SkIRect SkRTree::computeBounds(Node* n) {
SkIRect r = n->child(0)->fBounds;
for (int i = 1; i < n->fNumChildren; ++i) {
join_no_empty_check(n->child(i)->fBounds, &r);
}
return r;
}
int SkRTree::chooseSubtree(Node* root, Branch* branch) {
SkASSERT(!root->isLeaf());
if (1 < root->fLevel) {
// root's child pointers do not point to leaves, so minimize area increase
int32_t minAreaIncrease = SK_MaxS32;
int32_t minArea = SK_MaxS32;
int32_t bestSubtree = -1;
for (int i = 0; i < root->fNumChildren; ++i) {
const SkIRect& subtreeBounds = root->child(i)->fBounds;
int32_t areaIncrease = get_area_increase(subtreeBounds, branch->fBounds);
// break ties in favor of subtree with smallest area
if (areaIncrease < minAreaIncrease || (areaIncrease == minAreaIncrease &&
static_cast<int32_t>(get_area(subtreeBounds)) < minArea)) {
minAreaIncrease = areaIncrease;
minArea = get_area(subtreeBounds);
bestSubtree = i;
}
}
SkASSERT(-1 != bestSubtree);
return bestSubtree;
} else if (1 == root->fLevel) {
// root's child pointers do point to leaves, so minimize overlap increase
int32_t minOverlapIncrease = SK_MaxS32;
int32_t minAreaIncrease = SK_MaxS32;
int32_t bestSubtree = -1;
for (int32_t i = 0; i < root->fNumChildren; ++i) {
const SkIRect& subtreeBounds = root->child(i)->fBounds;
SkIRect expandedBounds = subtreeBounds;
join_no_empty_check(branch->fBounds, &expandedBounds);
int32_t overlap = 0;
for (int32_t j = 0; j < root->fNumChildren; ++j) {
if (j == i) continue;
// Note: this would be more correct if we subtracted the original pre-expanded
// overlap, but computing overlaps is expensive and omitting it doesn't seem to
// hurt query performance. See get_overlap_increase()
overlap += get_overlap(expandedBounds, root->child(j)->fBounds);
}
// break ties with lowest area increase
if (overlap < minOverlapIncrease || (overlap == minOverlapIncrease &&
static_cast<int32_t>(get_area_increase(branch->fBounds, subtreeBounds)) <
minAreaIncrease)) {
minOverlapIncrease = overlap;
minAreaIncrease = get_area_increase(branch->fBounds, subtreeBounds);
bestSubtree = i;
}
}
return bestSubtree;
} else {
SkASSERT(false);
return 0;
}
}
static inline uint32_t get_area_increase(const SkIRect& rect1, SkIRect rect2) {
join_no_empty_check(rect1, &rect2);
return get_area(rect2) - get_area(rect1);
}
int SkRTree::distributeChildren(Branch* children) {
// We have two sides to sort by on each of two axes:
const static SortSide sorts[2][2] = {
{&SkIRect::fLeft, &SkIRect::fRight},
{&SkIRect::fTop, &SkIRect::fBottom}
};
// We want to choose an axis to split on, then a distribution along that axis; we'll need
// three pieces of info: the split axis, the side to sort by on that axis, and the index
// to split the sorted array on.
int32_t sortSide = -1;
int32_t k = -1;
int32_t axis = -1;
int32_t bestS = SK_MaxS32;
// Evaluate each axis, we want the min summed margin-value (s) over all distributions
for (int i = 0; i < 2; ++i) {
int32_t minOverlap = SK_MaxS32;
int32_t minArea = SK_MaxS32;
int32_t axisBestK = 0;
int32_t axisBestSide = 0;
int32_t s = 0;
// Evaluate each sort
for (int j = 0; j < 2; ++j) {
SkTQSort(children, children + fMaxChildren, RectLessThan(sorts[i][j]));
// Evaluate each split index
for (int32_t k = 1; k <= fMaxChildren - 2 * fMinChildren + 2; ++k) {
SkIRect r1 = children[0].fBounds;
SkIRect r2 = children[fMinChildren + k - 1].fBounds;
for (int32_t l = 1; l < fMinChildren - 1 + k; ++l) {
join_no_empty_check(children[l].fBounds, &r1);
}
for (int32_t l = fMinChildren + k; l < fMaxChildren + 1; ++l) {
join_no_empty_check(children[l].fBounds, &r2);
}
int32_t area = get_area(r1) + get_area(r2);
int32_t overlap = get_overlap(r1, r2);
s += get_margin(r1) + get_margin(r2);
if (overlap < minOverlap || (overlap == minOverlap && area < minArea)) {
minOverlap = overlap;
minArea = area;
axisBestSide = j;
axisBestK = k;
}
}
}
if (s < bestS) {
bestS = s;
axis = i;
sortSide = axisBestSide;
k = axisBestK;
}
}
// replicate the sort of the winning distribution, (we can skip this if the last
// sort ended up being best)
if (!(axis == 1 && sortSide == 1)) {
SkTQSort(children, children + fMaxChildren, RectLessThan(sorts[axis][sortSide]));
}
return fMinChildren - 1 + k;
}
static inline uint32_t get_overlap_increase(const SkIRect& rect1, const SkIRect& rect2,
SkIRect expandBy) {
join_no_empty_check(rect1, &expandBy);
return get_overlap(expandBy, rect2) - get_overlap(rect1, rect2);
}
