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27 #include "platform/geometry/Region.h"
31 // A region class based on the paper "Scanline Coherent Shape Algebra"
32 // by Jonathan E. Steinhart from the book "Graphics Gems II".
34 // This implementation uses two vectors instead of linked list, and
35 // also compresses regions when possible.
43 Region::Region(const IntRect& rect)
49 Vector<IntRect> Region::rects() const
51 Vector<IntRect> rects;
53 for (Shape::SpanIterator span = m_shape.spansBegin(), end = m_shape.spansEnd(); span != end && span + 1 != end; ++span) {
55 int height = (span + 1)->y - y;
57 for (Shape::SegmentIterator segment = m_shape.segmentsBegin(span), end = m_shape.segmentsEnd(span); segment != end && segment + 1 != end; segment += 2) {
59 int width = *(segment + 1) - x;
61 rects.append(IntRect(x, y, width, height));
68 bool Region::contains(const Region& region) const
70 if (!m_bounds.contains(region.m_bounds))
73 return Shape::compareShapes<Shape::CompareContainsOperation>(m_shape, region.m_shape);
76 bool Region::contains(const IntPoint& point) const
78 if (!m_bounds.contains(point))
81 for (Shape::SpanIterator span = m_shape.spansBegin(), end = m_shape.spansEnd(); span != end && span + 1 != end; ++span) {
83 int maxY = (span + 1)->y;
87 if (maxY <= point.y())
90 for (Shape::SegmentIterator segment = m_shape.segmentsBegin(span), end = m_shape.segmentsEnd(span); segment != end && segment + 1 != end; segment += 2) {
92 int maxX = *(segment + 1);
104 bool Region::intersects(const Region& region) const
106 if (!m_bounds.intersects(region.m_bounds))
109 return Shape::compareShapes<Shape::CompareIntersectsOperation>(m_shape, region.m_shape);
112 unsigned Region::totalArea() const
114 Vector<IntRect> rects = this->rects();
115 size_t size = rects.size();
116 unsigned totalArea = 0;
118 for (size_t i = 0; i < size; ++i) {
119 IntRect rect = rects[i];
120 totalArea += (rect.width() * rect.height());
126 template<typename CompareOperation>
127 bool Region::Shape::compareShapes(const Shape& aShape, const Shape& bShape)
129 bool result = CompareOperation::defaultResult;
131 Shape::SpanIterator aSpan = aShape.spansBegin();
132 Shape::SpanIterator aSpanEnd = aShape.spansEnd();
133 Shape::SpanIterator bSpan = bShape.spansBegin();
134 Shape::SpanIterator bSpanEnd = bShape.spansEnd();
136 bool aHadSegmentInPreviousSpan = false;
137 bool bHadSegmentInPreviousSpan = false;
138 while (aSpan != aSpanEnd && aSpan + 1 != aSpanEnd && bSpan != bSpanEnd && bSpan + 1 != bSpanEnd) {
140 int aMaxY = (aSpan + 1)->y;
142 int bMaxY = (bSpan + 1)->y;
144 Shape::SegmentIterator aSegment = aShape.segmentsBegin(aSpan);
145 Shape::SegmentIterator aSegmentEnd = aShape.segmentsEnd(aSpan);
146 Shape::SegmentIterator bSegment = bShape.segmentsBegin(bSpan);
147 Shape::SegmentIterator bSegmentEnd = bShape.segmentsEnd(bSpan);
149 // 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.
150 bool aHasSegmentInSpan = aSegment != aSegmentEnd;
151 bool bHasSegmentInSpan = bSegment != bSegmentEnd;
152 if (aY < bY && !bHadSegmentInPreviousSpan && aHasSegmentInSpan && CompareOperation::aOutsideB(result))
154 if (bY < aY && !aHadSegmentInPreviousSpan && bHasSegmentInSpan && CompareOperation::bOutsideA(result))
157 aHadSegmentInPreviousSpan = aHasSegmentInSpan;
158 bHadSegmentInPreviousSpan = bHasSegmentInSpan;
160 bool spansOverlap = bMaxY > aY && bY < aMaxY;
162 while (aSegment != aSegmentEnd && bSegment != bSegmentEnd) {
164 int aMaxX = *(aSegment + 1);
166 int bMaxX = *(bSegment + 1);
168 bool segmentsOverlap = bMaxX > aX && bX < aMaxX;
169 if (segmentsOverlap && CompareOperation::aOverlapsB(result))
171 if (aX < bX && CompareOperation::aOutsideB(result))
173 if (bX < aX && CompareOperation::bOutsideA(result))
178 } else if (bMaxX < aMaxX) {
186 if (aSegment != aSegmentEnd && CompareOperation::aOutsideB(result))
188 if (bSegment != bSegmentEnd && CompareOperation::bOutsideA(result))
194 } else if (bMaxY < aMaxY) {
202 if (aSpan != aSpanEnd && aSpan + 1 != aSpanEnd && CompareOperation::aOutsideB(result))
204 if (bSpan != bSpanEnd && bSpan + 1 != bSpanEnd && CompareOperation::bOutsideA(result))
210 void Region::Shape::trimCapacities()
212 m_segments.shrinkToReasonableCapacity();
213 m_spans.shrinkToReasonableCapacity();
216 struct Region::Shape::CompareContainsOperation {
217 const static bool defaultResult = true;
218 inline static bool aOutsideB(bool& /* result */) { return false; }
219 inline static bool bOutsideA(bool& result) { result = false; return true; }
220 inline static bool aOverlapsB(bool& /* result */) { return false; }
223 struct Region::Shape::CompareIntersectsOperation {
224 const static bool defaultResult = false;
225 inline static bool aOutsideB(bool& /* result */) { return false; }
226 inline static bool bOutsideA(bool& /* result */) { return false; }
227 inline static bool aOverlapsB(bool& result) { result = true; return true; }
230 Region::Shape::Shape()
234 Region::Shape::Shape(const IntRect& rect)
236 appendSpan(rect.y());
237 appendSegment(rect.x());
238 appendSegment(rect.maxX());
239 appendSpan(rect.maxY());
242 Region::Shape::Shape(size_t segmentsCapacity, size_t spansCapacity)
244 m_segments.reserveCapacity(segmentsCapacity);
245 m_spans.reserveCapacity(spansCapacity);
248 void Region::Shape::appendSpan(int y)
250 m_spans.append(Span(y, m_segments.size()));
253 bool Region::Shape::canCoalesce(SegmentIterator begin, SegmentIterator end)
255 if (m_spans.isEmpty())
258 SegmentIterator lastSpanBegin = m_segments.data() + m_spans.last().segmentIndex;
259 SegmentIterator lastSpanEnd = m_segments.data() + m_segments.size();
261 // Check if both spans have an equal number of segments.
262 if (lastSpanEnd - lastSpanBegin != end - begin)
265 // Check if both spans are equal.
266 if (!std::equal(begin, end, lastSpanBegin))
269 // Since the segments are equal the second segment can just be ignored.
273 void Region::Shape::appendSpan(int y, SegmentIterator begin, SegmentIterator end)
275 if (canCoalesce(begin, end))
279 m_segments.appendRange(begin, end);
282 void Region::Shape::appendSpans(const Shape& shape, SpanIterator begin, SpanIterator end)
284 for (SpanIterator it = begin; it != end; ++it)
285 appendSpan(it->y, shape.segmentsBegin(it), shape.segmentsEnd(it));
288 void Region::Shape::appendSegment(int x)
290 m_segments.append(x);
293 Region::Shape::SpanIterator Region::Shape::spansBegin() const
295 return m_spans.data();
298 Region::Shape::SpanIterator Region::Shape::spansEnd() const
300 return m_spans.data() + m_spans.size();
303 Region::Shape::SegmentIterator Region::Shape::segmentsBegin(SpanIterator it) const
305 ASSERT(it >= m_spans.data());
306 ASSERT(it < m_spans.data() + m_spans.size());
308 // Check if this span has any segments.
309 if (it->segmentIndex == m_segments.size())
312 return &m_segments[it->segmentIndex];
315 Region::Shape::SegmentIterator Region::Shape::segmentsEnd(SpanIterator it) const
317 ASSERT(it >= m_spans.data());
318 ASSERT(it < m_spans.data() + m_spans.size());
320 // Check if this span has any segments.
321 if (it->segmentIndex == m_segments.size())
324 ASSERT(it + 1 < m_spans.data() + m_spans.size());
325 size_t segmentIndex = (it + 1)->segmentIndex;
327 ASSERT_WITH_SECURITY_IMPLICATION(segmentIndex <= m_segments.size());
328 return m_segments.data() + segmentIndex;
332 void Region::Shape::dump() const
334 for (Shape::SpanIterator span = spansBegin(), end = spansEnd(); span != end; ++span) {
335 printf("%6d: (", span->y);
337 for (Shape::SegmentIterator segment = segmentsBegin(span), end = segmentsEnd(span); segment != end; ++segment)
338 printf("%d ", *segment);
346 IntRect Region::Shape::bounds() const
351 SpanIterator span = spansBegin();
354 SpanIterator lastSpan = spansEnd() - 1;
355 int maxY = lastSpan->y;
357 int minX = std::numeric_limits<int>::max();
358 int maxX = std::numeric_limits<int>::min();
360 while (span != lastSpan) {
361 SegmentIterator firstSegment = segmentsBegin(span);
362 SegmentIterator lastSegment = segmentsEnd(span) - 1;
364 if (firstSegment && lastSegment) {
365 ASSERT(firstSegment != lastSegment);
367 if (*firstSegment < minX)
368 minX = *firstSegment;
370 if (*lastSegment > maxX)
377 ASSERT(minX <= maxX);
378 ASSERT(minY <= maxY);
380 return IntRect(minX, minY, maxX - minX, maxY - minY);
383 void Region::Shape::translate(const IntSize& offset)
385 for (size_t i = 0; i < m_segments.size(); ++i)
386 m_segments[i] += offset.width();
387 for (size_t i = 0; i < m_spans.size(); ++i)
388 m_spans[i].y += offset.height();
391 void Region::Shape::swap(Shape& other)
393 m_segments.swap(other.m_segments);
394 m_spans.swap(other.m_spans);
402 template<typename Operation>
403 Region::Shape Region::Shape::shapeOperation(const Shape& shape1, const Shape& shape2)
405 COMPILE_ASSERT(!(!Operation::shouldAddRemainingSegmentsFromSpan1 && Operation::shouldAddRemainingSegmentsFromSpan2), invalid_segment_combination);
406 COMPILE_ASSERT(!(!Operation::shouldAddRemainingSpansFromShape1 && Operation::shouldAddRemainingSpansFromShape2), invalid_span_combination);
408 size_t segmentsCapacity = shape1.segmentsSize() + shape2.segmentsSize();
409 size_t spansCapacity = shape1.spansSize() + shape2.spansSize();
410 Shape result(segmentsCapacity, spansCapacity);
411 if (Operation::trySimpleOperation(shape1, shape2, result))
414 SpanIterator spans1 = shape1.spansBegin();
415 SpanIterator spans1End = shape1.spansEnd();
417 SpanIterator spans2 = shape2.spansBegin();
418 SpanIterator spans2End = shape2.spansEnd();
420 SegmentIterator segments1 = 0;
421 SegmentIterator segments1End = 0;
423 SegmentIterator segments2 = 0;
424 SegmentIterator segments2End = 0;
426 Vector<int, 32> segments;
427 segments.reserveCapacity(std::max(shape1.segmentsSize(), shape2.segmentsSize()));
429 // Iterate over all spans.
430 while (spans1 != spans1End && spans2 != spans2End) {
432 int test = spans1->y - spans2->y;
437 segments1 = shape1.segmentsBegin(spans1);
438 segments1End = shape1.segmentsEnd(spans1);
444 segments2 = shape2.segmentsBegin(spans2);
445 segments2End = shape2.segmentsEnd(spans2);
452 SegmentIterator s1 = segments1;
453 SegmentIterator s2 = segments2;
455 // Clear vector without dropping capacity.
457 ASSERT(segments.capacity());
459 // Now iterate over the segments in each span and construct a new vector of segments.
460 while (s1 != segments1End && s2 != segments2End) {
461 int test = *s1 - *s2;
475 if (flag == Operation::opCode || oldFlag == Operation::opCode)
481 // Add any remaining segments.
482 if (Operation::shouldAddRemainingSegmentsFromSpan1 && s1 != segments1End)
483 segments.appendRange(s1, segments1End);
484 else if (Operation::shouldAddRemainingSegmentsFromSpan2 && s2 != segments2End)
485 segments.appendRange(s2, segments2End);
488 if (!segments.isEmpty() || !result.isEmpty())
489 result.appendSpan(y, segments.data(), segments.data() + segments.size());
492 // Add any remaining spans.
493 if (Operation::shouldAddRemainingSpansFromShape1 && spans1 != spans1End)
494 result.appendSpans(shape1, spans1, spans1End);
495 else if (Operation::shouldAddRemainingSpansFromShape2 && spans2 != spans2End)
496 result.appendSpans(shape2, spans2, spans2End);
498 result.trimCapacities();
503 struct Region::Shape::UnionOperation {
504 static bool trySimpleOperation(const Shape& shape1, const Shape& shape2, Shape& result)
506 if (shape1.isEmpty()) {
514 static const int opCode = 0;
516 static const bool shouldAddRemainingSegmentsFromSpan1 = true;
517 static const bool shouldAddRemainingSegmentsFromSpan2 = true;
518 static const bool shouldAddRemainingSpansFromShape1 = true;
519 static const bool shouldAddRemainingSpansFromShape2 = true;
522 Region::Shape Region::Shape::unionShapes(const Shape& shape1, const Shape& shape2)
524 return shapeOperation<UnionOperation>(shape1, shape2);
527 struct Region::Shape::IntersectOperation {
528 static bool trySimpleOperation(const Shape&, const Shape&, Shape&)
533 static const int opCode = 3;
535 static const bool shouldAddRemainingSegmentsFromSpan1 = false;
536 static const bool shouldAddRemainingSegmentsFromSpan2 = false;
537 static const bool shouldAddRemainingSpansFromShape1 = false;
538 static const bool shouldAddRemainingSpansFromShape2 = false;
541 Region::Shape Region::Shape::intersectShapes(const Shape& shape1, const Shape& shape2)
543 return shapeOperation<IntersectOperation>(shape1, shape2);
546 struct Region::Shape::SubtractOperation {
547 static bool trySimpleOperation(const Shape&, const Shape&, Region::Shape&)
552 static const int opCode = 1;
554 static const bool shouldAddRemainingSegmentsFromSpan1 = true;
555 static const bool shouldAddRemainingSegmentsFromSpan2 = false;
556 static const bool shouldAddRemainingSpansFromShape1 = true;
557 static const bool shouldAddRemainingSpansFromShape2 = false;
560 Region::Shape Region::Shape::subtractShapes(const Shape& shape1, const Shape& shape2)
562 return shapeOperation<SubtractOperation>(shape1, shape2);
566 void Region::dump() const
568 printf("Bounds: (%d, %d, %d, %d)\n", m_bounds.x(), m_bounds.y(), m_bounds.width(), m_bounds.height());
573 void Region::intersect(const Region& region)
575 if (m_bounds.isEmpty())
577 if (!m_bounds.intersects(region.m_bounds)) {
579 m_bounds = IntRect();
583 Shape intersectedShape = Shape::intersectShapes(m_shape, region.m_shape);
585 m_shape.swap(intersectedShape);
586 m_bounds = m_shape.bounds();
589 void Region::unite(const Region& region)
591 if (region.isEmpty())
593 if (isRect() && m_bounds.contains(region.m_bounds))
595 if (region.isRect() && region.m_bounds.contains(m_bounds)) {
596 m_shape = region.m_shape;
597 m_bounds = region.m_bounds;
600 // FIXME: We may want another way to construct a Region without doing this test when we expect it to be false.
601 if (!isRect() && contains(region))
604 Shape unitedShape = Shape::unionShapes(m_shape, region.m_shape);
606 m_shape.swap(unitedShape);
607 m_bounds.unite(region.m_bounds);
610 void Region::subtract(const Region& region)
612 if (m_bounds.isEmpty())
614 if (region.isEmpty())
616 if (!m_bounds.intersects(region.m_bounds))
619 Shape subtractedShape = Shape::subtractShapes(m_shape, region.m_shape);
621 m_shape.swap(subtractedShape);
622 m_bounds = m_shape.bounds();
625 void Region::translate(const IntSize& offset)
627 m_bounds.move(offset);
628 m_shape.translate(offset);