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Implement "space between" and "space around" options of stack layout justify content

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This commit is contained in:
Huy Nguyen
2015-11-15 20:01:13 +02:00
parent 390d16caef
commit 1162e02b06
9 changed files with 118 additions and 7 deletions
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60
AsyncDisplayKit/Private/ASStackPositionedLayout.mm
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@@ -15,6 +15,7 @@
#import "ASStackLayoutSpecUtilities.h"
#import "ASLayoutable.h"
#import "ASLayoutOptions.h"
#import "ASAssert.h"
static CGFloat crossOffset(const ASStackLayoutSpecStyle &style,
const ASStackUnpositionedItem &l,
@@ -33,8 +34,20 @@ static CGFloat crossOffset(const ASStackLayoutSpecStyle &style,
}
}
/**
* Positions children according to the stack style and positioning properties.
*
* @param style The layout style of the overall stack layout
* @param firstChildOffset Offset of the first child
* @param extraSpacing Spacing between children, in addition to spacing set to the stack's layout style
* @param lastChildOffset Offset of the last child
* @param unpositionedLayout Unpositioned children of the stack
* @param constrainedSize Constrained size of the stack
*/
static ASStackPositionedLayout stackedLayout(const ASStackLayoutSpecStyle &style,
const CGFloat offset,
const CGFloat firstChildOffset,
const CGFloat extraSpacing,
const CGFloat lastChildOffset,
const ASStackUnpositionedLayout &unpositionedLayout,
const ASSizeRange &constrainedSize)
{
@@ -48,12 +61,16 @@ static ASStackPositionedLayout stackedLayout(const ASStackLayoutSpecStyle &style
const auto maxCrossSize = crossDimension(style.direction, constrainedSize.max);
const CGFloat crossSize = MIN(MAX(minCrossSize, largestChildCrossSize), maxCrossSize);
CGPoint p = directionPoint(style.direction, offset, 0);
CGPoint p = directionPoint(style.direction, firstChildOffset, 0);
BOOL first = YES;
const auto lastChild = unpositionedLayout.items.back().child;
CGFloat offset = 0;
auto stackedChildren = AS::map(unpositionedLayout.items, [&](const ASStackUnpositionedItem &l) -> ASLayout *{
p = p + directionPoint(style.direction, l.child.spacingBefore, 0);
offset = (l.child == lastChild) ? lastChildOffset : 0;
p = p + directionPoint(style.direction, l.child.spacingBefore + offset, 0);
if (!first) {
p = p + directionPoint(style.direction, style.spacing, 0);
p = p + directionPoint(style.direction, style.spacing + extraSpacing, 0);
}
first = NO;
l.layout.position = p + directionPoint(style.direction, 0, crossOffset(style, l, crossSize));
@@ -64,16 +81,45 @@ static ASStackPositionedLayout stackedLayout(const ASStackLayoutSpecStyle &style
return {stackedChildren, crossSize};
}
static ASStackPositionedLayout stackedLayout(const ASStackLayoutSpecStyle &style,
const CGFloat firstChildOffset,
const ASStackUnpositionedLayout &unpositionedLayout,
const ASSizeRange &constrainedSize)
{
return stackedLayout(style, firstChildOffset, 0, 0, unpositionedLayout, constrainedSize);
}
ASStackPositionedLayout ASStackPositionedLayout::compute(const ASStackUnpositionedLayout &unpositionedLayout,
const ASStackLayoutSpecStyle &style,
const ASSizeRange &constrainedSize)
{
switch (style.justifyContent) {
const auto numOfItems = unpositionedLayout.items.size();
ASDisplayNodeCAssertTrue(numOfItems > 0);
const CGFloat violation = unpositionedLayout.violation;
ASStackLayoutJustifyContent justifyContent = style.justifyContent;
// Handle edge cases of "space between" and "space around"
if (justifyContent == ASStackLayoutJustifyContentSpaceBetween && (violation < 0 || numOfItems == 1)) {
justifyContent = ASStackLayoutJustifyContentStart;
} else if (justifyContent == ASStackLayoutJustifyContentSpaceAround && (violation < 0 || numOfItems == 1)) {
justifyContent = ASStackLayoutJustifyContentCenter;
}
switch (justifyContent) {
case ASStackLayoutJustifyContentStart:
return stackedLayout(style, 0, unpositionedLayout, constrainedSize);
case ASStackLayoutJustifyContentCenter:
return stackedLayout(style, floorf(unpositionedLayout.violation / 2), unpositionedLayout, constrainedSize);
return stackedLayout(style, floorf(violation / 2), unpositionedLayout, constrainedSize);
case ASStackLayoutJustifyContentEnd:
return stackedLayout(style, unpositionedLayout.violation, unpositionedLayout, constrainedSize);
return stackedLayout(style, violation, unpositionedLayout, constrainedSize);
case ASStackLayoutJustifyContentSpaceBetween: {
const auto numOfSpacings = numOfItems - 1;
return stackedLayout(style, 0, floorf(violation / numOfSpacings), fmodf(violation, numOfSpacings), unpositionedLayout, constrainedSize);
}
case ASStackLayoutJustifyContentSpaceAround: {
// Spacing between items are twice the spacing on the edges
CGFloat spacingUnit = floorf(violation / (numOfItems * 2));
return stackedLayout(style, spacingUnit, spacingUnit * 2, 0, unpositionedLayout, constrainedSize);
}
}
}