/* -*- 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 "mozilla/ToString.h"
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 nsRect &aRect) const {
// XXX this could be made faster by using pixman_region32_contains_rect
for (auto iter = RectIter(); !iter.Done(); iter.Next()) {
if (iter.Get().Intersects(aRect)) {
return true;
}
}
return false;
}
void nsRegion::Inflate(const nsMargin &aMargin) {
int n;
pixman_box32_t *boxes = pixman_region32_rectangles(&mImpl, &n);
for (int i = 0; i < n; i++) {
nsRect rect = BoxToRect(boxes[i]);
rect.Inflate(aMargin);
boxes[i] = RectToBox(rect);
}
pixman_region32_t region;
// This will union all of the rectangles and runs in about O(n lg(n))
pixman_region32_init_rects(®ion, boxes, n);
pixman_region32_fini(&mImpl);
mImpl = region;
}
void nsRegion::SimplifyOutward(uint32_t aMaxRects) {
MOZ_ASSERT(aMaxRects >= 1, "Invalid max rect count");
if (GetNumRects() <= aMaxRects) return;
pixman_box32_t *boxes;
int n;
boxes = pixman_region32_rectangles(&mImpl, &n);
// Try combining rects in horizontal bands into a single rect
int dest = 0;
for (int src = 1; src < n; src++) {
// 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
while ((src < (n)) && boxes[dest].y1 == boxes[src].y1) {
// merge box[i] and box[i+1]
boxes[dest].x2 = boxes[src].x2;
src++;
}
if (src < n) {
dest++;
boxes[dest] = boxes[src];
}
}
uint32_t reducedCount = dest + 1;
// pixman has a special representation for
// regions of 1 rectangle. So just use the
// bounds in that case
if (reducedCount > 1 && reducedCount <= aMaxRects) {
// reach into pixman and lower the number
// of rects stored in data.
mImpl.data->numRects = reducedCount;
} else {
*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
static uint32_t ComputeMergedAreaIncrease(pixman_box32_t *topRects,
pixman_box32_t *topRectsEnd,
pixman_box32_t *bottomRects,
pixman_box32_t *bottomRectsEnd) {
uint32_t totalArea = 0;
struct pt {
int32_t x, y;
};
pt *i = (pt *)topRects;
pt *end_i = (pt *)topRectsEnd;
pt *j = (pt *)bottomRects;
pt *end_j = (pt *)bottomRectsEnd;
bool top = false;
bool bottom = false;
int cur_x = i->x;
bool top_next = top;
bool bottom_next = bottom;
// XXX: we could probably simplify this condition and perhaps move it into the
// loop below
if (j->x < cur_x) {
cur_x = j->x;
j++;
bottom_next = !bottom;
} else if (j->x == cur_x) {
i++;
top_next = !top;
bottom_next = !bottom;
j++;
} else {
top_next = !top;
i++;
}
int topRectsHeight = topRects->y2 - topRects->y1;
int bottomRectsHeight = bottomRects->y2 - bottomRects->y1;
int inbetweenHeight = bottomRects->y1 - topRects->y2;
int width = cur_x;
// top and bottom are the in-status to the left of cur_x
do {
if (top && !bottom) {
totalArea += (inbetweenHeight + bottomRectsHeight) * width;
} else if (bottom && !top) {
totalArea += (inbetweenHeight + topRectsHeight) * width;
} else if (bottom && top) {
totalArea += (inbetweenHeight)*width;
}
top = top_next;
bottom = bottom_next;
// find the next edge
if (i->x < j->x) {
top_next = !top;
width = i->x - cur_x;
cur_x = i->x;
i++;
} else if (j->x < i->x) {
bottom_next = !bottom;
width = j->x - cur_x;
cur_x = j->x;
j++;
} else { // i->x == j->x
top_next = !top;
bottom_next = !bottom;
width = i->x - cur_x;
cur_x = i->x;
i++;
j++;
}
} while (i < end_i && j < end_j);
// handle any remaining rects
while (i < end_i) {
width = i->x - cur_x;
cur_x = i->x;
i++;
if (top) totalArea += (inbetweenHeight + bottomRectsHeight) * width;
top = !top;
}
while (j < end_j) {
width = j->x - cur_x;
cur_x = j->x;
j++;
if (bottom) totalArea += (inbetweenHeight + topRectsHeight) * width;
bottom = !bottom;
}
return totalArea;
}
static pixman_box32_t *CopyRow(pixman_box32_t *dest_it,
pixman_box32_t *src_start,
pixman_box32_t *src_end) {
// XXX: std::copy
pixman_box32_t *src_it = src_start;
while (src_it < src_end) {
*dest_it++ = *src_it++;
}
return dest_it;
}
#define WRITE_RECT(x1, x2, y1, y2) \
do { \
tmpRect->x1 = x1; \
tmpRect->x2 = x2; \
tmpRect->y1 = y1; \
tmpRect->y2 = y2; \
tmpRect++; \
} while (0)
/* If 'r' overlaps the current rect, then expand the current rect to include
* it. Otherwise write the current rect out to tmpRect, and set r as the
* updated current rect. */
#define MERGE_RECT(r) \
do { \
if (r->x1 <= x2) { \
if (x2 < r->x2) x2 = r->x2; \
} else { \
WRITE_RECT(x1, x2, y1, y2); \
x1 = r->x1; \
x2 = r->x2; \
} \
r++; \
} while (0)
/* Can we merge two sets of rects without extra space?
* Yes, but not easily. We can even do it stably
* but we don't need that property.
*
* This is written in the style of pixman_region_union_o */
static pixman_box32_t *MergeRects(pixman_box32_t *r1, pixman_box32_t *r1_end,
pixman_box32_t *r2, pixman_box32_t *r2_end,
pixman_box32_t *tmpRect) {
/* This routine works by maintaining the current
* rectangle in x1,x2,y1,y2 and either merging
* in the left most rectangle if it overlaps or
* outputing the current rectangle and setting
* it to the the left most one */
const int y1 = r1->y1;
const int y2 = r2->y2;
int x1;
int x2;
/* Find the left-most edge */
if (r1->x1 < r2->x1) {
x1 = r1->x1;
x2 = r1->x2;
r1++;
} else {
x1 = r2->x1;
x2 = r2->x2;
r2++;
}
while (r1 != r1_end && r2 != r2_end) {
/* Find and merge the left-most rectangle */
if (r1->x1 < r2->x1)
MERGE_RECT(r1);
else
MERGE_RECT(r2);
}
/* Finish up any left overs */
if (r1 != r1_end) {
do {
MERGE_RECT(r1);
} while (r1 != r1_end);
} else if (r2 != r2_end) {
do {
MERGE_RECT(r2);
} while (r2 != r2_end);
}
/* Finish up the last rectangle */
WRITE_RECT(x1, x2, y1, y2);
return tmpRect;
}
void nsRegion::SimplifyOutwardByArea(uint32_t aThreshold) {
pixman_box32_t *boxes;
int n;
boxes = pixman_region32_rectangles(&mImpl, &n);
// if we have no rectangles then we're done
if (!n) return;
pixman_box32_t *end = boxes + n;
pixman_box32_t *topRectsEnd = boxes + 1;
pixman_box32_t *topRects = boxes;
// we need some temporary storage for merging both rows of rectangles
AutoTArray<pixman_box32_t, 10> tmpStorage;
tmpStorage.SetCapacity(n);
pixman_box32_t *tmpRect = tmpStorage.Elements();
pixman_box32_t *destRect = boxes;
pixman_box32_t *rect = tmpRect;
// find the end of the first span of rectangles
while (topRectsEnd < end && topRectsEnd->y1 == topRects->y1) {
topRectsEnd++;
}
// if we only have one row we are done
if (topRectsEnd == end) return;
pixman_box32_t *bottomRects = topRectsEnd;
pixman_box32_t *bottomRectsEnd = bottomRects + 1;
do {
// find the end of the bottom span of rectangles
while (bottomRectsEnd < end && bottomRectsEnd->y1 == bottomRects->y1) {
bottomRectsEnd++;
}
uint32_t totalArea = ComputeMergedAreaIncrease(topRects, topRectsEnd,
bottomRects, bottomRectsEnd);
if (totalArea <= aThreshold) {
// merge the rects into tmpRect
rect = MergeRects(topRects, topRectsEnd, bottomRects, bottomRectsEnd,
tmpRect);
// set topRects to where the newly merged rects will be so that we use
// them as our next set of topRects
topRects = destRect;
// copy the merged rects back into the destination
topRectsEnd = CopyRow(destRect, tmpRect, rect);
} else {
// copy the unmerged rects
destRect = CopyRow(destRect, topRects, topRectsEnd);
topRects = bottomRects;
topRectsEnd = bottomRectsEnd;
if (bottomRectsEnd == end) {
// copy the last row when we are done
topRectsEnd = CopyRow(destRect, topRects, topRectsEnd);
}
}
bottomRects = bottomRectsEnd;
} while (bottomRectsEnd != end);
uint32_t reducedCount =
topRectsEnd - pixman_region32_rectangles(&this->mImpl, &n);
// pixman has a special representation for
// regions of 1 rectangle. So just use the
// bounds in that case
if (reducedCount > 1) {
// reach into pixman and lower the number
// of rects stored in data.
this->mImpl.data->numRects = reducedCount;
} else {
*this = GetBounds();
}
}
typedef void (*visit_fn)(void *closure, VisitSide side, int x1, int y1, int x2,
int y2);
static bool VisitNextEdgeBetweenRect(visit_fn visit, void *closure,
VisitSide side, pixman_box32_t *&r1,
pixman_box32_t *&r2, const int y,
int &x1) {
// check for overlap
if (r1->x2 >= r2->x1) {
MOZ_ASSERT(r2->x1 >= x1);
visit(closure, side, x1, y, r2->x1, y);
// find the rect that ends first or always drop the one that comes first?
if (r1->x2 < r2->x2) {
x1 = r1->x2;
r1++;
} else {
x1 = r2->x2;
r2++;
}
return true;
} else {
MOZ_ASSERT(r1->x2 < r2->x2);
// we handle the corners by just extending the top and bottom edges
visit(closure, side, x1, y, r1->x2 + 1, y);
r1++;
// we assign x1 because we can assume that x1 <= r2->x1 - 1
// However the caller may know better and if so, may update
// x1 to r1->x1
x1 = r2->x1 - 1;
return false;
}
}
// XXX: if we need to this can compute the end of the row
static void VisitSides(visit_fn visit, void *closure, pixman_box32_t *r,
pixman_box32_t *r_end) {
// XXX: we can drop LEFT/RIGHT and just use the orientation
// of the line if it makes sense
while (r != r_end) {
visit(closure, VisitSide::LEFT, r->x1, r->y1, r->x1, r->y2);
visit(closure, VisitSide::RIGHT, r->x2, r->y1, r->x2, r->y2);
r++;
}
}
static void VisitAbove(visit_fn visit, void *closure, pixman_box32_t *r,
pixman_box32_t *r_end) {
while (r != r_end) {
visit(closure, VisitSide::TOP, r->x1 - 1, r->y1, r->x2 + 1, r->y1);
r++;
}
}
static void VisitBelow(visit_fn visit, void *closure, pixman_box32_t *r,
pixman_box32_t *r_end) {
while (r != r_end) {
visit(closure, VisitSide::BOTTOM, r->x1 - 1, r->y2, r->x2 + 1, r->y2);
r++;
}
}
static pixman_box32_t *VisitInbetween(visit_fn visit, void *closure,
pixman_box32_t *r1,
pixman_box32_t *r1_end,
pixman_box32_t *r2,
pixman_box32_t *r2_end) {
const int y = r1->y2;
int x1;
bool overlap = false;
while (r1 != r1_end && r2 != r2_end) {
if (!overlap) {
/* Find the left-most edge */
if (r1->x1 < r2->x1) {
x1 = r1->x1 - 1;
} else {
x1 = r2->x1 - 1;
}
}
MOZ_ASSERT((x1 >= (r1->x1 - 1)) || (x1 >= (r2->x1 - 1)));
if (r1->x1 < r2->x1) {
overlap = VisitNextEdgeBetweenRect(visit, closure, VisitSide::BOTTOM, r1,
r2, y, x1);
} else {
overlap = VisitNextEdgeBetweenRect(visit, closure, VisitSide::TOP, r2, r1,
y, x1);
}
}
/* Finish up which ever row has remaining rects*/
if (r1 != r1_end) {
// top row
do {
visit(closure, VisitSide::BOTTOM, x1, y, r1->x2 + 1, y);
r1++;
if (r1 == r1_end) break;
x1 = r1->x1 - 1;
} while (true);
} else if (r2 != r2_end) {
// bottom row
do {
visit(closure, VisitSide::TOP, x1, y, r2->x2 + 1, y);
r2++;
if (r2 == r2_end) break;
x1 = r2->x1 - 1;
} while (true);
}
return 0;
}
void nsRegion::VisitEdges(visit_fn visit, void *closure) {
pixman_box32_t *boxes;
int n;
boxes = pixman_region32_rectangles(&mImpl, &n);
// if we have no rectangles then we're done
if (!n) return;
pixman_box32_t *end = boxes + n;
pixman_box32_t *topRectsEnd = boxes + 1;
pixman_box32_t *topRects = boxes;
// find the end of the first span of rectangles
while (topRectsEnd < end && topRectsEnd->y1 == topRects->y1) {
topRectsEnd++;
}
// In order to properly handle convex corners we always visit the sides first
// that way when we visit the corners we can pad using the value from the
// sides
VisitSides(visit, closure, topRects, topRectsEnd);
VisitAbove(visit, closure, topRects, topRectsEnd);
pixman_box32_t *bottomRects = topRects;
pixman_box32_t *bottomRectsEnd = topRectsEnd;
if (topRectsEnd != end) {
do {
// find the next row of rects
bottomRects = topRectsEnd;
bottomRectsEnd = topRectsEnd + 1;
while (bottomRectsEnd < end && bottomRectsEnd->y1 == bottomRects->y1) {
bottomRectsEnd++;
}
VisitSides(visit, closure, bottomRects, bottomRectsEnd);
if (topRects->y2 == bottomRects->y1) {
VisitInbetween(visit, closure, topRects, topRectsEnd, bottomRects,
bottomRectsEnd);
} else {
VisitBelow(visit, closure, topRects, topRectsEnd);
VisitAbove(visit, closure, bottomRects, bottomRectsEnd);
}
topRects = bottomRects;
topRectsEnd = bottomRectsEnd;
} while (bottomRectsEnd != end);
}
// the bottom of the region doesn't touch anything else so we
// can always visit it at the end
VisitBelow(visit, closure, bottomRects, bottomRectsEnd);
}
void nsRegion::SimplifyInward(uint32_t aMaxRects) {
NS_ASSERTION(aMaxRects >= 1, "Invalid max rect count");
if (GetNumRects() <= aMaxRects) return;
SetEmpty();
}
uint64_t nsRegion::Area() const {
uint64_t area = 0;
for (auto iter = RectIter(); !iter.Done(); iter.Next()) {
const nsRect &rect = iter.Get();
area += uint64_t(rect.Width()) * rect.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;
}
int n;
pixman_box32_t *boxes = pixman_region32_rectangles(&mImpl, &n);
for (int i = 0; i < n; i++) {
nsRect rect = BoxToRect(boxes[i]);
rect.ScaleRoundOut(aXScale, aYScale);
boxes[i] = RectToBox(rect);
}
pixman_region32_t region;
// This will union all of the rectangles and runs in about O(n lg(n))
pixman_region32_init_rects(®ion, boxes, n);
pixman_region32_fini(&mImpl);
mImpl = region;
return *this;
}
nsRegion &nsRegion::ScaleInverseRoundOut(float aXScale, float aYScale) {
int n;
pixman_box32_t *boxes = pixman_region32_rectangles(&mImpl, &n);
for (int i = 0; i < n; i++) {
nsRect rect = BoxToRect(boxes[i]);
rect.ScaleInverseRoundOut(aXScale, aYScale);
boxes[i] = RectToBox(rect);
}
pixman_region32_t region;
// This will union all of the rectangles and runs in about O(n lg(n))
pixman_region32_init_rects(®ion, boxes, n);
pixman_region32_fini(&mImpl);
mImpl = region;
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) {
int n;
pixman_box32_t *boxes = pixman_region32_rectangles(&mImpl, &n);
for (int i = 0; i < n; i++) {
nsRect rect = BoxToRect(boxes[i]);
boxes[i] = RectToBox(nsIntRegion::ToRect(
TransformRect(nsIntRegion::FromRect(rect), aTransform)));
}
pixman_region32_t region;
// This will union all of the rectangles and runs in about O(n lg(n))
pixman_region32_init_rects(®ion, boxes, n);
pixman_region32_fini(&mImpl);
mImpl = region;
return *this;
}
nsRegion nsRegion::ScaleToOtherAppUnitsRoundOut(int32_t aFromAPP,
int32_t aToAPP) const {
if (aFromAPP == aToAPP) {
return *this;
}
nsRegion region = *this;
int n;
pixman_box32_t *boxes = pixman_region32_rectangles(®ion.mImpl, &n);
for (int i = 0; i < n; i++) {
nsRect rect = BoxToRect(boxes[i]);
rect = rect.ScaleToOtherAppUnitsRoundOut(aFromAPP, aToAPP);
boxes[i] = RectToBox(rect);
}
pixman_region32_t pixmanRegion;
// This will union all of the rectangles and runs in about O(n lg(n))
pixman_region32_init_rects(&pixmanRegion, boxes, n);
pixman_region32_fini(®ion.mImpl);
region.mImpl = pixmanRegion;
return region;
}
nsRegion nsRegion::ScaleToOtherAppUnitsRoundIn(int32_t aFromAPP,
int32_t aToAPP) const {
if (aFromAPP == aToAPP) {
return *this;
}
nsRegion region = *this;
int n;
pixman_box32_t *boxes = pixman_region32_rectangles(®ion.mImpl, &n);
for (int i = 0; i < n; i++) {
nsRect rect = BoxToRect(boxes[i]);
rect = rect.ScaleToOtherAppUnitsRoundIn(aFromAPP, aToAPP);
boxes[i] = RectToBox(rect);
}
pixman_region32_t pixmanRegion;
// This will union all of the rectangles and runs in about O(n lg(n))
pixman_region32_init_rects(&pixmanRegion, boxes, n);
pixman_region32_fini(®ion.mImpl);
region.mImpl = pixmanRegion;
return region;
}
nsIntRegion nsRegion::ToPixels(nscoord aAppUnitsPerPixel,
bool aOutsidePixels) const {
nsRegion region = *this;
int n;
pixman_box32_t *boxes = pixman_region32_rectangles(®ion.mImpl, &n);
for (int i = 0; i < n; i++) {
nsRect rect = BoxToRect(boxes[i]);
mozilla::gfx::IntRect deviceRect;
if (aOutsidePixels)
deviceRect = rect.ToOutsidePixels(aAppUnitsPerPixel);
else
deviceRect = rect.ToNearestPixels(aAppUnitsPerPixel);
boxes[i] = RectToBox(deviceRect);
}
nsIntRegion intRegion;
pixman_region32_fini(&intRegion.mImpl.mImpl);
// This will union all of the rectangles and runs in about O(n lg(n))
pixman_region32_init_rects(&intRegion.mImpl.mImpl, boxes, n);
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
nsRegion region = *this;
int n;
pixman_box32_t *boxes = pixman_region32_rectangles(®ion.mImpl, &n);
boxes = pixman_region32_rectangles(®ion.mImpl, &n);
for (int i = 0; i < n; i++) {
nsRect rect = BoxToRect(boxes[i]);
mozilla::gfx::IntRect irect =
rect.ScaleToOutsidePixels(aScaleX, aScaleY, aAppUnitsPerPixel);
boxes[i] = RectToBox(irect);
}
nsIntRegion iRegion;
// clear out the initial pixman_region so that we can replace it below
pixman_region32_fini(&iRegion.mImpl.mImpl);
// This will union all of the rectangles and runs in about O(n lg(n))
pixman_region32_init_rects(&iRegion.mImpl.mImpl, boxes, n);
return iRegion;
}
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.
*/
// make a copy of this region so that we can mutate it in place
nsRegion region = *this;
int n;
pixman_box32_t *boxes = pixman_region32_rectangles(®ion.mImpl, &n);
nsIntRegion intRegion;
if (n) {
nsRect first = BoxToRect(boxes[0]);
mozilla::gfx::IntRect firstDeviceRect =
first.ScaleToInsidePixels(aScaleX, aScaleY, aAppUnitsPerPixel);
for (int i = 1; i < n; i++) {
nsRect rect = nsRect(boxes[i].x1, boxes[i].y1, boxes[i].x2 - boxes[i].x1,
boxes[i].y2 - boxes[i].y1);
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());
}
}
}
boxes[i] = RectToBox(deviceRect);
}
boxes[0] = RectToBox(firstDeviceRect);
pixman_region32_fini(&intRegion.mImpl.mImpl);
// This will union all of the rectangles and runs in about O(n lg(n))
pixman_region32_init_rects(&intRegion.mImpl.mImpl, boxes, n);
}
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 << "[";
int n;
pixman_box32_t *boxes =
pixman_region32_rectangles(const_cast<pixman_region32_t *>(&m.mImpl), &n);
for (int i = 0; i < n; i++) {
if (i != 0) {
stream << "; ";
}
stream << boxes[i].x1 << "," << boxes[i].y1 << "," << boxes[i].x2 << ","
<< boxes[i].y2;
}
stream << "]";
return stream;
}
nsCString nsRegion::ToString() const {
return nsCString(mozilla::ToString(*this).c_str());
}