint)
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{
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return IntPoint(RoundDownToMultiple(aPoint.x, kTileSize),
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RoundDownToMultiple(aPoint.y, kTileSize));
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}
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enum class IterationAction : uint8_t {
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CONTINUE,
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STOP
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};
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enum class IterationEndReason : uint8_t {
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NOT_STOPPED,
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STOPPED
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};
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template<
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typename HandleEmptyTilesFunction,
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typename HandleNonEmptyTileFunction,
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typename RectArrayT>
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IterationEndReason ProcessIntersectedTiles(const pixman_box32_t& aRect,
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RectArrayT& aRectArray,
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HandleEmptyTilesFunction aHandleEmptyTiles,
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HandleNonEmptyTileFunction aHandleNonEmptyTile)
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{
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pixman_box32_t tileBounds = {
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RoundDownToMultiple(aRect.x1, kTileSize),
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RoundDownToMultiple(aRect.y1, kTileSize),
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RoundUpToMultiple(aRect.x2, kTileSize),
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RoundUpToMultiple(aRect.y2, kTileSize)
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};
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if (tileBounds.x2 < tileBounds.x1 || tileBounds.y2 < tileBounds.y1) {
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// RoundUpToMultiple probably overflowed. Bail out.
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return IterationEndReason::STOPPED;
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}
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TileRange tileRange(tileBounds);
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TileIterator rangeEnd = tileRange.End();
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// tileIterator points to the next tile in tileRange, or to rangeEnd if we're
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// done.
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TileIterator tileIterator = tileRange.Begin();
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// We iterate over the rectangle array. Depending on the position of the
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// rectangle we encounter, we may need to advance tileIterator by zero, one,
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// or more tiles:
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// - Zero if the rectangle we encountered is outside the tiles that
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// intersect aRect.
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// - One if the rectangle is in the exact tile that we're interested in next
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// (i.e. the tile that tileIterator points at).
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// - More than one if the encountered rectangle is in a tile that's further
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// to the right or to the bottom than tileIterator. In that case there is
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// at least one empty tile between the last rectangle we encountered and
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// the current one.
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for (size_t i = 0; i < aRectArray.Length() && tileIterator != rangeEnd; i++) {
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MOZ_ASSERT(aRectArray[i].x1 < aRectArray[i].x2 && aRectArray[i].y1 < aRectArray[i].y2, "empty rect");
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IntPoint rectOrigin(aRectArray[i].x1, aRectArray[i].y1);
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if (tileIterator.IsBeforeTileContainingPoint(rectOrigin)) {
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IntPoint tileOrigin = TileContainingPoint(rectOrigin);
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IntPoint afterEmptyTiles = tileRange.MoveIntoBounds(tileOrigin);
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TileRange emptyTiles(tileBounds, *tileIterator, afterEmptyTiles);
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if (aHandleEmptyTiles(aRectArray, i, emptyTiles) == IterationAction::STOP) {
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return IterationEndReason::STOPPED;
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}
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tileIterator = afterEmptyTiles;
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if (tileIterator == rangeEnd) {
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return IterationEndReason::NOT_STOPPED;
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}
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}
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if (tileIterator.IsAtTileContainingPoint(rectOrigin)) {
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pixman_box32_t rectIntersection = tileIterator.IntersectionWith(aRect);
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if (aHandleNonEmptyTile(aRectArray, i, rectIntersection) == IterationAction::STOP) {
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return IterationEndReason::STOPPED;
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}
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++tileIterator;
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}
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}
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if (tileIterator != rangeEnd) {
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// We've looked at all of our existing rectangles but haven't covered all
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// of the tiles that we're interested in yet. So we need to deal with the
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// remaining tiles now.
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size_t endIndex = aRectArray.Length();
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TileRange emptyTiles(tileBounds, *tileIterator, *rangeEnd);
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if (aHandleEmptyTiles(aRectArray, endIndex, emptyTiles) == IterationAction::STOP) {
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return IterationEndReason::STOPPED;
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}
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}
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return IterationEndReason::NOT_STOPPED;
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}
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static pixman_box32_t
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UnionBoundsOfNonEmptyBoxes(const pixman_box32_t& aBox1,
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const pixman_box32_t& aBox2)
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{
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return { std::min(aBox1.x1, aBox2.x1),
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std::min(aBox1.y1, aBox2.y1),
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std::max(aBox1.x2, aBox2.x2),
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std::max(aBox1.y2, aBox2.y2) };
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}
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// Returns true when adding the rectangle was successful, and false if
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// allocation failed.
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// When this returns false, our internal state might not be consistent and we
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// need to be cleared.
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bool
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TiledRegionImpl::AddRect(const pixman_box32_t& aRect)
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{
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// We are adding a rectangle that can span multiple tiles.
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// For each empty tile that aRect intersects, we need to add the intersection
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// of aRect with that tile to mRects, respecting the order of mRects.
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// For each tile that already has a rectangle, we need to enlarge that
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// existing rectangle to include the intersection of aRect with the tile.
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return ProcessIntersectedTiles(aRect, mRects,
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[&aRect](nsTArray<pixman_box32_t>& rects, size_t& rectIndex, TileRange emptyTiles) {
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CheckedInt<size_t> newLength(rects.Length());
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newLength += emptyTiles.Length();
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if (!newLength.isValid() || newLength.value() >= kMaxTiles ||
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!rects.InsertElementsAt(rectIndex, emptyTiles.Length(), fallible)) {
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return IterationAction::STOP;
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}
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for (TileIterator tileIt = emptyTiles.Begin();
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tileIt != emptyTiles.End();
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++tileIt, ++rectIndex) {
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rects[rectIndex] = tileIt.IntersectionWith(aRect);
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}
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return IterationAction::CONTINUE;
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},
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[](nsTArray<pixman_box32_t>& rects, size_t rectIndex, const pixman_box32_t& rectIntersectionWithTile) {
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rects[rectIndex] =
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UnionBoundsOfNonEmptyBoxes(rects[rectIndex], rectIntersectionWithTile);
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return IterationAction::CONTINUE;
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}) == IterationEndReason::NOT_STOPPED;
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}
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static bool
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NonEmptyBoxesIntersect(const pixman_box32_t& aBox1, const pixman_box32_t& aBox2)
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{
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return aBox1.x1 < aBox2.x2 && aBox2.x1 < aBox1.x2 &&
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aBox1.y1 < aBox2.y2 && aBox2.y1 < aBox1.y2;
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}
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bool
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TiledRegionImpl::Intersects(const pixman_box32_t& aRect) const
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{
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// aRect intersects this region if it intersects any of our rectangles.
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return ProcessIntersectedTiles(aRect, mRects,
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[](const nsTArray<pixman_box32_t>& rects, size_t& rectIndex, TileRange emptyTiles) {
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// Ignore empty tiles and keep on iterating.
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return IterationAction::CONTINUE;
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},
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[](const nsTArray<pixman_box32_t>& rects, size_t rectIndex, const pixman_box32_t& rectIntersectionWithTile) {
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if (NonEmptyBoxesIntersect(rects[rectIndex], rectIntersectionWithTile)) {
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// Found an intersecting rectangle, so aRect intersects this region.
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return IterationAction::STOP;
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}
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return IterationAction::CONTINUE;
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}) == IterationEndReason::STOPPED;
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}
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static bool
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NonEmptyBoxContainsNonEmptyBox(const pixman_box32_t& aBox1, const pixman_box32_t& aBox2)
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{
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return aBox1.x1 <= aBox2.x1 && aBox2.x2 <= aBox1.x2 &&
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aBox1.y1 <= aBox2.y1 && aBox2.y2 <= aBox1.y2;
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}
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bool
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TiledRegionImpl::Contains(const pixman_box32_t& aRect) const
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{
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// aRect is contained in this region if aRect does not intersect any empty
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// tiles and, for each non-empty tile, if the intersection of aRect with that
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// tile is contained in the existing rectangle we have in that tile.
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return ProcessIntersectedTiles(aRect, mRects,
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[](const nsTArray<pixman_box32_t>& rects, size_t& rectIndex, TileRange emptyTiles) {
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// Found an empty tile that intersects aRect, so aRect is not contained
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// in this region.
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return IterationAction::STOP;
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},
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[](const nsTArray<pixman_box32_t>& rects, size_t rectIndex, const pixman_box32_t& rectIntersectionWithTile) {
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if (!NonEmptyBoxContainsNonEmptyBox(rects[rectIndex], rectIntersectionWithTile)) {
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// Our existing rectangle in this tile does not cover the part of aRect that
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// intersects this tile, so aRect is not contained in this region.
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return IterationAction::STOP;
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}
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return IterationAction::CONTINUE;
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}) == IterationEndReason::NOT_STOPPED;
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}
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} // namespace gfx
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} // namespace mozilla
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