/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 "TiledRegion.h"
#include <algorithm>
#include "mozilla/fallible.h"
namespace mozilla {
namespace gfx {
static const int32_t kTileSize = 256;
static const size_t kMaxTiles = 1000;
/**
* TiledRegionImpl stores an array of non-empty rectangles (pixman_box32_ts) to
* represent the region. Each rectangle is contained in a single tile;
* rectangles never cross tile boundaries. The rectangles are sorted by their
* tile's origin in top-to-bottom, left-to-right order.
* (Note that this can mean that a rectangle r1 can come before another
* rectangle r2 even if r2.y1 < r1.y1, as long as the two rects are in the same
* row of tiles and r1.x1 < r2.x1.)
* Empty tiles take up no space in the array - there is no rectangle stored for
* them. As a result, any algorithm that needs to deal with empty tiles will
* iterate through the mRects array and compare the positions of two
* consecutive rects to figure out whether there are any empty tiles between
* them.
*/
static pixman_box32_t IntersectionOfNonEmptyBoxes(const pixman_box32_t& aBox1,
const pixman_box32_t& aBox2) {
return pixman_box32_t{
std::max(aBox1.x1, aBox2.x1), std::max(aBox1.y1, aBox2.y1),
std::min(aBox1.x2, aBox2.x2), std::min(aBox1.y2, aBox2.y2)};
}
// A TileIterator points to a specific tile inside a certain tile range, or to
// the end of the tile range. Advancing a TileIterator will move to the next
// tile inside the range (or to the range end). The next tile is either the
// tile to the right of the current one, or the first tile of the next tile
// row if the current tile is already the last tile in the row.
class TileIterator {
public:
TileIterator(const pixman_box32_t& aTileBounds, const IntPoint& aPosition)
: mTileBounds(aTileBounds), mPos(aPosition) {}
bool operator!=(const TileIterator& aOther) { return mPos != aOther.mPos; }
bool operator==(const TileIterator& aOther) { return mPos == aOther.mPos; }
IntPoint operator*() const { return mPos; }
const TileIterator& operator++() {
mPos.x += kTileSize;
if (mPos.x >= mTileBounds.x2) {
mPos.x = mTileBounds.x1;
mPos.y += kTileSize;
}
return *this;
}
TileIterator& operator=(const IntPoint& aPosition) {
mPos = aPosition;
return *this;
}
bool IsBeforeTileContainingPoint(const IntPoint& aPoint) const {
return (mPos.y + kTileSize) <= aPoint.y ||
(mPos.y <= aPoint.y && (mPos.x + kTileSize) <= aPoint.x);
}
bool IsAtTileContainingPoint(const IntPoint& aPoint) const {
return mPos.y <= aPoint.y && aPoint.y < (mPos.y + kTileSize) &&
mPos.x <= aPoint.x && aPoint.x < (mPos.x + kTileSize);
}
pixman_box32_t IntersectionWith(const pixman_box32_t& aRect) const {
pixman_box32_t tile = {mPos.x, mPos.y, mPos.x + kTileSize,
mPos.y + kTileSize};
return IntersectionOfNonEmptyBoxes(tile, aRect);
}
private:
const pixman_box32_t& mTileBounds;
IntPoint mPos;
};
// A TileRange describes a range of tiles contained inside a certain tile
// bounds (which is a rectangle that includes all tiles that you're
// interested in). The tile range can start and end at any point inside a
// tile row.
// The tile range end is described by the tile that starts at the bottom
// left corner of the tile bounds, i.e. the first tile under the tile
// bounds.
class TileRange {
public:
// aTileBounds, aStart and aEnd need to be aligned with the tile grid.
TileRange(const pixman_box32_t& aTileBounds, const IntPoint& aStart,
const IntPoint& aEnd)
: mTileBounds(aTileBounds), mStart(aStart), mEnd(aEnd) {}
// aTileBounds needs to be aligned with the tile grid.
explicit TileRange(const pixman_box32_t& aTileBounds)
: mTileBounds(aTileBounds),
mStart(mTileBounds.x1, mTileBounds.y1),
mEnd(mTileBounds.x1, mTileBounds.y2) {}
TileIterator Begin() const { return TileIterator(mTileBounds, mStart); }
TileIterator End() const { return TileIterator(mTileBounds, mEnd); }
// The number of tiles in this tile range.
size_t Length() const {
if (mEnd.y == mStart.y) {
return (mEnd.x - mStart.x) / kTileSize;
}
int64_t numberOfFullRows =
(((int64_t)mEnd.y - (int64_t)mStart.y) / kTileSize) - 1;
int64_t tilesInFirstRow =
((int64_t)mTileBounds.x2 - (int64_t)mStart.x) / kTileSize;
int64_t tilesInLastRow =
((int64_t)mEnd.x - (int64_t)mTileBounds.x1) / kTileSize;
int64_t tilesInFullRow =
((int64_t)mTileBounds.x2 - (int64_t)mTileBounds.x1) / kTileSize;
int64_t total =
tilesInFirstRow + (tilesInFullRow * numberOfFullRows) + tilesInLastRow;
MOZ_ASSERT(total > 0);
// On 32bit systems the total may be larger than what fits in a size_t (4
// bytes), so clamp it to size_t's max value in that case.
return static_cast<uint64_t>(total) >=
static_cast<uint64_t>(std::numeric_limits<size_t>::max())
? std::numeric_limits<size_t>::max()
: static_cast<size_t>(total);
}
// If aTileOrigin does not describe a tile inside our tile bounds, move it
// to the next tile that you'd encounter by "advancing" a tile iterator
// inside these tile bounds. If aTileOrigin is after the last tile inside
// our tile bounds, move it to the range end tile.
// The result of this method is a valid end tile for a tile range with our
// tile bounds.
IntPoint MoveIntoBounds(const IntPoint& aTileOrigin) const {
IntPoint p = aTileOrigin;
if (p.x < mTileBounds.x1) {
p.x = mTileBounds.x1;
} else if (p.x >= mTileBounds.x2) {
p.x = mTileBounds.x1;
p.y += kTileSize;
}
if (p.y < mTileBounds.y1) {
p.y = mTileBounds.y1;
p.x = mTileBounds.x1;
} else if (p.y >= mTileBounds.y2) {
// There's only one valid state after the end of the tile range, and
// that's the bottom left point of the tile bounds.
p.x = mTileBounds.x1;
p.y = mTileBounds.y2;
}
return p;
}
private:
const pixman_box32_t& mTileBounds;
const IntPoint mStart;
const IntPoint mEnd;
};
static IntPoint TileContainingPoint(const IntPoint& aPoint) {
return IntPoint(RoundDownToMultiple(aPoint.x, kTileSize),
RoundDownToMultiple(aPoint.y, kTileSize));
}
enum class IterationAction : uint8_t { CONTINUE, STOP };
enum class IterationEndReason : uint8_t { NOT_STOPPED, STOPPED };
template <typename HandleEmptyTilesFunction,
typename HandleNonEmptyTileFunction, typename RectArrayT>
IterationEndReason ProcessIntersectedTiles(
const pixman_box32_t& aRect, RectArrayT& aRectArray,
HandleEmptyTilesFunction aHandleEmptyTiles,
HandleNonEmptyTileFunction aHandleNonEmptyTile) {
pixman_box32_t tileBounds = {RoundDownToMultiple(aRect.x1, kTileSize),
RoundDownToMultiple(aRect.y1, kTileSize),
RoundUpToMultiple(aRect.x2, kTileSize),
RoundUpToMultiple(aRect.y2, kTileSize)};
if (tileBounds.x2 < tileBounds.x1 || tileBounds.y2 < tileBounds.y1) {
// RoundUpToMultiple probably overflowed. Bail out.
return IterationEndReason::STOPPED;
}
TileRange tileRange(tileBounds);
TileIterator rangeEnd = tileRange.End();
// tileIterator points to the next tile in tileRange, or to rangeEnd if we're
// done.
TileIterator tileIterator = tileRange.Begin();
// We iterate over the rectangle array. Depending on the position of the
// rectangle we encounter, we may need to advance tileIterator by zero, one,
// or more tiles:
// - Zero if the rectangle we encountered is outside the tiles that
// intersect aRect.
// - One if the rectangle is in the exact tile that we're interested in next
// (i.e. the tile that tileIterator points at).
// - More than one if the encountered rectangle is in a tile that's further
// to the right or to the bottom than tileIterator. In that case there is
// at least one empty tile between the last rectangle we encountered and
// the current one.
for (size_t i = 0; i < aRectArray.Length() && tileIterator != rangeEnd; i++) {
MOZ_ASSERT(aRectArray[i].x1 < aRectArray[i].x2 &&
aRectArray[i].y1 < aRectArray[i].y2,
"empty rect");
IntPoint rectOrigin(aRectArray[i].x1, aRectArray[i].y1);
if (tileIterator.IsBeforeTileContainingPoint(rectOrigin)) {
IntPoint tileOrigin = TileContainingPoint(rectOrigin);
IntPoint afterEmptyTiles = tileRange.MoveIntoBounds(tileOrigin);
TileRange emptyTiles(tileBounds, *tileIterator, afterEmptyTiles);
if (aHandleEmptyTiles(aRectArray, i, emptyTiles) ==
IterationAction::STOP) {
return IterationEndReason::STOPPED;
}
tileIterator = afterEmptyTiles;
if (tileIterator == rangeEnd) {
return IterationEndReason::NOT_STOPPED;
}
}
if (tileIterator.IsAtTileContainingPoint(rectOrigin)) {
pixman_box32_t rectIntersection = tileIterator.IntersectionWith(aRect);
if (aHandleNonEmptyTile(aRectArray, i, rectIntersection) ==
IterationAction::STOP) {
return IterationEndReason::STOPPED;
}
++tileIterator;
}
}
if (tileIterator != rangeEnd) {
// We've looked at all of our existing rectangles but haven't covered all
// of the tiles that we're interested in yet. So we need to deal with the
// remaining tiles now.
size_t endIndex = aRectArray.Length();
TileRange emptyTiles(tileBounds, *tileIterator, *rangeEnd);
if (aHandleEmptyTiles(aRectArray, endIndex, emptyTiles) ==
IterationAction::STOP) {
return IterationEndReason::STOPPED;
}
}
return IterationEndReason::NOT_STOPPED;
}
static pixman_box32_t UnionBoundsOfNonEmptyBoxes(const pixman_box32_t& aBox1,
const pixman_box32_t& aBox2) {
return {std::min(aBox1.x1, aBox2.x1), std::min(aBox1.y1, aBox2.y1),
std::max(aBox1.x2, aBox2.x2), std::max(aBox1.y2, aBox2.y2)};
}
// Returns true when adding the rectangle was successful, and false if
// allocation failed.
// When this returns false, our internal state might not be consistent and we
// need to be cleared.
bool TiledRegionImpl::AddRect(const pixman_box32_t& aRect) {
// We are adding a rectangle that can span multiple tiles.
// For each empty tile that aRect intersects, we need to add the intersection
// of aRect with that tile to mRects, respecting the order of mRects.
// For each tile that already has a rectangle, we need to enlarge that
// existing rectangle to include the intersection of aRect with the tile.
return ProcessIntersectedTiles(
aRect, mRects,
[&aRect](nsTArray<pixman_box32_t>& rects, size_t& rectIndex,
TileRange emptyTiles) {
CheckedInt<size_t> newLength(rects.Length());
newLength += emptyTiles.Length();
if (!newLength.isValid() || newLength.value() >= kMaxTiles ||
!rects.InsertElementsAt(rectIndex, emptyTiles.Length(),
fallible)) {
return IterationAction::STOP;
}
for (TileIterator tileIt = emptyTiles.Begin();
tileIt != emptyTiles.End(); ++tileIt, ++rectIndex) {
rects[rectIndex] = tileIt.IntersectionWith(aRect);
}
return IterationAction::CONTINUE;
},
[](nsTArray<pixman_box32_t>& rects, size_t rectIndex,
const pixman_box32_t& rectIntersectionWithTile) {
rects[rectIndex] = UnionBoundsOfNonEmptyBoxes(
rects[rectIndex], rectIntersectionWithTile);
return IterationAction::CONTINUE;
}) == IterationEndReason::NOT_STOPPED;
}
static bool NonEmptyBoxesIntersect(const pixman_box32_t& aBox1,
const pixman_box32_t& aBox2) {
return aBox1.x1 < aBox2.x2 && aBox2.x1 < aBox1.x2 && aBox1.y1 < aBox2.y2 &&
aBox2.y1 < aBox1.y2;
}
bool TiledRegionImpl::Intersects(const pixman_box32_t& aRect) const {
// aRect intersects this region if it intersects any of our rectangles.
return ProcessIntersectedTiles(
aRect, mRects,
[](const nsTArray<pixman_box32_t>& rects, size_t& rectIndex,
TileRange emptyTiles) {
// Ignore empty tiles and keep on iterating.
return IterationAction::CONTINUE;
},
[](const nsTArray<pixman_box32_t>& rects, size_t rectIndex,
const pixman_box32_t& rectIntersectionWithTile) {
if (NonEmptyBoxesIntersect(rects[rectIndex],
rectIntersectionWithTile)) {
// Found an intersecting rectangle, so aRect intersects this
// region.
return IterationAction::STOP;
}
return IterationAction::CONTINUE;
}) == IterationEndReason::STOPPED;
}
static bool NonEmptyBoxContainsNonEmptyBox(const pixman_box32_t& aBox1,
const pixman_box32_t& aBox2) {
return aBox1.x1 <= aBox2.x1 && aBox2.x2 <= aBox1.x2 && aBox1.y1 <= aBox2.y1 &&
aBox2.y2 <= aBox1.y2;
}
bool TiledRegionImpl::Contains(const pixman_box32_t& aRect) const {
// aRect is contained in this region if aRect does not intersect any empty
// tiles and, for each non-empty tile, if the intersection of aRect with that
// tile is contained in the existing rectangle we have in that tile.
return ProcessIntersectedTiles(
aRect, mRects,
[](const nsTArray<pixman_box32_t>& rects, size_t& rectIndex,
TileRange emptyTiles) {
// Found an empty tile that intersects aRect, so aRect is not
// contained in this region.
return IterationAction::STOP;
},
[](const nsTArray<pixman_box32_t>& rects, size_t rectIndex,
const pixman_box32_t& rectIntersectionWithTile) {
if (!NonEmptyBoxContainsNonEmptyBox(rects[rectIndex],
rectIntersectionWithTile)) {
// Our existing rectangle in this tile does not cover the part
// of aRect that intersects this tile, so aRect is not
// contained in this region.
return IterationAction::STOP;
}
return IterationAction::CONTINUE;
}) == IterationEndReason::NOT_STOPPED;
}
} // namespace gfx
} // namespace mozilla