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Reduce search range of flexible children

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We were traversing all children to only perform calculations/changes to
flexible children in order to avoid new allocations during layout. This
diff ensures we only visit flexible children during layout calculations
if any are present. We accomplish this by keeping a private linked list
of flexible children.
This commit is contained in:
Lucas Rocha
2015-09-07 13:54:27 +01:00
parent 793220faf8
commit d1a49a4f0b
6 changed files with 151 additions and 105 deletions
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84
src/Layout.js
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@@ -504,11 +504,15 @@ var computeLayout = (function() {
var/*float*/ totalFlexible = 0;
var/*int*/ nonFlexibleChildrenCount = 0;
var/*css_node_t**/ firstFlexChild = null;
var/*css_node_t**/ currentFlexChild = null;
var/*float*/ maxWidth;
for (i = startLine; i < childCount; ++i) {
child = node.children[i];
child.nextAbsoluteChild = null;
child.nextFlexChild = null;
// Pre-fill cross axis dimensions when the child is using stretch before
// we call the recursive layout pass
@@ -562,6 +566,16 @@ var computeLayout = (function() {
flexibleChildrenCount++;
totalFlexible += child.style.flex;
// Store a private linked list of flexible children so that we can
// efficiently traverse them later.
if (firstFlexChild === null) {
firstFlexChild = child;
}
if (currentFlexChild !== null) {
currentFlexChild.nextFlexChild = child;
}
currentFlexChild = child;
// Even if we don't know its exact size yet, we already know the padding,
// border and margin. We'll use this partial information, which represents
// the smallest possible size for the child, to compute the remaining
@@ -635,21 +649,20 @@ var computeLayout = (function() {
var/*float*/ baseMainDim;
var/*float*/ boundMainDim;
// Iterate over every child in the axis. If the flex share of remaining
// space doesn't meet min/max bounds, remove this child from flex
// calculations.
for (i = startLine; i < endLine; ++i) {
child = node.children[i];
if (isFlex(child)) {
baseMainDim = flexibleMainDim * child.style.flex +
getPaddingAndBorderAxis(child, mainAxis);
boundMainDim = boundAxis(child, mainAxis, baseMainDim);
// If the flex share of remaining space doesn't meet min/max bounds,
// remove this child from flex calculations.
currentFlexChild = firstFlexChild;
while (currentFlexChild !== null) {
baseMainDim = flexibleMainDim * currentFlexChild.style.flex +
getPaddingAndBorderAxis(currentFlexChild, mainAxis);
boundMainDim = boundAxis(currentFlexChild, mainAxis, baseMainDim);
if (baseMainDim !== boundMainDim) {
remainingMainDim -= boundMainDim;
totalFlexible -= child.style.flex;
}
if (baseMainDim !== boundMainDim) {
remainingMainDim -= boundMainDim;
totalFlexible -= currentFlexChild.style.flex;
}
currentFlexChild = currentFlexChild.nextFlexChild;
}
flexibleMainDim = remainingMainDim / totalFlexible;
@@ -658,31 +671,32 @@ var computeLayout = (function() {
if (flexibleMainDim < 0) {
flexibleMainDim = 0;
}
// We iterate over the full array and only apply the action on flexible
// children. This is faster than actually allocating a new array that
// contains only flexible children.
for (i = startLine; i < endLine; ++i) {
child = node.children[i];
if (isFlex(child)) {
// At this point we know the final size of the element in the main
// dimension
child.layout[dim[mainAxis]] = boundAxis(child, mainAxis,
flexibleMainDim * child.style.flex + getPaddingAndBorderAxis(child, mainAxis)
);
maxWidth = CSS_UNDEFINED;
if (isDimDefined(node, resolvedRowAxis)) {
maxWidth = node.layout[dim[resolvedRowAxis]] -
paddingAndBorderAxisResolvedRow;
} else if (!isMainRowDirection) {
maxWidth = parentMaxWidth -
getMarginAxis(node, resolvedRowAxis) -
paddingAndBorderAxisResolvedRow;
}
currentFlexChild = firstFlexChild;
while (currentFlexChild !== null) {
// At this point we know the final size of the element in the main
// dimension
currentFlexChild.layout[dim[mainAxis]] = boundAxis(currentFlexChild, mainAxis,
flexibleMainDim * currentFlexChild.style.flex +
getPaddingAndBorderAxis(currentFlexChild, mainAxis)
);
// And we recursively call the layout algorithm for this child
layoutNode(/*(java)!layoutContext, */child, maxWidth, direction);
maxWidth = CSS_UNDEFINED;
if (isDimDefined(node, resolvedRowAxis)) {
maxWidth = node.layout[dim[resolvedRowAxis]] -
paddingAndBorderAxisResolvedRow;
} else if (!isMainRowDirection) {
maxWidth = parentMaxWidth -
getMarginAxis(node, resolvedRowAxis) -
paddingAndBorderAxisResolvedRow;
}
// And we recursively call the layout algorithm for this child
layoutNode(/*(java)!layoutContext, */currentFlexChild, maxWidth, direction);
child = currentFlexChild;
currentFlexChild = currentFlexChild.nextFlexChild;
child.nextFlexChild = null;
}
// We use justifyContent to figure out how to allocate the remaining