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ASStackLayoutSpec utilizes multiple threads if it runs on main (#3116)

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Huy Nguyen 2017-03-02 18:12:53 +00:00 committed by Adlai Holler
parent bccfc6c779
commit 415005b6fc
1 changed files with 80 additions and 43 deletions
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123
Source/Private/Layout/ASStackUnpositionedLayout.mm
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@ -13,8 +13,10 @@
#import <tgmath.h>
#import <numeric>
#import <AsyncDisplayKit/ASDispatch.h>
#import <AsyncDisplayKit/ASLayoutSpecUtilities.h>
#import <AsyncDisplayKit/ASLayoutElementStylePrivate.h>
#import <AsyncDisplayKit/ASThread.h>
CGFloat const kViolationEpsilon = 0.01;
@ -67,6 +69,28 @@ static ASLayout *crossChildLayout(const ASStackLayoutSpecChild &child,
return layout ? : [ASLayout layoutWithLayoutElement:child.element size:{0, 0}];
}
static void dispatchApplyIfNeeded(size_t iterationCount, void(^work)(size_t i))
{
if (iterationCount == 0) {
return;
}
if (iterationCount == 1) {
work(0);
return;
}
if (ASDisplayNodeThreadIsMain() == NO) {
for (size_t i = 0; i < iterationCount; i++) {
work(i);
}
return;
}
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
ASDispatchApply(iterationCount, queue, 0, work);
}
/**
Computes the consumed cross dimension length for the given vector of lines and stacking style.
@ -175,21 +199,20 @@ static void stretchItemsAlongCrossDimension(std::vector<ASStackLayoutSpecItem> &
const CGSize parentSize,
const CGFloat crossSize)
{
for (auto &item : items) {
dispatchApplyIfNeeded(items.size(), ^(size_t i) {
auto &item = items[i];
const ASStackLayoutAlignItems alignItems = alignment(item.child.style.alignSelf, style.alignItems);
if (alignItems != ASStackLayoutAlignItemsStretch) {
continue;
if (alignItems == ASStackLayoutAlignItemsStretch) {
const CGFloat cross = crossDimension(style.direction, item.layout.size);
const CGFloat stack = stackDimension(style.direction, item.layout.size);
const CGFloat violation = crossSize - cross;
// Only stretch if violation is positive. Compare against kViolationEpsilon here to avoid stretching against a tiny violation.
if (violation > kViolationEpsilon) {
item.layout = crossChildLayout(item.child, style, stack, stack, crossSize, crossSize, parentSize);
}
}
const CGFloat cross = crossDimension(style.direction, item.layout.size);
const CGFloat stack = stackDimension(style.direction, item.layout.size);
const CGFloat violation = crossSize - cross;
// Only stretch if violation is positive. Compare against kViolationEpsilon here to avoid stretching against a tiny violation.
if (violation > kViolationEpsilon) {
item.layout = crossChildLayout(item.child, style, stack, stack, crossSize, crossSize, parentSize);
}
}
});
}
/**
@ -405,7 +428,8 @@ static void layoutFlexibleChildrenAtZeroSize(std::vector<ASStackLayoutSpecItem>
const ASSizeRange &sizeRange,
const CGSize parentSize)
{
for (ASStackLayoutSpecItem &item : items) {
dispatchApplyIfNeeded(items.size(), ^(size_t i) {
auto &item = items[i];
if (isFlexibleInBothDirections(item.child)) {
item.layout = crossChildLayout(item.child,
style,
@ -415,7 +439,7 @@ static void layoutFlexibleChildrenAtZeroSize(std::vector<ASStackLayoutSpecItem>
crossDimension(style.direction, sizeRange.max),
parentSize);
}
}
});
}
/**
@ -556,14 +580,25 @@ static void flexLinesAlongStackDimension(std::vector<ASStackUnpositionedLine> &l
const CGFloat remainingViolation = std::accumulate(items.begin(), items.end(), violation, [&](CGFloat x, const ASStackLayoutSpecItem &item) {
return x - flexAdjustment(item);
});
BOOL isFirstFlex = YES;
for (ASStackLayoutSpecItem &item : items) {
size_t firstFlexItem = -1;
for(size_t i = 0; i < items.size(); i++) {
// Children are consider inflexible if they do not need to make a flex adjustment.
if (flexAdjustment(items[i]) != 0) {
firstFlexItem = i;
break;
}
}
ASDisplayNodeCAssert(firstFlexItem != -1, @"At this point there must be at least 1 flexible item");
dispatchApplyIfNeeded(items.size(), ^(size_t i) {
auto &item = items[i];
const CGFloat currentFlexAdjustment = flexAdjustment(item);
// Children are consider inflexible if they do not need to make a flex adjustment.
if (currentFlexAdjustment != 0) {
const CGFloat originalStackSize = stackDimension(style.direction, item.layout.size);
// Only apply the remaining violation for the first flexible child that has a flex grow factor.
const CGFloat flexedStackSize = originalStackSize + currentFlexAdjustment + (isFirstFlex && item.child.style.flexGrow > 0 ? remainingViolation : 0);
const CGFloat flexedStackSize = originalStackSize + currentFlexAdjustment + (i == firstFlexItem && item.child.style.flexGrow > 0 ? remainingViolation : 0);
item.layout = crossChildLayout(item.child,
style,
MAX(flexedStackSize, 0),
@ -571,9 +606,8 @@ static void flexLinesAlongStackDimension(std::vector<ASStackUnpositionedLine> &l
crossDimension(style.direction, sizeRange.min),
crossDimension(style.direction, sizeRange.max),
parentSize);
isFirstFlex = NO;
}
}
});
}
}
@ -619,28 +653,27 @@ static std::vector<ASStackUnpositionedLine> collectChildrenIntoLines(const std::
Performs the first unconstrained layout of the children, generating the unpositioned items that are then flexed and
stretched.
*/
static std::vector<ASStackLayoutSpecItem> layoutChildrenAlongUnconstrainedStackDimension(const std::vector<ASStackLayoutSpecChild> &children,
const ASStackLayoutSpecStyle &style,
const ASSizeRange &sizeRange,
const CGSize parentSize,
const BOOL useOptimizedFlexing)
static void layoutItemsAlongUnconstrainedStackDimension(std::vector<ASStackLayoutSpecItem> &items,
const ASStackLayoutSpecStyle &style,
const ASSizeRange &sizeRange,
const CGSize parentSize,
const BOOL useOptimizedFlexing)
{
const CGFloat minCrossDimension = crossDimension(style.direction, sizeRange.min);
const CGFloat maxCrossDimension = crossDimension(style.direction, sizeRange.max);
return AS::map(children, [&](const ASStackLayoutSpecChild &child) -> ASStackLayoutSpecItem {
if (useOptimizedFlexing && isFlexibleInBothDirections(child)) {
return {child, [ASLayout layoutWithLayoutElement:child.element size:{0, 0}]};
dispatchApplyIfNeeded(items.size(), ^(size_t i) {
auto &item = items[i];
if (useOptimizedFlexing && isFlexibleInBothDirections(item.child)) {
item.layout = [ASLayout layoutWithLayoutElement:item.child.element size:{0, 0}];
} else {
return {
child,
crossChildLayout(child,
style,
ASDimensionResolve(child.style.flexBasis, stackDimension(style.direction, parentSize), 0),
ASDimensionResolve(child.style.flexBasis, stackDimension(style.direction, parentSize), INFINITY),
minCrossDimension,
maxCrossDimension,
parentSize)
};
item.layout = crossChildLayout(item.child,
style,
ASDimensionResolve(item.child.style.flexBasis, stackDimension(style.direction, parentSize), 0),
ASDimensionResolve(item.child.style.flexBasis, stackDimension(style.direction, parentSize), INFINITY),
minCrossDimension,
maxCrossDimension,
parentSize);
}
});
}
@ -663,14 +696,18 @@ ASStackUnpositionedLayout ASStackUnpositionedLayout::compute(const std::vector<A
// We may be able to avoid some redundant layout passes
const BOOL optimizedFlexing = useOptimizedFlexing(children, style, sizeRange);
std::vector<ASStackLayoutSpecItem> items = AS::map(children, [&](const ASStackLayoutSpecChild &child) -> ASStackLayoutSpecItem {
return {child, nil};
});
// We do a first pass of all the children, generating an unpositioned layout for each with an unbounded range along
// the stack dimension. This allows us to compute the "intrinsic" size of each child and find the available violation
// which determines whether we must grow or shrink the flexible children.
std::vector<ASStackLayoutSpecItem> items = layoutChildrenAlongUnconstrainedStackDimension(children,
style,
sizeRange,
parentSize,
optimizedFlexing);
layoutItemsAlongUnconstrainedStackDimension(items,
style,
sizeRange,
parentSize,
optimizedFlexing);
// Collect items into lines (https://www.w3.org/TR/css-flexbox-1/#algo-line-break)
std::vector<ASStackUnpositionedLine> lines = collectChildrenIntoLines(items, style, sizeRange);