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[ASStackLayoutSpec] Performance improvements (#2470)

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* Initial commit for ASStackLayoutSpec improvements

* Remove the lock in ASStackLayoutSpec and make the ASStackLayoutSpecStyle const

I think we don't need lock here as the style already has a lock while we set the value

* Add ASStackLayoutSpecItem  that replaces layout specific items

* Prevent baseline pass if not needed

* Update comments
This commit is contained in:
Michael Schneider
2016-10-30 12:07:18 -07:00
committed by GitHub
parent ca203158da
commit 611894329a
7 changed files with 185 additions and 140 deletions
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76
AsyncDisplayKit/Layout/ASStackLayoutSpec.mm
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@@ -13,6 +13,8 @@
#import "ASInternalHelpers.h"
#import "ASLayoutElement.h"
#import "ASLayoutElementStylePrivate.h"
#import "ASLayoutSpecUtilities.h"
#import "ASStackBaselinePositionedLayout.h"
#import "ASThread.h"
@@ -120,43 +122,65 @@
- (ASLayout *)calculateLayoutThatFits:(ASSizeRange)constrainedSize
{
std::vector<id<ASLayoutElement>> stackChildren;
for (id<ASLayoutElement> child in self.children) {
stackChildren.push_back(child);
}
if (stackChildren.empty()) {
NSArray *children = self.children;
if (children.count == 0) {
return [ASLayout layoutWithLayoutElement:self size:constrainedSize.min];
}
// Accessing the style and size property is pretty costly we create layout spec children we use to figure
// out the layout for each child
const auto stackChildren = AS::map(children, [&](const id<ASLayoutElement> child) -> ASStackLayoutSpecChild {
ASLayoutElementStyle *style = child.style;
return {child, style, style.size};
});
ASStackLayoutSpecStyle style = {.direction = _direction, .spacing = _spacing, .justifyContent = _justifyContent, .alignItems = _alignItems, .baselineRelativeArrangement = _baselineRelativeArrangement};
BOOL needsBaselinePass = _baselineRelativeArrangement || _alignItems == ASStackLayoutAlignItemsBaselineFirst || _alignItems == ASStackLayoutAlignItemsBaselineLast;
const ASStackLayoutSpecStyle style = {.direction = _direction, .spacing = _spacing, .justifyContent = _justifyContent, .alignItems = _alignItems, .baselineRelativeArrangement = _baselineRelativeArrangement};
// First pass is to get the children into a positioned state
const auto unpositionedLayout = ASStackUnpositionedLayout::compute(stackChildren, style, constrainedSize);
const auto positionedLayout = ASStackPositionedLayout::compute(unpositionedLayout, style, constrainedSize);
CGSize finalSize = CGSizeZero;
NSArray *sublayouts = nil;
// Figure out if a baseline pass is really needed
const BOOL directionIsVertical = (style.direction == ASStackLayoutDirectionVertical);
const BOOL needsBaselineAlignment = ASStackBaselinePositionedLayout::needsBaselineAlignment(style);
const BOOL needsBaselinePositioning = (directionIsVertical == NO || needsBaselineAlignment == YES);
// regardless of whether or not this stack aligns to baseline, we should let ASStackBaselinePositionedLayout::compute find the max ascender
// and min descender in case this spec is a child in another spec that wants to align to a baseline.
const auto baselinePositionedLayout = ASStackBaselinePositionedLayout::compute(positionedLayout, style, constrainedSize);
if (self.direction == ASStackLayoutDirectionVertical) {
ASDN::MutexLocker l(__instanceLock__);
self.style.ascender = stackChildren.front().style.ascender;
self.style.descender = stackChildren.back().style.descender;
} else {
ASDN::MutexLocker l(__instanceLock__);
self.style.ascender = baselinePositionedLayout.ascender;
self.style.descender = baselinePositionedLayout.descender;
NSMutableArray *sublayouts = [NSMutableArray array];
CGSize finalSize = CGSizeZero;
if (needsBaselinePositioning) {
// All horizontal stacks, regardless of whether or not they are baseline aligned, should go through a baseline
// computation. They could be used in another horizontal stack that is baseline aligned and will need to have
// computed the proper ascender/descender.
// Vertical stacks do not need to go through this computation since we can easily compute ascender/descender by
// looking at their first/last child's ascender/descender.
const auto baselinePositionedLayout = ASStackBaselinePositionedLayout::compute(positionedLayout, style, constrainedSize);
if (directionIsVertical == NO) {
self.style.ascender = baselinePositionedLayout.ascender;
self.style.descender = baselinePositionedLayout.descender;
}
if (needsBaselineAlignment == YES) {
finalSize = directionSize(style.direction, unpositionedLayout.stackDimensionSum, baselinePositionedLayout.crossSize);
for (const auto &l : baselinePositionedLayout.items) {
[sublayouts addObject:l.layout];
}
}
}
if (needsBaselinePass) {
finalSize = directionSize(style.direction, unpositionedLayout.stackDimensionSum, baselinePositionedLayout.crossSize);
sublayouts = [NSArray arrayWithObjects:&baselinePositionedLayout.sublayouts[0] count:baselinePositionedLayout.sublayouts.size()];
} else {
if (directionIsVertical == YES) {
self.style.ascender = stackChildren.front().style.ascender;
self.style.descender = stackChildren.back().style.descender;
}
if (needsBaselineAlignment == NO) {
finalSize = directionSize(style.direction, unpositionedLayout.stackDimensionSum, positionedLayout.crossSize);
sublayouts = [NSArray arrayWithObjects:&positionedLayout.sublayouts[0] count:positionedLayout.sublayouts.size()];
for (const auto &l : positionedLayout.items) {
[sublayouts addObject:l.layout];
}
}
return [ASLayout layoutWithLayoutElement:self size:ASSizeRangeClamp(constrainedSize, finalSize) sublayouts:sublayouts];