1#[cfg(not(feature = "std"))]
2use alloc::{vec, vec::Vec};
3#[cfg(not(feature = "std"))]
4use libm::F32Ext;
5
6use core::f32;
7
8use crate::layout;
9use crate::ref_eq::ref_eq;
10
11use crate::style;
12use crate::style::*;
13
14use crate::number::Number::*;
15use crate::number::*;
16
17use crate::geometry::{Point, Rect, Size};
18
19#[derive(Debug, Clone)]
20pub struct ComputeResult {
21 pub size: Size<f32>,
22 pub children: Vec<layout::Node>,
23}
24
25struct FlexItem<'a> {
26 node: &'a style::Node,
27
28 size: Size<Number>,
29 min_size: Size<Number>,
30 max_size: Size<Number>,
31
32 position: Rect<Number>,
33 margin: Rect<f32>,
34 padding: Rect<f32>,
35 border: Rect<f32>,
36
37 flex_basis: f32,
38 inner_flex_basis: f32,
39 violation: f32,
40 frozen: bool,
41
42 hypothetical_inner_size: Size<f32>,
43 hypothetical_outer_size: Size<f32>,
44 target_size: Size<f32>,
45 outer_target_size: Size<f32>,
46
47 baseline: f32,
48
49 // temporary values for holding offset in the main / cross direction.
50 // offset is the relative position from the item's natural flow position based on
51 // relative position values, alignment, and justification. Does not unclude margin/padding/border.
52 offset_main: f32,
53 offset_cross: f32,
54}
55
56struct FlexLine<'a> {
57 items: Vec<FlexItem<'a>>,
58 cross_size: f32,
59 offset_cross: f32,
60}
61
62pub fn compute(root: &style::Node, size: Size<Number>) -> layout::Node {
63 let has_root_min_max = root.min_size.width.is_defined()
64 || root.min_size.height.is_defined()
65 || root.max_size.width.is_defined()
66 || root.max_size.height.is_defined();
67
68 let result = if has_root_min_max {
69 let first_pass = compute_internal(
70 root,
71 Size { width: root.size.width.resolve(size.width), height: root.size.height.resolve(size.height) },
72 size,
73 size.width,
74 false,
75 );
76
77 compute_internal(
78 root,
79 Size {
80 width: first_pass
81 .size
82 .width
83 .maybe_max(root.min_size.width.resolve(size.width))
84 .maybe_min(root.max_size.width.resolve(size.width))
85 .to_number(),
86 height: first_pass
87 .size
88 .height
89 .maybe_max(root.min_size.height.resolve(size.height))
90 .maybe_min(root.max_size.height.resolve(size.height))
91 .to_number(),
92 },
93 size,
94 size.width,
95 true,
96 )
97 } else {
98 compute_internal(
99 root,
100 Size { width: root.size.width.resolve(size.width), height: root.size.height.resolve(size.height) },
101 size,
102 size.width,
103 true,
104 )
105 };
106
107 let mut layout = layout::Node {
108 order: 0,
109 size: Size { width: result.size.width, height: result.size.height },
110 location: Point { x: 0.0, y: 0.0 },
111 children: result.children,
112 };
113
114 round_layout(&mut layout, 0.0, 0.0);
115 layout
116}
117
118fn round_layout(layout: &mut layout::Node, abs_x: f32, abs_y: f32) {
119 let abs_x = abs_x + layout.location.x;
120 let abs_y = abs_y + layout.location.y;
121
122 layout.location.x = layout.location.x.round();
123 layout.location.y = layout.location.y.round();
124 layout.size.width = (abs_x + layout.size.width).round() - abs_x.round();
125 layout.size.height = (abs_y + layout.size.height).round() - abs_y.round();
126 layout.children.iter_mut().for_each(|child| round_layout(child, abs_x, abs_y));
127}
128
129fn compute_internal(
130 node: &style::Node,
131 node_size: Size<Number>,
132 parent_size: Size<Number>,
133 percent_calc_base: Number,
134 perform_layout: bool,
135) -> ComputeResult {
136 // First we check if we have a result for the given input
137 {
138 let layout_cache = node.layout_cache.borrow();
139 if layout_cache.is_some() {
140 let cache = layout_cache.as_ref().unwrap();
141 if cache.perform_layout || !perform_layout {
142 let width_compatible = if let Number::Defined(width) = node_size.width {
143 (width - cache.result.size.width).abs() < f32::EPSILON
144 } else {
145 cache.node_size.width.is_undefined()
146 };
147
148 let height_compatible = if let Number::Defined(height) = node_size.height {
149 (height - cache.result.size.height).abs() < f32::EPSILON
150 } else {
151 cache.node_size.height.is_undefined()
152 };
153
154 if width_compatible && height_compatible {
155 return cache.result.clone();
156 }
157
158 if cache.node_size == node_size
159 && cache.parent_size == parent_size
160 && cache.percent_calc_base == percent_calc_base
161 {
162 return cache.result.clone();
163 }
164 }
165 }
166 }
167
168 // If this is a leaf node we can skip a lot of this function in some cases
169 if node.children.is_empty() {
170 if node_size.width.is_defined() && node_size.height.is_defined() {
171 return ComputeResult { size: node_size.map(|s| s.or_else(0.0)), children: vec![] };
172 }
173
174 if let Some(ref measure) = node.measure {
175 let result = ComputeResult { size: measure(node_size), children: vec![] };
176 node.layout_cache.replace(Some(LayoutCache {
177 node_size,
178 parent_size,
179 percent_calc_base,
180 perform_layout,
181 result: result.clone(),
182 }));
183 return result;
184 }
185 }
186
187 // Define some general constants we will need for the remainder
188 // of the algorithm.
189
190 let dir = node.flex_direction;
191 let is_row = dir.is_row();
192 let is_column = dir.is_column();
193 let is_wrap_reverse = node.flex_wrap == FlexWrap::WrapReverse;
194
195 let margin = node.margin.map(|n| n.resolve(percent_calc_base).or_else(0.0));
196 let padding = node.padding.map(|n| n.resolve(percent_calc_base).or_else(0.0));
197 let border = node.border.map(|n| n.resolve(percent_calc_base).or_else(0.0));
198
199 let padding_border = Rect {
200 start: padding.start + border.start,
201 end: padding.end + border.end,
202 top: padding.top + border.top,
203 bottom: padding.bottom + border.bottom,
204 };
205
206 let node_inner_size = Size {
207 width: node_size.width - padding_border.horizontal(),
208 height: node_size.height - padding_border.vertical(),
209 };
210
211 let percent_calc_base_child = node_inner_size.width;
212 let mut container_size = Size { width: 0.0, height: 0.0 };
213 let mut inner_container_size = Size { width: 0.0, height: 0.0 };
214
215 // 9.2. Line Length Determination
216
217 // 1. Generate anonymous flex items as described in §4 Flex Items.
218
219 // 2. Determine the available main and cross space for the flex items.
220 // For each dimension, if that dimension of the flex container’s content box
221 // is a definite size, use that; if that dimension of the flex container is
222 // being sized under a min or max-content constraint, the available space in
223 // that dimension is that constraint; otherwise, subtract the flex container’s
224 // margin, border, and padding from the space available to the flex container
225 // in that dimension and use that value. This might result in an infinite value.
226
227 let available_space = Size {
228 width: node_size.width.or_else(parent_size.width - margin.horizontal()) - padding_border.horizontal(),
229 height: node_size.height.or_else(parent_size.height - margin.vertical()) - padding_border.vertical(),
230 };
231
232 let mut flex_items: Vec<FlexItem> = node
233 .children
234 .iter()
235 .filter(|child| child.position_type != PositionType::Absolute)
236 .filter(|child| child.display != Display::None)
237 .map(|child| FlexItem {
238 node: child,
239
240 size: child.size.map(|s| s.resolve(percent_calc_base_child)),
241 min_size: child.min_size.map(|s| s.resolve(percent_calc_base_child)),
242 max_size: child.max_size.map(|s| s.resolve(percent_calc_base_child)),
243
244 position: child.position.map(|p| p.resolve(percent_calc_base_child)),
245 margin: child.margin.map(|m| m.resolve(percent_calc_base_child).or_else(0.0)),
246 padding: child.padding.map(|p| p.resolve(percent_calc_base_child).or_else(0.0)),
247 border: child.border.map(|b| b.resolve(percent_calc_base_child).or_else(0.0)),
248
249 flex_basis: 0.0,
250 inner_flex_basis: 0.0,
251 violation: 0.0,
252 frozen: false,
253
254 hypothetical_inner_size: Size { width: 0.0, height: 0.0 },
255 hypothetical_outer_size: Size { width: 0.0, height: 0.0 },
256 target_size: Size { width: 0.0, height: 0.0 },
257 outer_target_size: Size { width: 0.0, height: 0.0 },
258
259 baseline: 0.0,
260
261 offset_main: 0.0,
262 offset_cross: 0.0,
263 })
264 .collect();
265
266 // TODO - this does not follow spec. See commented out code below
267 // 3. Determine the flex base size and hypothetical main size of each item:
268 flex_items.iter_mut().for_each(|child| {
269 // A. If the item has a definite used flex basis, that’s the flex base size.
270
271 let flex_basis = child.node.flex_basis.resolve(percent_calc_base_child);
272 if flex_basis.is_defined() {
273 child.flex_basis = flex_basis.or_else(0.0);
274 return;
275 };
276
277 // B. If the flex item has an intrinsic aspect ratio,
278 // a used flex basis of content, and a definite cross size,
279 // then the flex base size is calculated from its inner
280 // cross size and the flex item’s intrinsic aspect ratio.
281
282 if let Defined(ratio) = child.node.aspect_ratio {
283 if let Defined(cross) = node_size.cross(dir) {
284 if child.node.flex_basis == Dimension::Auto {
285 child.flex_basis = cross * ratio;
286 return;
287 }
288 }
289 }
290
291 // C. If the used flex basis is content or depends on its available space,
292 // and the flex container is being sized under a min-content or max-content
293 // constraint (e.g. when performing automatic table layout [CSS21]),
294 // size the item under that constraint. The flex base size is the item’s
295 // resulting main size.
296
297 // TODO - Probably need to cover this case in future
298
299 // D. Otherwise, if the used flex basis is content or depends on its
300 // available space, the available main size is infinite, and the flex item’s
301 // inline axis is parallel to the main axis, lay the item out using the rules
302 // for a box in an orthogonal flow [CSS3-WRITING-MODES]. The flex base size
303 // is the item’s max-content main size.
304
305 // TODO - Probably need to cover this case in future
306
307 // E. Otherwise, size the item into the available space using its used flex basis
308 // in place of its main size, treating a value of content as max-content.
309 // If a cross size is needed to determine the main size (e.g. when the
310 // flex item’s main size is in its block axis) and the flex item’s cross size
311 // is auto and not definite, in this calculation use fit-content as the
312 // flex item’s cross size. The flex base size is the item’s resulting main size.
313
314 let width: Number = if !child.size.width.is_defined()
315 && child.node.align_self(node) == style::AlignSelf::Stretch
316 && is_column
317 {
318 available_space.width
319 } else {
320 child.size.width
321 };
322
323 let height: Number =
324 if !child.size.height.is_defined() && child.node.align_self(node) == style::AlignSelf::Stretch && is_row {
325 available_space.height
326 } else {
327 child.size.height
328 };
329
330 child.flex_basis = compute_internal(
331 child.node,
332 Size {
333 width: width.maybe_max(child.min_size.width).maybe_min(child.max_size.width),
334 height: height.maybe_max(child.min_size.height).maybe_min(child.max_size.height),
335 },
336 available_space,
337 percent_calc_base_child,
338 false,
339 )
340 .size
341 .main(dir)
342 .maybe_max(child.min_size.main(dir))
343 .maybe_min(child.max_size.main(dir));
344 });
345
346 // The hypothetical main size is the item’s flex base size clamped according to its
347 // used min and max main sizes (and flooring the content box size at zero).
348
349 flex_items.iter_mut().for_each(|child| {
350 child.inner_flex_basis = child.flex_basis - child.padding.main(dir) - child.border.main(dir);
351
352 // TODO - not really spec abiding but needs to be done somewhere. probably somewhere else though.
353 // The following logic was developed not from the spec but by trail and error looking into how
354 // webkit handled various scenarios. Can probably be solved better by passing in
355 // min-content max-content constraints fromt the top
356 let min_main = if is_row {
357 compute_internal(
358 child.node,
359 Size { width: Undefined, height: Undefined },
360 available_space,
361 percent_calc_base_child,
362 false,
363 )
364 .size
365 .width
366 .maybe_max(child.min_size.width)
367 .maybe_min(child.size.width)
368 .to_number()
369 } else {
370 child.min_size.main(dir)
371 };
372
373 child
374 .hypothetical_inner_size
375 .set_main(dir, child.flex_basis.maybe_max(min_main).maybe_min(child.max_size.main(dir)));
376
377 child.hypothetical_outer_size.set_main(dir, child.hypothetical_inner_size.main(dir) + child.margin.main(dir));
378 });
379
380 // 9.3. Main Size Determination
381
382 // 5. Collect flex items into flex lines:
383 // - If the flex container is single-line, collect all the flex items into
384 // a single flex line.
385 // - Otherwise, starting from the first uncollected item, collect consecutive
386 // items one by one until the first time that the next collected item would
387 // not fit into the flex container’s inner main size (or until a forced break
388 // is encountered, see §10 Fragmenting Flex Layout). If the very first
389 // uncollected item wouldn’t fit, collect just it into the line.
390 //
391 // For this step, the size of a flex item is its outer hypothetical main size. (Note: This can be negative.)
392 // Repeat until all flex items have been collected into flex lines
393 //
394 // Note that the "collect as many" line will collect zero-sized flex items onto
395 // the end of the previous line even if the last non-zero item exactly "filled up" the line.
396
397 let mut flex_lines = {
398 let mut lines: Vec<FlexLine> = vec![];
399 let mut line_length = 0.0;
400
401 if node.flex_wrap == FlexWrap::NoWrap {
402 lines.push(FlexLine { items: flex_items, cross_size: 0.0, offset_cross: 0.0 });
403 } else {
404 let mut line = FlexLine { items: vec![], cross_size: 0.0, offset_cross: 0.0 };
405
406 for child in flex_items {
407 line_length += child.hypothetical_outer_size.main(dir);
408
409 if let Defined(main) = available_space.main(dir) {
410 if line_length > main && !line.items.is_empty() {
411 line_length = child.hypothetical_outer_size.main(dir);
412 lines.push(line);
413 line = FlexLine { items: vec![], cross_size: 0.0, offset_cross: 0.0 };
414 }
415 }
416
417 line.items.push(child);
418 }
419
420 lines.push(line);
421 }
422
423 lines
424 };
425
426 // 6. Resolve the flexible lengths of all the flex items to find their used main size.
427 // See §9.7 Resolving Flexible Lengths.
428 //
429 // 9.7. Resolving Flexible Lengths
430
431 flex_lines.iter_mut().for_each(|line| {
432 // 1. Determine the used flex factor. Sum the outer hypothetical main sizes of all
433 // items on the line. If the sum is less than the flex container’s inner main size,
434 // use the flex grow factor for the rest of this algorithm; otherwise, use the
435 // flex shrink factor.
436
437 let used_flex_factor: f32 = line.items.iter().map(|child| child.hypothetical_outer_size.main(dir)).sum();
438 let growing = used_flex_factor < node_inner_size.main(dir).or_else(0.0);
439 let shrinking = !growing;
440
441 // 2. Size inflexible items. Freeze, setting its target main size to its hypothetical main size
442 // - Any item that has a flex factor of zero
443 // - If using the flex grow factor: any item that has a flex base size
444 // greater than its hypothetical main size
445 // - If using the flex shrink factor: any item that has a flex base size
446 // smaller than its hypothetical main size
447
448 line.items.iter_mut().for_each(|child| {
449 // TODO - This is not found by reading the spec. Maybe this can be done in some other place
450 // instead. This was found by trail and error fixing tests to align with webkit output.
451 if node_inner_size.main(dir).is_undefined() && is_row {
452 child.target_size.set_main(
453 dir,
454 compute_internal(
455 child.node,
456 Size {
457 width: child.size.width.maybe_max(child.min_size.width).maybe_min(child.max_size.width),
458 height: child.size.height.maybe_max(child.min_size.height).maybe_min(child.max_size.height),
459 },
460 available_space,
461 percent_calc_base_child,
462 false,
463 )
464 .size
465 .main(dir)
466 .maybe_max(child.min_size.main(dir))
467 .maybe_min(child.max_size.main(dir)),
468 );
469 } else {
470 child.target_size.set_main(dir, child.hypothetical_inner_size.main(dir));
471 }
472
473 // TODO this should really only be set inside the if-statement below but
474 // that casues the target_main_size to never be set for some items
475
476 child.outer_target_size.set_main(dir, child.target_size.main(dir) + child.margin.main(dir));
477
478 if (child.node.flex_grow == 0.0 && child.node.flex_shrink == 0.0)
479 || (growing && child.flex_basis > child.hypothetical_inner_size.main(dir))
480 || (shrinking && child.flex_basis < child.hypothetical_inner_size.main(dir))
481 {
482 child.frozen = true;
483 }
484 });
485
486 // 3. Calculate initial free space. Sum the outer sizes of all items on the line,
487 // and subtract this from the flex container’s inner main size. For frozen items,
488 // use their outer target main size; for other items, use their outer flex base size.
489
490 let used_space: f32 = line
491 .items
492 .iter()
493 .map(|child| {
494 child.margin.main(dir) + if child.frozen { child.target_size.main(dir) } else { child.flex_basis }
495 })
496 .sum();
497
498 let initial_free_space = (node_inner_size.main(dir) - used_space).or_else(0.0);
499
500 // 4. Loop
501
502 loop {
503 // a. Check for flexible items. If all the flex items on the line are frozen,
504 // free space has been distributed; exit this loop.
505
506 let mut frozen: Vec<&mut FlexItem> = vec![];
507 let mut unfrozen: Vec<&mut FlexItem> = vec![];
508
509 line.items.iter_mut().for_each(|child| {
510 if child.frozen {
511 frozen.push(child);
512 } else {
513 unfrozen.push(child);
514 }
515 });
516
517 if unfrozen.is_empty() {
518 break;
519 }
520
521 // b. Calculate the remaining free space as for initial free space, above.
522 // If the sum of the unfrozen flex items’ flex factors is less than one,
523 // multiply the initial free space by this sum. If the magnitude of this
524 // value is less than the magnitude of the remaining free space, use this
525 // as the remaining free space.
526
527 let used_space: f32 = Iterator::chain(frozen.iter(), unfrozen.iter())
528 .map(|child| {
529 child.margin.main(dir) + if child.frozen { child.target_size.main(dir) } else { child.flex_basis }
530 })
531 .sum();
532
533 let sum_flex_grow: f32 = unfrozen.iter().map(|item| item.node.flex_grow).sum();
534 let sum_flex_shrink: f32 = unfrozen.iter().map(|item| item.node.flex_shrink).sum();
535
536 let free_space = if growing && sum_flex_grow < 1.0 {
537 (initial_free_space * sum_flex_grow).maybe_min(node_inner_size.main(dir) - used_space)
538 } else if shrinking && sum_flex_shrink < 1.0 {
539 (initial_free_space * sum_flex_shrink).maybe_max(node_inner_size.main(dir) - used_space)
540 } else {
541 (node_inner_size.main(dir) - used_space).or_else(0.0)
542 };
543
544 // c. Distribute free space proportional to the flex factors.
545 // - If the remaining free space is zero
546 // Do Nothing
547 // - If using the flex grow factor
548 // Find the ratio of the item’s flex grow factor to the sum of the
549 // flex grow factors of all unfrozen items on the line. Set the item’s
550 // target main size to its flex base size plus a fraction of the remaining
551 // free space proportional to the ratio.
552 // - If using the flex shrink factor
553 // For every unfrozen item on the line, multiply its flex shrink factor by
554 // its inner flex base size, and note this as its scaled flex shrink factor.
555 // Find the ratio of the item’s scaled flex shrink factor to the sum of the
556 // scaled flex shrink factors of all unfrozen items on the line. Set the item’s
557 // target main size to its flex base size minus a fraction of the absolute value
558 // of the remaining free space proportional to the ratio. Note this may result
559 // in a negative inner main size; it will be corrected in the next step.
560 // - Otherwise
561 // Do Nothing
562
563 if free_space.is_normal() {
564 if growing && sum_flex_grow > 0.0 {
565 unfrozen.iter_mut().for_each(|child| {
566 child
567 .target_size
568 .set_main(dir, child.flex_basis + free_space * (child.node.flex_grow / sum_flex_grow));
569 });
570 } else if shrinking && sum_flex_shrink > 0.0 {
571 let sum_scaled_shrink_factor: f32 =
572 unfrozen.iter().map(|child| child.inner_flex_basis * child.node.flex_shrink).sum();
573
574 if sum_scaled_shrink_factor > 0.0 {
575 unfrozen.iter_mut().for_each(|child| {
576 let scaled_shrink_factor = child.inner_flex_basis * child.node.flex_shrink;
577 child.target_size.set_main(
578 dir,
579 child.flex_basis + free_space * (scaled_shrink_factor / sum_scaled_shrink_factor),
580 )
581 });
582 }
583 }
584 }
585
586 // d. Fix min/max violations. Clamp each non-frozen item’s target main size by its
587 // used min and max main sizes and floor its content-box size at zero. If the
588 // item’s target main size was made smaller by this, it’s a max violation.
589 // If the item’s target main size was made larger by this, it’s a min violation.
590
591 let total_violation = unfrozen.iter_mut().fold(0.0, |acc, child| {
592 // TODO - not really spec abiding but needs to be done somewhere. probably somewhere else though.
593 // The following logic was developed not from the spec but by trail and error looking into how
594 // webkit handled various scenarios. Can probably be solved better by passing in
595 // min-content max-content constraints fromt the top. Need to figure out correct thing to do here as
596 // just piling on more conditionals.
597 let min_main = if is_row && child.node.measure.is_none() {
598 compute_internal(
599 child.node,
600 Size { width: Undefined, height: Undefined },
601 available_space,
602 percent_calc_base_child,
603 false,
604 )
605 .size
606 .width
607 .maybe_min(child.size.width)
608 .maybe_max(child.min_size.width)
609 .to_number()
610 } else {
611 child.min_size.main(dir)
612 };
613
614 let max_main = child.max_size.main(dir);
615 let clamped = child.target_size.main(dir).maybe_min(max_main).maybe_max(min_main).max(0.0);
616 child.violation = clamped - child.target_size.main(dir);
617 child.target_size.set_main(dir, clamped);
618 child.outer_target_size.set_main(dir, child.target_size.main(dir) + child.margin.main(dir));
619
620 acc + child.violation
621 });
622
623 // e. Freeze over-flexed items. The total violation is the sum of the adjustments
624 // from the previous step ∑(clamped size - unclamped size). If the total violation is:
625 // - Zero
626 // Freeze all items.
627 // - Positive
628 // Freeze all the items with min violations.
629 // - Negative
630 // Freeze all the items with max violations.
631
632 unfrozen.iter_mut().for_each(|child| match total_violation {
633 v if v > 0.0 => child.frozen = child.violation > 0.0,
634 v if v < 0.0 => child.frozen = child.violation < 0.0,
635 _ => child.frozen = true,
636 })
637
638 // f. Return to the start of this loop.
639 }
640 });
641
642 // Not part of the spec from what i can see but seems correct
643 container_size.set_main(
644 dir,
645 node_size.main(dir).or_else({
646 let longest_line = flex_lines.iter().fold(f32::MIN, |acc, line| {
647 let length: f32 = line.items.iter().map(|item| item.outer_target_size.main(dir)).sum();
648 acc.max(length)
649 });
650
651 let size = longest_line + padding_border.main(dir);
652 match available_space.main(dir) {
653 Defined(val) if flex_lines.len() > 1 && size < val => val,
654 _ => size,
655 }
656 }),
657 );
658
659 inner_container_size.set_main(dir, container_size.main(dir) - padding_border.main(dir));
660
661 // 9.4. Cross Size Determination
662
663 // 7. Determine the hypothetical cross size of each item by performing layout with the
664 // used main size and the available space, treating auto as fit-content.
665
666 flex_lines.iter_mut().for_each(|line| {
667 line.items.iter_mut().for_each(|child| {
668 let child_cross =
669 child.size.cross(dir).maybe_max(child.min_size.cross(dir)).maybe_min(child.max_size.cross(dir));
670
671 child.hypothetical_inner_size.set_cross(
672 dir,
673 compute_internal(
674 child.node,
675 Size {
676 width: if is_row { child.target_size.width.to_number() } else { child_cross },
677 height: if is_row { child_cross } else { child.target_size.height.to_number() },
678 },
679 Size {
680 width: if is_row { container_size.main(dir).to_number() } else { available_space.width },
681 height: if is_row { available_space.height } else { container_size.main(dir).to_number() },
682 },
683 percent_calc_base_child,
684 false,
685 )
686 .size
687 .cross(dir)
688 .maybe_max(child.min_size.cross(dir))
689 .maybe_min(child.max_size.cross(dir)),
690 );
691
692 child
693 .hypothetical_outer_size
694 .set_cross(dir, child.hypothetical_inner_size.cross(dir) + child.margin.cross(dir));
695 });
696 });
697
698 // TODO - probably should move this somewhere else as it doesn't make a ton of sense here but we need it below
699 // TODO - This is expensive and should only be done if we really require a baseline. aka, make it lazy
700
701 fn calc_baseline(layout: &layout::Node) -> f32 {
702 if layout.children.is_empty() {
703 layout.size.height
704 } else {
705 calc_baseline(&layout.children[0])
706 }
707 };
708
709 flex_lines.iter_mut().for_each(|line| {
710 line.items.iter_mut().for_each(|child| {
711 let result = compute_internal(
712 child.node,
713 Size {
714 width: if is_row {
715 child.target_size.width.to_number()
716 } else {
717 child.hypothetical_inner_size.width.to_number()
718 },
719 height: if is_row {
720 child.hypothetical_inner_size.height.to_number()
721 } else {
722 child.target_size.height.to_number()
723 },
724 },
725 Size {
726 width: if is_row { container_size.width.to_number() } else { node_size.width },
727 height: if is_row { node_size.height } else { container_size.height.to_number() },
728 },
729 percent_calc_base_child,
730 true,
731 );
732 child.baseline = calc_baseline(&layout::Node {
733 order: node.children.iter().position(|n| ref_eq(n, child.node)).unwrap() as u32,
734 size: result.size,
735 location: Point { x: 0.0, y: 0.0 },
736 children: result.children,
737 });
738 });
739 });
740
741 // 8. Calculate the cross size of each flex line.
742 // If the flex container is single-line and has a definite cross size, the cross size
743 // of the flex line is the flex container’s inner cross size. Otherwise, for each flex line:
744 //
745 // If the flex container is single-line, then clamp the line’s cross-size to be within
746 // the container’s computed min and max cross sizes. Note that if CSS 2.1’s definition
747 // of min/max-width/height applied more generally, this behavior would fall out automatically.
748
749 if flex_lines.len() == 1 && node_size.cross(dir).is_defined() {
750 flex_lines[0].cross_size = (node_size.cross(dir) - padding_border.cross(dir)).or_else(0.0);
751 } else {
752 flex_lines.iter_mut().for_each(|line| {
753 // 1. Collect all the flex items whose inline-axis is parallel to the main-axis, whose
754 // align-self is baseline, and whose cross-axis margins are both non-auto. Find the
755 // largest of the distances between each item’s baseline and its hypothetical outer
756 // cross-start edge, and the largest of the distances between each item’s baseline
757 // and its hypothetical outer cross-end edge, and sum these two values.
758
759 // 2. Among all the items not collected by the previous step, find the largest
760 // outer hypothetical cross size.
761
762 // 3. The used cross-size of the flex line is the largest of the numbers found in the
763 // previous two steps and zero.
764
765 let max_baseline: f32 = line.items.iter().map(|child| child.baseline).fold(0.0, |acc, x| acc.max(x));
766 line.cross_size = line
767 .items
768 .iter()
769 .map(|child| {
770 if child.node.align_self(node) == AlignSelf::Baseline
771 && child.node.cross_margin_start(dir) != Dimension::Auto
772 && child.node.cross_margin_end(dir) != Dimension::Auto
773 && child.node.cross_size(dir) == Dimension::Auto
774 {
775 max_baseline - child.baseline + child.hypothetical_outer_size.cross(dir)
776 } else {
777 child.hypothetical_outer_size.cross(dir)
778 }
779 })
780 .fold(0.0, |acc, x| acc.max(x));
781 });
782 }
783
784 // 9. Handle 'align-content: stretch'. If the flex container has a definite cross size,
785 // align-content is stretch, and the sum of the flex lines' cross sizes is less than
786 // the flex container’s inner cross size, increase the cross size of each flex line
787 // by equal amounts such that the sum of their cross sizes exactly equals the
788 // flex container’s inner cross size.
789
790 if node.align_content == AlignContent::Stretch && node_size.cross(dir).is_defined() {
791 let total_cross: f32 = flex_lines.iter().map(|line| line.cross_size).sum();
792 let inner_cross = (node_size.cross(dir) - padding_border.cross(dir)).or_else(0.0);
793
794 if total_cross < inner_cross {
795 let remaining = inner_cross - total_cross;
796 let addition = remaining / flex_lines.len() as f32;
797 flex_lines.iter_mut().for_each(|line| line.cross_size += addition);
798 }
799 }
800
801 // 10. Collapse visibility:collapse items. If any flex items have visibility: collapse,
802 // note the cross size of the line they’re in as the item’s strut size, and restart
803 // layout from the beginning.
804 //
805 // In this second layout round, when collecting items into lines, treat the collapsed
806 // items as having zero main size. For the rest of the algorithm following that step,
807 // ignore the collapsed items entirely (as if they were display:none) except that after
808 // calculating the cross size of the lines, if any line’s cross size is less than the
809 // largest strut size among all the collapsed items in the line, set its cross size to
810 // that strut size.
811 //
812 // Skip this step in the second layout round.
813
814 // TODO implement once (if ever) we support visibility:collapse
815
816 // 11. Determine the used cross size of each flex item. If a flex item has align-self: stretch,
817 // its computed cross size property is auto, and neither of its cross-axis margins are auto,
818 // the used outer cross size is the used cross size of its flex line, clamped according to
819 // the item’s used min and max cross sizes. Otherwise, the used cross size is the item’s
820 // hypothetical cross size.
821 //
822 // If the flex item has align-self: stretch, redo layout for its contents, treating this
823 // used size as its definite cross size so that percentage-sized children can be resolved.
824 //
825 // Note that this step does not affect the main size of the flex item, even if it has an
826 // intrinsic aspect ratio.
827
828 flex_lines.iter_mut().for_each(|line| {
829 let line_cross_size = line.cross_size;
830
831 line.items.iter_mut().for_each(|child| {
832 child.target_size.set_cross(
833 dir,
834 if child.node.align_self(node) == AlignSelf::Stretch
835 && child.node.cross_margin_start(dir) != Dimension::Auto
836 && child.node.cross_margin_end(dir) != Dimension::Auto
837 && child.node.cross_size(dir) == Dimension::Auto
838 {
839 (line_cross_size - child.margin.cross(dir))
840 .maybe_max(child.min_size.cross(dir))
841 .maybe_min(child.max_size.cross(dir))
842 } else {
843 child.hypothetical_inner_size.cross(dir)
844 },
845 );
846
847 child.outer_target_size.set_cross(dir, child.target_size.cross(dir) + child.margin.cross(dir));
848 });
849 });
850
851 // 9.5. Main-Axis Alignment
852
853 // 12. Distribute any remaining free space. For each flex line:
854 // 1. If the remaining free space is positive and at least one main-axis margin on this
855 // line is auto, distribute the free space equally among these margins. Otherwise,
856 // set all auto margins to zero.
857 // 2. Align the items along the main-axis per justify-content.
858
859 flex_lines.iter_mut().for_each(|line| {
860 let used_space: f32 = line.items.iter().map(|child| child.outer_target_size.main(dir)).sum();
861 let free_space = inner_container_size.main(dir) - used_space;
862 let mut num_auto_margins = 0;
863
864 line.items.iter_mut().for_each(|child| {
865 if child.node.main_margin_start(dir) == Dimension::Auto {
866 num_auto_margins += 1;
867 }
868 if child.node.main_margin_end(dir) == Dimension::Auto {
869 num_auto_margins += 1;
870 }
871 });
872
873 if free_space > 0.0 && num_auto_margins > 0 {
874 let margin = free_space / num_auto_margins as f32;
875
876 line.items.iter_mut().for_each(|child| {
877 if child.node.main_margin_start(dir) == Dimension::Auto {
878 if is_row {
879 child.margin.start = margin;
880 } else {
881 child.margin.top = margin;
882 }
883 }
884 if child.node.main_margin_end(dir) == Dimension::Auto {
885 if is_row {
886 child.margin.end = margin;
887 } else {
888 child.margin.bottom = margin;
889 }
890 }
891 });
892 } else {
893 let num_items = line.items.len();
894 let layout_reverse = dir.is_reverse();
895
896 let justify_item = |(i, child): (usize, &mut FlexItem)| {
897 let is_first = i == 0;
898
899 child.offset_main = match node.justify_content {
900 JustifyContent::FlexStart => {
901 if layout_reverse && is_first {
902 free_space
903 } else {
904 0.0
905 }
906 }
907 JustifyContent::Center => {
908 if is_first {
909 free_space / 2.0
910 } else {
911 0.0
912 }
913 }
914 JustifyContent::FlexEnd => {
915 if is_first && !layout_reverse {
916 free_space
917 } else {
918 0.0
919 }
920 }
921 JustifyContent::SpaceBetween => {
922 if is_first {
923 0.0
924 } else {
925 free_space / (num_items - 1) as f32
926 }
927 }
928 JustifyContent::SpaceAround => {
929 if is_first {
930 (free_space / num_items as f32) / 2.0
931 } else {
932 free_space / num_items as f32
933 }
934 }
935 JustifyContent::SpaceEvenly => free_space / (num_items + 1) as f32,
936 };
937 };
938
939 if layout_reverse {
940 line.items.iter_mut().rev().enumerate().for_each(justify_item);
941 } else {
942 line.items.iter_mut().enumerate().for_each(justify_item);
943 }
944 }
945 });
946
947 // 9.6. Cross-Axis Alignment
948
949 // 13. Resolve cross-axis auto margins. If a flex item has auto cross-axis margins:
950 // - If its outer cross size (treating those auto margins as zero) is less than the
951 // cross size of its flex line, distribute the difference in those sizes equally
952 // to the auto margins.
953 // - Otherwise, if the block-start or inline-start margin (whichever is in the cross axis)
954 // is auto, set it to zero. Set the opposite margin so that the outer cross size of the
955 // item equals the cross size of its flex line.
956
957 flex_lines.iter_mut().for_each(|line| {
958 let line_cross_size = line.cross_size;
959 let max_baseline: f32 = line.items.iter_mut().map(|child| child.baseline).fold(0.0, |acc, x| acc.max(x));
960
961 line.items.iter_mut().for_each(|child| {
962 let free_space = line_cross_size - child.outer_target_size.cross(dir);
963
964 if child.node.cross_margin_start(dir) == Dimension::Auto
965 && child.node.cross_margin_end(dir) == Dimension::Auto
966 {
967 if is_row {
968 child.margin.top = free_space / 2.0;
969 child.margin.bottom = free_space / 2.0;
970 } else {
971 child.margin.start = free_space / 2.0;
972 child.margin.end = free_space / 2.0;
973 }
974 } else if child.node.cross_margin_start(dir) == Dimension::Auto {
975 if is_row {
976 child.margin.top = free_space;
977 } else {
978 child.margin.start = free_space;
979 }
980 } else if child.node.cross_margin_end(dir) == Dimension::Auto {
981 if is_row {
982 child.margin.bottom = free_space;
983 } else {
984 child.margin.end = free_space;
985 }
986 } else {
987 // 14. Align all flex items along the cross-axis per align-self, if neither of the item’s
988 // cross-axis margins are auto.
989
990 child.offset_cross = match child.node.align_self(node) {
991 AlignSelf::Auto => 0.0, // Should never happen
992 AlignSelf::FlexStart => {
993 if is_wrap_reverse {
994 free_space
995 } else {
996 0.0
997 }
998 }
999 AlignSelf::FlexEnd => {
1000 if is_wrap_reverse {
1001 0.0
1002 } else {
1003 free_space
1004 }
1005 }
1006 AlignSelf::Center => free_space / 2.0,
1007 AlignSelf::Baseline => {
1008 if is_row {
1009 max_baseline - child.baseline
1010 } else {
1011 // basline alignment only makes sense if the direction is row
1012 // we treat it as flex-start alignment in columns.
1013 if is_wrap_reverse {
1014 free_space
1015 } else {
1016 0.0
1017 }
1018 }
1019 }
1020 AlignSelf::Stretch => {
1021 if is_wrap_reverse {
1022 free_space
1023 } else {
1024 0.0
1025 }
1026 }
1027 };
1028 }
1029 });
1030 });
1031
1032 // 15. Determine the flex container’s used cross size:
1033 // - If the cross size property is a definite size, use that, clamped by the used
1034 // min and max cross sizes of the flex container.
1035 // - Otherwise, use the sum of the flex lines' cross sizes, clamped by the used
1036 // min and max cross sizes of the flex container.
1037
1038 let total_cross_size: f32 = flex_lines.iter().map(|line| line.cross_size).sum();
1039 container_size.set_cross(dir, node_size.cross(dir).or_else(total_cross_size + padding_border.cross(dir)));
1040 inner_container_size.set_cross(dir, container_size.cross(dir) - padding_border.cross(dir));
1041
1042 // We have the container size. If our caller does not care about performing
1043 // layout we are done now.
1044 if !perform_layout {
1045 let result = ComputeResult { size: container_size, children: vec![] };
1046 node.layout_cache.replace(Some(LayoutCache {
1047 node_size,
1048 parent_size,
1049 percent_calc_base,
1050 perform_layout,
1051 result: result.clone(),
1052 }));
1053 return result;
1054 }
1055
1056 // 16. Align all flex lines per align-content.
1057
1058 let free_space = inner_container_size.cross(dir) - total_cross_size;
1059 let num_lines = flex_lines.len();
1060
1061 let align_line = |(i, line): (usize, &mut FlexLine)| {
1062 let is_first = i == 0;
1063
1064 line.offset_cross = match node.align_content {
1065 AlignContent::FlexStart => {
1066 if is_first && is_wrap_reverse {
1067 free_space
1068 } else {
1069 0.0
1070 }
1071 }
1072 AlignContent::FlexEnd => {
1073 if is_first && !is_wrap_reverse {
1074 free_space
1075 } else {
1076 0.0
1077 }
1078 }
1079 AlignContent::Center => {
1080 if is_first {
1081 free_space / 2.0
1082 } else {
1083 0.0
1084 }
1085 }
1086 AlignContent::Stretch => 0.0,
1087 AlignContent::SpaceBetween => {
1088 if is_first {
1089 0.0
1090 } else {
1091 free_space / (num_lines - 1) as f32
1092 }
1093 }
1094 AlignContent::SpaceAround => {
1095 if is_first {
1096 (free_space / num_lines as f32) / 2.0
1097 } else {
1098 free_space / num_lines as f32
1099 }
1100 }
1101 };
1102 };
1103
1104 if is_wrap_reverse {
1105 flex_lines.iter_mut().rev().enumerate().for_each(align_line);
1106 } else {
1107 flex_lines.iter_mut().enumerate().for_each(align_line);
1108 }
1109
1110 // Do a final layout pass and gather the resulting layouts
1111 let mut children: Vec<layout::Node> = {
1112 let mut lines: Vec<Vec<layout::Node>> = vec![];
1113 let mut total_offset_cross = padding_border.cross_start(dir);
1114
1115 let layout_line = |line: &mut FlexLine| {
1116 let mut children: Vec<layout::Node> = vec![];
1117 let mut total_offset_main = padding_border.main_start(dir);
1118 let line_offset_cross = line.offset_cross;
1119
1120 let layout_item = |child: &mut FlexItem| {
1121 let result = compute_internal(
1122 child.node,
1123 child.target_size.map(|s| s.to_number()),
1124 container_size.map(|s| s.to_number()),
1125 percent_calc_base_child,
1126 true,
1127 );
1128
1129 let offset_main = total_offset_main
1130 + child.offset_main
1131 + child.margin.main_start(dir)
1132 + (child.position.main_start(dir).or_else(0.0) - child.position.main_end(dir).or_else(0.0));
1133
1134 let offset_cross = total_offset_cross
1135 + child.offset_cross
1136 + line_offset_cross
1137 + child.margin.cross_start(dir)
1138 + (child.position.cross_start(dir).or_else(0.0) - child.position.cross_end(dir).or_else(0.0));
1139
1140 children.push(layout::Node {
1141 order: node.children.iter().position(|n| ref_eq(n, child.node)).unwrap() as u32,
1142 size: result.size,
1143 location: Point {
1144 x: if is_row { offset_main } else { offset_cross },
1145 y: if is_column { offset_main } else { offset_cross },
1146 },
1147 children: result.children,
1148 });
1149
1150 total_offset_main += child.offset_main + child.margin.main(dir) + result.size.main(dir);
1151 };
1152
1153 if dir.is_reverse() {
1154 line.items.iter_mut().rev().for_each(layout_item);
1155 } else {
1156 line.items.iter_mut().for_each(layout_item);
1157 }
1158
1159 total_offset_cross += line_offset_cross + line.cross_size;
1160
1161 if dir.is_reverse() {
1162 children.reverse();
1163 }
1164
1165 lines.push(children);
1166 };
1167
1168 if is_wrap_reverse {
1169 flex_lines.iter_mut().rev().for_each(layout_line);
1170 } else {
1171 flex_lines.iter_mut().for_each(layout_line);
1172 }
1173
1174 if is_wrap_reverse {
1175 lines.into_iter().rev().flat_map(|x| x).collect()
1176 } else {
1177 lines.into_iter().flat_map(|x| x).collect()
1178 }
1179 };
1180
1181 // Before returning we perform absolute layout on all absolutely positioned children
1182 let mut absolute_children: Vec<layout::Node> = node
1183 .children
1184 .iter()
1185 .filter(|child| child.position_type == PositionType::Absolute)
1186 .map(|child| {
1187 let container_width = container_size.width.to_number();
1188 let container_height = container_size.height.to_number();
1189
1190 let start = child.position.start.resolve(container_width) + child.margin.start.resolve(container_width);
1191 let end = child.position.end.resolve(container_width) + child.margin.end.resolve(container_width);
1192 let top = child.position.top.resolve(container_height) + child.margin.top.resolve(container_height);
1193 let bottom =
1194 child.position.bottom.resolve(container_height) + child.margin.bottom.resolve(container_height);
1195
1196 let (start_main, end_main) = if is_row { (start, end) } else { (top, bottom) };
1197 let (start_cross, end_cross) = if is_row { (top, bottom) } else { (start, end) };
1198
1199 let width = child
1200 .size
1201 .width
1202 .resolve(container_width)
1203 .maybe_max(child.min_size.width.resolve(container_width))
1204 .maybe_min(child.max_size.width.resolve(container_width))
1205 .or_else(if start.is_defined() && end.is_defined() {
1206 container_width - start - end
1207 } else {
1208 Undefined
1209 });
1210
1211 let height = child
1212 .size
1213 .height
1214 .resolve(container_height)
1215 .maybe_max(child.min_size.height.resolve(container_height))
1216 .maybe_min(child.max_size.height.resolve(container_height))
1217 .or_else(if top.is_defined() && bottom.is_defined() {
1218 container_height - top - bottom
1219 } else {
1220 Undefined
1221 });
1222
1223 let result = compute_internal(
1224 child,
1225 Size { width, height },
1226 Size { width: container_width, height: container_height },
1227 container_width,
1228 true,
1229 );
1230
1231 let free_main_space = container_size.main(dir)
1232 - result
1233 .size
1234 .main(dir)
1235 .maybe_max(child.min_main_size(dir).resolve(percent_calc_base_child))
1236 .maybe_min(child.max_main_size(dir).resolve(percent_calc_base_child));
1237
1238 let free_cross_space = container_size.cross(dir)
1239 - result
1240 .size
1241 .cross(dir)
1242 .maybe_max(child.min_cross_size(dir).resolve(percent_calc_base_child))
1243 .maybe_min(child.max_cross_size(dir).resolve(percent_calc_base_child));
1244
1245 let offset_main = if start_main.is_defined() {
1246 start_main.or_else(0.0) + border.main_start(dir)
1247 } else if end_main.is_defined() {
1248 free_main_space - end_main.or_else(0.0) - border.main_end(dir)
1249 } else {
1250 match node.justify_content {
1251 JustifyContent::SpaceBetween | JustifyContent::FlexStart => padding_border.main_start(dir),
1252 JustifyContent::FlexEnd => free_main_space - padding_border.main_end(dir),
1253 JustifyContent::SpaceEvenly | JustifyContent::SpaceAround | JustifyContent::Center => {
1254 free_main_space / 2.0
1255 }
1256 }
1257 };
1258
1259 let offset_cross = if start_cross.is_defined() {
1260 start_cross.or_else(0.0) + border.cross_start(dir)
1261 } else if end_cross.is_defined() {
1262 free_cross_space - end_cross.or_else(0.0) - border.cross_end(dir)
1263 } else {
1264 match child.align_self(node) {
1265 AlignSelf::Auto => 0.0, // Should never happen
1266 AlignSelf::FlexStart => {
1267 if is_wrap_reverse {
1268 free_cross_space - padding_border.cross_end(dir)
1269 } else {
1270 padding_border.cross_start(dir)
1271 }
1272 }
1273 AlignSelf::FlexEnd => {
1274 if is_wrap_reverse {
1275 padding_border.cross_start(dir)
1276 } else {
1277 free_cross_space - padding_border.cross_end(dir)
1278 }
1279 }
1280 AlignSelf::Center => free_cross_space / 2.0,
1281 AlignSelf::Baseline => free_cross_space / 2.0, // Treat as center for now until we have baseline support
1282 AlignSelf::Stretch => {
1283 if is_wrap_reverse {
1284 free_cross_space - padding_border.cross_end(dir)
1285 } else {
1286 padding_border.cross_start(dir)
1287 }
1288 }
1289 }
1290 };
1291
1292 layout::Node {
1293 order: node.children.iter().position(|n| ref_eq(n, child)).unwrap() as u32,
1294 size: result.size,
1295 location: Point {
1296 x: if is_row { offset_main } else { offset_cross },
1297 y: if is_column { offset_main } else { offset_cross },
1298 },
1299 children: result.children,
1300 }
1301 })
1302 .collect();
1303
1304 children.append(&mut absolute_children);
1305
1306 fn hidden_layout(parent: &style::Node, node: &style::Node) -> layout::Node {
1307 layout::Node {
1308 order: parent.children.iter().position(|n| ref_eq(n, node)).unwrap() as u32,
1309 size: Size { width: 0.0, height: 0.0 },
1310 location: Point { x: 0.0, y: 0.0 },
1311 children: node.children.iter().map(|child| hidden_layout(node, child)).collect(),
1312 }
1313 }
1314
1315 let mut hidden_children: Vec<layout::Node> = node
1316 .children
1317 .iter()
1318 .filter(|child| child.display == Display::None)
1319 .map(|child| hidden_layout(node, child))
1320 .collect();
1321
1322 children.append(&mut hidden_children);
1323
1324 children.sort_by(|c1, c2| c1.order.cmp(&c2.order));
1325
1326 let result = ComputeResult { size: container_size, children };
1327 node.layout_cache.replace(Some(LayoutCache {
1328 node_size,
1329 parent_size,
1330 percent_calc_base,
1331 perform_layout,
1332 result: result.clone(),
1333 }));
1334 result
1335}