1# Changelog
2
3## 0.7.2
4
5### Added
6
7- The ability to access computed track sizes and item positions of a CSS Grid layout (#772).
8  This information can be accessed using the `LayoutGridContainer::set_detailed_grid_info` method
9  in the low-level API or the `TaffyTree::detailed_layout_info` method in the high-level API.
10
11## 0.7.1
12
13### Fixed
14
15- Improve interaction of abspos children of block containers with margin collapsing (#760)
16
17### Added
18
19- Add `TaffyTree::unrounded_layout` getter (#765)
20
21### Removed
22
23- The `num-traits` dependency was removed (#761) (#762)
24
25## 0.7.0
26
27### Changed
28
29- BREAKING: The `cache_mut` method on the `LayoutPartialTree` trait has been replaced with a separate `CacheTree` trait. This allows
30  Taffy to be more easily used without caching or with a custom cache implementation.
31- BREAKING: the `TaffyTree::set_children` method now removes the children from their previous parent (if they have one).
32
33### Added
34
35- Helper methods to retrieve content-box sizes were added to `Layout`
36
37## 0.6.3
38
39### Fixes
40
41- Block: ignore margin collapsing when computing static position of abspos items (#747)
42
43## 0.6.2
44
45### Fixes
46
47- Fix: clamp indefinite available space by min- and max- size as appropriate (#742)
48
49## 0.6.1
50
51### Fixes
52
53- Fix calculation of `auto-fill`/`auto-fit` repetition count when container has a definite percentage size (#722)
54- Fix min-size style not affecting intrinsic sizes (#723)
55- Fix documentation of dirty and mark_dirty functions (#724)
56- Fix intrinsic size of scroll containers that have a small explicit flex-basis (#728)
57
58## 0.6.0
59
60### Highlights
61
62- The `Style` struct has been "traitified". This supports Taffy's integration in Servo and generally makes Taffy more flexible. The
63  `Style` struct still exists and implements the new traits so existing uses of Taffy will continue to work as before.
64- The `box-sizing` style is supported
65- Computed margins are output in `Layout`
66
67### Fixes
68
69- Fix `print_tree()` when rounding is disabled (#680)
70- Absolute Insets should be resolved against the container size minus border (#666)
71- Fix flooring hypothetical_main_size by computed min size (#689)
72- Fix flex line cross-size determination (#690)
73- Fix panics in the grid algorithm (#691)
74- Fix resolving flexible lengths (WPT css/flexbox-multiline-min-max test) (#692)
75- Fix wrapping when a max main size style is present (#694)
76- Fix case where Taffy allowed margins to collapse through an element when it shouldn't have (#695)
77
78### Added
79
80- Legacy text align (for laying out `<center>` and `<div align="..">`) is supported
81- Add `is_table` for block items (#701)
82- Impl `Debug` and `Clone` for `Cache` (#688)
83- Implement `Debug` and `PartialEq` for tree types (#697)
84
85## 0.5.2
86
87- Fix block stretch sizing (don't always apply stretch sizing to block containers) (#674)
88- Fix computation of intrinsic main size when it depends on a child's known cross size (#673)
89- Fix panic when GridLine 0 is specified (#671)
90- Docs: Document feature flags and scrape examples (#672)
91- Docs: Update cosmic-text example to cosmic-text 0.12 (#670)
92
93## 0.5.1
94
95- Fix: Clamp block item stretch widths by their min and max width (#664)
96- Fix: Auto margin computation in block layout (#663)
97
98## 0.5.0
99
100The changes in 0.5 are relatively small but the new measure function parameter is a breaking change so it requires a minor version bump.
101
102- Added: A `style: &Style` parameter has been added to measure functions.
103- Added: The `MaybeMath`, `MaybeResolve`, and `ResolveOrZero` traits have been made public.
104- Fix: use SizingMode::Inherent when sizing absolute children of flexbox nodes.
105
106## 0.4.4
107
108### Fixes
109
110- Content alignment (`align-content`/`justify-content`) behaviour was updated to match the latest spec (and Chrome 123+) (#635)
111- Ensure that root Flexbox nodes are floored by their padding-border (#651, #655)
112- Use grid area size not available space when applying aspect ratio to grid containers (#656)
113
114## 0.4.3
115
116### Fixes
117
118- Fix compilation error in `evenly_sized_tracks` style helper in recent versions of rustc caused by a change/regression in type
119  inference (#643). Note that 3rd-party code that call style helpers that take an `Into<f32>` parameter may still be affected by this issue,
120  but they should be able to fix on their side by clarifying the type passed in
121
122## 0.4.2
123
124- Fixed: single-line flex-container should clamp the line's cross-size (#638)
125- Reduced binary footprint of Taffy from around 300kb to around 150kb (#636)
126
127## 0.4.1
128
129- Fixed: CSS Grid track sizing not respecting growth limits in some circumstances (#624)
130
131## 0.4.0
132
133### Highlights
134
135- Support for CSS Block layout (`display: block`)
136- Support for the `overflow` property (+ `scrollbar_width` for `overflow: scroll`)
137- Improved measure function API
138- Completely refactored low-level API
139- Simplified module hierarchy (+ most types/functions are now exported from the crate root)
140- Expanded set of examples which better document integration with other layout systems (e.g. text layout)
141- Computed values for `padding` and `border` are now output into the `Layout` struct
142
143### Block layout
144
145Support for [CSS Block layout](https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Flow_Layout/Block_and_Inline_Layout_in_Normal_Flow#elements_participating_in_a_block_formatting_context) has been added. This can be used via the new `Display::Block` variant of the `Display` enum. Note that  full flow layout: inline, inline-block and float layout have *not* been implemented. The use case supported is block container nodes which contain block-level children.
146
147### Overflow property
148
149Support has been added for a new `overflow` style property with `Visible`, `Clip`, `Hidden`, and `Scroll` values (`Auto` is not currently implemented). Additionally a `scrollbar_width` property has been added to control the size of scrollbars for nodes with `Overflow::Scroll` set.
150
151- Overflow is settable indpendently in each axis.
152- `Visible` and `Clip` will produce layouts equivalent to the Taffy 0.3. `Clip` will affect the new `content_size` output by restricting it to the available space.
153- `Hidden` and `Scroll` affect layout by changing the automatic minimum size of Flexbox and Grid children
154- `Scroll` additionally reserves `scrollbar_width` pixels for a scrollbar in the opposite axis to which scrolling is enabled. `Scroll` with `scrollbar_width` set to zero is equivalent to `Hidden`.
155
156### Measure function changes
157
158The "measure function" API for integrating Taffy with other measurement systems (such as text layout) has been changed to be more flexible
159and to interact better with borrow checking (you can now borrow external data in your measure function!).
160
161- There are no longer per-node measure functions.
162- There is now a single "global" measure function, and a per-node "context" of a user-defined type
163- The `Taffy` tree is now a generic `TaffyTree<T>` where `T` is the "context" type.
164- The measure function is now called for all leaf nodes (nodes without children). If you wish to maintain compatibility with the previous
165  behaviour then your measure function should return `Size::ZERO` for leaf nodes whose context is `None`.
166
167If you are not using measure functions, then the only change you will need to make is from:
168
169```rust
170let mut tree = Taffy::new();
171```
172
173to
174
175```rust
176let mut tree : TaffyTree<()> = TaffyTree::new();
177```
178
179And generally update any uses of `Taffy` in your codebase to `TaffyTree<()>`.
180
181If you are using measure functions then you will need to make some bigger (but straightforward) changes. The following Taffy 0.3 code:
182
183```rust
184let mut tree = Taffy::new();
185let leaf = tree.new_leaf_with_measure(
186  Style::DEFAULT,
187  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>| Size { width: 100.0, height: 200.0 }
188);
189tree.compute_layout(leaf, Size::MAX_CONTENT);
190```
191
192Should become something like the following with Taffy 0.4:
193
194```rust
195let mut tree : TaffyTree<Size> = TaffyTree::new();
196let leaf = tree.new_leaf_with_context(Style::DEFAULT, Size { width: 100.0, height: 200.0 });
197tree.compute_layout_with_measure(
198  leaf,
199  Size::MAX_CONTENT,
200  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>, node_id: NodeId, node_context: Option<Size>| {
201    node_context.unwrap_or(Size::ZERO)
202  }
203);
204```
205
206Note that:
207
208- You can choose any type instead of `Size` in the above example. This includes your own custom type (which can be an enum or a trait object).
209- If you don't need a context then you can use `()` for the context type
210- As the single "global" measure function passed to `compute_layout_with_measure` only needs to exist for the duration of a single layout run,
211  it can (mutably) borrow data from it's environment
212
213### Low-level API (`LayoutTree` trait) refactor
214
215The low-level API has been completely reworked:
216
217- The `LayoutTree` trait has been split into 5 smaller traits which live in the `taffy::tree:traits` module (along with their associated documentation)
218- The following methods have been removed from split `LayoutTree` traits entirely: `parent`, `is_childless`, `measure_node`, `needs_measure`, and `mark_dirty`.
219- `taffy::node::Node` has been replaced with `taffy::NodeId`. This should make it much easier to implement the low-level traits as the underlying type backing the node id now a `u64` rather than a `slotmap::DefaultKey`.
220- Support for running each layout algorithm individually on a single node via the following top-level functions:
221  - `compute_flexbox_layout`
222  - `compute_grid_layout`
223  - `compute_block_layout`
224  - `compute_leaf_layout`
225  - `compute_root_layout`
226  - `compute_hidden_layout`
227
228It is believed that nobody was previously using the low-level API so we are not providing a migration guide. However, along with the refactor we have greatly
229improved both the documentation and have added examples using the new API, both of which are linked to from the [main documentation page](https://docs.rs/taffy).
230
231### Module hierarchy changes
232
233The specific changes are detailed below. However for most users the most significant change will be that almost all types are now re-exported from the root module. This means that module specific imports like `use taffy::layout::Layout` can now in almost all cases be replaced with the simpler `use taffy::Layout`.
234
235Specific changes:
236
237- The `math` module has been made private
238- The `axis` module has been merged into the `geometry` module
239- The debug module is no longer public. The `print_tree` function is now accessible under `util`.
240- All types from the `node`, `data`, `layout`, `error` and `cache` modules have been moved to the  the `tree` module.
241- The `layout_flexbox()` function has been removed from the prelude. Use `taffy::compute_flexbox_layout` instead.
242
243### Many APIs have been renamed to replace `points` or `Points` with `length` or `Length`
244
245This new name better describes one-dimensional measure of space in some unspecified unit
246which is often unrelated to the PostScript point or the CSS `pt` unit.
247
248This also removes a misleading similarity with the 2D `Point`,
249whose components can have any unit and are not even necessarily absolute lengths.
250
251Example usage change:
252
253```diff
254 use taffy::prelude::*;
255
256 // …
257
258 let header_node = taffy
259     .new_leaf(
260         Style {
261-            size: Size { width: points(800.0), height: points(100.0) },
262+            size: Size { width: length(800.0), height: length(100.0) },
263             ..Default::default()
264         },
265     ).unwrap();
266```
267
268### Other Changes
269
270- The `Taffy` type was renamed to `TaffyTree` and made generic of a context parameter
271- The Flexbox algorithm has now been moved behind the `flexbox` feature. The `flexbox` feature is enabled by default.
272- The `justify_self` property has been moved behind the `grid` feature.
273- Fixed misspelling: `RunMode::PeformLayout` renamed into `RunMode::PerformLayout` (added missing `r`).
274- `serde` dependency has been made compatible with `no_std` environments
275- `slotmap` dependency has been made compatible with `no_std` environments
276- Added `insert_child_at_index()` method to the `TaffyTree`. This can be used to insert a child node at any position instead of just the end.
277- Added `total_node_count()` method to the `TaffyTree` which returns the total number of nodes in the tree.
278- Added `get_disjoint_node_context_mut()` method to the `TaffyTree`. This can be used to safely get multiple mutable borrows at the same time.
279
280## 0.3.19
281
282### Fixes
283
284- Fix compilation error in `evenly_sized_tracks` style helper in recent versions of rustc caused by a change/regression in type
285  inference (#643). Note that 3rd-party code that call style helpers that take an `Into<f32>` parameter may still be affected by this issue,
286  but they should be able to fix on their side by clarifying the type passed in
287
288## 0.3.18
289
290### Fixes
291
292- Fix computation of Flexbox automatic minimum size when grid or flexbox child has an explicit width/height style set (#576)
293
294## 0.3.17
295
296### Added
297
298- Added `total_node_count` method to the `Taffy` struct. Returns the total number of nodes in the tree.
299
300## 0.3.16
301
302### Fixes
303
304- Improve performance of flexbox columns
305
306## 0.3.15
307
308### Fixes
309
310- Fix justify-content and align-content when free space is negative (content overflows container) (#549) (#551)
311
312## 0.3.14
313
314### Fixes
315
316- Flex: Fix issue where constraints were not being propagated, causing nodes with inherent aspect-ratio (typically images) to not apply that aspect-ratio (#545) (Fixes bevyengine/bevy#9841)
317
318## 0.3.13
319
320### Fixes
321
322- Fix rounding accumulation bug (#521) (Fixes #501 and bevyengine/bevy#8911)
323- Flexbox: pass correct cross-axis available space when computing an item's intrinsic main size (#522)(Fixes bevyengine/bevy#9350)
324- Flexbox: Subtract child margin not parent margin when computing stretch-alignment known size
325- Grid: Make CSS Grid algorithm correctly apply max width/height and available space when it is the root node (#491)
326- Grid: Fix CSS Grid "auto track" / placement bugs #481
327  - Fix divide by zero when using grid_auto_rows/grid_auto_columns with zero negative implicit tracks
328  - Fix over counting of tracks (leading to incorrect container heights) when auto-placing in grids that contain negative implicit tracks.
329  - Fix axis conflation in auto-placement code when grid_auto_flow is column
330  - Fix assignment of auto track sizes when initializing negative implicit tracks
331- Leaf: Apply margins to leaf nodes when computing available space for measure functions
332- Leaf: Reserve space for padding/borders in nodes with measure functions (#497)
333  
334  **NOTE: This has the potential to break layouts relying on the old behaviour.** However, such layouts would be relying on a style having no effect, so it is judged that such layouts are unlikely to exist in the wild. If this turns out not to be true then this fix will be reverted on the 0.3.x branch.
335
336### Dependencies
337
338- Upgrade `grid` to `0.10`. This eliminates the transitive dependency on `no-std-compat`.
339
340## 0.3.12
341
342### Fixes
343
344- Fix caching issue when toggling `display:none` on and off
345
346## 0.3.11
347
348### Fixes
349
350- Fix exponential blowup when laying out trees containing nodes with min and max sizes.
351
352## 0.3.10
353
354### Fixes
355
356- Fix sizing of children when the available_space < min_size (#407)
357
358## 0.3.9
359
360### Fixes
361
362- Fix caching bug where a cached result would sometimes be incorrectly used when the amount of available space increased (bevyengine/bevy#8111) and (bevyengine/bevy#8124)
363
364## 0.3.8
365
366### Fixes
367
368- Fix incorrect min-content size for `flex-wrap: wrap` nodes (bevyengine/bevy#8082)
369
370## 0.3.7
371
372### Fixes
373
374- Fix: Make `padding` and `border` floor node sizes (#372)
375- Fix: Prevent percentages contributing to min-content sizes (#388) (also fixes bevyengine/bevy#8017)
376
377## 0.3.6
378
379### Fixes
380
381- Fix: Ignore `align_content` when `flex_wrap` is set to `nowrap` (#383)
382
383## 0.3.5
384
385### Fixes
386
387- Fix `display: none` when it is set on a flexbox child (#380)
388- Fix `display: none` when it is set on a grid child (#381)
389
390## 0.3.4
391
392### Fixes
393
394- Fix `display: none` when it is set for the only node in the hierarchy (#377)
395
396## 0.3.3
397
398### Added
399
400- Added `enable_rounding` and `disable_rounding` methods to the `Taffy` struct which enable consumers of Taffy to obtain unrounded `f32` values for the computed layouts if they want them. Rounding remains enabled by default.
401
402### Fixes
403
404- Fixed rounding algorithm such that it never leaves gaps between adjacent nodes (#369)
405- Fixed compiling with the `grid` feature disabled (#370)
406- Fixed compiling with the `std` feature disabled
407
408## 0.3.2
409
410### Fixes
411
412- Allow partial nested values to be deserialized into a `Style` using the `serde` feature.
413
414## 0.3.1
415
416### Fixes
417
418- The `serde` feature now works when the `grid` feature is enabled
419
420## 0.3.0
421
422### Highlights
423
424- [CSS Grid algorithm support](#new-feature-css-grid)
425- [Style helper functions](#new-feature-style-helpers)
426
427See below for details of breaking changes.
428
429### New Feature: CSS Grid
430
431We very excited to report that we now have support for CSS Grid layout. This is in addition to the existing Flexbox layout support, and the two modes interoperate. You can set a node to use Grid layout by setting the `display` property to `Display::Grid`.
432
433#### Learning Resources
434
435Taffy implements the CSS Grid specification faithfully, so documentation designed for the web should translate cleanly to Taffy's implementation. If you are interested in learning how to use CSS Grid, we would recommend the following resources:
436
437- [CSS Grid Garden](https://cssgridgarden.com/). This is an interactive tutorial/game that allows you to learn the essential parts of CSS Grid in a fun engaging way.
438- [A Complete Guide To CSS Grid](https://css-tricks.com/snippets/css/complete-guide-grid/) by CSS Tricks. This is detailed guide with illustrations and comprehensive written explanation of the different Grid properties and how they work.
439
440#### Supported Features & Properties
441
442In addition to the usual sizing/spacing properties (size, min_size, padding, margin, etc), the following Grid style properties are supported on Grid Containers:
443
444| Property                  | Explanation                                                                                    |
445| ---                       | ---                                                                                            |
446| [`grid-template-columns`] | The track sizing functions of the grid's explicit columns                                      |
447| [`grid-template-rows`]    | The track sizing functions of the grid's explicit rows                                         |
448| [`grid-auto-rows`]        | Track sizing functions for the grid's implicitly generated rows                                |
449| [`grid-auto-columns`]     | Track sizing functions for the grid's implicitly generated columns                             |
450| [`grid-auto-flow`]        | Whether auto-placed items are placed row-wise or column-wise. And sparsely or densely.         |
451| [`gap`]                   | The size of the vertical and horizontal gaps between grid rows/columns                         |
452| [`align-content`]         | Align grid tracks within the container in the inline (horizontal) axis                         |
453| [`justify-content`]       | Align grid tracks within the container in the block (vertical) axis                            |
454| [`align-items`]           | Align the child items within their grid areas in the inline (horizontal) axis                  |
455| [`justify-items`]         | Align the child items within their grid areas in the block (vertical) axis                     |
456
457And the following Grid style properties are supported on Grid Items (children):
458
459| Property                  | Explanation                                                                                    |
460| ---                       | ---                                                                                            |
461| [`grid-row`]              | The (row) grid line the item starts at (or a span)                                             |
462| [`grid-column`]           | The (column) grid line the item end at (or a span)                                             |
463| [`align-self`]            | Align the item within it's grid area in the inline (horizontal) axis. Overrides `align-items`. |
464| [`justify-self`]          | Align the item within it's grid area in the block (vertical) axis. Overrides `justify-items`.  |
465
466[`grid-template-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-columns
467[`grid-template-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-rows
468[`grid-auto-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-rows
469[`grid-auto-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-columns
470[`grid-auto-flow`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-flow
471[`gap`]: https://developer.mozilla.org/en-US/docs/Web/CSS/gap
472[`align-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align_content
473[`justify-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify_content
474[`align-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-items
475[`justify-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-items
476[`grid-row`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-row
477[`grid-column`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-column
478[`align-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-self
479[`justify-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-self
480
481The following properties and features are not currently supported:
482
483- Subgrids
484- Masonry grid layout
485- Named grid lines
486- Named areas: `grid-template-areas` and `grid-area`
487- `grid-template` or `grid` shorthand
488
489#### Example
490
491See [examples/grid_holy_grail.rs](https://github.com/DioxusLabs/taffy/blob/main/examples/grid_holy_grail.rs) for an example using Taffy to implement the so-called [Holy Grail Layout](https://en.wikipedia.org/wiki/Holy_grail_(web_design)). If you want to run this example, the don't forget the enable the CSS Grid cargo feature:
492
493```bash
494cargo run --example grid_holy_grail --features grid
495```
496
497### New Feature: Style Helpers
498
499Ten new helper functions have added to the taffy prelude. These helper functions have short, intuitive names, and have generic return types which allow them to magically return the correct type depending on context. They make defining styles much easier, and means you won't typically need to use types like `Dimension` or `TrackSizingFunction` directly.
500
501For example, instead of:
502
503```rust
504let size : Size<Dimension> = Size { width: Dimension::Points(100.0), height: Dimension::Percent(50.0) };
505```
506
507you can now write
508
509```rust
510let size : Size<Dimension> = Size { width: points(100.0), height: percent(50.0) };
511```
512
513And that same helper function will work other types like `LengthPercentage` and `MinTrackSizingFunction` that also have a `Points` variant. There are also generic impl's for `Size<T>`, `Rect<T>` and `Line<T>` which means if your node is the same size in all dimensions you can even write
514
515```rust
516let size : Size<Dimension> = points(100.0);
517```
518
519Available style helpers:
520
521<table>
522  <thead><tr><th>Type(s)</th><th colspan="2">Helpers that work with that type</th></tr></thead>
523  <tbody>
524    <tr>
525      <td rowspan="3"><code>LengthPercentage</code></td>
526      <td><code>zero()</code></td>
527      <td>Generates a <code>Points</code> variant with the value <code>0.0</code></td>
528    </tr>
529    <tr>
530      <td><code>points(val:&nbsp;f32)</code></td>
531      <td>Generates a <code>Points</code> variant with the specified value</td>
532    </tr>
533    <tr>
534      <td><code>percent(val:&nbsp;f32)</code></td>
535      <td>Generates a <code>Percent</code> variant with the specified value.<br />Note that the scale of 0-1 not 0-100.</td>
536    </tr>
537    <tr>
538      <td rowspan="2"><code>LengthPercentageAuto</code><br /><code>Dimension</code></td>
539      <td colspan="2"><i>All helpers from <code>LengthPercentage</code> and...</i></td>
540    </tr>
541    <tr>
542      <td><code>auto()</code></td>
543      <td>Generates an <code>Auto</code> variant</td>
544    </tr>
545    <tr>
546      <td rowspan="3"><code>MinTrackSizingFunction</code></td>
547      <td colspan="2"><i>All helpers from <code>LengthPercentageAuto</code>/<code>Dimension</code> and...</i></td>
548    </tr>
549    <tr>
550      <td><code>min_content()</code></td>
551      <td>Generates an <code>MinContent</code> variant</td>
552    </tr>
553      <tr>
554      <td><code>max_content()</code></td>
555      <td>Generates an <code>MinContent</code> variant</td>
556    </tr>
557    <tr>
558      <td rowspan="3"><code>MaxTrackSizingFunction</code></td>
559      <td colspan="2"><i>All helpers from <code>MinTrackSizingFunction</code> and...</i></td>
560    </tr>
561    <tr>
562      <td><code>fit_content(limit:&nbsp;LengthPercentage)</code></td>
563      <td>Generates a <code>FitContent</code> variant with the specified limit.<br />Nest the <code>points</code> or <code>percent</code> helper inside this function to specified the limit.</td>
564    </tr>
565      <tr>
566      <td><code>fr(fraction:&nbsp;f32)</code></td>
567      <td>Generates a <code>Fraction</code> (<code>fr</code>) variant with the specified flex fraction </td>
568    </tr>
569    <tr>
570      <td rowspan="3"><code>NonRepeatingTrackSizingFunction</code></td>
571      <td colspan="2"><i>All helpers from <code>MaxTrackSizingFunction</code> and...</i></td>
572    </tr>
573    <tr>
574      <td><code>minmax(min: MinTrackSizingFunction, max: MaxTrackSizingFunction)</code></td>
575      <td>Equivalent to CSS <code>minmax()</code> function.</td>
576    </tr>
577    <tr>
578      <td><code>flex(fraction:&nbsp;f32)</code></td>
579      <td>Equivalent to CSS <code>minmax(0px, 1fr)</code>. This is likely what you want if you want evenly sized rows/columns.</td>
580    </tr>
581    <tr>
582      <td rowspan="2"><code>TrackSizingFunction</code></td>
583      <td colspan="2"><i>All helpers from <code>NonRepeatingTrackSizingFunction</code> and...</i></td>
584    </tr>
585    <tr>
586      <td><code>repeat(rep: GridTrackRepetition, tracks: Vec&lt;TrackSizingFunction&gt;)</code></td>
587      <td>Equivalent to css <code>repeat()</code> function.</td>
588    </tr>
589    <tr>
590      <td><code>Vec&lt;TrackSizingFunction&gt;</code></td>
591      <td><code>evenly_sized_tracks(count:&nbsp;u16)</code></td>
592      <td>Equivalent to CSS <code>repeat(count, minmax(0px, 1fr)</code></td>
593    </tr>
594    <tr>
595      <td rowspan="3"><code>AvailableSpace</code></td>
596      <td><code>auto()</code></td>
597      <td>Generates an <code>Auto</code> variant</td>
598    </tr>
599    <tr>
600      <td><code>min_content()</code></td>
601      <td>Generates an <code>MinContent</code> variant</td>
602    </tr>
603      <tr>
604      <td><code>max_content()</code></td>
605      <td>Generates an <code>MinContent</code> variant</td>
606    </tr>
607    <tr>
608      <td><code>Size&lt;T&gt;</code></td>
609      <td colspan="2">Any helper that works for <code>T</code> will also work for <code>Size&lt;T&gt;</code> and will set both <code>width</code> and <code>height</code> to that value</td>
610    </tr>
611    <tr>
612      <td><code>Rect&lt;T&gt;</code></td>
613      <td colspan="2">Any helper that works for <code>T</code> will also work for <code>Rect&lt;T&gt;</code> and will set <code>top</code>, <code>left</code>, <code>bottom</code>, and <code>right</code> to that value</td>
614    </tr>
615  </tbody>
616</table>
617
618### Breaking API changes
619
620#### Changes to alignment style types
621
622- `AlignContent` and `JustifyContent` has been merged.
623  - `JustifyContent` is now an alias of `AlignContent` and contains the `Stretch` variant.
624  - This variant will be *ignored* (falling back to `Start`) when applied Flexbox containers. It is valid value for Grid containers.
625- `AlignItems` and `AlignSelf` have been merged.
626  - The `Auto` variant of `AlignSelf` has been removed. You should now use `Option::None` if you wish to specify `AlignSelf::Auto`.
627  - `AlignSelf` is now an alias of `AlignItems`.
628  - `JustifyItems` and `JustifySelf` aliases have been added. These properties have no affect on Flexbox containers, but apply to Grid containers.
629- `Default` impls have been removed from all alignment types. This is because the correct default varies by property, and the types are now shared between multiple properties. The `Style` struct still has a default for each alignment property, so this is considered unlikely to affect you in practice.
630
631#### Strict style types
632
633- New types `LengthPercentage` and `LengthPercentageAuto` have been added.
634  - `LengthPercentage` is like `Dimension` but only contains the `Points` and `Percent` variants, which allows us to increase type safety for properties that don't support the `Auto` value.
635  - `LengthPercentageAuto` is currently identical to `Dimension` but will allow us to expand dimension in future to support values like `MinContent`, `MaxContent` and `FitContent`.
636- Some style properties have been updated to use either `LengthPercentage` or `LengthPercentageAuto` instead of `Dimension`. You will need to update your code, but it is recommended that you use the new style helpers (see above) rather than using the new types directly (although you certainly can use them directly if you want to).
637
638#### Position properties renamed
639
640- The `position` property is now renamed to `inset` and is now in line with [CSS inset specs](https://developer.mozilla.org/en-US/docs/Web/CSS/inset)
641- The `position_type` property is now renamed to `position` and is now in line with [CSS position specs](https://developer.mozilla.org/en-US/docs/Web/CSS/position). The `PositionType` enum has been similarly renamed to `Position`.
642
643#### Changes to `LayoutTree`
644
645- Added generic associated type to `LayoutTree` for a `ChildIter`, an iterator on the children of a given node.
646- Changed the `children` method of `LayoutTree` to return the `ChildIter` generic associated type to allow for custom tree storage implementations which do not store the children of a node contiguously.
647- Added `child_count`  method to `LayoutTree` for querying the number of children of a node. Required because the `children` method now returns an iterator instead of an array.
648- Added `is_childless` method to `LayoutTree` for querying whether a node has no children.
649
650#### `AvailableSpace` has been moved
651
652The `AvailableSpace` enum has been moved from the `layout` module to the `style` module. If you are importing it via the prelude then you will unaffected by the change.
653
654### Fixes
655
656- Flexbox nodes sized under a min-content constraint now size correctly (#291)
657- Aspect ratio is now applied correctly in many circumstances
658- Absolutely positioned items now apply margins correctly
659- Min/max size are now applied correctly
660- Inset applied incorrectly to relatively positioned flexbox children when both `top` and `bottom` or `left` and `right` were specified (#348)
661- Fix case where column-gap style could be used in place of row-gap style (when using a percentage gap with an indefinite container size)
662
663### Removed
664
665- Removed `top_from_points`, `bot_from_points`, `top_from_percent`, and `bot_from_percent` methods removed from `Rect<Dimension>`. These functions were incredibly specific for an unusual use case, so we would be surprised if anyone was using them. Please use the new style helpers instead.
666- Removed `min_main_size`, `max_main_size`, `min_cross_size`, `max_cross_size`, and `cross_size` methods from `Style`. Use the more general `cross` and `main` methods directly on the `size`, `min_size`, and `max_size` properties instead.
667- Removed `main_margin_start`, `main_margin_end`, `cross_margin_start`, `cross_margin_end` from `Style`. Use the more general `main_start`, `main_end`, `cross_start`, and `cross_end` on the `margin` property instead.
668
669## 0.2.2
670
671### Fixes
672
673- Border or padding on the horizontal axis could, in some cases, increase the height of nodes.
674
675## 0.2.1
676
677### Fixes
678
679- In case of conflicts, `min_size` now overrides `max_size` which overrides `size` (#261). This is the behaviour specified in the CSS specification, and was also the behaviour in Taffy `v0.1.0`, but a regression was introduced in Taffy `v0.2.0`.
680- `taffy::compute_layout` has been made public allowing Taffy to be used with custom storage (#263)
681
682## 0.2.0
683
684### New features
685
686#### Flexbox "gap" and `AlignContent::SpaceEvenly`
687
688The [gap](https://developer.mozilla.org/en-US/docs/Web/CSS/gap) property is now supported on flex containers. This can make it much easier to create even spacing or "gutters" between nodes.
689
690Additionally we have a `SpaceEvenly` variant to the `AlignContent` enum to support evenly spaced justification in the cross axis (equivalent to  `align-content: space-evenly` in CSS)
691
692#### Debug module and cargo feature
693
694Two debugging features have been added:
695
696- `taffy::debug::print_tree(&Taffy, root)` - This will print a debug representation of the computed layout of an entire node tree (starting at `root`), which can be useful for debugging layouts.
697- A cargo feature `debug`. This enabled debug logging of the layout computation process itself (this is probably mainly useful for those working taffy itself).
698
699### Performance improvements
700
701A number of performance improvements have landed since taffy 0.1:
702
703- Firstly, our custom `taffy::forest` storage implementation was ripped out and replaced with a much simpler implementation using the `slotmap` crate. This led to performance increases of up to 90%.
704- Secondly, the caching implementation was improved by upping the number of cache slots from 2 to 4 and tweaking how computed results are allocated to cache slots to better match the actual usage patterns of the flexbox layout algorithm. This had a particularly dramatic effect on deep hierarchies (which often involve recomputing the same results repeatedly), fixing the exponential blowup that was previously exhibited on these trees and improving performance by over 1000x in some cases!
705
706#### Benchmarks vs. Taffy 0.1
707
708| Benchmark                                 | Taffy 0.1 | Taffy 0.2 | % change (0.1 -> 0.2) |
709| ---                                       | ---       | ---       | ---                   |
710| wide/1_000 nodes (2-level hierarchy)      | 699.18 µs | 445.01 µs | -36.279%              |
711| wide/10_000 nodes (2-level hierarchy)     | 8.8244 ms | 7.1313 ms | -16.352%              |
712| wide/100_000 nodes (2-level hierarchy)    | 204.48 ms | 242.93 ms | +18.803%              |
713| deep/4000 nodes (12-level hierarchy))     | 5.2320 s  | 2.7363 ms | -99.947%              |
714| deep/10_000 nodes (14-level hierarchy)    | 75.207 s  | 6.9415 ms | -99.991%              |
715| deep/100_000 nodes (17-level hierarchy)   | -         | 102.72 ms | -                     |
716| deep/1_000_000 nodes (20-level hierarchy) | -         | 799.35 ms | -                     |
717
718(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
719
720As you can see, we have actually regressed slightly in the "wide" benchmarks (where all nodes are siblings of a single parent node). Although it should be noted our results in these benchmarks are still very fast, especially on the 10,000 node benchmark which we consider to be the most realistic size where the result is measured in microseconds.
721
722However, in the "deep" benchmarks we see dramatic improvements. The previous version of Taffy suffered from exponential blowup in the case of deeply nested hierarchies. This has resulted in somewhat silly improvements like the 10,000 node (14-level) hierarchy where Taffy 0.2 is a full 1 million times faster than Taffy 0.1. We've also included results with larger numbers of nodes (although you're unlikely to need that many) to demonstrate that this scalability continues up to even deeper levels of nesting.
723
724#### Benchmarks vs. [Yoga](https://github.com/facebook/yoga)
725
726Yoga benchmarks run via it's node.js bindings (the `yoga-layout-prebuilt` npm package), they were run a few times manually and it was verified that variance in the numbers of each run was minimal. It should be noted that this is using an old version of Yoga.
727
728| Benchmark | Yoga | Taffy 0.2 |
729| --- | --- | --- |
730| yoga/10 nodes (1-level hierarchy) | 45.1670 µs | 33.297 ns |
731| yoga/100 nodes (2-level hierarchy) | 134.1250 µs | 336.53 ns |
732| yoga/1_000 nodes (3-level hierarchy) | 1.2221 ms | 3.8928 µs |
733| yoga/10_000 nodes (4-level hierarchy) | 13.8672 ms | 36.162 µs |
734| yoga/100_000 nodes (5-level hierarchy) | 141.5307 ms | 1.6404 ms |
735
736(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
737
738While we're trying not to get too excited (there could easily be an issue with our benchmarking methodology which make this an unfair comparison), we are pleased to see that we seem to be anywhere between 100x and 1000x times faster depending on the node count!
739
740### Breaking API changes
741
742#### Node creation changes
743
744- `taffy::Node` is now unique only to the Taffy instance from which it was created.
745- Renamed `Taffy.new_node(..)` -> `Taffy.new_with_children(..)`
746- Renamed `Taffy.new_leaf()` -> `Taffy.new_leaf_with_measure()`
747- Added `taffy::node::Taffy.new_leaf()` which allows the creation of new leaf-nodes without having to supply a measure function
748
749#### Error handling/representation improvements
750
751- Renamed `taffy::Error` -> `taffy::error::TaffyError`
752- Replaced `taffy::error::InvalidChild` with a new `InvalidChild` variant of `taffy::error::TaffyError`
753- Replaced `taffy::error::InvalidNode` with a new `InvalidNode` variant of `taffy::error::TaffyError`
754- The following method new return `Err(TaffyError::ChildIndexOutOfBounds)` instead of panicking:
755  - `taffy::Taffy::remove_child_at_index`
756  - `taffy::Taffy::replace_child_at_index`
757  - `taffy::Taffy::child_at_index`
758- `Taffy::remove` now returns a `Result<usize, Error>`, to indicate if the operation was successful (and if it was, which ID was invalidated).
759
760#### Some uses of `Option<f32>` replaced with a new `AvailableSpace` enum
761
762A new enum `Taffy::layout::AvailableSpace` has been added.
763
764The definition looks like this:
765
766```rust
767/// The amount of space available to a node in a given axis
768pub enum AvailableSpace {
769    /// The amount of space available is the specified number of pixels
770    Definite(f32),
771    /// The amount of space available is indefinite and the node should be laid out under a min-content constraint
772    MinContent,
773    /// The amount of space available is indefinite and the node should be laid out under a max-content constraint
774    MaxContent,
775}
776```
777
778This enum is now used instead of `Option<f32>` when calling `Taffy.compute_layout` (if you previously passing `Size::NONE` to `compute_layout`, then you will need to change this to `Size::MAX_CONTENT`).
779
780And a different instance of it is passed as a new second parameter to `MeasureFunc`. `MeasureFunc`s may choose to use this parameter in their computation or ignore it as they see fit. The canonical example of when it makes sense to use it is when laying out text. If `MinContent` has been passed in the axis in which the text is flowing (i.e. the horizontal axis for left-to-right text), then you should line-break at every possible opportunity (e.g. all word boundaries), whereas if `MaxContent` has been passed then you shouldn't line break at all..
781
782#### Builder methods are now `const` where possible
783
784- Several convenience constants have been defined: notably `Style::DEFAULT`
785- `Size<f32>.zero()` is now `Size::<f32>::ZERO`
786- `Point<f32>.zero()` is now  `Point::<f32>::ZERO`
787- `Size::undefined()` is now `Size::NONE`
788
789#### Removals
790
791- Removed `taffy::forest::Forest`. `taffy::node::Taffy` now handles it's own storage using a slotmap (which comes with a performance boost up to 90%).
792- Removed `taffy::number::Number`. Use `Option<f32>` is used instead
793  - the associated public `MinMax` and `OrElse` traits have also been removed; these should never have been public
794- Removed unused dependencies `hashbrown`, `hash32`, and `typenum`. `slotmap` is now the only required dependency (`num_traits` and `arrayvec` are also required if you wish to use taffy in a `no_std` environment).
795
796### Fixes
797
798- Miscellaneous correctness fixes which align our implementation with Chrome:
799
800  - Nodes can only ever have one parent
801  - Fixed rounding of fractional values to follow latest Chrome - values are now rounded the same regardless of their position
802  - Fixed computing free space when using both `flex-grow` and a minimum size
803  - Padding is now only subtracted when determining the available space if the node size is unspecified, following [section 9.2.2 of the flexbox spec](https://www.w3.org/TR/css-flexbox-1/#line-sizing)
804  - `MeasureFunc` (and hence `NodeData` and hence `Forest` and hence the public `Taffy` type) are now `Send` and `Sync`, enabling their use in async and parallel applications
805- Taffy can now be vendored using `cargo-vendor` (README.md is now included in package).
806
807## 0.1.0
808
809### 0.1.0 Changed
810
811- the `order` field of `Layout` is now public, and describes the relative z-ordering of nodes
812- renamed crate from `stretch2` to `taffy`
813- updated to the latest version of all dependencies to reduce upstream pain caused by duplicate dependencies
814- renamed `stretch::node::Stretch` -> `taffy::node::Taffy`
815
816### 0.1.0 Fixed
817
818- fixed feature strategy for `alloc` and `std`: these can now be compiled together, with `std`'s types taking priority
819
820### 0.1.0 Removed
821
822- removed Javascript / Kotlin / Swift bindings
823  - the maintainer team lacks expertise to keep these working
824  - more serious refactors are planned, and this will be challenging to keep working through that process
825  - if you are interested in helping us maintain bindings to other languages, [get in touch](https://github.com/DioxusLabs/taffy/discussions)!
826- the `serde_camel_case` and `serde_kebab_case` features have been removed: they were poorly motivated and were not correctly additive (if both were enabled compilation would fail)
827- removed the `Direction` and `Overflow` structs, and the corresponding `direction` and `overflow` fields from `Style`
828  - these had no effect in the current code base and were actively misleading
829
830## stretch2 0.4.3
831
832This is the final release of `stretch`: migrate to the crate named `taffy` for future fixes and features!
833
834These notes describe the differences between this release and `stretch` 0.3.2, the abandoned crate from which this library was forked.
835
836### Changed
837
838- updated [assorted dependencies](https://github.com/vislyhq/stretch/commit/a6491117379cea52dedc9584d892594a143e8cb0)
839
840### Fixed
841
842- fixed an exponential performance blow-up with deep nesting
843- fixed percent height values, which were using parent width
844- recomputing layout no longer moves children of non-zero-positioned parent
845- fixed broken Swift bindings