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react-native/React/CSSLayout/CSSLayout.c

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/**
* Copyright (c) 2014-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*/
#include <assert.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "CSSLayout-internal.h"
#ifdef _MSC_VER
#include <float.h>
#define isnan _isnan
/* define fmaxf if < VC12 */
#if _MSC_VER < 1800
__forceinline const float fmaxf(const float a, const float b) {
return (a > b) ? a : b;
}
#endif
#endif
#define POSITIVE_FLEX_IS_AUTO 0
CSSNodeRef CSSNodeNew() {
CSSNodeRef node = calloc(1, sizeof(CSSNode));
assert(node != NULL);
node->children = CSSNodeListNew(4);
CSSNodeInit(node);
return node;
}
void CSSNodeFree(CSSNodeRef node) {
CSSNodeListFree(node->children);
free(node);
}
void CSSNodeInit(CSSNodeRef node) {
node->style.alignItems = CSSAlignStretch;
node->style.alignContent = CSSAlignFlexStart;
node->style.direction = CSSDirectionInherit;
node->style.flexDirection = CSSFlexDirectionColumn;
node->style.overflow = CSSOverflowVisible;
// Some of the fields default to undefined and not 0
node->style.dimensions[CSSDimensionWidth] = CSSUndefined;
node->style.dimensions[CSSDimensionHeight] = CSSUndefined;
node->style.minDimensions[CSSDimensionWidth] = CSSUndefined;
node->style.minDimensions[CSSDimensionHeight] = CSSUndefined;
node->style.maxDimensions[CSSDimensionWidth] = CSSUndefined;
node->style.maxDimensions[CSSDimensionHeight] = CSSUndefined;
node->style.position[CSSPositionLeft] = CSSUndefined;
node->style.position[CSSPositionTop] = CSSUndefined;
node->style.position[CSSPositionRight] = CSSUndefined;
node->style.position[CSSPositionBottom] = CSSUndefined;
node->style.margin[CSSPositionStart] = CSSUndefined;
node->style.margin[CSSPositionEnd] = CSSUndefined;
node->style.padding[CSSPositionStart] = CSSUndefined;
node->style.padding[CSSPositionEnd] = CSSUndefined;
node->style.border[CSSPositionStart] = CSSUndefined;
node->style.border[CSSPositionEnd] = CSSUndefined;
node->layout.dimensions[CSSDimensionWidth] = CSSUndefined;
node->layout.dimensions[CSSDimensionHeight] = CSSUndefined;
// Such that the comparison is always going to be false
node->layout.lastParentDirection = (CSSDirection)-1;
node->shouldUpdate = true;
node->layout.nextCachedMeasurementsIndex = 0;
node->layout.measuredDimensions[CSSDimensionWidth] = CSSUndefined;
node->layout.measuredDimensions[CSSDimensionHeight] = CSSUndefined;
node->layout.cached_layout.widthMeasureMode = (CSSMeasureMode)-1;
node->layout.cached_layout.heightMeasureMode = (CSSMeasureMode)-1;
}
void CSSNodeInsertChild(CSSNodeRef node, CSSNodeRef child, unsigned int index) {
CSSNodeListInsert(node->children, child, index);
}
void CSSNodeRemoveChild(CSSNodeRef node, CSSNodeRef child) {
CSSNodeListDelete(node->children, child);
}
CSSNodeRef CSSNodeGetChild(CSSNodeRef node, unsigned int index) {
return CSSNodeListGet(node->children, index);
}
unsigned int CSSNodeChildCount(CSSNodeRef node) {
return CSSNodeListCount(node->children);
}
#define CSS_NODE_PROPERTY_IMPL(type, name, paramName, instanceName) \
void CSSNodeSet##name(CSSNodeRef node, type paramName) { \
node->instanceName = paramName;\
} \
\
type CSSNodeGet##name(CSSNodeRef node) { \
return node->instanceName;\
} \
#define CSS_NODE_STYLE_PROPERTY_IMPL(type, name, paramName, instanceName) \
void CSSNodeStyleSet##name(CSSNodeRef node, type paramName) { \
node->style.instanceName = paramName;\
} \
\
type CSSNodeStyleGet##name(CSSNodeRef node) { \
return node->style.instanceName;\
} \
#define CSS_NODE_LAYOUT_PROPERTY_IMPL(type, name, instanceName) \
type CSSNodeLayoutGet##name(CSSNodeRef node) { \
return node->layout.instanceName;\
} \
CSS_NODE_PROPERTY_IMPL(void*, Context, context, context);
CSS_NODE_PROPERTY_IMPL(CSSMeasureFunc, MeasureFunc, measureFunc, measure);
CSS_NODE_PROPERTY_IMPL(CSSIsDirtyFunc, IsDirtyFunc, isDirtyFunc, isDirty);
CSS_NODE_PROPERTY_IMPL(CSSPrintFunc, PrintFunc, printFunc, print);
CSS_NODE_PROPERTY_IMPL(bool, IsTextnode, isTextNode, isTextNode);
CSS_NODE_PROPERTY_IMPL(bool, ShouldUpdate, shouldUpdate, shouldUpdate);
CSS_NODE_STYLE_PROPERTY_IMPL(CSSDirection, Direction, direction, direction);
CSS_NODE_STYLE_PROPERTY_IMPL(CSSFlexDirection, FlexDirection, flexDirection, flexDirection);
CSS_NODE_STYLE_PROPERTY_IMPL(CSSJustify, JustifyContent, justifyContent, justifyContent);
CSS_NODE_STYLE_PROPERTY_IMPL(CSSAlign, AlignContent, alignContent, alignContent);
CSS_NODE_STYLE_PROPERTY_IMPL(CSSAlign, AlignItems, alignItems, alignItems);
CSS_NODE_STYLE_PROPERTY_IMPL(CSSAlign, AlignSelf, alignSelf, alignSelf);
CSS_NODE_STYLE_PROPERTY_IMPL(CSSPositionType, PositionType, positionType, positionType);
CSS_NODE_STYLE_PROPERTY_IMPL(CSSWrapType, FlexWrap, flexWrap, flexWrap);
CSS_NODE_STYLE_PROPERTY_IMPL(CSSOverflow, Overflow, overflow, overflow);
CSS_NODE_STYLE_PROPERTY_IMPL(float, Flex, flex, flex);
CSS_NODE_STYLE_PROPERTY_IMPL(float, PositionLeft, positionLeft, position[CSSPositionLeft]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, PositionTop, positionTop, position[CSSPositionTop]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, PositionRight, positionRight, position[CSSPositionRight]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, PositionBottom, positionBottom, position[CSSPositionBottom]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, MarginLeft, marginLeft, margin[CSSPositionLeft]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, MarginTop, marginTop, margin[CSSPositionTop]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, MarginRight, marginRight, margin[CSSPositionRight]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, MarginBottom, marginBottom, margin[CSSPositionBottom]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, MarginStart, marginStart, margin[CSSPositionStart]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, MarginEnd, marginEnd, margin[CSSPositionEnd]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, PaddingLeft, paddingLeft, padding[CSSPositionLeft]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, PaddingTop, paddingTop, padding[CSSPositionTop]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, PaddingRight, paddingRight, padding[CSSPositionRight]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, PaddingBottom, paddingBottom, padding[CSSPositionBottom]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, PaddingStart, paddingStart, padding[CSSPositionStart]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, PaddingEnd, paddingEnd, padding[CSSPositionEnd]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, BorderLeft, borderLeft, border[CSSPositionLeft]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, BorderTop, borderTop, border[CSSPositionTop]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, BorderRight, borderRight, border[CSSPositionRight]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, BorderBottom, borderBottom, border[CSSPositionBottom]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, BorderStart, borderStart, border[CSSPositionStart]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, BorderEnd, BorderEnd, border[CSSPositionEnd]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, Width, width, dimensions[CSSDimensionWidth]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, Height, height, dimensions[CSSDimensionHeight]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, MinWidth, minWidth, minDimensions[CSSDimensionWidth]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, MinHeight, minHeight, minDimensions[CSSDimensionHeight]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, MaxWidth, maxWidth, maxDimensions[CSSDimensionWidth]);
CSS_NODE_STYLE_PROPERTY_IMPL(float, MaxHeight, maxHeight, maxDimensions[CSSDimensionHeight]);
CSS_NODE_LAYOUT_PROPERTY_IMPL(float, Left, position[CSSPositionLeft]);
CSS_NODE_LAYOUT_PROPERTY_IMPL(float, Top, position[CSSPositionTop]);
CSS_NODE_LAYOUT_PROPERTY_IMPL(float, Right, position[CSSPositionRight]);
CSS_NODE_LAYOUT_PROPERTY_IMPL(float, Bottom, position[CSSPositionBottom]);
CSS_NODE_LAYOUT_PROPERTY_IMPL(float, Width, dimensions[CSSDimensionWidth]);
CSS_NODE_LAYOUT_PROPERTY_IMPL(float, Height, dimensions[CSSDimensionHeight]);
int gCurrentGenerationCount = 0;
bool layoutNodeInternal(CSSNode* node, float availableWidth, float availableHeight, CSSDirection parentDirection,
CSSMeasureMode widthMeasureMode, CSSMeasureMode heightMeasureMode, bool performLayout, char* reason);
bool isUndefined(float value) {
return isnan(value);
}
static bool eq(float a, float b) {
if (isUndefined(a)) {
return isUndefined(b);
}
return fabs(a - b) < 0.0001;
}
static void indent(int n) {
for (int i = 0; i < n; ++i) {
printf(" ");
}
}
static void print_number_0(const char* str, float number) {
if (!eq(number, 0)) {
printf("%s: %g, ", str, number);
}
}
static void print_number_nan(const char* str, float number) {
if (!isnan(number)) {
printf("%s: %g, ", str, number);
}
}
static bool four_equal(float four[4]) {
return
eq(four[0], four[1]) &&
eq(four[0], four[2]) &&
eq(four[0], four[3]);
}
static void print_css_node_rec(
CSSNode* node,
CSSPrintOptions options,
int level
) {
indent(level);
printf("{");
if (node->print) {
node->print(node->context);
}
if (options & CSSPrintOptionsLayout) {
printf("layout: {");
printf("width: %g, ", node->layout.dimensions[CSSDimensionWidth]);
printf("height: %g, ", node->layout.dimensions[CSSDimensionHeight]);
printf("top: %g, ", node->layout.position[CSSPositionTop]);
printf("left: %g", node->layout.position[CSSPositionLeft]);
printf("}, ");
}
if (options & CSSPrintOptionsStyle) {
if (node->style.flexDirection == CSSFlexDirectionColumn) {
printf("flexDirection: 'column', ");
} else if (node->style.flexDirection == CSSFlexDirectionColumnReverse) {
printf("flexDirection: 'column-reverse', ");
} else if (node->style.flexDirection == CSSFlexDirectionRow) {
printf("flexDirection: 'row', ");
} else if (node->style.flexDirection == CSSFlexDirectionRowReverse) {
printf("flexDirection: 'row-reverse', ");
}
if (node->style.justifyContent == CSSJustifyCenter) {
printf("justifyContent: 'center', ");
} else if (node->style.justifyContent == CSSJustifyFlexEnd) {
printf("justifyContent: 'flex-end', ");
} else if (node->style.justifyContent == CSSJustifySpaceAround) {
printf("justifyContent: 'space-around', ");
} else if (node->style.justifyContent == CSSJustifySpaceBetween) {
printf("justifyContent: 'space-between', ");
}
if (node->style.alignItems == CSSAlignCenter) {
printf("alignItems: 'center', ");
} else if (node->style.alignItems == CSSAlignFlexEnd) {
printf("alignItems: 'flex-end', ");
} else if (node->style.alignItems == CSSAlignStretch) {
printf("alignItems: 'stretch', ");
}
if (node->style.alignContent == CSSAlignCenter) {
printf("alignContent: 'center', ");
} else if (node->style.alignContent == CSSAlignFlexEnd) {
printf("alignContent: 'flex-end', ");
} else if (node->style.alignContent == CSSAlignStretch) {
printf("alignContent: 'stretch', ");
}
if (node->style.alignSelf == CSSAlignFlexStart) {
printf("alignSelf: 'flex-start', ");
} else if (node->style.alignSelf == CSSAlignCenter) {
printf("alignSelf: 'center', ");
} else if (node->style.alignSelf == CSSAlignFlexEnd) {
printf("alignSelf: 'flex-end', ");
} else if (node->style.alignSelf == CSSAlignStretch) {
printf("alignSelf: 'stretch', ");
}
print_number_nan("flex", node->style.flex);
if (node->style.overflow == CSSOverflowHidden) {
printf("overflow: 'hidden', ");
} else if (node->style.overflow == CSSOverflowVisible) {
printf("overflow: 'visible', ");
}
if (four_equal(node->style.margin)) {
print_number_0("margin", node->style.margin[CSSPositionLeft]);
} else {
print_number_0("marginLeft", node->style.margin[CSSPositionLeft]);
print_number_0("marginRight", node->style.margin[CSSPositionRight]);
print_number_0("marginTop", node->style.margin[CSSPositionTop]);
print_number_0("marginBottom", node->style.margin[CSSPositionBottom]);
print_number_0("marginStart", node->style.margin[CSSPositionStart]);
print_number_0("marginEnd", node->style.margin[CSSPositionEnd]);
}
if (four_equal(node->style.padding)) {
print_number_0("padding", node->style.padding[CSSPositionLeft]);
} else {
print_number_0("paddingLeft", node->style.padding[CSSPositionLeft]);
print_number_0("paddingRight", node->style.padding[CSSPositionRight]);
print_number_0("paddingTop", node->style.padding[CSSPositionTop]);
print_number_0("paddingBottom", node->style.padding[CSSPositionBottom]);
print_number_0("paddingStart", node->style.padding[CSSPositionStart]);
print_number_0("paddingEnd", node->style.padding[CSSPositionEnd]);
}
if (four_equal(node->style.border)) {
print_number_0("borderWidth", node->style.border[CSSPositionLeft]);
} else {
print_number_0("borderLeftWidth", node->style.border[CSSPositionLeft]);
print_number_0("borderRightWidth", node->style.border[CSSPositionRight]);
print_number_0("borderTopWidth", node->style.border[CSSPositionTop]);
print_number_0("borderBottomWidth", node->style.border[CSSPositionBottom]);
print_number_0("borderStartWidth", node->style.border[CSSPositionStart]);
print_number_0("borderEndWidth", node->style.border[CSSPositionEnd]);
}
print_number_nan("width", node->style.dimensions[CSSDimensionWidth]);
print_number_nan("height", node->style.dimensions[CSSDimensionHeight]);
print_number_nan("maxWidth", node->style.maxDimensions[CSSDimensionWidth]);
print_number_nan("maxHeight", node->style.maxDimensions[CSSDimensionHeight]);
print_number_nan("minWidth", node->style.minDimensions[CSSDimensionWidth]);
print_number_nan("minHeight", node->style.minDimensions[CSSDimensionHeight]);
if (node->style.positionType == CSSPositionTypeAbsolute) {
printf("position: 'absolute', ");
}
print_number_nan("left", node->style.position[CSSPositionLeft]);
print_number_nan("right", node->style.position[CSSPositionRight]);
print_number_nan("top", node->style.position[CSSPositionTop]);
print_number_nan("bottom", node->style.position[CSSPositionBottom]);
}
unsigned int childCount = CSSNodeListCount(node->children);
if (options & CSSPrintOptionsChildren && childCount > 0) {
printf("children: [\n");
for (unsigned int i = 0; i < childCount; ++i) {
print_css_node_rec(CSSNodeGetChild(node, i), options, level + 1);
}
indent(level);
printf("]},\n");
} else {
printf("},\n");
}
}
void CSSNodePrint(CSSNode* node, CSSPrintOptions options) {
print_css_node_rec(node, options, 0);
}
static CSSPosition leading[4] = {
/* CSSFlexDirectionColumn = */ CSSPositionTop,
/* CSSFlexDirectionColumnReverse = */ CSSPositionBottom,
/* CSSFlexDirectionRow = */ CSSPositionLeft,
/* CSSFlexDirectionRowReverse = */ CSSPositionRight
};
static CSSPosition trailing[4] = {
/* CSSFlexDirectionColumn = */ CSSPositionBottom,
/* CSSFlexDirectionColumnReverse = */ CSSPositionTop,
/* CSSFlexDirectionRow = */ CSSPositionRight,
/* CSSFlexDirectionRowReverse = */ CSSPositionLeft
};
static CSSPosition pos[4] = {
/* CSSFlexDirectionColumn = */ CSSPositionTop,
/* CSSFlexDirectionColumnReverse = */ CSSPositionBottom,
/* CSSFlexDirectionRow = */ CSSPositionLeft,
/* CSSFlexDirectionRowReverse = */ CSSPositionRight
};
static CSSDimension dim[4] = {
/* CSSFlexDirectionColumn = */ CSSDimensionHeight,
/* CSSFlexDirectionColumnReverse = */ CSSDimensionHeight,
/* CSSFlexDirectionRow = */ CSSDimensionWidth,
/* CSSFlexDirectionRowReverse = */ CSSDimensionWidth
};
static bool isRowDirection(CSSFlexDirection flexDirection) {
return flexDirection == CSSFlexDirectionRow ||
flexDirection == CSSFlexDirectionRowReverse;
}
static bool isColumnDirection(CSSFlexDirection flexDirection) {
return flexDirection == CSSFlexDirectionColumn ||
flexDirection == CSSFlexDirectionColumnReverse;
}
static bool isFlexBasisAuto(CSSNode* node) {
#if POSITIVE_FLEX_IS_AUTO
// All flex values are auto.
(void) node;
return true;
#else
// A flex value > 0 implies a basis of zero.
return node->style.flex <= 0;
#endif
}
static float getFlexGrowFactor(CSSNode* node) {
// Flex grow is implied by positive values for flex.
if (node->style.flex > 0) {
return node->style.flex;
}
return 0;
}
static float getFlexShrinkFactor(CSSNode* node) {
#if POSITIVE_FLEX_IS_AUTO
// A flex shrink factor of 1 is implied by non-zero values for flex.
if (node->style.flex != 0) {
return 1;
}
#else
// A flex shrink factor of 1 is implied by negative values for flex.
if (node->style.flex < 0) {
return 1;
}
#endif
return 0;
}
static float getLeadingMargin(CSSNode* node, CSSFlexDirection axis) {
if (isRowDirection(axis) && !isUndefined(node->style.margin[CSSPositionStart])) {
return node->style.margin[CSSPositionStart];
}
return node->style.margin[leading[axis]];
}
static float getTrailingMargin(CSSNode* node, CSSFlexDirection axis) {
if (isRowDirection(axis) && !isUndefined(node->style.margin[CSSPositionEnd])) {
return node->style.margin[CSSPositionEnd];
}
return node->style.margin[trailing[axis]];
}
static float getLeadingPadding(CSSNode* node, CSSFlexDirection axis) {
if (isRowDirection(axis) &&
!isUndefined(node->style.padding[CSSPositionStart]) &&
node->style.padding[CSSPositionStart] >= 0) {
return node->style.padding[CSSPositionStart];
}
if (node->style.padding[leading[axis]] >= 0) {
return node->style.padding[leading[axis]];
}
return 0;
}
static float getTrailingPadding(CSSNode* node, CSSFlexDirection axis) {
if (isRowDirection(axis) &&
!isUndefined(node->style.padding[CSSPositionEnd]) &&
node->style.padding[CSSPositionEnd] >= 0) {
return node->style.padding[CSSPositionEnd];
}
if (node->style.padding[trailing[axis]] >= 0) {
return node->style.padding[trailing[axis]];
}
return 0;
}
static float getLeadingBorder(CSSNode* node, CSSFlexDirection axis) {
if (isRowDirection(axis) &&
!isUndefined(node->style.border[CSSPositionStart]) &&
node->style.border[CSSPositionStart] >= 0) {
return node->style.border[CSSPositionStart];
}
if (node->style.border[leading[axis]] >= 0) {
return node->style.border[leading[axis]];
}
return 0;
}
static float getTrailingBorder(CSSNode* node, CSSFlexDirection axis) {
if (isRowDirection(axis) &&
!isUndefined(node->style.border[CSSPositionEnd]) &&
node->style.border[CSSPositionEnd] >= 0) {
return node->style.border[CSSPositionEnd];
}
if (node->style.border[trailing[axis]] >= 0) {
return node->style.border[trailing[axis]];
}
return 0;
}
static float getLeadingPaddingAndBorder(CSSNode* node, CSSFlexDirection axis) {
return getLeadingPadding(node, axis) + getLeadingBorder(node, axis);
}
static float getTrailingPaddingAndBorder(CSSNode* node, CSSFlexDirection axis) {
return getTrailingPadding(node, axis) + getTrailingBorder(node, axis);
}
static float getMarginAxis(CSSNode* node, CSSFlexDirection axis) {
return getLeadingMargin(node, axis) + getTrailingMargin(node, axis);
}
static float getPaddingAndBorderAxis(CSSNode* node, CSSFlexDirection axis) {
return getLeadingPaddingAndBorder(node, axis) + getTrailingPaddingAndBorder(node, axis);
}
static CSSAlign getAlignItem(CSSNode* node, CSSNode* child) {
if (child->style.alignSelf != CSSAlignAuto) {
return child->style.alignSelf;
}
return node->style.alignItems;
}
static CSSDirection resolveDirection(CSSNode* node, CSSDirection parentDirection) {
CSSDirection direction = node->style.direction;
if (direction == CSSDirectionInherit) {
direction = parentDirection > CSSDirectionInherit ? parentDirection : CSSDirectionLTR;
}
return direction;
}
static CSSFlexDirection getFlexDirection(CSSNode* node) {
return node->style.flexDirection;
}
static CSSFlexDirection resolveAxis(CSSFlexDirection flexDirection, CSSDirection direction) {
if (direction == CSSDirectionRTL) {
if (flexDirection == CSSFlexDirectionRow) {
return CSSFlexDirectionRowReverse;
} else if (flexDirection == CSSFlexDirectionRowReverse) {
return CSSFlexDirectionRow;
}
}
return flexDirection;
}
static CSSFlexDirection getCrossFlexDirection(CSSFlexDirection flexDirection, CSSDirection direction) {
if (isColumnDirection(flexDirection)) {
return resolveAxis(CSSFlexDirectionRow, direction);
} else {
return CSSFlexDirectionColumn;
}
}
static float getFlex(CSSNode* node) {
return node->style.flex;
}
static bool isFlex(CSSNode* node) {
return (
node->style.positionType == CSSPositionTypeRelative &&
getFlex(node) != 0
);
}
static bool isFlexWrap(CSSNode* node) {
return node->style.flexWrap == CSSWrapTypeWrap;
}
static float getDimWithMargin(CSSNode* node, CSSFlexDirection axis) {
return node->layout.measuredDimensions[dim[axis]] +
getLeadingMargin(node, axis) +
getTrailingMargin(node, axis);
}
static bool isStyleDimDefined(CSSNode* node, CSSFlexDirection axis) {
float value = node->style.dimensions[dim[axis]];
return !isUndefined(value) && value >= 0.0;
}
static bool isLayoutDimDefined(CSSNode* node, CSSFlexDirection axis) {
float value = node->layout.measuredDimensions[dim[axis]];
return !isUndefined(value) && value >= 0.0;
}
static bool isPosDefined(CSSNode* node, CSSPosition position) {
return !isUndefined(node->style.position[position]);
}
static bool isMeasureDefined(CSSNode* node) {
return node->measure;
}
static float getPosition(CSSNode* node, CSSPosition position) {
float result = node->style.position[position];
if (!isUndefined(result)) {
return result;
}
return 0;
}
static float boundAxisWithinMinAndMax(CSSNode* node, CSSFlexDirection axis, float value) {
float min = CSSUndefined;
float max = CSSUndefined;
if (isColumnDirection(axis)) {
min = node->style.minDimensions[CSSDimensionHeight];
max = node->style.maxDimensions[CSSDimensionHeight];
} else if (isRowDirection(axis)) {
min = node->style.minDimensions[CSSDimensionWidth];
max = node->style.maxDimensions[CSSDimensionWidth];
}
float boundValue = value;
if (!isUndefined(max) && max >= 0.0 && boundValue > max) {
boundValue = max;
}
if (!isUndefined(min) && min >= 0.0 && boundValue < min) {
boundValue = min;
}
return boundValue;
}
// Like boundAxisWithinMinAndMax but also ensures that the value doesn't go below the
// padding and border amount.
static float boundAxis(CSSNode* node, CSSFlexDirection axis, float value) {
return fmaxf(boundAxisWithinMinAndMax(node, axis, value), getPaddingAndBorderAxis(node, axis));
}
static void setTrailingPosition(CSSNode* node, CSSNode* child, CSSFlexDirection axis) {
float size = child->style.positionType == CSSPositionTypeAbsolute ?
0 :
child->layout.measuredDimensions[dim[axis]];
child->layout.position[trailing[axis]] = node->layout.measuredDimensions[dim[axis]] - size - child->layout.position[pos[axis]];
}
// If both left and right are defined, then use left. Otherwise return
// +left or -right depending on which is defined.
static float getRelativePosition(CSSNode* node, CSSFlexDirection axis) {
float lead = node->style.position[leading[axis]];
if (!isUndefined(lead)) {
return lead;
}
return -getPosition(node, trailing[axis]);
}
static void setPosition(CSSNode* node, CSSDirection direction) {
CSSFlexDirection mainAxis = resolveAxis(getFlexDirection(node), direction);
CSSFlexDirection crossAxis = getCrossFlexDirection(mainAxis, direction);
node->layout.position[leading[mainAxis]] = getLeadingMargin(node, mainAxis) +
getRelativePosition(node, mainAxis);
node->layout.position[trailing[mainAxis]] = getTrailingMargin(node, mainAxis) +
getRelativePosition(node, mainAxis);
node->layout.position[leading[crossAxis]] = getLeadingMargin(node, crossAxis) +
getRelativePosition(node, crossAxis);
node->layout.position[trailing[crossAxis]] = getTrailingMargin(node, crossAxis) +
getRelativePosition(node, crossAxis);
}
//
// This is the main routine that implements a subset of the flexbox layout algorithm
// described in the W3C CSS documentation: https://www.w3.org/TR/css3-flexbox/.
//
// Limitations of this algorithm, compared to the full standard:
// * Display property is always assumed to be 'flex' except for Text nodes, which
// are assumed to be 'inline-flex'.
// * The 'zIndex' property (or any form of z ordering) is not supported. Nodes are
// stacked in document order.
// * The 'order' property is not supported. The order of flex items is always defined
// by document order.
// * The 'visibility' property is always assumed to be 'visible'. Values of 'collapse'
// and 'hidden' are not supported.
// * The 'wrap' property supports only 'nowrap' (which is the default) or 'wrap'. The
// rarely-used 'wrap-reverse' is not supported.
// * Rather than allowing arbitrary combinations of flexGrow, flexShrink and
// flexBasis, this algorithm supports only the three most common combinations:
// flex: 0 is equiavlent to flex: 0 0 auto
// flex: n (where n is a positive value) is equivalent to flex: n 1 auto
// If POSITIVE_FLEX_IS_AUTO is 0, then it is equivalent to flex: n 0 0
// This is faster because the content doesn't need to be measured, but it's
// less flexible because the basis is always 0 and can't be overriden with
// the width/height attributes.
// flex: -1 (or any negative value) is equivalent to flex: 0 1 auto
// * Margins cannot be specified as 'auto'. They must be specified in terms of pixel
// values, and the default value is 0.
// * The 'baseline' value is not supported for alignItems and alignSelf properties.
// * Values of width, maxWidth, minWidth, height, maxHeight and minHeight must be
// specified as pixel values, not as percentages.
// * There is no support for calculation of dimensions based on intrinsic aspect ratios
// (e.g. images).
// * There is no support for forced breaks.
// * It does not support vertical inline directions (top-to-bottom or bottom-to-top text).
//
// Deviations from standard:
// * Section 4.5 of the spec indicates that all flex items have a default minimum
// main size. For text blocks, for example, this is the width of the widest word.
// Calculating the minimum width is expensive, so we forego it and assume a default
// minimum main size of 0.
// * Min/Max sizes in the main axis are not honored when resolving flexible lengths.
// * The spec indicates that the default value for 'flexDirection' is 'row', but
// the algorithm below assumes a default of 'column'.
//
// Input parameters:
// - node: current node to be sized and layed out
// - availableWidth & availableHeight: available size to be used for sizing the node
// or CSSUndefined if the size is not available; interpretation depends on layout
// flags
// - parentDirection: the inline (text) direction within the parent (left-to-right or
// right-to-left)
// - widthMeasureMode: indicates the sizing rules for the width (see below for explanation)
// - heightMeasureMode: indicates the sizing rules for the height (see below for explanation)
// - performLayout: specifies whether the caller is interested in just the dimensions
// of the node or it requires the entire node and its subtree to be layed out
// (with final positions)
//
// Details:
// This routine is called recursively to lay out subtrees of flexbox elements. It uses the
// information in node.style, which is treated as a read-only input. It is responsible for
// setting the layout.direction and layout.measuredDimensions fields for the input node as well
// as the layout.position and layout.lineIndex fields for its child nodes. The
// layout.measuredDimensions field includes any border or padding for the node but does
// not include margins.
//
// The spec describes four different layout modes: "fill available", "max content", "min content",
// and "fit content". Of these, we don't use "min content" because we don't support default
// minimum main sizes (see above for details). Each of our measure modes maps to a layout mode
// from the spec (https://www.w3.org/TR/css3-sizing/#terms):
// - CSSMeasureModeUndefined: max content
// - CSSMeasureModeExactly: fill available
// - CSSMeasureModeAtMost: fit content
//
// When calling layoutNodeImpl and layoutNodeInternal, if the caller passes an available size of
// undefined then it must also pass a measure mode of CSSMeasureModeUndefined in that dimension.
//
static void layoutNodeImpl(CSSNode* node, float availableWidth, float availableHeight,
CSSDirection parentDirection, CSSMeasureMode widthMeasureMode, CSSMeasureMode heightMeasureMode, bool performLayout) {
assert(isUndefined(availableWidth) ? widthMeasureMode == CSSMeasureModeUndefined : true); // availableWidth is indefinite so widthMeasureMode must be CSSMeasureModeUndefined
assert(isUndefined(availableHeight) ? heightMeasureMode == CSSMeasureModeUndefined : true); // availableHeight is indefinite so heightMeasureMode must be CSSMeasureModeUndefined
float paddingAndBorderAxisRow = getPaddingAndBorderAxis(node, CSSFlexDirectionRow);
float paddingAndBorderAxisColumn = getPaddingAndBorderAxis(node, CSSFlexDirectionColumn);
float marginAxisRow = getMarginAxis(node, CSSFlexDirectionRow);
float marginAxisColumn = getMarginAxis(node, CSSFlexDirectionColumn);
// Set the resolved resolution in the node's layout.
CSSDirection direction = resolveDirection(node, parentDirection);
node->layout.direction = direction;
// For content (text) nodes, determine the dimensions based on the text contents.
if (isMeasureDefined(node)) {
float innerWidth = availableWidth - marginAxisRow - paddingAndBorderAxisRow;
float innerHeight = availableHeight - marginAxisColumn - paddingAndBorderAxisColumn;
if (widthMeasureMode == CSSMeasureModeExactly && heightMeasureMode == CSSMeasureModeExactly) {
// Don't bother sizing the text if both dimensions are already defined.
node->layout.measuredDimensions[CSSDimensionWidth] = boundAxis(node, CSSFlexDirectionRow, availableWidth - marginAxisRow);
node->layout.measuredDimensions[CSSDimensionHeight] = boundAxis(node, CSSFlexDirectionColumn, availableHeight - marginAxisColumn);
} else if (innerWidth <= 0 || innerHeight <= 0) {
// Don't bother sizing the text if there's no horizontal or vertical space.
node->layout.measuredDimensions[CSSDimensionWidth] = boundAxis(node, CSSFlexDirectionRow, 0);
node->layout.measuredDimensions[CSSDimensionHeight] = boundAxis(node, CSSFlexDirectionColumn, 0);
} else {
// Measure the text under the current constraints.
CSSSize measuredSize = node->measure(
node->context,
innerWidth,
widthMeasureMode,
innerHeight,
heightMeasureMode
);
node->layout.measuredDimensions[CSSDimensionWidth] = boundAxis(node, CSSFlexDirectionRow,
(widthMeasureMode == CSSMeasureModeUndefined || widthMeasureMode == CSSMeasureModeAtMost) ?
measuredSize.width + paddingAndBorderAxisRow :
availableWidth - marginAxisRow);
node->layout.measuredDimensions[CSSDimensionHeight] = boundAxis(node, CSSFlexDirectionColumn,
(heightMeasureMode == CSSMeasureModeUndefined || heightMeasureMode == CSSMeasureModeAtMost) ?
measuredSize.height + paddingAndBorderAxisColumn :
availableHeight - marginAxisColumn);
}
return;
}
// For nodes with no children, use the available values if they were provided, or
// the minimum size as indicated by the padding and border sizes.
unsigned int childCount = CSSNodeListCount(node->children);
if (childCount == 0) {
node->layout.measuredDimensions[CSSDimensionWidth] = boundAxis(node, CSSFlexDirectionRow,
(widthMeasureMode == CSSMeasureModeUndefined || widthMeasureMode == CSSMeasureModeAtMost) ?
paddingAndBorderAxisRow :
availableWidth - marginAxisRow);
node->layout.measuredDimensions[CSSDimensionHeight] = boundAxis(node, CSSFlexDirectionColumn,
(heightMeasureMode == CSSMeasureModeUndefined || heightMeasureMode == CSSMeasureModeAtMost) ?
paddingAndBorderAxisColumn :
availableHeight - marginAxisColumn);
return;
}
// If we're not being asked to perform a full layout, we can handle a number of common
// cases here without incurring the cost of the remaining function.
if (!performLayout) {
// If we're being asked to size the content with an at most constraint but there is no available width,
// the measurement will always be zero.
if (widthMeasureMode == CSSMeasureModeAtMost && availableWidth <= 0 &&
heightMeasureMode == CSSMeasureModeAtMost && availableHeight <= 0) {
node->layout.measuredDimensions[CSSDimensionWidth] = boundAxis(node, CSSFlexDirectionRow, 0);
node->layout.measuredDimensions[CSSDimensionHeight] = boundAxis(node, CSSFlexDirectionColumn, 0);
return;
}
if (widthMeasureMode == CSSMeasureModeAtMost && availableWidth <= 0) {
node->layout.measuredDimensions[CSSDimensionWidth] = boundAxis(node, CSSFlexDirectionRow, 0);
node->layout.measuredDimensions[CSSDimensionHeight] = boundAxis(node, CSSFlexDirectionColumn, isUndefined(availableHeight) ? 0 : (availableHeight - marginAxisColumn));
return;
}
if (heightMeasureMode == CSSMeasureModeAtMost && availableHeight <= 0) {
node->layout.measuredDimensions[CSSDimensionWidth] = boundAxis(node, CSSFlexDirectionRow, isUndefined(availableWidth) ? 0 : (availableWidth - marginAxisRow));
node->layout.measuredDimensions[CSSDimensionHeight] = boundAxis(node, CSSFlexDirectionColumn, 0);
return;
}
// If we're being asked to use an exact width/height, there's no need to measure the children.
if (widthMeasureMode == CSSMeasureModeExactly && heightMeasureMode == CSSMeasureModeExactly) {
node->layout.measuredDimensions[CSSDimensionWidth] = boundAxis(node, CSSFlexDirectionRow, availableWidth - marginAxisRow);
node->layout.measuredDimensions[CSSDimensionHeight] = boundAxis(node, CSSFlexDirectionColumn, availableHeight - marginAxisColumn);
return;
}
}
// STEP 1: CALCULATE VALUES FOR REMAINDER OF ALGORITHM
CSSFlexDirection mainAxis = resolveAxis(getFlexDirection(node), direction);
CSSFlexDirection crossAxis = getCrossFlexDirection(mainAxis, direction);
bool isMainAxisRow = isRowDirection(mainAxis);
CSSJustify justifyContent = node->style.justifyContent;
bool isNodeFlexWrap = isFlexWrap(node);
CSSNode* firstAbsoluteChild = NULL;
CSSNode* currentAbsoluteChild = NULL;
float leadingPaddingAndBorderMain = getLeadingPaddingAndBorder(node, mainAxis);
float trailingPaddingAndBorderMain = getTrailingPaddingAndBorder(node, mainAxis);
float leadingPaddingAndBorderCross = getLeadingPaddingAndBorder(node, crossAxis);
float paddingAndBorderAxisMain = getPaddingAndBorderAxis(node, mainAxis);
float paddingAndBorderAxisCross = getPaddingAndBorderAxis(node, crossAxis);
CSSMeasureMode measureModeMainDim = isMainAxisRow ? widthMeasureMode : heightMeasureMode;
CSSMeasureMode measureModeCrossDim = isMainAxisRow ? heightMeasureMode : widthMeasureMode;
// STEP 2: DETERMINE AVAILABLE SIZE IN MAIN AND CROSS DIRECTIONS
float availableInnerWidth = availableWidth - marginAxisRow - paddingAndBorderAxisRow;
float availableInnerHeight = availableHeight - marginAxisColumn - paddingAndBorderAxisColumn;
float availableInnerMainDim = isMainAxisRow ? availableInnerWidth : availableInnerHeight;
float availableInnerCrossDim = isMainAxisRow ? availableInnerHeight : availableInnerWidth;
// STEP 3: DETERMINE FLEX BASIS FOR EACH ITEM
CSSNode* child;
unsigned int i;
float childWidth;
float childHeight;
CSSMeasureMode childWidthMeasureMode;
CSSMeasureMode childHeightMeasureMode;
for (i = 0; i < childCount; i++) {
child = CSSNodeListGet(node->children, i);
if (performLayout) {
// Set the initial position (relative to the parent).
CSSDirection childDirection = resolveDirection(child, direction);
setPosition(child, childDirection);
}
// Absolute-positioned children don't participate in flex layout. Add them
// to a list that we can process later.
if (child->style.positionType == CSSPositionTypeAbsolute) {
// Store a private linked list of absolutely positioned children
// so that we can efficiently traverse them later.
if (firstAbsoluteChild == NULL) {
firstAbsoluteChild = child;
}
if (currentAbsoluteChild != NULL) {
currentAbsoluteChild->nextChild = child;
}
currentAbsoluteChild = child;
child->nextChild = NULL;
} else {
if (isMainAxisRow && isStyleDimDefined(child, CSSFlexDirectionRow)) {
// The width is definite, so use that as the flex basis.
child->layout.flexBasis = fmaxf(child->style.dimensions[CSSDimensionWidth], getPaddingAndBorderAxis(child, CSSFlexDirectionRow));
} else if (!isMainAxisRow && isStyleDimDefined(child, CSSFlexDirectionColumn)) {
// The height is definite, so use that as the flex basis.
child->layout.flexBasis = fmaxf(child->style.dimensions[CSSDimensionHeight], getPaddingAndBorderAxis(child, CSSFlexDirectionColumn));
} else if (!isFlexBasisAuto(child) && !isUndefined(availableInnerMainDim)) {
// If the basis isn't 'auto', it is assumed to be zero.
child->layout.flexBasis = fmaxf(0, getPaddingAndBorderAxis(child, mainAxis));
} else {
// Compute the flex basis and hypothetical main size (i.e. the clamped flex basis).
childWidth = CSSUndefined;
childHeight = CSSUndefined;
childWidthMeasureMode = CSSMeasureModeUndefined;
childHeightMeasureMode = CSSMeasureModeUndefined;
if (isStyleDimDefined(child, CSSFlexDirectionRow)) {
childWidth = child->style.dimensions[CSSDimensionWidth] + getMarginAxis(child, CSSFlexDirectionRow);
childWidthMeasureMode = CSSMeasureModeExactly;
}
if (isStyleDimDefined(child, CSSFlexDirectionColumn)) {
childHeight = child->style.dimensions[CSSDimensionHeight] + getMarginAxis(child, CSSFlexDirectionColumn);
childHeightMeasureMode = CSSMeasureModeExactly;
}
// According to the spec, if the main size is not definite and the
// child's inline axis is parallel to the main axis (i.e. it's
// horizontal), the child should be sized using "UNDEFINED" in
// the main size. Otherwise use "AT_MOST" in the cross axis.
if (!isMainAxisRow && isUndefined(childWidth) && !isUndefined(availableInnerWidth)) {
childWidth = availableInnerWidth;
childWidthMeasureMode = CSSMeasureModeAtMost;
}
// The W3C spec doesn't say anything about the 'overflow' property,
// but all major browsers appear to implement the following logic.
if (node->style.overflow == CSSOverflowHidden) {
if (isMainAxisRow && isUndefined(childHeight) && !isUndefined(availableInnerHeight)) {
childHeight = availableInnerHeight;
childHeightMeasureMode = CSSMeasureModeAtMost;
}
}
// If child has no defined size in the cross axis and is set to stretch, set the cross
// axis to be measured exactly with the available inner width
if (!isMainAxisRow &&
!isUndefined(availableInnerWidth) &&
!isStyleDimDefined(child, CSSFlexDirectionRow) &&
widthMeasureMode == CSSMeasureModeExactly &&
getAlignItem(node, child) == CSSAlignStretch) {
childWidth = availableInnerWidth;
childWidthMeasureMode = CSSMeasureModeExactly;
}
if (isMainAxisRow &&
!isUndefined(availableInnerHeight) &&
!isStyleDimDefined(child, CSSFlexDirectionColumn) &&
heightMeasureMode == CSSMeasureModeExactly &&
getAlignItem(node, child) == CSSAlignStretch) {
childHeight = availableInnerHeight;
childHeightMeasureMode = CSSMeasureModeExactly;
}
// Measure the child
layoutNodeInternal(child, childWidth, childHeight, direction, childWidthMeasureMode, childHeightMeasureMode, false, "measure");
child->layout.flexBasis = fmaxf(isMainAxisRow ? child->layout.measuredDimensions[CSSDimensionWidth] : child->layout.measuredDimensions[CSSDimensionHeight], getPaddingAndBorderAxis(child, mainAxis));
}
}
}
// STEP 4: COLLECT FLEX ITEMS INTO FLEX LINES
// Indexes of children that represent the first and last items in the line.
int startOfLineIndex = 0;
int endOfLineIndex = 0;
// Number of lines.
int lineCount = 0;
// Accumulated cross dimensions of all lines so far.
float totalLineCrossDim = 0;
// Max main dimension of all the lines.
float maxLineMainDim = 0;
while (endOfLineIndex < childCount) {
// Number of items on the currently line. May be different than the difference
// between start and end indicates because we skip over absolute-positioned items.
int itemsOnLine = 0;
// sizeConsumedOnCurrentLine is accumulation of the dimensions and margin
// of all the children on the current line. This will be used in order to
// either set the dimensions of the node if none already exist or to compute
// the remaining space left for the flexible children.
float sizeConsumedOnCurrentLine = 0;
float totalFlexGrowFactors = 0;
float totalFlexShrinkScaledFactors = 0;
i = startOfLineIndex;
// Maintain a linked list of the child nodes that can shrink and/or grow.
CSSNode* firstRelativeChild = NULL;
CSSNode* currentRelativeChild = NULL;
// Add items to the current line until it's full or we run out of items.
while (i < childCount) {
child = CSSNodeListGet(node->children, i);
child->lineIndex = lineCount;
if (child->style.positionType != CSSPositionTypeAbsolute) {
float outerFlexBasis = child->layout.flexBasis + getMarginAxis(child, mainAxis);
// If this is a multi-line flow and this item pushes us over the available size, we've
// hit the end of the current line. Break out of the loop and lay out the current line.
if (sizeConsumedOnCurrentLine + outerFlexBasis > availableInnerMainDim && isNodeFlexWrap && itemsOnLine > 0) {
break;
}
sizeConsumedOnCurrentLine += outerFlexBasis;
itemsOnLine++;
if (isFlex(child)) {
totalFlexGrowFactors += getFlexGrowFactor(child);
// Unlike the grow factor, the shrink factor is scaled relative to the child
// dimension.
totalFlexShrinkScaledFactors += getFlexShrinkFactor(child) * child->layout.flexBasis;
}
// Store a private linked list of children that need to be layed out.
if (firstRelativeChild == NULL) {
firstRelativeChild = child;
}
if (currentRelativeChild != NULL) {
currentRelativeChild->nextChild = child;
}
currentRelativeChild = child;
child->nextChild = NULL;
}
i++;
endOfLineIndex++;
}
// If we don't need to measure the cross axis, we can skip the entire flex step.
bool canSkipFlex = !performLayout && measureModeCrossDim == CSSMeasureModeExactly;
// In order to position the elements in the main axis, we have two
// controls. The space between the beginning and the first element
// and the space between each two elements.
float leadingMainDim = 0;
float betweenMainDim = 0;
// STEP 5: RESOLVING FLEXIBLE LENGTHS ON MAIN AXIS
// Calculate the remaining available space that needs to be allocated.
// If the main dimension size isn't known, it is computed based on
// the line length, so there's no more space left to distribute.
float remainingFreeSpace = 0;
if (!isUndefined(availableInnerMainDim)) {
remainingFreeSpace = availableInnerMainDim - sizeConsumedOnCurrentLine;
} else if (sizeConsumedOnCurrentLine < 0) {
// availableInnerMainDim is indefinite which means the node is being sized based on its content.
// sizeConsumedOnCurrentLine is negative which means the node will allocate 0 pixels for
// its content. Consequently, remainingFreeSpace is 0 - sizeConsumedOnCurrentLine.
remainingFreeSpace = -sizeConsumedOnCurrentLine;
}
float originalRemainingFreeSpace = remainingFreeSpace;
float deltaFreeSpace = 0;
if (!canSkipFlex) {
float childFlexBasis;
float flexShrinkScaledFactor;
float flexGrowFactor;
float baseMainSize;
float boundMainSize;
// Do two passes over the flex items to figure out how to distribute the remaining space.
// The first pass finds the items whose min/max constraints trigger, freezes them at those
// sizes, and excludes those sizes from the remaining space. The second pass sets the size
// of each flexible item. It distributes the remaining space amongst the items whose min/max
// constraints didn't trigger in pass 1. For the other items, it sets their sizes by forcing
// their min/max constraints to trigger again.
//
// This two pass approach for resolving min/max constraints deviates from the spec. The
// spec (https://www.w3.org/TR/css-flexbox-1/#resolve-flexible-lengths) describes a process
// that needs to be repeated a variable number of times. The algorithm implemented here
// won't handle all cases but it was simpler to implement and it mitigates performance
// concerns because we know exactly how many passes it'll do.
// First pass: detect the flex items whose min/max constraints trigger
float deltaFlexShrinkScaledFactors = 0;
float deltaFlexGrowFactors = 0;
currentRelativeChild = firstRelativeChild;
while (currentRelativeChild != NULL) {
childFlexBasis = currentRelativeChild->layout.flexBasis;
if (remainingFreeSpace < 0) {
flexShrinkScaledFactor = getFlexShrinkFactor(currentRelativeChild) * childFlexBasis;
// Is this child able to shrink?
if (flexShrinkScaledFactor != 0) {
baseMainSize = childFlexBasis +
remainingFreeSpace / totalFlexShrinkScaledFactors * flexShrinkScaledFactor;
boundMainSize = boundAxis(currentRelativeChild, mainAxis, baseMainSize);
if (baseMainSize != boundMainSize) {
// By excluding this item's size and flex factor from remaining, this item's
// min/max constraints should also trigger in the second pass resulting in the
// item's size calculation being identical in the first and second passes.
deltaFreeSpace -= boundMainSize - childFlexBasis;
deltaFlexShrinkScaledFactors -= flexShrinkScaledFactor;
}
}
} else if (remainingFreeSpace > 0) {
flexGrowFactor = getFlexGrowFactor(currentRelativeChild);
// Is this child able to grow?
if (flexGrowFactor != 0) {
baseMainSize = childFlexBasis +
remainingFreeSpace / totalFlexGrowFactors * flexGrowFactor;
boundMainSize = boundAxis(currentRelativeChild, mainAxis, baseMainSize);
if (baseMainSize != boundMainSize) {
// By excluding this item's size and flex factor from remaining, this item's
// min/max constraints should also trigger in the second pass resulting in the
// item's size calculation being identical in the first and second passes.
deltaFreeSpace -= boundMainSize - childFlexBasis;
deltaFlexGrowFactors -= flexGrowFactor;
}
}
}
currentRelativeChild = currentRelativeChild->nextChild;
}
totalFlexShrinkScaledFactors += deltaFlexShrinkScaledFactors;
totalFlexGrowFactors += deltaFlexGrowFactors;
remainingFreeSpace += deltaFreeSpace;
// Second pass: resolve the sizes of the flexible items
deltaFreeSpace = 0;
currentRelativeChild = firstRelativeChild;
while (currentRelativeChild != NULL) {
childFlexBasis = currentRelativeChild->layout.flexBasis;
float updatedMainSize = childFlexBasis;
if (remainingFreeSpace < 0) {
flexShrinkScaledFactor = getFlexShrinkFactor(currentRelativeChild) * childFlexBasis;
// Is this child able to shrink?
if (flexShrinkScaledFactor != 0) {
updatedMainSize = boundAxis(currentRelativeChild, mainAxis, childFlexBasis +
remainingFreeSpace / totalFlexShrinkScaledFactors * flexShrinkScaledFactor);
}
} else if (remainingFreeSpace > 0) {
flexGrowFactor = getFlexGrowFactor(currentRelativeChild);
// Is this child able to grow?
if (flexGrowFactor != 0) {
updatedMainSize = boundAxis(currentRelativeChild, mainAxis, childFlexBasis +
remainingFreeSpace / totalFlexGrowFactors * flexGrowFactor);
}
}
deltaFreeSpace -= updatedMainSize - childFlexBasis;
if (isMainAxisRow) {
childWidth = updatedMainSize + getMarginAxis(currentRelativeChild, CSSFlexDirectionRow);
childWidthMeasureMode = CSSMeasureModeExactly;
if (!isUndefined(availableInnerCrossDim) &&
!isStyleDimDefined(currentRelativeChild, CSSFlexDirectionColumn) &&
heightMeasureMode == CSSMeasureModeExactly &&
getAlignItem(node, currentRelativeChild) == CSSAlignStretch) {
childHeight = availableInnerCrossDim;
childHeightMeasureMode = CSSMeasureModeExactly;
} else if (!isStyleDimDefined(currentRelativeChild, CSSFlexDirectionColumn)) {
childHeight = availableInnerCrossDim;
childHeightMeasureMode = isUndefined(childHeight) ? CSSMeasureModeUndefined : CSSMeasureModeAtMost;
} else {
childHeight = currentRelativeChild->style.dimensions[CSSDimensionHeight] + getMarginAxis(currentRelativeChild, CSSFlexDirectionColumn);
childHeightMeasureMode = CSSMeasureModeExactly;
}
} else {
childHeight = updatedMainSize + getMarginAxis(currentRelativeChild, CSSFlexDirectionColumn);
childHeightMeasureMode = CSSMeasureModeExactly;
if (!isUndefined(availableInnerCrossDim) &&
!isStyleDimDefined(currentRelativeChild, CSSFlexDirectionRow) &&
widthMeasureMode == CSSMeasureModeExactly &&
getAlignItem(node, currentRelativeChild) == CSSAlignStretch) {
childWidth = availableInnerCrossDim;
childWidthMeasureMode = CSSMeasureModeExactly;
} else if (!isStyleDimDefined(currentRelativeChild, CSSFlexDirectionRow)) {
childWidth = availableInnerCrossDim;
childWidthMeasureMode = isUndefined(childWidth) ? CSSMeasureModeUndefined : CSSMeasureModeAtMost;
} else {
childWidth = currentRelativeChild->style.dimensions[CSSDimensionWidth] + getMarginAxis(currentRelativeChild, CSSFlexDirectionRow);
childWidthMeasureMode = CSSMeasureModeExactly;
}
}
bool requiresStretchLayout = !isStyleDimDefined(currentRelativeChild, crossAxis) &&
getAlignItem(node, currentRelativeChild) == CSSAlignStretch;
// Recursively call the layout algorithm for this child with the updated main size.
layoutNodeInternal(currentRelativeChild, childWidth, childHeight, direction, childWidthMeasureMode, childHeightMeasureMode, performLayout && !requiresStretchLayout, "flex");
currentRelativeChild = currentRelativeChild->nextChild;
}
}
remainingFreeSpace = originalRemainingFreeSpace + deltaFreeSpace;
// STEP 6: MAIN-AXIS JUSTIFICATION & CROSS-AXIS SIZE DETERMINATION
// At this point, all the children have their dimensions set in the main axis.
// Their dimensions are also set in the cross axis with the exception of items
// that are aligned "stretch". We need to compute these stretch values and
// set the final positions.
// If we are using "at most" rules in the main axis, we won't distribute
// any remaining space at this point.
if (measureModeMainDim == CSSMeasureModeAtMost) {
remainingFreeSpace = 0;
}
// Use justifyContent to figure out how to allocate the remaining space
// available in the main axis.
if (justifyContent != CSSJustifyFlexStart) {
if (justifyContent == CSSJustifyCenter) {
leadingMainDim = remainingFreeSpace / 2;
} else if (justifyContent == CSSJustifyFlexEnd) {
leadingMainDim = remainingFreeSpace;
} else if (justifyContent == CSSJustifySpaceBetween) {
remainingFreeSpace = fmaxf(remainingFreeSpace, 0);
if (itemsOnLine > 1) {
betweenMainDim = remainingFreeSpace / (itemsOnLine - 1);
} else {
betweenMainDim = 0;
}
} else if (justifyContent == CSSJustifySpaceAround) {
// Space on the edges is half of the space between elements
betweenMainDim = remainingFreeSpace / itemsOnLine;
leadingMainDim = betweenMainDim / 2;
}
}
float mainDim = leadingPaddingAndBorderMain + leadingMainDim;
float crossDim = 0;
for (i = startOfLineIndex; i < endOfLineIndex; ++i) {
child = CSSNodeListGet(node->children, i);
if (child->style.positionType == CSSPositionTypeAbsolute &&
isPosDefined(child, leading[mainAxis])) {
if (performLayout) {
// In case the child is position absolute and has left/top being
// defined, we override the position to whatever the user said
// (and margin/border).
child->layout.position[pos[mainAxis]] = getPosition(child, leading[mainAxis]) +
getLeadingBorder(node, mainAxis) +
getLeadingMargin(child, mainAxis);
}
} else {
if (performLayout) {
// If the child is position absolute (without top/left) or relative,
// we put it at the current accumulated offset.
child->layout.position[pos[mainAxis]] += mainDim;
}
// Now that we placed the element, we need to update the variables.
// We need to do that only for relative elements. Absolute elements
// do not take part in that phase.
if (child->style.positionType == CSSPositionTypeRelative) {
if (canSkipFlex) {
// If we skipped the flex step, then we can't rely on the measuredDims because
// they weren't computed. This means we can't call getDimWithMargin.
mainDim += betweenMainDim + getMarginAxis(child, mainAxis) + child->layout.flexBasis;
crossDim = availableInnerCrossDim;
} else {
// The main dimension is the sum of all the elements dimension plus
// the spacing.
mainDim += betweenMainDim + getDimWithMargin(child, mainAxis);
// The cross dimension is the max of the elements dimension since there
// can only be one element in that cross dimension.
crossDim = fmaxf(crossDim, getDimWithMargin(child, crossAxis));
}
}
}
}
mainDim += trailingPaddingAndBorderMain;
float containerCrossAxis = availableInnerCrossDim;
if (measureModeCrossDim == CSSMeasureModeUndefined || measureModeCrossDim == CSSMeasureModeAtMost) {
// Compute the cross axis from the max cross dimension of the children.
containerCrossAxis = boundAxis(node, crossAxis, crossDim + paddingAndBorderAxisCross) - paddingAndBorderAxisCross;
if (measureModeCrossDim == CSSMeasureModeAtMost) {
containerCrossAxis = fminf(containerCrossAxis, availableInnerCrossDim);
}
}
// If there's no flex wrap, the cross dimension is defined by the container.
if (!isNodeFlexWrap && measureModeCrossDim == CSSMeasureModeExactly) {
crossDim = availableInnerCrossDim;
}
// Clamp to the min/max size specified on the container.
crossDim = boundAxis(node, crossAxis, crossDim + paddingAndBorderAxisCross) - paddingAndBorderAxisCross;
// STEP 7: CROSS-AXIS ALIGNMENT
// We can skip child alignment if we're just measuring the container.
if (performLayout) {
for (i = startOfLineIndex; i < endOfLineIndex; ++i) {
child = CSSNodeListGet(node->children, i);
if (child->style.positionType == CSSPositionTypeAbsolute) {
// If the child is absolutely positioned and has a top/left/bottom/right
// set, override all the previously computed positions to set it correctly.
if (isPosDefined(child, leading[crossAxis])) {
child->layout.position[pos[crossAxis]] = getPosition(child, leading[crossAxis]) +
getLeadingBorder(node, crossAxis) +
getLeadingMargin(child, crossAxis);
} else {
child->layout.position[pos[crossAxis]] = leadingPaddingAndBorderCross +
getLeadingMargin(child, crossAxis);
}
} else {
float leadingCrossDim = leadingPaddingAndBorderCross;
// For a relative children, we're either using alignItems (parent) or
// alignSelf (child) in order to determine the position in the cross axis
CSSAlign alignItem = getAlignItem(node, child);
// If the child uses align stretch, we need to lay it out one more time, this time
// forcing the cross-axis size to be the computed cross size for the current line.
if (alignItem == CSSAlignStretch) {
childWidth = child->layout.measuredDimensions[CSSDimensionWidth] + getMarginAxis(child, CSSFlexDirectionRow);
childHeight = child->layout.measuredDimensions[CSSDimensionHeight] + getMarginAxis(child, CSSFlexDirectionColumn);
bool isCrossSizeDefinite = false;
if (isMainAxisRow) {
isCrossSizeDefinite = isStyleDimDefined(child, CSSFlexDirectionColumn);
childHeight = crossDim;
} else {
isCrossSizeDefinite = isStyleDimDefined(child, CSSFlexDirectionRow);
childWidth = crossDim;
}
// If the child defines a definite size for its cross axis, there's no need to stretch.
if (!isCrossSizeDefinite) {
childWidthMeasureMode = isUndefined(childWidth) ? CSSMeasureModeUndefined : CSSMeasureModeExactly;
childHeightMeasureMode = isUndefined(childHeight) ? CSSMeasureModeUndefined : CSSMeasureModeExactly;
layoutNodeInternal(child, childWidth, childHeight, direction, childWidthMeasureMode, childHeightMeasureMode, true, "stretch");
}
} else if (alignItem != CSSAlignFlexStart) {
float remainingCrossDim = containerCrossAxis - getDimWithMargin(child, crossAxis);
if (alignItem == CSSAlignCenter) {
leadingCrossDim += remainingCrossDim / 2;
} else { // CSSAlignFlexEnd
leadingCrossDim += remainingCrossDim;
}
}
// And we apply the position
child->layout.position[pos[crossAxis]] += totalLineCrossDim + leadingCrossDim;
}
}
}
totalLineCrossDim += crossDim;
maxLineMainDim = fmaxf(maxLineMainDim, mainDim);
// Reset variables for new line.
lineCount++;
startOfLineIndex = endOfLineIndex;
endOfLineIndex = startOfLineIndex;
}
// STEP 8: MULTI-LINE CONTENT ALIGNMENT
if (lineCount > 1 && performLayout && !isUndefined(availableInnerCrossDim)) {
float remainingAlignContentDim = availableInnerCrossDim - totalLineCrossDim;
float crossDimLead = 0;
float currentLead = leadingPaddingAndBorderCross;
CSSAlign alignContent = node->style.alignContent;
if (alignContent == CSSAlignFlexEnd) {
currentLead += remainingAlignContentDim;
} else if (alignContent == CSSAlignCenter) {
currentLead += remainingAlignContentDim / 2;
} else if (alignContent == CSSAlignStretch) {
if (availableInnerCrossDim > totalLineCrossDim) {
crossDimLead = (remainingAlignContentDim / lineCount);
}
}
int endIndex = 0;
for (i = 0; i < lineCount; ++i) {
int startIndex = endIndex;
int j;
// compute the line's height and find the endIndex
float lineHeight = 0;
for (j = startIndex; j < childCount; ++j) {
child = CSSNodeListGet(node->children, j);
if (child->style.positionType != CSSPositionTypeRelative) {
continue;
}
if (child->lineIndex != i) {
break;
}
if (isLayoutDimDefined(child, crossAxis)) {
lineHeight = fmaxf(lineHeight,
child->layout.measuredDimensions[dim[crossAxis]] + getMarginAxis(child, crossAxis));
}
}
endIndex = j;
lineHeight += crossDimLead;
if (performLayout) {
for (j = startIndex; j < endIndex; ++j) {
child = CSSNodeListGet(node->children, j);
if (child->style.positionType != CSSPositionTypeRelative) {
continue;
}
CSSAlign alignContentAlignItem = getAlignItem(node, child);
if (alignContentAlignItem == CSSAlignFlexStart) {
child->layout.position[pos[crossAxis]] = currentLead + getLeadingMargin(child, crossAxis);
} else if (alignContentAlignItem == CSSAlignFlexEnd) {
child->layout.position[pos[crossAxis]] = currentLead + lineHeight - getTrailingMargin(child, crossAxis) - child->layout.measuredDimensions[dim[crossAxis]];
} else if (alignContentAlignItem == CSSAlignCenter) {
childHeight = child->layout.measuredDimensions[dim[crossAxis]];
child->layout.position[pos[crossAxis]] = currentLead + (lineHeight - childHeight) / 2;
} else if (alignContentAlignItem == CSSAlignStretch) {
child->layout.position[pos[crossAxis]] = currentLead + getLeadingMargin(child, crossAxis);
// TODO(prenaux): Correctly set the height of items with indefinite
// (auto) crossAxis dimension.
}
}
}
currentLead += lineHeight;
}
}
// STEP 9: COMPUTING FINAL DIMENSIONS
node->layout.measuredDimensions[CSSDimensionWidth] = boundAxis(node, CSSFlexDirectionRow, availableWidth - marginAxisRow);
node->layout.measuredDimensions[CSSDimensionHeight] = boundAxis(node, CSSFlexDirectionColumn, availableHeight - marginAxisColumn);
// If the user didn't specify a width or height for the node, set the
// dimensions based on the children.
if (measureModeMainDim == CSSMeasureModeUndefined) {
// Clamp the size to the min/max size, if specified, and make sure it
// doesn't go below the padding and border amount.
node->layout.measuredDimensions[dim[mainAxis]] = boundAxis(node, mainAxis, maxLineMainDim);
} else if (measureModeMainDim == CSSMeasureModeAtMost) {
node->layout.measuredDimensions[dim[mainAxis]] = fmaxf(
fminf(availableInnerMainDim + paddingAndBorderAxisMain,
boundAxisWithinMinAndMax(node, mainAxis, maxLineMainDim)),
paddingAndBorderAxisMain);
}
if (measureModeCrossDim == CSSMeasureModeUndefined) {
// Clamp the size to the min/max size, if specified, and make sure it
// doesn't go below the padding and border amount.
node->layout.measuredDimensions[dim[crossAxis]] = boundAxis(node, crossAxis, totalLineCrossDim + paddingAndBorderAxisCross);
} else if (measureModeCrossDim == CSSMeasureModeAtMost) {
node->layout.measuredDimensions[dim[crossAxis]] = fmaxf(
fminf(availableInnerCrossDim + paddingAndBorderAxisCross,
boundAxisWithinMinAndMax(node, crossAxis, totalLineCrossDim + paddingAndBorderAxisCross)),
paddingAndBorderAxisCross);
}
// STEP 10: SETTING TRAILING POSITIONS FOR CHILDREN
if (performLayout) {
bool needsMainTrailingPos = false;
bool needsCrossTrailingPos = false;
if (mainAxis == CSSFlexDirectionRowReverse ||
mainAxis == CSSFlexDirectionColumnReverse) {
needsMainTrailingPos = true;
}
if (crossAxis == CSSFlexDirectionRowReverse ||
crossAxis == CSSFlexDirectionColumnReverse) {
needsCrossTrailingPos = true;
}
// Set trailing position if necessary.
if (needsMainTrailingPos || needsCrossTrailingPos) {
for (i = 0; i < childCount; ++i) {
child = CSSNodeListGet(node->children, i);
if (needsMainTrailingPos) {
setTrailingPosition(node, child, mainAxis);
}
if (needsCrossTrailingPos) {
setTrailingPosition(node, child, crossAxis);
}
}
}
}
// STEP 11: SIZING AND POSITIONING ABSOLUTE CHILDREN
currentAbsoluteChild = firstAbsoluteChild;
while (currentAbsoluteChild != NULL) {
// Now that we know the bounds of the container, perform layout again on the
// absolutely-positioned children.
if (performLayout) {
childWidth = CSSUndefined;
childHeight = CSSUndefined;
if (isStyleDimDefined(currentAbsoluteChild, CSSFlexDirectionRow)) {
childWidth = currentAbsoluteChild->style.dimensions[CSSDimensionWidth] + getMarginAxis(currentAbsoluteChild, CSSFlexDirectionRow);
} else {
// If the child doesn't have a specified width, compute the width based on the left/right offsets if they're defined.
if (isPosDefined(currentAbsoluteChild, CSSPositionLeft) && isPosDefined(currentAbsoluteChild, CSSPositionRight)) {
childWidth = node->layout.measuredDimensions[CSSDimensionWidth] -
(getLeadingBorder(node, CSSFlexDirectionRow) + getTrailingBorder(node, CSSFlexDirectionRow)) -
(currentAbsoluteChild->style.position[CSSPositionLeft] + currentAbsoluteChild->style.position[CSSPositionRight]);
childWidth = boundAxis(currentAbsoluteChild, CSSFlexDirectionRow, childWidth);
}
}
if (isStyleDimDefined(currentAbsoluteChild, CSSFlexDirectionColumn)) {
childHeight = currentAbsoluteChild->style.dimensions[CSSDimensionHeight] + getMarginAxis(currentAbsoluteChild, CSSFlexDirectionColumn);
} else {
// If the child doesn't have a specified height, compute the height based on the top/bottom offsets if they're defined.
if (isPosDefined(currentAbsoluteChild, CSSPositionTop) && isPosDefined(currentAbsoluteChild, CSSPositionBottom)) {
childHeight = node->layout.measuredDimensions[CSSDimensionHeight] -
(getLeadingBorder(node, CSSFlexDirectionColumn) + getTrailingBorder(node, CSSFlexDirectionColumn)) -
(currentAbsoluteChild->style.position[CSSPositionTop] + currentAbsoluteChild->style.position[CSSPositionBottom]);
childHeight = boundAxis(currentAbsoluteChild, CSSFlexDirectionColumn, childHeight);
}
}
// If we're still missing one or the other dimension, measure the content.
if (isUndefined(childWidth) || isUndefined(childHeight)) {
childWidthMeasureMode = isUndefined(childWidth) ? CSSMeasureModeUndefined : CSSMeasureModeExactly;
childHeightMeasureMode = isUndefined(childHeight) ? CSSMeasureModeUndefined : CSSMeasureModeExactly;
// According to the spec, if the main size is not definite and the
// child's inline axis is parallel to the main axis (i.e. it's
// horizontal), the child should be sized using "UNDEFINED" in
// the main size. Otherwise use "AT_MOST" in the cross axis.
if (!isMainAxisRow && isUndefined(childWidth) && !isUndefined(availableInnerWidth)) {
childWidth = availableInnerWidth;
childWidthMeasureMode = CSSMeasureModeAtMost;
}
// The W3C spec doesn't say anything about the 'overflow' property,
// but all major browsers appear to implement the following logic.
if (node->style.overflow == CSSOverflowHidden) {
if (isMainAxisRow && isUndefined(childHeight) && !isUndefined(availableInnerHeight)) {
childHeight = availableInnerHeight;
childHeightMeasureMode = CSSMeasureModeAtMost;
}
}
layoutNodeInternal(currentAbsoluteChild, childWidth, childHeight, direction, childWidthMeasureMode, childHeightMeasureMode, false, "abs-measure");
childWidth = currentAbsoluteChild->layout.measuredDimensions[CSSDimensionWidth] + getMarginAxis(currentAbsoluteChild, CSSFlexDirectionRow);
childHeight = currentAbsoluteChild->layout.measuredDimensions[CSSDimensionHeight] + getMarginAxis(currentAbsoluteChild, CSSFlexDirectionColumn);
}
layoutNodeInternal(currentAbsoluteChild, childWidth, childHeight, direction, CSSMeasureModeExactly, CSSMeasureModeExactly, true, "abs-layout");
if (isPosDefined(currentAbsoluteChild, trailing[CSSFlexDirectionRow]) &&
!isPosDefined(currentAbsoluteChild, leading[CSSFlexDirectionRow])) {
currentAbsoluteChild->layout.position[leading[CSSFlexDirectionRow]] =
node->layout.measuredDimensions[dim[CSSFlexDirectionRow]] -
currentAbsoluteChild->layout.measuredDimensions[dim[CSSFlexDirectionRow]] -
getPosition(currentAbsoluteChild, trailing[CSSFlexDirectionRow]);
}
if (isPosDefined(currentAbsoluteChild, trailing[CSSFlexDirectionColumn]) &&
!isPosDefined(currentAbsoluteChild, leading[CSSFlexDirectionColumn])) {
currentAbsoluteChild->layout.position[leading[CSSFlexDirectionColumn]] =
node->layout.measuredDimensions[dim[CSSFlexDirectionColumn]] -
currentAbsoluteChild->layout.measuredDimensions[dim[CSSFlexDirectionColumn]] -
getPosition(currentAbsoluteChild, trailing[CSSFlexDirectionColumn]);
}
}
currentAbsoluteChild = currentAbsoluteChild->nextChild;
}
}
int gDepth = 0;
bool gPrintTree = false;
bool gPrintChanges = false;
bool gPrintSkips = false;
static const char* spacer = " ";
static const char* getSpacer(unsigned long level) {
unsigned long spacerLen = strlen(spacer);
if (level > spacerLen) {
level = spacerLen;
}
return &spacer[spacerLen - level];
}
static const char* getModeName(CSSMeasureMode mode, bool performLayout) {
const char* kMeasureModeNames[CSSMeasureModeCount] = {
"UNDEFINED",
"EXACTLY",
"AT_MOST"
};
const char* kLayoutModeNames[CSSMeasureModeCount] = {
"LAY_UNDEFINED",
"LAY_EXACTLY",
"LAY_AT_MOST"
};
if (mode >= CSSMeasureModeCount) {
return "";
}
return performLayout? kLayoutModeNames[mode] : kMeasureModeNames[mode];
}
static bool canUseCachedMeasurement(
bool isTextNode,
float availableWidth,
float availableHeight,
float margin_row,
float margin_column,
CSSMeasureMode widthMeasureMode,
CSSMeasureMode heightMeasureMode,
CSSCachedMeasurement cached_layout) {
bool is_height_same =
(cached_layout.heightMeasureMode == CSSMeasureModeUndefined && heightMeasureMode == CSSMeasureModeUndefined) ||
(cached_layout.heightMeasureMode == heightMeasureMode && eq(cached_layout.availableHeight, availableHeight));
bool is_width_same =
(cached_layout.widthMeasureMode == CSSMeasureModeUndefined && widthMeasureMode == CSSMeasureModeUndefined) ||
(cached_layout.widthMeasureMode == widthMeasureMode && eq(cached_layout.availableWidth, availableWidth));
if (is_height_same && is_width_same) {
return true;
}
bool is_height_valid =
(cached_layout.heightMeasureMode == CSSMeasureModeUndefined && heightMeasureMode == CSSMeasureModeAtMost && cached_layout.computedHeight <= (availableHeight - margin_column)) ||
(heightMeasureMode == CSSMeasureModeExactly && eq(cached_layout.computedHeight, availableHeight - margin_column));
if (is_width_same && is_height_valid) {
return true;
}
bool is_width_valid =
(cached_layout.widthMeasureMode == CSSMeasureModeUndefined && widthMeasureMode == CSSMeasureModeAtMost && cached_layout.computedWidth <= (availableWidth - margin_row)) ||
(widthMeasureMode == CSSMeasureModeExactly && eq(cached_layout.computedWidth, availableWidth - margin_row));
if (is_height_same && is_width_valid) {
return true;
}
if (is_height_valid && is_width_valid) {
return true;
}
// We know this to be text so we can apply some more specialized heuristics.
if (isTextNode) {
if (is_width_same) {
if (heightMeasureMode == CSSMeasureModeUndefined) {
// Width is the same and height is not restricted. Re-use cahced value.
return true;
}
if (heightMeasureMode == CSSMeasureModeAtMost &&
cached_layout.computedHeight < (availableHeight - margin_column)) {
// Width is the same and height restriction is greater than the cached height. Re-use cached value.
return true;
}
// Width is the same but height restriction imposes smaller height than previously measured.
// Update the cached value to respect the new height restriction.
cached_layout.computedHeight = availableHeight - margin_column;
return true;
}
if (cached_layout.widthMeasureMode == CSSMeasureModeUndefined) {
if (widthMeasureMode == CSSMeasureModeUndefined ||
(widthMeasureMode == CSSMeasureModeAtMost &&
cached_layout.computedWidth <= (availableWidth - margin_row))) {
// Previsouly this text was measured with no width restriction, if width is now restricted
// but to a larger value than the previsouly measured width we can re-use the measurement
// as we know it will fit.
return true;
}
}
}
return false;
}
//
// This is a wrapper around the layoutNodeImpl function. It determines
// whether the layout request is redundant and can be skipped.
//
// Parameters:
// Input parameters are the same as layoutNodeImpl (see above)
// Return parameter is true if layout was performed, false if skipped
//
bool layoutNodeInternal(CSSNode* node, float availableWidth, float availableHeight,
CSSDirection parentDirection, CSSMeasureMode widthMeasureMode, CSSMeasureMode heightMeasureMode, bool performLayout, char* reason) {
CSSLayout* layout = &node->layout;
gDepth++;
bool needToVisitNode = (node->isDirty(node->context) && layout->generationCount != gCurrentGenerationCount) ||
layout->lastParentDirection != parentDirection;
if (needToVisitNode) {
// Invalidate the cached results.
layout->nextCachedMeasurementsIndex = 0;
layout->cached_layout.widthMeasureMode = (CSSMeasureMode)-1;
layout->cached_layout.heightMeasureMode = (CSSMeasureMode)-1;
}
CSSCachedMeasurement* cachedResults = NULL;
// Determine whether the results are already cached. We maintain a separate
// cache for layouts and measurements. A layout operation modifies the positions
// and dimensions for nodes in the subtree. The algorithm assumes that each node
// gets layed out a maximum of one time per tree layout, but multiple measurements
// may be required to resolve all of the flex dimensions.
// We handle nodes with measure functions specially here because they are the most
// expensive to measure, so it's worth avoiding redundant measurements if at all possible.
if (isMeasureDefined(node)) {
float marginAxisRow = getMarginAxis(node, CSSFlexDirectionRow);
float marginAxisColumn = getMarginAxis(node, CSSFlexDirectionColumn);
// First, try to use the layout cache.
if (canUseCachedMeasurement(node->isTextNode, availableWidth, availableHeight, marginAxisRow, marginAxisColumn,
widthMeasureMode, heightMeasureMode, layout->cached_layout)) {
cachedResults = &layout->cached_layout;
} else {
// Try to use the measurement cache.
for (int i = 0; i < layout->nextCachedMeasurementsIndex; i++) {
if (canUseCachedMeasurement(node->isTextNode, availableWidth, availableHeight, marginAxisRow, marginAxisColumn,
widthMeasureMode, heightMeasureMode, layout->cachedMeasurements[i])) {
cachedResults = &layout->cachedMeasurements[i];
break;
}
}
}
} else if (performLayout) {
if (eq(layout->cached_layout.availableWidth, availableWidth) &&
eq(layout->cached_layout.availableHeight, availableHeight) &&
layout->cached_layout.widthMeasureMode == widthMeasureMode &&
layout->cached_layout.heightMeasureMode == heightMeasureMode) {
cachedResults = &layout->cached_layout;
}
} else {
for (int i = 0; i < layout->nextCachedMeasurementsIndex; i++) {
if (eq(layout->cachedMeasurements[i].availableWidth, availableWidth) &&
eq(layout->cachedMeasurements[i].availableHeight, availableHeight) &&
layout->cachedMeasurements[i].widthMeasureMode == widthMeasureMode &&
layout->cachedMeasurements[i].heightMeasureMode == heightMeasureMode) {
cachedResults = &layout->cachedMeasurements[i];
break;
}
}
}
if (!needToVisitNode && cachedResults != NULL) {
layout->measuredDimensions[CSSDimensionWidth] = cachedResults->computedWidth;
layout->measuredDimensions[CSSDimensionHeight] = cachedResults->computedHeight;
if (gPrintChanges && gPrintSkips) {
printf("%s%d.{[skipped] ", getSpacer(gDepth), gDepth);
if (node->print) {
node->print(node->context);
}
printf("wm: %s, hm: %s, aw: %f ah: %f => d: (%f, %f) %s\n",
getModeName(widthMeasureMode, performLayout),
getModeName(heightMeasureMode, performLayout),
availableWidth, availableHeight,
cachedResults->computedWidth, cachedResults->computedHeight, reason);
}
} else {
if (gPrintChanges) {
printf("%s%d.{%s", getSpacer(gDepth), gDepth, needToVisitNode ? "*" : "");
if (node->print) {
node->print(node->context);
}
printf("wm: %s, hm: %s, aw: %f ah: %f %s\n",
getModeName(widthMeasureMode, performLayout),
getModeName(heightMeasureMode, performLayout),
availableWidth, availableHeight, reason);
}
layoutNodeImpl(node, availableWidth, availableHeight, parentDirection, widthMeasureMode, heightMeasureMode, performLayout);
if (gPrintChanges) {
printf("%s%d.}%s", getSpacer(gDepth), gDepth, needToVisitNode ? "*" : "");
if (node->print) {
node->print(node->context);
}
printf("wm: %s, hm: %s, d: (%f, %f) %s\n",
getModeName(widthMeasureMode, performLayout),
getModeName(heightMeasureMode, performLayout),
layout->measuredDimensions[CSSDimensionWidth], layout->measuredDimensions[CSSDimensionHeight], reason);
}
layout->lastParentDirection = parentDirection;
if (cachedResults == NULL) {
if (layout->nextCachedMeasurementsIndex == CSS_MAX_CACHED_RESULT_COUNT) {
if (gPrintChanges) {
printf("Out of cache entries!\n");
}
layout->nextCachedMeasurementsIndex = 0;
}
CSSCachedMeasurement* newCacheEntry;
if (performLayout) {
// Use the single layout cache entry.
newCacheEntry = &layout->cached_layout;
} else {
// Allocate a new measurement cache entry.
newCacheEntry = &layout->cachedMeasurements[layout->nextCachedMeasurementsIndex];
layout->nextCachedMeasurementsIndex++;
}
newCacheEntry->availableWidth = availableWidth;
newCacheEntry->availableHeight = availableHeight;
newCacheEntry->widthMeasureMode = widthMeasureMode;
newCacheEntry->heightMeasureMode = heightMeasureMode;
newCacheEntry->computedWidth = layout->measuredDimensions[CSSDimensionWidth];
newCacheEntry->computedHeight = layout->measuredDimensions[CSSDimensionHeight];
}
}
if (performLayout) {
node->layout.dimensions[CSSDimensionWidth] = node->layout.measuredDimensions[CSSDimensionWidth];
node->layout.dimensions[CSSDimensionHeight] = node->layout.measuredDimensions[CSSDimensionHeight];
node->shouldUpdate = true;
}
gDepth--;
layout->generationCount = gCurrentGenerationCount;
return (needToVisitNode || cachedResults == NULL);
}
void CSSNodeCalculateLayout(CSSNode* node, float availableWidth, float availableHeight, CSSDirection parentDirection) {
// Increment the generation count. This will force the recursive routine to visit
// all dirty nodes at least once. Subsequent visits will be skipped if the input
// parameters don't change.
gCurrentGenerationCount++;
CSSMeasureMode widthMeasureMode = CSSMeasureModeUndefined;
CSSMeasureMode heightMeasureMode = CSSMeasureModeUndefined;
if (!isUndefined(availableWidth)) {
widthMeasureMode = CSSMeasureModeExactly;
} else if (isStyleDimDefined(node, CSSFlexDirectionRow)) {
availableWidth = node->style.dimensions[dim[CSSFlexDirectionRow]] + getMarginAxis(node, CSSFlexDirectionRow);
widthMeasureMode = CSSMeasureModeExactly;
} else if (node->style.maxDimensions[CSSDimensionWidth] >= 0.0) {
availableWidth = node->style.maxDimensions[CSSDimensionWidth];
widthMeasureMode = CSSMeasureModeAtMost;
}
if (!isUndefined(availableHeight)) {
heightMeasureMode = CSSMeasureModeExactly;
} else if (isStyleDimDefined(node, CSSFlexDirectionColumn)) {
availableHeight = node->style.dimensions[dim[CSSFlexDirectionColumn]] + getMarginAxis(node, CSSFlexDirectionColumn);
heightMeasureMode = CSSMeasureModeExactly;
} else if (node->style.maxDimensions[CSSDimensionHeight] >= 0.0) {
availableHeight = node->style.maxDimensions[CSSDimensionHeight];
heightMeasureMode = CSSMeasureModeAtMost;
}
if (layoutNodeInternal(node, availableWidth, availableHeight, parentDirection, widthMeasureMode, heightMeasureMode, true, "initial")) {
setPosition(node, node->layout.direction);
if (gPrintTree) {
CSSNodePrint(node, CSSPrintOptionsLayout | CSSPrintOptionsChildren | CSSPrintOptionsStyle);
}
}
}
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