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-rw-r--r--gfx/src/nsRegion.cpp1024
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diff --git a/gfx/src/nsRegion.cpp b/gfx/src/nsRegion.cpp
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+++ b/gfx/src/nsRegion.cpp
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+/* -*- 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 "nsRegion.h"
+#include "nsTArray.h"
+#include "gfxUtils.h"
+#include "gfx2DGlue.h"
+#include "mozilla/ToString.h"
+
+void nsRegion::AssertStateInternal() const {
+ bool failed = false;
+ // Verify consistent state inside the region.
+ int32_t lastY = INT32_MIN;
+ int32_t lowestX = INT32_MAX;
+ int32_t highestX = INT32_MIN;
+ for (auto iter = mBands.begin(); iter != mBands.end(); iter++) {
+ const Band& band = *iter;
+ if (band.bottom <= band.top) {
+ failed = true;
+ break;
+ }
+ if (band.top < lastY) {
+ failed = true;
+ break;
+ }
+ lastY = band.bottom;
+
+ lowestX = std::min(lowestX, band.mStrips.begin()->left);
+ highestX = std::max(highestX, band.mStrips.LastElement().right);
+
+ int32_t lastX = INT32_MIN;
+ if (iter != mBands.begin()) {
+ auto prev = iter;
+ prev--;
+
+ if (prev->bottom == iter->top) {
+ if (band.EqualStrips(*prev)) {
+ failed = true;
+ break;
+ }
+ }
+ }
+ for (const Strip& strip : band.mStrips) {
+ if (strip.right <= strip.left) {
+ failed = true;
+ break;
+ }
+ if (strip.left <= lastX) {
+ failed = true;
+ break;
+ }
+ lastX = strip.right;
+ }
+ if (failed) {
+ break;
+ }
+ }
+
+ if (!(mBounds.IsEqualEdges(CalculateBounds()))) {
+ failed = true;
+ }
+
+ if (failed) {
+#ifdef DEBUG_REGIONS
+ if (mCurrentOpGenerator) {
+ mCurrentOpGenerator->OutputOp();
+ }
+#endif
+ MOZ_ASSERT(false);
+ }
+}
+
+bool nsRegion::Contains(const nsRegion& aRgn) const {
+ // XXX this could be made faster by iterating over
+ // both regions at the same time some how
+ for (auto iter = aRgn.RectIter(); !iter.Done(); iter.Next()) {
+ if (!Contains(iter.Get())) {
+ return false;
+ }
+ }
+ return true;
+}
+
+bool nsRegion::Intersects(const nsRectAbsolute& aRect) const {
+ if (mBands.IsEmpty()) {
+ return mBounds.Intersects(aRect);
+ }
+
+ if (!mBounds.Intersects(aRect)) {
+ return false;
+ }
+
+ Strip rectStrip(aRect.X(), aRect.XMost());
+
+ auto iter = mBands.begin();
+ while (iter != mBands.end()) {
+ if (iter->top >= aRect.YMost()) {
+ return false;
+ }
+
+ if (iter->bottom <= aRect.Y()) {
+ // This band is entirely before aRect, move on.
+ iter++;
+ continue;
+ }
+
+ if (!iter->Intersects(rectStrip)) {
+ // This band does not intersect aRect horizontally. Move on.
+ iter++;
+ continue;
+ }
+
+ // This band intersects with aRect.
+ return true;
+ }
+
+ return false;
+}
+
+void nsRegion::Inflate(const nsMargin& aMargin) {
+ nsRegion newRegion;
+ for (RectIterator iter = RectIterator(*this); !iter.Done(); iter.Next()) {
+ nsRectAbsolute rect = iter.GetAbsolute();
+ rect.Inflate(aMargin);
+ newRegion.AddRect(rect);
+ }
+
+ *this = std::move(newRegion);
+}
+
+void nsRegion::SimplifyOutward(uint32_t aMaxRects) {
+ MOZ_ASSERT(aMaxRects >= 1, "Invalid max rect count");
+
+ if (GetNumRects() <= aMaxRects) {
+ return;
+ }
+
+ // Try combining rects in horizontal bands into a single rect
+ // The goal here is to try to keep groups of rectangles that are vertically
+ // discontiguous as separate rectangles in the final region. This is
+ // simple and fast to implement and page contents tend to vary more
+ // vertically than horizontally (which is why our rectangles are stored
+ // sorted by y-coordinate, too).
+ //
+ // Note: if boxes share y1 because of the canonical representation they
+ // will share y2
+
+ size_t idx = 0;
+
+ while (idx < mBands.Length()) {
+ size_t oldIdx = idx;
+ mBands[idx].mStrips.begin()->right =
+ mBands[idx].mStrips.LastElement().right;
+ mBands[idx].mStrips.TruncateLength(1);
+ idx++;
+
+ // Merge any bands with the same bounds.
+ while (idx < mBands.Length() &&
+ mBands[idx].mStrips.begin()->left ==
+ mBands[oldIdx].mStrips.begin()->left &&
+ mBands[idx].mStrips.LastElement().right ==
+ mBands[oldIdx].mStrips.begin()->right) {
+ mBands[oldIdx].bottom = mBands[idx].bottom;
+ mBands.RemoveElementAt(idx);
+ }
+ }
+
+ AssertState();
+
+ // mBands.size() is now equal to our rect count.
+ if (mBands.Length() > aMaxRects) {
+ *this = GetBounds();
+ }
+}
+
+// compute the covered area difference between two rows.
+// by iterating over both rows simultaneously and adding up
+// the additional increase in area caused by extending each
+// of the rectangles to the combined height of both rows
+uint32_t nsRegion::ComputeMergedAreaIncrease(const Band& aTopBand,
+ const Band& aBottomBand) {
+ uint32_t totalArea = 0;
+
+ uint32_t topHeight = aBottomBand.top - aTopBand.top;
+ uint32_t bottomHeight = aBottomBand.bottom - aTopBand.bottom;
+ uint32_t currentStripBottom = 0;
+
+ // This could be done with slightly better worse case performance by merging
+ // these two for-loops, but this makes the code a lot easier to understand.
+ for (auto& strip : aTopBand.mStrips) {
+ if (currentStripBottom == aBottomBand.mStrips.Length() ||
+ strip.right < aBottomBand.mStrips[currentStripBottom].left) {
+ totalArea += bottomHeight * strip.Size();
+ continue;
+ }
+
+ int32_t currentX = strip.left;
+ while (currentStripBottom != aBottomBand.mStrips.Length() &&
+ aBottomBand.mStrips[currentStripBottom].left < strip.right) {
+ if (currentX >= strip.right) {
+ break;
+ }
+ if (currentX < aBottomBand.mStrips[currentStripBottom].left) {
+ // Add the part that's not intersecting.
+ totalArea += (aBottomBand.mStrips[currentStripBottom].left - currentX) *
+ bottomHeight;
+ }
+
+ currentX =
+ std::max(aBottomBand.mStrips[currentStripBottom].right, currentX);
+ currentStripBottom++;
+ }
+
+ // Add remainder of this strip.
+ if (currentX < strip.right) {
+ totalArea += (strip.right - currentX) * bottomHeight;
+ }
+ if (currentStripBottom) {
+ currentStripBottom--;
+ }
+ }
+ uint32_t currentStripTop = 0;
+ for (auto& strip : aBottomBand.mStrips) {
+ if (currentStripTop == aTopBand.mStrips.Length() ||
+ strip.right < aTopBand.mStrips[currentStripTop].left) {
+ totalArea += topHeight * strip.Size();
+ continue;
+ }
+
+ int32_t currentX = strip.left;
+ while (currentStripTop != aTopBand.mStrips.Length() &&
+ aTopBand.mStrips[currentStripTop].left < strip.right) {
+ if (currentX >= strip.right) {
+ break;
+ }
+ if (currentX < aTopBand.mStrips[currentStripTop].left) {
+ // Add the part that's not intersecting.
+ totalArea +=
+ (aTopBand.mStrips[currentStripTop].left - currentX) * topHeight;
+ }
+
+ currentX = std::max(aTopBand.mStrips[currentStripTop].right, currentX);
+ currentStripTop++;
+ }
+
+ // Add remainder of this strip.
+ if (currentX < strip.right) {
+ totalArea += (strip.right - currentX) * topHeight;
+ }
+ if (currentStripTop) {
+ currentStripTop--;
+ }
+ }
+ return totalArea;
+}
+
+void nsRegion::SimplifyOutwardByArea(uint32_t aThreshold) {
+ if (mBands.Length() < 2) {
+ // We have only one or no row and we're done.
+ return;
+ }
+
+ uint32_t currentBand = 0;
+ do {
+ Band& band = mBands[currentBand];
+
+ uint32_t totalArea =
+ ComputeMergedAreaIncrease(band, mBands[currentBand + 1]);
+
+ if (totalArea <= aThreshold) {
+ for (Strip& strip : mBands[currentBand + 1].mStrips) {
+ // This could use an optimized function to merge two bands.
+ band.InsertStrip(strip);
+ }
+ band.bottom = mBands[currentBand + 1].bottom;
+ mBands.RemoveElementAt(currentBand + 1);
+ } else {
+ currentBand++;
+ }
+ } while (currentBand + 1 < mBands.Length());
+
+ EnsureSimplified();
+ AssertState();
+}
+
+typedef void (*visit_fn)(void* closure, VisitSide side, int x1, int y1, int x2,
+ int y2);
+
+void nsRegion::VisitEdges(visit_fn visit, void* closure) const {
+ if (mBands.IsEmpty()) {
+ visit(closure, VisitSide::LEFT, mBounds.X(), mBounds.Y(), mBounds.X(),
+ mBounds.YMost());
+ visit(closure, VisitSide::RIGHT, mBounds.XMost(), mBounds.Y(),
+ mBounds.XMost(), mBounds.YMost());
+ visit(closure, VisitSide::TOP, mBounds.X() - 1, mBounds.Y(),
+ mBounds.XMost() + 1, mBounds.Y());
+ visit(closure, VisitSide::BOTTOM, mBounds.X() - 1, mBounds.YMost(),
+ mBounds.XMost() + 1, mBounds.YMost());
+ return;
+ }
+
+ auto band = std::begin(mBands);
+ auto bandFinal = std::end(mBands);
+ bandFinal--;
+ for (const Strip& strip : band->mStrips) {
+ visit(closure, VisitSide::LEFT, strip.left, band->top, strip.left,
+ band->bottom);
+ visit(closure, VisitSide::RIGHT, strip.right, band->top, strip.right,
+ band->bottom);
+ visit(closure, VisitSide::TOP, strip.left - 1, band->top, strip.right + 1,
+ band->top);
+ }
+
+ if (band != bandFinal) {
+ do {
+ const Band& topBand = *band;
+ band++;
+
+ for (const Strip& strip : band->mStrips) {
+ visit(closure, VisitSide::LEFT, strip.left, band->top, strip.left,
+ band->bottom);
+ visit(closure, VisitSide::RIGHT, strip.right, band->top, strip.right,
+ band->bottom);
+ }
+
+ if (band->top == topBand.bottom) {
+ // Two bands touching each other vertically.
+ const Band& bottomBand = *band;
+ auto topStrip = std::begin(topBand.mStrips);
+ auto bottomStrip = std::begin(bottomBand.mStrips);
+
+ int y = topBand.bottom;
+
+ // State from this point on along the vertical edge:
+ // 0 - Empty
+ // 1 - Touched by top rect
+ // 2 - Touched by bottom rect
+ // 3 - Touched on both sides
+ int state;
+ const int TouchedByNothing = 0;
+ const int TouchedByTop = 1;
+ const int TouchedByBottom = 2;
+ // We always start with nothing.
+ int oldState = TouchedByNothing;
+ // Last state change, adjusted by -1 if the last state change was
+ // a change away from 0.
+ int lastX = std::min(topStrip->left, bottomStrip->left) - 1;
+
+ // Current edge being considered for top and bottom,
+ // 0 - left, 1 - right.
+ bool topEdgeIsLeft = true;
+ bool bottomEdgeIsLeft = true;
+ while (topStrip != std::end(topBand.mStrips) &&
+ bottomStrip != std::end(bottomBand.mStrips)) {
+ int topPos;
+ int bottomPos;
+ if (topEdgeIsLeft) {
+ topPos = topStrip->left;
+ } else {
+ topPos = topStrip->right;
+ }
+ if (bottomEdgeIsLeft) {
+ bottomPos = bottomStrip->left;
+ } else {
+ bottomPos = bottomStrip->right;
+ }
+
+ int currentX = std::min(topPos, bottomPos);
+ if (topPos < bottomPos) {
+ if (topEdgeIsLeft) {
+ state = oldState | TouchedByTop;
+ } else {
+ state = oldState ^ TouchedByTop;
+ topStrip++;
+ }
+ topEdgeIsLeft = !topEdgeIsLeft;
+ } else if (bottomPos < topPos) {
+ if (bottomEdgeIsLeft) {
+ state = oldState | TouchedByBottom;
+ } else {
+ state = oldState ^ TouchedByBottom;
+ bottomStrip++;
+ }
+ bottomEdgeIsLeft = !bottomEdgeIsLeft;
+ } else {
+ // bottomPos == topPos
+ state = TouchedByNothing;
+ if (bottomEdgeIsLeft) {
+ state = TouchedByBottom;
+ } else {
+ bottomStrip++;
+ }
+ if (topEdgeIsLeft) {
+ state |= TouchedByTop;
+ } else {
+ topStrip++;
+ }
+ topEdgeIsLeft = !topEdgeIsLeft;
+ bottomEdgeIsLeft = !bottomEdgeIsLeft;
+ }
+
+ MOZ_ASSERT(state != oldState);
+ if (oldState == TouchedByNothing) {
+ // We had nothing before, make sure the left edge will be padded.
+ lastX = currentX - 1;
+ } else if (oldState == TouchedByTop) {
+ if (state == TouchedByNothing) {
+ visit(closure, VisitSide::BOTTOM, lastX, y, currentX + 1, y);
+ } else {
+ visit(closure, VisitSide::BOTTOM, lastX, y, currentX, y);
+ lastX = currentX;
+ }
+ } else if (oldState == TouchedByBottom) {
+ if (state == TouchedByNothing) {
+ visit(closure, VisitSide::TOP, lastX, y, currentX + 1, y);
+ } else {
+ visit(closure, VisitSide::TOP, lastX, y, currentX, y);
+ lastX = currentX;
+ }
+ } else {
+ lastX = currentX;
+ }
+ oldState = state;
+ }
+
+ MOZ_ASSERT(!state || (topEdgeIsLeft || bottomEdgeIsLeft));
+ if (topStrip != std::end(topBand.mStrips)) {
+ if (!topEdgeIsLeft) {
+ visit(closure, VisitSide::BOTTOM, lastX, y, topStrip->right + 1, y);
+ topStrip++;
+ }
+ while (topStrip != std::end(topBand.mStrips)) {
+ visit(closure, VisitSide::BOTTOM, topStrip->left - 1, y,
+ topStrip->right + 1, y);
+ topStrip++;
+ }
+ } else if (bottomStrip != std::end(bottomBand.mStrips)) {
+ if (!bottomEdgeIsLeft) {
+ visit(closure, VisitSide::TOP, lastX, y, bottomStrip->right + 1, y);
+ bottomStrip++;
+ }
+ while (bottomStrip != std::end(bottomBand.mStrips)) {
+ visit(closure, VisitSide::TOP, bottomStrip->left - 1, y,
+ bottomStrip->right + 1, y);
+ bottomStrip++;
+ }
+ }
+ } else {
+ for (const Strip& strip : topBand.mStrips) {
+ visit(closure, VisitSide::BOTTOM, strip.left - 1, topBand.bottom,
+ strip.right + 1, topBand.bottom);
+ }
+ for (const Strip& strip : band->mStrips) {
+ visit(closure, VisitSide::TOP, strip.left - 1, band->top,
+ strip.right + 1, band->top);
+ }
+ }
+ } while (band != bandFinal);
+ }
+
+ for (const Strip& strip : band->mStrips) {
+ visit(closure, VisitSide::BOTTOM, strip.left - 1, band->bottom,
+ strip.right + 1, band->bottom);
+ }
+}
+
+void nsRegion::SimplifyInward(uint32_t aMaxRects) {
+ NS_ASSERTION(aMaxRects >= 1, "Invalid max rect count");
+
+ if (GetNumRects() <= aMaxRects) return;
+
+ SetEmpty();
+}
+
+uint64_t nsRegion::Area() const {
+ if (mBands.IsEmpty()) {
+ return mBounds.Area();
+ }
+
+ uint64_t area = 0;
+ for (const Band& band : mBands) {
+ uint32_t height = band.bottom - band.top;
+ for (const Strip& strip : band.mStrips) {
+ area += (strip.right - strip.left) * height;
+ }
+ }
+
+ return area;
+}
+
+nsRegion& nsRegion::ScaleRoundOut(float aXScale, float aYScale) {
+ if (mozilla::gfx::FuzzyEqual(aXScale, 1.0f) &&
+ mozilla::gfx::FuzzyEqual(aYScale, 1.0f)) {
+ return *this;
+ }
+
+ nsRegion newRegion;
+ for (RectIterator iter = RectIterator(*this); !iter.Done(); iter.Next()) {
+ nsRectAbsolute rect = iter.GetAbsolute();
+ rect.ScaleRoundOut(aXScale, aYScale);
+ newRegion.AddRect(rect);
+ }
+
+ *this = std::move(newRegion);
+ return *this;
+}
+
+nsRegion& nsRegion::ScaleInverseRoundOut(float aXScale, float aYScale) {
+ nsRegion newRegion;
+ for (RectIterator iter = RectIterator(*this); !iter.Done(); iter.Next()) {
+ nsRectAbsolute rect = iter.GetAbsolute();
+ rect.ScaleInverseRoundOut(aXScale, aYScale);
+ newRegion.AddRect(rect);
+ }
+
+ *this = std::move(newRegion);
+ return *this;
+}
+
+static mozilla::gfx::IntRect TransformRect(
+ const mozilla::gfx::IntRect& aRect,
+ const mozilla::gfx::Matrix4x4& aTransform) {
+ if (aRect.IsEmpty()) {
+ return mozilla::gfx::IntRect();
+ }
+
+ mozilla::gfx::RectDouble rect(aRect.X(), aRect.Y(), aRect.Width(),
+ aRect.Height());
+ rect = aTransform.TransformAndClipBounds(
+ rect, mozilla::gfx::RectDouble::MaxIntRect());
+ rect.RoundOut();
+
+ mozilla::gfx::IntRect intRect;
+ if (!gfxUtils::GfxRectToIntRect(ThebesRect(rect), &intRect)) {
+ return mozilla::gfx::IntRect();
+ }
+
+ return intRect;
+}
+
+nsRegion& nsRegion::Transform(const mozilla::gfx::Matrix4x4& aTransform) {
+ nsRegion newRegion;
+ for (RectIterator iter = RectIterator(*this); !iter.Done(); iter.Next()) {
+ nsRect rect = nsIntRegion::ToRect(
+ TransformRect(nsIntRegion::FromRect(iter.Get()), aTransform));
+ newRegion.AddRect(nsRectAbsolute::FromRect(rect));
+ }
+
+ *this = std::move(newRegion);
+ return *this;
+}
+
+nsRegion nsRegion::ScaleToOtherAppUnitsRoundOut(int32_t aFromAPP,
+ int32_t aToAPP) const {
+ if (aFromAPP == aToAPP) {
+ return *this;
+ }
+ nsRegion newRegion;
+ for (RectIterator iter = RectIterator(*this); !iter.Done(); iter.Next()) {
+ nsRect rect = iter.Get();
+ rect = rect.ScaleToOtherAppUnitsRoundOut(aFromAPP, aToAPP);
+ newRegion.AddRect(nsRectAbsolute::FromRect(rect));
+ }
+
+ return newRegion;
+}
+
+nsRegion nsRegion::ScaleToOtherAppUnitsRoundIn(int32_t aFromAPP,
+ int32_t aToAPP) const {
+ if (aFromAPP == aToAPP) {
+ return *this;
+ }
+
+ nsRegion newRegion;
+ for (RectIterator iter = RectIterator(*this); !iter.Done(); iter.Next()) {
+ nsRect rect = iter.Get();
+ rect = rect.ScaleToOtherAppUnitsRoundIn(aFromAPP, aToAPP);
+ newRegion.AddRect(nsRectAbsolute::FromRect(rect));
+ }
+
+ return newRegion;
+}
+
+nsIntRegion nsRegion::ToPixels(nscoord aAppUnitsPerPixel,
+ bool aOutsidePixels) const {
+ nsIntRegion intRegion;
+ for (RectIterator iter = RectIterator(*this); !iter.Done(); iter.Next()) {
+ mozilla::gfx::IntRect deviceRect;
+ nsRect rect = iter.Get();
+ if (aOutsidePixels)
+ deviceRect = rect.ToOutsidePixels(aAppUnitsPerPixel);
+ else
+ deviceRect = rect.ToNearestPixels(aAppUnitsPerPixel);
+ intRegion.OrWith(deviceRect);
+ }
+
+ return intRegion;
+}
+
+nsIntRegion nsRegion::ToOutsidePixels(nscoord aAppUnitsPerPixel) const {
+ return ToPixels(aAppUnitsPerPixel, true);
+}
+
+nsIntRegion nsRegion::ToNearestPixels(nscoord aAppUnitsPerPixel) const {
+ return ToPixels(aAppUnitsPerPixel, false);
+}
+
+nsIntRegion nsRegion::ScaleToNearestPixels(float aScaleX, float aScaleY,
+ nscoord aAppUnitsPerPixel) const {
+ nsIntRegion result;
+ for (auto iter = RectIter(); !iter.Done(); iter.Next()) {
+ mozilla::gfx::IntRect deviceRect =
+ iter.Get().ScaleToNearestPixels(aScaleX, aScaleY, aAppUnitsPerPixel);
+ result.Or(result, deviceRect);
+ }
+ return result;
+}
+
+nsIntRegion nsRegion::ScaleToOutsidePixels(float aScaleX, float aScaleY,
+ nscoord aAppUnitsPerPixel) const {
+ // make a copy of the region so that we can mutate it inplace
+ nsIntRegion intRegion;
+ for (RectIterator iter = RectIterator(*this); !iter.Done(); iter.Next()) {
+ nsRect rect = iter.Get();
+ intRegion.OrWith(
+ rect.ScaleToOutsidePixels(aScaleX, aScaleY, aAppUnitsPerPixel));
+ }
+ return intRegion;
+}
+
+nsIntRegion nsRegion::ScaleToInsidePixels(float aScaleX, float aScaleY,
+ nscoord aAppUnitsPerPixel) const {
+ /* When scaling a rect, walk forward through the rect list up until the y
+ * value is greater than the current rect's YMost() value.
+ *
+ * For each rect found, check if the rects have a touching edge (in unscaled
+ * coordinates), and if one edge is entirely contained within the other.
+ *
+ * If it is, then the contained edge can be moved (in scaled pixels) to ensure
+ * that no gap exists.
+ *
+ * Since this could be potentially expensive - O(n^2), we only attempt this
+ * algorithm for the first rect.
+ */
+
+ if (mBands.IsEmpty()) {
+ nsIntRect rect = mBounds.ToNSRect().ScaleToInsidePixels(aScaleX, aScaleY,
+ aAppUnitsPerPixel);
+ return nsIntRegion(rect);
+ }
+
+ nsIntRegion intRegion;
+ RectIterator iter = RectIterator(*this);
+
+ nsRect first = iter.Get();
+
+ mozilla::gfx::IntRect firstDeviceRect =
+ first.ScaleToInsidePixels(aScaleX, aScaleY, aAppUnitsPerPixel);
+
+ for (iter.Next(); !iter.Done(); iter.Next()) {
+ nsRect rect = iter.Get();
+ mozilla::gfx::IntRect deviceRect =
+ rect.ScaleToInsidePixels(aScaleX, aScaleY, aAppUnitsPerPixel);
+
+ if (rect.Y() <= first.YMost()) {
+ if (rect.XMost() == first.X() && rect.YMost() <= first.YMost()) {
+ // rect is touching on the left edge of the first rect and contained
+ // within the length of its left edge
+ deviceRect.SetRightEdge(firstDeviceRect.X());
+ } else if (rect.X() == first.XMost() && rect.YMost() <= first.YMost()) {
+ // rect is touching on the right edge of the first rect and contained
+ // within the length of its right edge
+ deviceRect.SetLeftEdge(firstDeviceRect.XMost());
+ } else if (rect.Y() == first.YMost()) {
+ // The bottom of the first rect is on the same line as the top of rect,
+ // but they aren't necessarily contained.
+ if (rect.X() <= first.X() && rect.XMost() >= first.XMost()) {
+ // The top of rect contains the bottom of the first rect
+ firstDeviceRect.SetBottomEdge(deviceRect.Y());
+ } else if (rect.X() >= first.X() && rect.XMost() <= first.XMost()) {
+ // The bottom of the first contains the top of rect
+ deviceRect.SetTopEdge(firstDeviceRect.YMost());
+ }
+ }
+ }
+
+ intRegion.OrWith(deviceRect);
+ }
+
+ intRegion.OrWith(firstDeviceRect);
+ return intRegion;
+}
+
+// A cell's "value" is a pair consisting of
+// a) the area of the subrectangle it corresponds to, if it's in
+// aContainingRect and in the region, 0 otherwise
+// b) the area of the subrectangle it corresponds to, if it's in the region,
+// 0 otherwise
+// Addition, subtraction and identity are defined on these values in the
+// obvious way. Partial order is lexicographic.
+// A "large negative value" is defined with large negative numbers for both
+// fields of the pair. This negative value has the property that adding any
+// number of non-negative values to it always results in a negative value.
+//
+// The GetLargestRectangle algorithm works in three phases:
+// 1) Convert the region into a grid by adding vertical/horizontal lines for
+// each edge of each rectangle in the region.
+// 2) For each rectangle in the region, for each cell it contains, set that
+// cells's value as described above.
+// 3) Calculate the submatrix with the largest sum such that none of its cells
+// contain any 0s (empty regions). The rectangle represented by the
+// submatrix is the largest rectangle in the region.
+//
+// Let k be the number of rectangles in the region.
+// Let m be the height of the grid generated in step 1.
+// Let n be the width of the grid generated in step 1.
+//
+// Step 1 is O(k) in time and O(m+n) in space for the sparse grid.
+// Step 2 is O(mn) in time and O(mn) in additional space for the full grid.
+// Step 3 is O(m^2 n) in time and O(mn) in additional space
+//
+// The implementation of steps 1 and 2 are rather straightforward. However our
+// implementation of step 3 uses dynamic programming to achieve its efficiency.
+//
+// Psuedo code for step 3 is as follows where G is the grid from step 1 and A
+// is the array from step 2:
+// Phase3 = function (G, A, m, n) {
+// let (t,b,l,r,_) = MaxSum2D(A,m,n)
+// return rect(G[t],G[l],G[r],G[b]);
+// }
+// MaxSum2D = function (A, m, n) {
+// S = array(m+1,n+1)
+// S[0][i] = 0 for i in [0,n]
+// S[j][0] = 0 for j in [0,m]
+// S[j][i] = (if A[j-1][i-1] = 0 then some large negative value
+// else A[j-1][i-1])
+// + S[j-1][n] + S[j][i-1] - S[j-1][i-1]
+//
+// // top, bottom, left, right, area
+// var maxRect = (-1, -1, -1, -1, 0);
+//
+// for all (m',m'') in [0, m]^2 {
+// let B = { S[m'][i] - S[m''][i] | 0 <= i <= n }
+// let ((l,r),area) = MaxSum1D(B,n+1)
+// if (area > maxRect.area) {
+// maxRect := (m', m'', l, r, area)
+// }
+// }
+//
+// return maxRect;
+// }
+//
+// Originally taken from Improved algorithms for the k-maximum subarray problem
+// for small k - SE Bae, T Takaoka but modified to show the explicit tracking
+// of indices and we already have the prefix sums from our one call site so
+// there's no need to construct them.
+// MaxSum1D = function (A,n) {
+// var minIdx = 0;
+// var min = 0;
+// var maxIndices = (0,0);
+// var max = 0;
+// for i in range(n) {
+// let cand = A[i] - min;
+// if (cand > max) {
+// max := cand;
+// maxIndices := (minIdx, i)
+// }
+// if (min > A[i]) {
+// min := A[i];
+// minIdx := i;
+// }
+// }
+// return (minIdx, maxIdx, max);
+// }
+
+namespace {
+// This class represents a partitioning of an axis delineated by coordinates.
+// It internally maintains a sorted array of coordinates.
+class AxisPartition {
+ public:
+ // Adds a new partition at the given coordinate to this partitioning. If
+ // the coordinate is already present in the partitioning, this does nothing.
+ void InsertCoord(nscoord c) {
+ uint32_t i = mStops.IndexOfFirstElementGt(c);
+ if (i == 0 || mStops[i - 1] != c) {
+ mStops.InsertElementAt(i, c);
+ }
+ }
+
+ // Returns the array index of the given partition point. The partition
+ // point must already be present in the partitioning.
+ int32_t IndexOf(nscoord p) const { return mStops.BinaryIndexOf(p); }
+
+ // Returns the partition at the given index which must be non-zero and
+ // less than the number of partitions in this partitioning.
+ nscoord StopAt(int32_t index) const { return mStops[index]; }
+
+ // Returns the size of the gap between the partition at the given index and
+ // the next partition in this partitioning. If the index is the last index
+ // in the partitioning, the result is undefined.
+ nscoord StopSize(int32_t index) const {
+ return mStops[index + 1] - mStops[index];
+ }
+
+ // Returns the number of partitions in this partitioning.
+ int32_t GetNumStops() const { return mStops.Length(); }
+
+ private:
+ nsTArray<nscoord> mStops;
+};
+
+const int64_t kVeryLargeNegativeNumber = 0xffff000000000000ll;
+
+struct SizePair {
+ int64_t mSizeContainingRect;
+ int64_t mSize;
+
+ SizePair() : mSizeContainingRect(0), mSize(0) {}
+
+ static SizePair VeryLargeNegative() {
+ SizePair result;
+ result.mSize = result.mSizeContainingRect = kVeryLargeNegativeNumber;
+ return result;
+ }
+ bool operator<(const SizePair& aOther) const {
+ if (mSizeContainingRect < aOther.mSizeContainingRect) return true;
+ if (mSizeContainingRect > aOther.mSizeContainingRect) return false;
+ return mSize < aOther.mSize;
+ }
+ bool operator>(const SizePair& aOther) const {
+ return aOther.operator<(*this);
+ }
+ SizePair operator+(const SizePair& aOther) const {
+ SizePair result = *this;
+ result.mSizeContainingRect += aOther.mSizeContainingRect;
+ result.mSize += aOther.mSize;
+ return result;
+ }
+ SizePair operator-(const SizePair& aOther) const {
+ SizePair result = *this;
+ result.mSizeContainingRect -= aOther.mSizeContainingRect;
+ result.mSize -= aOther.mSize;
+ return result;
+ }
+};
+
+// Returns the sum and indices of the subarray with the maximum sum of the
+// given array (A,n), assuming the array is already in prefix sum form.
+SizePair MaxSum1D(const nsTArray<SizePair>& A, int32_t n, int32_t* minIdx,
+ int32_t* maxIdx) {
+ // The min/max indicies of the largest subarray found so far
+ SizePair min, max;
+ int32_t currentMinIdx = 0;
+
+ *minIdx = 0;
+ *maxIdx = 0;
+
+ // Because we're given the array in prefix sum form, we know the first
+ // element is 0
+ for (int32_t i = 1; i < n; i++) {
+ SizePair cand = A[i] - min;
+ if (cand > max) {
+ max = cand;
+ *minIdx = currentMinIdx;
+ *maxIdx = i;
+ }
+ if (min > A[i]) {
+ min = A[i];
+ currentMinIdx = i;
+ }
+ }
+
+ return max;
+}
+} // namespace
+
+nsRect nsRegion::GetLargestRectangle(const nsRect& aContainingRect) const {
+ nsRect bestRect;
+
+ if (GetNumRects() <= 1) {
+ bestRect = GetBounds();
+ return bestRect;
+ }
+
+ AxisPartition xaxis, yaxis;
+
+ // Step 1: Calculate the grid lines
+ for (auto iter = RectIter(); !iter.Done(); iter.Next()) {
+ const nsRect& rect = iter.Get();
+ xaxis.InsertCoord(rect.X());
+ xaxis.InsertCoord(rect.XMost());
+ yaxis.InsertCoord(rect.Y());
+ yaxis.InsertCoord(rect.YMost());
+ }
+ if (!aContainingRect.IsEmpty()) {
+ xaxis.InsertCoord(aContainingRect.X());
+ xaxis.InsertCoord(aContainingRect.XMost());
+ yaxis.InsertCoord(aContainingRect.Y());
+ yaxis.InsertCoord(aContainingRect.YMost());
+ }
+
+ // Step 2: Fill out the grid with the areas
+ // Note: due to the ordering of rectangles in the region, it is not always
+ // possible to combine steps 2 and 3 so we don't try to be clever.
+ int32_t matrixHeight = yaxis.GetNumStops() - 1;
+ int32_t matrixWidth = xaxis.GetNumStops() - 1;
+ int32_t matrixSize = matrixHeight * matrixWidth;
+ nsTArray<SizePair> areas(matrixSize);
+ areas.SetLength(matrixSize);
+
+ for (auto iter = RectIter(); !iter.Done(); iter.Next()) {
+ const nsRect& rect = iter.Get();
+ int32_t xstart = xaxis.IndexOf(rect.X());
+ int32_t xend = xaxis.IndexOf(rect.XMost());
+ int32_t y = yaxis.IndexOf(rect.Y());
+ int32_t yend = yaxis.IndexOf(rect.YMost());
+
+ for (; y < yend; y++) {
+ nscoord height = yaxis.StopSize(y);
+ for (int32_t x = xstart; x < xend; x++) {
+ nscoord width = xaxis.StopSize(x);
+ int64_t size = width * int64_t(height);
+ if (rect.Intersects(aContainingRect)) {
+ areas[y * matrixWidth + x].mSizeContainingRect = size;
+ }
+ areas[y * matrixWidth + x].mSize = size;
+ }
+ }
+ }
+
+ // Step 3: Find the maximum submatrix sum that does not contain a rectangle
+ {
+ // First get the prefix sum array
+ int32_t m = matrixHeight + 1;
+ int32_t n = matrixWidth + 1;
+ nsTArray<SizePair> pareas(m * n);
+ pareas.SetLength(m * n);
+ for (int32_t y = 1; y < m; y++) {
+ for (int32_t x = 1; x < n; x++) {
+ SizePair area = areas[(y - 1) * matrixWidth + x - 1];
+ if (!area.mSize) {
+ area = SizePair::VeryLargeNegative();
+ }
+ area = area + pareas[y * n + x - 1] + pareas[(y - 1) * n + x] -
+ pareas[(y - 1) * n + x - 1];
+ pareas[y * n + x] = area;
+ }
+ }
+
+ // No longer need the grid
+ areas.SetLength(0);
+
+ SizePair bestArea;
+ struct {
+ int32_t left, top, right, bottom;
+ } bestRectIndices = {0, 0, 0, 0};
+ for (int32_t m1 = 0; m1 < m; m1++) {
+ for (int32_t m2 = m1 + 1; m2 < m; m2++) {
+ nsTArray<SizePair> B;
+ B.SetLength(n);
+ for (int32_t i = 0; i < n; i++) {
+ B[i] = pareas[m2 * n + i] - pareas[m1 * n + i];
+ }
+ int32_t minIdx, maxIdx;
+ SizePair area = MaxSum1D(B, n, &minIdx, &maxIdx);
+ if (area > bestArea) {
+ bestRectIndices.left = minIdx;
+ bestRectIndices.top = m1;
+ bestRectIndices.right = maxIdx;
+ bestRectIndices.bottom = m2;
+ bestArea = area;
+ }
+ }
+ }
+
+ bestRect.MoveTo(xaxis.StopAt(bestRectIndices.left),
+ yaxis.StopAt(bestRectIndices.top));
+ bestRect.SizeTo(xaxis.StopAt(bestRectIndices.right) - bestRect.X(),
+ yaxis.StopAt(bestRectIndices.bottom) - bestRect.Y());
+ }
+
+ return bestRect;
+}
+
+std::ostream& operator<<(std::ostream& stream, const nsRegion& m) {
+ stream << "[";
+
+ bool first = true;
+ for (auto iter = m.RectIter(); !iter.Done(); iter.Next()) {
+ if (!first) {
+ stream << "; ";
+ } else {
+ first = false;
+ }
+ const nsRect& rect = iter.Get();
+ stream << rect.X() << "," << rect.Y() << "," << rect.XMost() << ","
+ << rect.YMost();
+ }
+
+ stream << "]";
+ return stream;
+}
+
+void nsRegion::OutputToStream(std::string aObjName,
+ std::ostream& stream) const {
+ auto iter = RectIter();
+ nsRect r = iter.Get();
+ stream << "nsRegion " << aObjName << "(nsRect(" << r.X() << ", " << r.Y()
+ << ", " << r.Width() << ", " << r.Height() << "));\n";
+ iter.Next();
+
+ for (; !iter.Done(); iter.Next()) {
+ nsRect r = iter.Get();
+ stream << aObjName << ".OrWith(nsRect(" << r.X() << ", " << r.Y() << ", "
+ << r.Width() << ", " << r.Height() << "));\n";
+ }
+}
+
+nsCString nsRegion::ToString() const {
+ return nsCString(mozilla::ToString(*this).c_str());
+}
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