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/*
* Copyright (C) 2010, 2011 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "Region.h"
#include <stdio.h>
// A region class based on the paper "Scanline Coherent Shape Algebra"
// by Jonathan E. Steinhart from the book "Graphics Gems II".
//
// This implementation uses two vectors instead of linked list, and
// also compresses regions when possible.
namespace WebCore {
Region::Region()
{
}
Region::Region(const IntRect& rect)
: m_bounds(rect)
, m_shape(rect)
{
}
Vector<IntRect> Region::rects() const
{
Vector<IntRect> rects;
for (Shape::SpanIterator span = m_shape.spans_begin(), end = m_shape.spans_end(); span != end && span + 1 != end; ++span) {
int y = span->y;
int height = (span + 1)->y - y;
for (Shape::SegmentIterator segment = m_shape.segments_begin(span), end = m_shape.segments_end(span); segment != end && segment + 1 != end; segment += 2) {
int x = *segment;
int width = *(segment + 1) - x;
rects.append(IntRect(x, y, width, height));
}
}
return rects;
}
bool Region::contains(const Region& region) const
{
if (!m_bounds.contains(region.m_bounds))
return false;
return Shape::compareShapes<Shape::CompareContainsOperation>(m_shape, region.m_shape);
}
bool Region::contains(const IntPoint& point) const
{
if (!m_bounds.contains(point))
return false;
for (Shape::SpanIterator span = m_shape.spans_begin(), end = m_shape.spans_end(); span != end && span + 1 != end; ++span) {
int y = span->y;
int maxY = (span + 1)->y;
if (y > point.y())
break;
if (maxY <= point.y())
continue;
for (Shape::SegmentIterator segment = m_shape.segments_begin(span), end = m_shape.segments_end(span); segment != end && segment + 1 != end; segment += 2) {
int x = *segment;
int maxX = *(segment + 1);
if (x > point.x())
break;
if (maxX > point.x())
return true;
}
}
return false;
}
bool Region::intersects(const Region& region) const
{
if (!m_bounds.intersects(region.m_bounds))
return false;
return Shape::compareShapes<Shape::CompareIntersectsOperation>(m_shape, region.m_shape);
}
unsigned Region::totalArea() const
{
Vector<IntRect> rects = this->rects();
size_t size = rects.size();
unsigned totalArea = 0;
for (size_t i = 0; i < size; ++i) {
IntRect rect = rects[i];
totalArea += (rect.width() * rect.height());
}
return totalArea;
}
template<typename CompareOperation>
bool Region::Shape::compareShapes(const Shape& aShape, const Shape& bShape)
{
bool result = CompareOperation::defaultResult;
Shape::SpanIterator aSpan = aShape.spans_begin();
Shape::SpanIterator aSpanEnd = aShape.spans_end();
Shape::SpanIterator bSpan = bShape.spans_begin();
Shape::SpanIterator bSpanEnd = bShape.spans_end();
bool aHadSegmentInPreviousSpan = false;
bool bHadSegmentInPreviousSpan = false;
while (aSpan != aSpanEnd && aSpan + 1 != aSpanEnd && bSpan != bSpanEnd && bSpan + 1 != bSpanEnd) {
int aY = aSpan->y;
int aMaxY = (aSpan + 1)->y;
int bY = bSpan->y;
int bMaxY = (bSpan + 1)->y;
Shape::SegmentIterator aSegment = aShape.segments_begin(aSpan);
Shape::SegmentIterator aSegmentEnd = aShape.segments_end(aSpan);
Shape::SegmentIterator bSegment = bShape.segments_begin(bSpan);
Shape::SegmentIterator bSegmentEnd = bShape.segments_end(bSpan);
// Look for a non-overlapping part of the spans. If B had a segment in its previous span, then we already tested A against B within that span.
bool aHasSegmentInSpan = aSegment != aSegmentEnd;
bool bHasSegmentInSpan = bSegment != bSegmentEnd;
if (aY < bY && !bHadSegmentInPreviousSpan && aHasSegmentInSpan && CompareOperation::aOutsideB(result))
return result;
if (bY < aY && !aHadSegmentInPreviousSpan && bHasSegmentInSpan && CompareOperation::bOutsideA(result))
return result;
aHadSegmentInPreviousSpan = aHasSegmentInSpan;
bHadSegmentInPreviousSpan = bHasSegmentInSpan;
bool spansOverlap = bMaxY > aY && bY < aMaxY;
if (spansOverlap) {
while (aSegment != aSegmentEnd && bSegment != bSegmentEnd) {
int aX = *aSegment;
int aMaxX = *(aSegment + 1);
int bX = *bSegment;
int bMaxX = *(bSegment + 1);
bool segmentsOverlap = bMaxX > aX && bX < aMaxX;
if (segmentsOverlap && CompareOperation::aOverlapsB(result))
return result;
if (aX < bX && CompareOperation::aOutsideB(result))
return result;
if (bX < aX && CompareOperation::bOutsideA(result))
return result;
if (aMaxX < bMaxX)
aSegment += 2;
else if (bMaxX < aMaxX)
bSegment += 2;
else {
aSegment += 2;
bSegment += 2;
}
}
if (aSegment != aSegmentEnd && CompareOperation::aOutsideB(result))
return result;
if (bSegment != bSegmentEnd && CompareOperation::bOutsideA(result))
return result;
}
if (aMaxY < bMaxY)
aSpan += 1;
else if (bMaxY < aMaxY)
bSpan += 1;
else {
aSpan += 1;
bSpan += 1;
}
}
if (aSpan != aSpanEnd && aSpan + 1 != aSpanEnd && CompareOperation::aOutsideB(result))
return result;
if (bSpan != bSpanEnd && bSpan + 1 != bSpanEnd && CompareOperation::bOutsideA(result))
return result;
return result;
}
struct Region::Shape::CompareContainsOperation {
const static bool defaultResult = true;
inline static bool aOutsideB(bool& /* result */) { return false; }
inline static bool bOutsideA(bool& result) { result = false; return true; }
inline static bool aOverlapsB(bool& /* result */) { return false; }
};
struct Region::Shape::CompareIntersectsOperation {
const static bool defaultResult = false;
inline static bool aOutsideB(bool& /* result */) { return false; }
inline static bool bOutsideA(bool& /* result */) { return false; }
inline static bool aOverlapsB(bool& result) { result = true; return true; }
};
Region::Shape::Shape()
{
}
Region::Shape::Shape(const IntRect& rect)
{
appendSpan(rect.y());
appendSegment(rect.x());
appendSegment(rect.maxX());
appendSpan(rect.maxY());
}
void Region::Shape::appendSpan(int y)
{
m_spans.append(Span(y, m_segments.size()));
}
bool Region::Shape::canCoalesce(SegmentIterator begin, SegmentIterator end)
{
if (m_spans.isEmpty())
return false;
SegmentIterator lastSpanBegin = m_segments.data() + m_spans.last().segmentIndex;
SegmentIterator lastSpanEnd = m_segments.data() + m_segments.size();
// Check if both spans have an equal number of segments.
if (lastSpanEnd - lastSpanBegin != end - begin)
return false;
// Check if both spans are equal.
if (!std::equal(begin, end, lastSpanBegin))
return false;
// Since the segments are equal the second segment can just be ignored.
return true;
}
void Region::Shape::appendSpan(int y, SegmentIterator begin, SegmentIterator end)
{
if (canCoalesce(begin, end))
return;
appendSpan(y);
m_segments.appendRange(begin, end);
}
void Region::Shape::appendSpans(const Shape& shape, SpanIterator begin, SpanIterator end)
{
for (SpanIterator it = begin; it != end; ++it)
appendSpan(it->y, shape.segments_begin(it), shape.segments_end(it));
}
void Region::Shape::appendSegment(int x)
{
m_segments.append(x);
}
Region::Shape::SpanIterator Region::Shape::spans_begin() const
{
return m_spans.data();
}
Region::Shape::SpanIterator Region::Shape::spans_end() const
{
return m_spans.data() + m_spans.size();
}
Region::Shape::SegmentIterator Region::Shape::segments_begin(SpanIterator it) const
{
ASSERT(it >= m_spans.data());
ASSERT(it < m_spans.data() + m_spans.size());
// Check if this span has any segments.
if (it->segmentIndex == m_segments.size())
return 0;
return &m_segments[it->segmentIndex];
}
Region::Shape::SegmentIterator Region::Shape::segments_end(SpanIterator it) const
{
ASSERT(it >= m_spans.data());
ASSERT(it < m_spans.data() + m_spans.size());
// Check if this span has any segments.
if (it->segmentIndex == m_segments.size())
return 0;
ASSERT(it + 1 < m_spans.data() + m_spans.size());
size_t segmentIndex = (it + 1)->segmentIndex;
ASSERT_WITH_SECURITY_IMPLICATION(segmentIndex <= m_segments.size());
return m_segments.data() + segmentIndex;
}
#ifndef NDEBUG
void Region::Shape::dump() const
{
for (auto span = spans_begin(), end = spans_end(); span != end; ++span) {
printf("%6d: (", span->y);
for (auto segment = segments_begin(span), end = segments_end(span); segment != end; ++segment)
printf("%d ", *segment);
printf(")\n");
}
printf("\n");
}
#endif
bool Region::Shape::isValid() const
{
for (auto span = spans_begin(), end = spans_end(); span != end && span + 1 != end; ++span) {
int y = span->y;
int height = (span + 1)->y - y;
if (height < 0)
return false;
for (auto segment = segments_begin(span), end = segments_end(span); segment != end && segment + 1 != end; segment += 2) {
int x = *segment;
int width = *(segment + 1) - x;
if (width < 0)
return false;
}
}
return true;
}
IntRect Region::Shape::bounds() const
{
if (isEmpty())
return IntRect();
SpanIterator span = spans_begin();
int minY = span->y;
SpanIterator lastSpan = spans_end() - 1;
int maxY = lastSpan->y;
int minX = std::numeric_limits<int>::max();
int maxX = std::numeric_limits<int>::min();
while (span != lastSpan) {
SegmentIterator firstSegment = segments_begin(span);
SegmentIterator lastSegment = segments_end(span) - 1;
if (firstSegment && lastSegment) {
ASSERT(firstSegment != lastSegment);
if (*firstSegment < minX)
minX = *firstSegment;
if (*lastSegment > maxX)
maxX = *lastSegment;
}
++span;
}
ASSERT(minX <= maxX);
ASSERT(minY <= maxY);
return IntRect(minX, minY, maxX - minX, maxY - minY);
}
void Region::Shape::translate(const IntSize& offset)
{
for (size_t i = 0; i < m_segments.size(); ++i)
m_segments[i] += offset.width();
for (size_t i = 0; i < m_spans.size(); ++i)
m_spans[i].y += offset.height();
}
void Region::Shape::swap(Shape& other)
{
m_segments.swap(other.m_segments);
m_spans.swap(other.m_spans);
}
enum {
Shape1,
Shape2,
};
template<typename Operation>
Region::Shape Region::Shape::shapeOperation(const Shape& shape1, const Shape& shape2)
{
COMPILE_ASSERT(!(!Operation::shouldAddRemainingSegmentsFromSpan1 && Operation::shouldAddRemainingSegmentsFromSpan2), invalid_segment_combination);
COMPILE_ASSERT(!(!Operation::shouldAddRemainingSpansFromShape1 && Operation::shouldAddRemainingSpansFromShape2), invalid_span_combination);
Shape result;
if (Operation::trySimpleOperation(shape1, shape2, result))
return result;
SpanIterator spans1 = shape1.spans_begin();
SpanIterator spans1End = shape1.spans_end();
SpanIterator spans2 = shape2.spans_begin();
SpanIterator spans2End = shape2.spans_end();
SegmentIterator segments1 = 0;
SegmentIterator segments1End = 0;
SegmentIterator segments2 = 0;
SegmentIterator segments2End = 0;
// Iterate over all spans.
while (spans1 != spans1End && spans2 != spans2End) {
int y = 0;
int test = spans1->y - spans2->y;
if (test <= 0) {
y = spans1->y;
segments1 = shape1.segments_begin(spans1);
segments1End = shape1.segments_end(spans1);
++spans1;
}
if (test >= 0) {
y = spans2->y;
segments2 = shape2.segments_begin(spans2);
segments2End = shape2.segments_end(spans2);
++spans2;
}
int flag = 0;
int oldFlag = 0;
SegmentIterator s1 = segments1;
SegmentIterator s2 = segments2;
Vector<int, 32> segments;
// Now iterate over the segments in each span and construct a new vector of segments.
while (s1 != segments1End && s2 != segments2End) {
int test = *s1 - *s2;
int x;
if (test <= 0) {
x = *s1;
flag = flag ^ 1;
++s1;
}
if (test >= 0) {
x = *s2;
flag = flag ^ 2;
++s2;
}
if (flag == Operation::opCode || oldFlag == Operation::opCode)
segments.append(x);
oldFlag = flag;
}
// Add any remaining segments.
if (Operation::shouldAddRemainingSegmentsFromSpan1 && s1 != segments1End)
segments.appendRange(s1, segments1End);
else if (Operation::shouldAddRemainingSegmentsFromSpan2 && s2 != segments2End)
segments.appendRange(s2, segments2End);
// Add the span.
if (!segments.isEmpty() || !result.isEmpty())
result.appendSpan(y, segments.data(), segments.data() + segments.size());
}
// Add any remaining spans.
if (Operation::shouldAddRemainingSpansFromShape1 && spans1 != spans1End)
result.appendSpans(shape1, spans1, spans1End);
else if (Operation::shouldAddRemainingSpansFromShape2 && spans2 != spans2End)
result.appendSpans(shape2, spans2, spans2End);
return result;
}
struct Region::Shape::UnionOperation {
static bool trySimpleOperation(const Shape& shape1, const Shape& shape2, Shape& result)
{
if (shape1.isEmpty()) {
result = shape2;
return true;
}
return false;
}
static const int opCode = 0;
static const bool shouldAddRemainingSegmentsFromSpan1 = true;
static const bool shouldAddRemainingSegmentsFromSpan2 = true;
static const bool shouldAddRemainingSpansFromShape1 = true;
static const bool shouldAddRemainingSpansFromShape2 = true;
};
Region::Shape Region::Shape::unionShapes(const Shape& shape1, const Shape& shape2)
{
return shapeOperation<UnionOperation>(shape1, shape2);
}
struct Region::Shape::IntersectOperation {
static bool trySimpleOperation(const Shape&, const Shape&, Shape&)
{
return false;
}
static const int opCode = 3;
static const bool shouldAddRemainingSegmentsFromSpan1 = false;
static const bool shouldAddRemainingSegmentsFromSpan2 = false;
static const bool shouldAddRemainingSpansFromShape1 = false;
static const bool shouldAddRemainingSpansFromShape2 = false;
};
Region::Shape Region::Shape::intersectShapes(const Shape& shape1, const Shape& shape2)
{
return shapeOperation<IntersectOperation>(shape1, shape2);
}
struct Region::Shape::SubtractOperation {
static bool trySimpleOperation(const Shape&, const Shape&, Region::Shape&)
{
return false;
}
static const int opCode = 1;
static const bool shouldAddRemainingSegmentsFromSpan1 = true;
static const bool shouldAddRemainingSegmentsFromSpan2 = false;
static const bool shouldAddRemainingSpansFromShape1 = true;
static const bool shouldAddRemainingSpansFromShape2 = false;
};
Region::Shape Region::Shape::subtractShapes(const Shape& shape1, const Shape& shape2)
{
return shapeOperation<SubtractOperation>(shape1, shape2);
}
#ifndef NDEBUG
void Region::dump() const
{
printf("Bounds: (%d, %d, %d, %d)\n",
m_bounds.x(), m_bounds.y(), m_bounds.width(), m_bounds.height());
m_shape.dump();
}
#endif
void Region::updateBoundsFromShape()
{
m_bounds = m_shape.bounds();
}
void Region::intersect(const Region& region)
{
if (m_bounds.isEmpty())
return;
if (!m_bounds.intersects(region.m_bounds)) {
m_shape = Shape();
m_bounds = IntRect();
return;
}
Shape intersectedShape = Shape::intersectShapes(m_shape, region.m_shape);
m_shape.swap(intersectedShape);
m_bounds = m_shape.bounds();
}
void Region::unite(const Region& region)
{
if (region.isEmpty())
return;
if (isRect() && m_bounds.contains(region.m_bounds))
return;
if (region.isRect() && region.m_bounds.contains(m_bounds)) {
m_shape = region.m_shape;
m_bounds = region.m_bounds;
return;
}
// FIXME: We may want another way to construct a Region without doing this test when we expect it to be false.
if (!isRect() && contains(region))
return;
Shape unitedShape = Shape::unionShapes(m_shape, region.m_shape);
m_shape.swap(unitedShape);
m_bounds.unite(region.m_bounds);
}
void Region::subtract(const Region& region)
{
if (m_bounds.isEmpty())
return;
if (region.isEmpty())
return;
if (!m_bounds.intersects(region.m_bounds))
return;
Shape subtractedShape = Shape::subtractShapes(m_shape, region.m_shape);
m_shape.swap(subtractedShape);
m_bounds = m_shape.bounds();
}
void Region::translate(const IntSize& offset)
{
m_bounds.move(offset);
m_shape.translate(offset);
}
} // namespace WebCore