1# Changelog
2
3## 0.7.3
4
5### Fixed
6
7- Make `TaffyTree::detailed_layout_info` take `&self` rather than `&mut self` (#779)
8
9## 0.7.2
10
11### Added
12
13- The ability to access computed track sizes and item positions of a CSS Grid layout (#772).
14  This information can be accessed using the `LayoutGridContainer::set_detailed_grid_info` method
15  in the low-level API or the `TaffyTree::detailed_layout_info` method in the high-level API.
16
17## 0.7.1
18
19### Fixed
20
21- Improve interaction of abspos children of block containers with margin collapsing (#760)
22
23### Added
24
25- Add `TaffyTree::unrounded_layout` getter (#765)
26
27### Removed
28
29- The `num-traits` dependency was removed (#761) (#762)
30
31## 0.7.0
32
33### Changed
34
35- BREAKING: The `cache_mut` method on the `LayoutPartialTree` trait has been replaced with a separate `CacheTree` trait. This allows
36  Taffy to be more easily used without caching or with a custom cache implementation.
37- BREAKING: the `TaffyTree::set_children` method now removes the children from their previous parent (if they have one).
38
39### Added
40
41- Helper methods to retrieve content-box sizes were added to `Layout`
42
43## 0.6.3
44
45### Fixes
46
47- Block: ignore margin collapsing when computing static position of abspos items (#747)
48
49## 0.6.2
50
51### Fixes
52
53- Fix: clamp indefinite available space by min- and max- size as appropriate (#742)
54
55## 0.6.1
56
57### Fixes
58
59- Fix calculation of `auto-fill`/`auto-fit` repetition count when container has a definite percentage size (#722)
60- Fix min-size style not affecting intrinsic sizes (#723)
61- Fix documentation of dirty and mark_dirty functions (#724)
62- Fix intrinsic size of scroll containers that have a small explicit flex-basis (#728)
63
64## 0.6.0
65
66### Highlights
67
68- The `Style` struct has been "traitified". This supports Taffy's integration in Servo and generally makes Taffy more flexible. The
69  `Style` struct still exists and implements the new traits so existing uses of Taffy will continue to work as before.
70- The `box-sizing` style is supported
71- Computed margins are output in `Layout`
72
73### Fixes
74
75- Fix `print_tree()` when rounding is disabled (#680)
76- Absolute Insets should be resolved against the container size minus border (#666)
77- Fix flooring hypothetical_main_size by computed min size (#689)
78- Fix flex line cross-size determination (#690)
79- Fix panics in the grid algorithm (#691)
80- Fix resolving flexible lengths (WPT css/flexbox-multiline-min-max test) (#692)
81- Fix wrapping when a max main size style is present (#694)
82- Fix case where Taffy allowed margins to collapse through an element when it shouldn't have (#695)
83
84### Added
85
86- Legacy text align (for laying out `<center>` and `<div align="..">`) is supported
87- Add `is_table` for block items (#701)
88- Impl `Debug` and `Clone` for `Cache` (#688)
89- Implement `Debug` and `PartialEq` for tree types (#697)
90
91## 0.5.2
92
93- Fix block stretch sizing (don't always apply stretch sizing to block containers) (#674)
94- Fix computation of intrinsic main size when it depends on a child's known cross size (#673)
95- Fix panic when GridLine 0 is specified (#671)
96- Docs: Document feature flags and scrape examples (#672)
97- Docs: Update cosmic-text example to cosmic-text 0.12 (#670)
98
99## 0.5.1
100
101- Fix: Clamp block item stretch widths by their min and max width (#664)
102- Fix: Auto margin computation in block layout (#663)
103
104## 0.5.0
105
106The changes in 0.5 are relatively small but the new measure function parameter is a breaking change so it requires a minor version bump.
107
108- Added: A `style: &Style` parameter has been added to measure functions.
109- Added: The `MaybeMath`, `MaybeResolve`, and `ResolveOrZero` traits have been made public.
110- Fix: use SizingMode::Inherent when sizing absolute children of flexbox nodes.
111
112## 0.4.4
113
114### Fixes
115
116- Content alignment (`align-content`/`justify-content`) behaviour was updated to match the latest spec (and Chrome 123+) (#635)
117- Ensure that root Flexbox nodes are floored by their padding-border (#651, #655)
118- Use grid area size not available space when applying aspect ratio to grid containers (#656)
119
120## 0.4.3
121
122### Fixes
123
124- Fix compilation error in `evenly_sized_tracks` style helper in recent versions of rustc caused by a change/regression in type
125  inference (#643). Note that 3rd-party code that call style helpers that take an `Into<f32>` parameter may still be affected by this issue,
126  but they should be able to fix on their side by clarifying the type passed in
127
128## 0.4.2
129
130- Fixed: single-line flex-container should clamp the line's cross-size (#638)
131- Reduced binary footprint of Taffy from around 300kb to around 150kb (#636)
132
133## 0.4.1
134
135- Fixed: CSS Grid track sizing not respecting growth limits in some circumstances (#624)
136
137## 0.4.0
138
139### Highlights
140
141- Support for CSS Block layout (`display: block`)
142- Support for the `overflow` property (+ `scrollbar_width` for `overflow: scroll`)
143- Improved measure function API
144- Completely refactored low-level API
145- Simplified module hierarchy (+ most types/functions are now exported from the crate root)
146- Expanded set of examples which better document integration with other layout systems (e.g. text layout)
147- Computed values for `padding` and `border` are now output into the `Layout` struct
148
149### Block layout
150
151Support 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.
152
153### Overflow property
154
155Support 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.
156
157- Overflow is settable indpendently in each axis.
158- `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.
159- `Hidden` and `Scroll` affect layout by changing the automatic minimum size of Flexbox and Grid children
160- `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`.
161
162### Measure function changes
163
164The "measure function" API for integrating Taffy with other measurement systems (such as text layout) has been changed to be more flexible
165and to interact better with borrow checking (you can now borrow external data in your measure function!).
166
167- There are no longer per-node measure functions.
168- There is now a single "global" measure function, and a per-node "context" of a user-defined type
169- The `Taffy` tree is now a generic `TaffyTree<T>` where `T` is the "context" type.
170- The measure function is now called for all leaf nodes (nodes without children). If you wish to maintain compatibility with the previous
171  behaviour then your measure function should return `Size::ZERO` for leaf nodes whose context is `None`.
172
173If you are not using measure functions, then the only change you will need to make is from:
174
175```rust
176let mut tree = Taffy::new();
177```
178
179to
180
181```rust
182let mut tree : TaffyTree<()> = TaffyTree::new();
183```
184
185And generally update any uses of `Taffy` in your codebase to `TaffyTree<()>`.
186
187If you are using measure functions then you will need to make some bigger (but straightforward) changes. The following Taffy 0.3 code:
188
189```rust
190let mut tree = Taffy::new();
191let leaf = tree.new_leaf_with_measure(
192  Style::DEFAULT,
193  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>| Size { width: 100.0, height: 200.0 }
194);
195tree.compute_layout(leaf, Size::MAX_CONTENT);
196```
197
198Should become something like the following with Taffy 0.4:
199
200```rust
201let mut tree : TaffyTree<Size> = TaffyTree::new();
202let leaf = tree.new_leaf_with_context(Style::DEFAULT, Size { width: 100.0, height: 200.0 });
203tree.compute_layout_with_measure(
204  leaf,
205  Size::MAX_CONTENT,
206  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>, node_id: NodeId, node_context: Option<Size>| {
207    node_context.unwrap_or(Size::ZERO)
208  }
209);
210```
211
212Note that:
213
214- 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).
215- If you don't need a context then you can use `()` for the context type
216- As the single "global" measure function passed to `compute_layout_with_measure` only needs to exist for the duration of a single layout run,
217  it can (mutably) borrow data from it's environment
218
219### Low-level API (`LayoutTree` trait) refactor
220
221The low-level API has been completely reworked:
222
223- The `LayoutTree` trait has been split into 5 smaller traits which live in the `taffy::tree:traits` module (along with their associated documentation)
224- The following methods have been removed from split `LayoutTree` traits entirely: `parent`, `is_childless`, `measure_node`, `needs_measure`, and `mark_dirty`.
225- `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`.
226- Support for running each layout algorithm individually on a single node via the following top-level functions:
227  - `compute_flexbox_layout`
228  - `compute_grid_layout`
229  - `compute_block_layout`
230  - `compute_leaf_layout`
231  - `compute_root_layout`
232  - `compute_hidden_layout`
233
234It 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
235improved 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).
236
237### Module hierarchy changes
238
239The 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`.
240
241Specific changes:
242
243- The `math` module has been made private
244- The `axis` module has been merged into the `geometry` module
245- The debug module is no longer public. The `print_tree` function is now accessible under `util`.
246- All types from the `node`, `data`, `layout`, `error` and `cache` modules have been moved to the  the `tree` module.
247- The `layout_flexbox()` function has been removed from the prelude. Use `taffy::compute_flexbox_layout` instead.
248
249### Many APIs have been renamed to replace `points` or `Points` with `length` or `Length`
250
251This new name better describes one-dimensional measure of space in some unspecified unit
252which is often unrelated to the PostScript point or the CSS `pt` unit.
253
254This also removes a misleading similarity with the 2D `Point`,
255whose components can have any unit and are not even necessarily absolute lengths.
256
257Example usage change:
258
259```diff
260 use taffy::prelude::*;
261
262 // …
263
264 let header_node = taffy
265     .new_leaf(
266         Style {
267-            size: Size { width: points(800.0), height: points(100.0) },
268+            size: Size { width: length(800.0), height: length(100.0) },
269             ..Default::default()
270         },
271     ).unwrap();
272```
273
274### Other Changes
275
276- The `Taffy` type was renamed to `TaffyTree` and made generic of a context parameter
277- The Flexbox algorithm has now been moved behind the `flexbox` feature. The `flexbox` feature is enabled by default.
278- The `justify_self` property has been moved behind the `grid` feature.
279- Fixed misspelling: `RunMode::PeformLayout` renamed into `RunMode::PerformLayout` (added missing `r`).
280- `serde` dependency has been made compatible with `no_std` environments
281- `slotmap` dependency has been made compatible with `no_std` environments
282- 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.
283- Added `total_node_count()` method to the `TaffyTree` which returns the total number of nodes in the tree.
284- Added `get_disjoint_node_context_mut()` method to the `TaffyTree`. This can be used to safely get multiple mutable borrows at the same time.
285
286## 0.3.19
287
288### Fixes
289
290- Fix compilation error in `evenly_sized_tracks` style helper in recent versions of rustc caused by a change/regression in type
291  inference (#643). Note that 3rd-party code that call style helpers that take an `Into<f32>` parameter may still be affected by this issue,
292  but they should be able to fix on their side by clarifying the type passed in
293
294## 0.3.18
295
296### Fixes
297
298- Fix computation of Flexbox automatic minimum size when grid or flexbox child has an explicit width/height style set (#576)
299
300## 0.3.17
301
302### Added
303
304- Added `total_node_count` method to the `Taffy` struct. Returns the total number of nodes in the tree.
305
306## 0.3.16
307
308### Fixes
309
310- Improve performance of flexbox columns
311
312## 0.3.15
313
314### Fixes
315
316- Fix justify-content and align-content when free space is negative (content overflows container) (#549) (#551)
317
318## 0.3.14
319
320### Fixes
321
322- 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)
323
324## 0.3.13
325
326### Fixes
327
328- Fix rounding accumulation bug (#521) (Fixes #501 and bevyengine/bevy#8911)
329- Flexbox: pass correct cross-axis available space when computing an item's intrinsic main size (#522)(Fixes bevyengine/bevy#9350)
330- Flexbox: Subtract child margin not parent margin when computing stretch-alignment known size
331- Grid: Make CSS Grid algorithm correctly apply max width/height and available space when it is the root node (#491)
332- Grid: Fix CSS Grid "auto track" / placement bugs #481
333  - Fix divide by zero when using grid_auto_rows/grid_auto_columns with zero negative implicit tracks
334  - Fix over counting of tracks (leading to incorrect container heights) when auto-placing in grids that contain negative implicit tracks.
335  - Fix axis conflation in auto-placement code when grid_auto_flow is column
336  - Fix assignment of auto track sizes when initializing negative implicit tracks
337- Leaf: Apply margins to leaf nodes when computing available space for measure functions
338- Leaf: Reserve space for padding/borders in nodes with measure functions (#497)
339  
340  **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.
341
342### Dependencies
343
344- Upgrade `grid` to `0.10`. This eliminates the transitive dependency on `no-std-compat`.
345
346## 0.3.12
347
348### Fixes
349
350- Fix caching issue when toggling `display:none` on and off
351
352## 0.3.11
353
354### Fixes
355
356- Fix exponential blowup when laying out trees containing nodes with min and max sizes.
357
358## 0.3.10
359
360### Fixes
361
362- Fix sizing of children when the available_space < min_size (#407)
363
364## 0.3.9
365
366### Fixes
367
368- 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)
369
370## 0.3.8
371
372### Fixes
373
374- Fix incorrect min-content size for `flex-wrap: wrap` nodes (bevyengine/bevy#8082)
375
376## 0.3.7
377
378### Fixes
379
380- Fix: Make `padding` and `border` floor node sizes (#372)
381- Fix: Prevent percentages contributing to min-content sizes (#388) (also fixes bevyengine/bevy#8017)
382
383## 0.3.6
384
385### Fixes
386
387- Fix: Ignore `align_content` when `flex_wrap` is set to `nowrap` (#383)
388
389## 0.3.5
390
391### Fixes
392
393- Fix `display: none` when it is set on a flexbox child (#380)
394- Fix `display: none` when it is set on a grid child (#381)
395
396## 0.3.4
397
398### Fixes
399
400- Fix `display: none` when it is set for the only node in the hierarchy (#377)
401
402## 0.3.3
403
404### Added
405
406- 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.
407
408### Fixes
409
410- Fixed rounding algorithm such that it never leaves gaps between adjacent nodes (#369)
411- Fixed compiling with the `grid` feature disabled (#370)
412- Fixed compiling with the `std` feature disabled
413
414## 0.3.2
415
416### Fixes
417
418- Allow partial nested values to be deserialized into a `Style` using the `serde` feature.
419
420## 0.3.1
421
422### Fixes
423
424- The `serde` feature now works when the `grid` feature is enabled
425
426## 0.3.0
427
428### Highlights
429
430- [CSS Grid algorithm support](#new-feature-css-grid)
431- [Style helper functions](#new-feature-style-helpers)
432
433See below for details of breaking changes.
434
435### New Feature: CSS Grid
436
437We 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`.
438
439#### Learning Resources
440
441Taffy 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:
442
443- [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.
444- [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.
445
446#### Supported Features & Properties
447
448In addition to the usual sizing/spacing properties (size, min_size, padding, margin, etc), the following Grid style properties are supported on Grid Containers:
449
450| Property                  | Explanation                                                                                    |
451| ---                       | ---                                                                                            |
452| [`grid-template-columns`] | The track sizing functions of the grid's explicit columns                                      |
453| [`grid-template-rows`]    | The track sizing functions of the grid's explicit rows                                         |
454| [`grid-auto-rows`]        | Track sizing functions for the grid's implicitly generated rows                                |
455| [`grid-auto-columns`]     | Track sizing functions for the grid's implicitly generated columns                             |
456| [`grid-auto-flow`]        | Whether auto-placed items are placed row-wise or column-wise. And sparsely or densely.         |
457| [`gap`]                   | The size of the vertical and horizontal gaps between grid rows/columns                         |
458| [`align-content`]         | Align grid tracks within the container in the inline (horizontal) axis                         |
459| [`justify-content`]       | Align grid tracks within the container in the block (vertical) axis                            |
460| [`align-items`]           | Align the child items within their grid areas in the inline (horizontal) axis                  |
461| [`justify-items`]         | Align the child items within their grid areas in the block (vertical) axis                     |
462
463And the following Grid style properties are supported on Grid Items (children):
464
465| Property                  | Explanation                                                                                    |
466| ---                       | ---                                                                                            |
467| [`grid-row`]              | The (row) grid line the item starts at (or a span)                                             |
468| [`grid-column`]           | The (column) grid line the item end at (or a span)                                             |
469| [`align-self`]            | Align the item within it's grid area in the inline (horizontal) axis. Overrides `align-items`. |
470| [`justify-self`]          | Align the item within it's grid area in the block (vertical) axis. Overrides `justify-items`.  |
471
472[`grid-template-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-columns
473[`grid-template-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-rows
474[`grid-auto-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-rows
475[`grid-auto-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-columns
476[`grid-auto-flow`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-flow
477[`gap`]: https://developer.mozilla.org/en-US/docs/Web/CSS/gap
478[`align-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align_content
479[`justify-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify_content
480[`align-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-items
481[`justify-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-items
482[`grid-row`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-row
483[`grid-column`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-column
484[`align-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-self
485[`justify-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-self
486
487The following properties and features are not currently supported:
488
489- Subgrids
490- Masonry grid layout
491- Named grid lines
492- Named areas: `grid-template-areas` and `grid-area`
493- `grid-template` or `grid` shorthand
494
495#### Example
496
497See [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:
498
499```bash
500cargo run --example grid_holy_grail --features grid
501```
502
503### New Feature: Style Helpers
504
505Ten 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.
506
507For example, instead of:
508
509```rust
510let size : Size<Dimension> = Size { width: Dimension::Points(100.0), height: Dimension::Percent(50.0) };
511```
512
513you can now write
514
515```rust
516let size : Size<Dimension> = Size { width: points(100.0), height: percent(50.0) };
517```
518
519And 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
520
521```rust
522let size : Size<Dimension> = points(100.0);
523```
524
525Available style helpers:
526
527<table>
528  <thead><tr><th>Type(s)</th><th colspan="2">Helpers that work with that type</th></tr></thead>
529  <tbody>
530    <tr>
531      <td rowspan="3"><code>LengthPercentage</code></td>
532      <td><code>zero()</code></td>
533      <td>Generates a <code>Points</code> variant with the value <code>0.0</code></td>
534    </tr>
535    <tr>
536      <td><code>points(val:&nbsp;f32)</code></td>
537      <td>Generates a <code>Points</code> variant with the specified value</td>
538    </tr>
539    <tr>
540      <td><code>percent(val:&nbsp;f32)</code></td>
541      <td>Generates a <code>Percent</code> variant with the specified value.<br />Note that the scale of 0-1 not 0-100.</td>
542    </tr>
543    <tr>
544      <td rowspan="2"><code>LengthPercentageAuto</code><br /><code>Dimension</code></td>
545      <td colspan="2"><i>All helpers from <code>LengthPercentage</code> and...</i></td>
546    </tr>
547    <tr>
548      <td><code>auto()</code></td>
549      <td>Generates an <code>Auto</code> variant</td>
550    </tr>
551    <tr>
552      <td rowspan="3"><code>MinTrackSizingFunction</code></td>
553      <td colspan="2"><i>All helpers from <code>LengthPercentageAuto</code>/<code>Dimension</code> and...</i></td>
554    </tr>
555    <tr>
556      <td><code>min_content()</code></td>
557      <td>Generates an <code>MinContent</code> variant</td>
558    </tr>
559      <tr>
560      <td><code>max_content()</code></td>
561      <td>Generates an <code>MinContent</code> variant</td>
562    </tr>
563    <tr>
564      <td rowspan="3"><code>MaxTrackSizingFunction</code></td>
565      <td colspan="2"><i>All helpers from <code>MinTrackSizingFunction</code> and...</i></td>
566    </tr>
567    <tr>
568      <td><code>fit_content(limit:&nbsp;LengthPercentage)</code></td>
569      <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>
570    </tr>
571      <tr>
572      <td><code>fr(fraction:&nbsp;f32)</code></td>
573      <td>Generates a <code>Fraction</code> (<code>fr</code>) variant with the specified flex fraction </td>
574    </tr>
575    <tr>
576      <td rowspan="3"><code>NonRepeatingTrackSizingFunction</code></td>
577      <td colspan="2"><i>All helpers from <code>MaxTrackSizingFunction</code> and...</i></td>
578    </tr>
579    <tr>
580      <td><code>minmax(min: MinTrackSizingFunction, max: MaxTrackSizingFunction)</code></td>
581      <td>Equivalent to CSS <code>minmax()</code> function.</td>
582    </tr>
583    <tr>
584      <td><code>flex(fraction:&nbsp;f32)</code></td>
585      <td>Equivalent to CSS <code>minmax(0px, 1fr)</code>. This is likely what you want if you want evenly sized rows/columns.</td>
586    </tr>
587    <tr>
588      <td rowspan="2"><code>TrackSizingFunction</code></td>
589      <td colspan="2"><i>All helpers from <code>NonRepeatingTrackSizingFunction</code> and...</i></td>
590    </tr>
591    <tr>
592      <td><code>repeat(rep: GridTrackRepetition, tracks: Vec&lt;TrackSizingFunction&gt;)</code></td>
593      <td>Equivalent to css <code>repeat()</code> function.</td>
594    </tr>
595    <tr>
596      <td><code>Vec&lt;TrackSizingFunction&gt;</code></td>
597      <td><code>evenly_sized_tracks(count:&nbsp;u16)</code></td>
598      <td>Equivalent to CSS <code>repeat(count, minmax(0px, 1fr)</code></td>
599    </tr>
600    <tr>
601      <td rowspan="3"><code>AvailableSpace</code></td>
602      <td><code>auto()</code></td>
603      <td>Generates an <code>Auto</code> variant</td>
604    </tr>
605    <tr>
606      <td><code>min_content()</code></td>
607      <td>Generates an <code>MinContent</code> variant</td>
608    </tr>
609      <tr>
610      <td><code>max_content()</code></td>
611      <td>Generates an <code>MinContent</code> variant</td>
612    </tr>
613    <tr>
614      <td><code>Size&lt;T&gt;</code></td>
615      <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>
616    </tr>
617    <tr>
618      <td><code>Rect&lt;T&gt;</code></td>
619      <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>
620    </tr>
621  </tbody>
622</table>
623
624### Breaking API changes
625
626#### Changes to alignment style types
627
628- `AlignContent` and `JustifyContent` has been merged.
629  - `JustifyContent` is now an alias of `AlignContent` and contains the `Stretch` variant.
630  - This variant will be *ignored* (falling back to `Start`) when applied Flexbox containers. It is valid value for Grid containers.
631- `AlignItems` and `AlignSelf` have been merged.
632  - The `Auto` variant of `AlignSelf` has been removed. You should now use `Option::None` if you wish to specify `AlignSelf::Auto`.
633  - `AlignSelf` is now an alias of `AlignItems`.
634  - `JustifyItems` and `JustifySelf` aliases have been added. These properties have no affect on Flexbox containers, but apply to Grid containers.
635- `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.
636
637#### Strict style types
638
639- New types `LengthPercentage` and `LengthPercentageAuto` have been added.
640  - `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.
641  - `LengthPercentageAuto` is currently identical to `Dimension` but will allow us to expand dimension in future to support values like `MinContent`, `MaxContent` and `FitContent`.
642- 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).
643
644#### Position properties renamed
645
646- 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)
647- 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`.
648
649#### Changes to `LayoutTree`
650
651- Added generic associated type to `LayoutTree` for a `ChildIter`, an iterator on the children of a given node.
652- 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.
653- 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.
654- Added `is_childless` method to `LayoutTree` for querying whether a node has no children.
655
656#### `AvailableSpace` has been moved
657
658The `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.
659
660### Fixes
661
662- Flexbox nodes sized under a min-content constraint now size correctly (#291)
663- Aspect ratio is now applied correctly in many circumstances
664- Absolutely positioned items now apply margins correctly
665- Min/max size are now applied correctly
666- Inset applied incorrectly to relatively positioned flexbox children when both `top` and `bottom` or `left` and `right` were specified (#348)
667- 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)
668
669### Removed
670
671- 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.
672- 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.
673- 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.
674
675## 0.2.2
676
677### Fixes
678
679- Border or padding on the horizontal axis could, in some cases, increase the height of nodes.
680
681## 0.2.1
682
683### Fixes
684
685- 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`.
686- `taffy::compute_layout` has been made public allowing Taffy to be used with custom storage (#263)
687
688## 0.2.0
689
690### New features
691
692#### Flexbox "gap" and `AlignContent::SpaceEvenly`
693
694The [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.
695
696Additionally 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)
697
698#### Debug module and cargo feature
699
700Two debugging features have been added:
701
702- `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.
703- A cargo feature `debug`. This enabled debug logging of the layout computation process itself (this is probably mainly useful for those working taffy itself).
704
705### Performance improvements
706
707A number of performance improvements have landed since taffy 0.1:
708
709- 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%.
710- 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!
711
712#### Benchmarks vs. Taffy 0.1
713
714| Benchmark                                 | Taffy 0.1 | Taffy 0.2 | % change (0.1 -> 0.2) |
715| ---                                       | ---       | ---       | ---                   |
716| wide/1_000 nodes (2-level hierarchy)      | 699.18 µs | 445.01 µs | -36.279%              |
717| wide/10_000 nodes (2-level hierarchy)     | 8.8244 ms | 7.1313 ms | -16.352%              |
718| wide/100_000 nodes (2-level hierarchy)    | 204.48 ms | 242.93 ms | +18.803%              |
719| deep/4000 nodes (12-level hierarchy))     | 5.2320 s  | 2.7363 ms | -99.947%              |
720| deep/10_000 nodes (14-level hierarchy)    | 75.207 s  | 6.9415 ms | -99.991%              |
721| deep/100_000 nodes (17-level hierarchy)   | -         | 102.72 ms | -                     |
722| deep/1_000_000 nodes (20-level hierarchy) | -         | 799.35 ms | -                     |
723
724(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
725
726As 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.
727
728However, 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.
729
730#### Benchmarks vs. [Yoga](https://github.com/facebook/yoga)
731
732Yoga 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.
733
734| Benchmark | Yoga | Taffy 0.2 |
735| --- | --- | --- |
736| yoga/10 nodes (1-level hierarchy) | 45.1670 µs | 33.297 ns |
737| yoga/100 nodes (2-level hierarchy) | 134.1250 µs | 336.53 ns |
738| yoga/1_000 nodes (3-level hierarchy) | 1.2221 ms | 3.8928 µs |
739| yoga/10_000 nodes (4-level hierarchy) | 13.8672 ms | 36.162 µs |
740| yoga/100_000 nodes (5-level hierarchy) | 141.5307 ms | 1.6404 ms |
741
742(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
743
744While 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!
745
746### Breaking API changes
747
748#### Node creation changes
749
750- `taffy::Node` is now unique only to the Taffy instance from which it was created.
751- Renamed `Taffy.new_node(..)` -> `Taffy.new_with_children(..)`
752- Renamed `Taffy.new_leaf()` -> `Taffy.new_leaf_with_measure()`
753- Added `taffy::node::Taffy.new_leaf()` which allows the creation of new leaf-nodes without having to supply a measure function
754
755#### Error handling/representation improvements
756
757- Renamed `taffy::Error` -> `taffy::error::TaffyError`
758- Replaced `taffy::error::InvalidChild` with a new `InvalidChild` variant of `taffy::error::TaffyError`
759- Replaced `taffy::error::InvalidNode` with a new `InvalidNode` variant of `taffy::error::TaffyError`
760- The following method new return `Err(TaffyError::ChildIndexOutOfBounds)` instead of panicking:
761  - `taffy::Taffy::remove_child_at_index`
762  - `taffy::Taffy::replace_child_at_index`
763  - `taffy::Taffy::child_at_index`
764- `Taffy::remove` now returns a `Result<usize, Error>`, to indicate if the operation was successful (and if it was, which ID was invalidated).
765
766#### Some uses of `Option<f32>` replaced with a new `AvailableSpace` enum
767
768A new enum `Taffy::layout::AvailableSpace` has been added.
769
770The definition looks like this:
771
772```rust
773/// The amount of space available to a node in a given axis
774pub enum AvailableSpace {
775    /// The amount of space available is the specified number of pixels
776    Definite(f32),
777    /// The amount of space available is indefinite and the node should be laid out under a min-content constraint
778    MinContent,
779    /// The amount of space available is indefinite and the node should be laid out under a max-content constraint
780    MaxContent,
781}
782```
783
784This 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`).
785
786And 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..
787
788#### Builder methods are now `const` where possible
789
790- Several convenience constants have been defined: notably `Style::DEFAULT`
791- `Size<f32>.zero()` is now `Size::<f32>::ZERO`
792- `Point<f32>.zero()` is now  `Point::<f32>::ZERO`
793- `Size::undefined()` is now `Size::NONE`
794
795#### Removals
796
797- 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%).
798- Removed `taffy::number::Number`. Use `Option<f32>` is used instead
799  - the associated public `MinMax` and `OrElse` traits have also been removed; these should never have been public
800- 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).
801
802### Fixes
803
804- Miscellaneous correctness fixes which align our implementation with Chrome:
805
806  - Nodes can only ever have one parent
807  - Fixed rounding of fractional values to follow latest Chrome - values are now rounded the same regardless of their position
808  - Fixed computing free space when using both `flex-grow` and a minimum size
809  - 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)
810  - `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
811- Taffy can now be vendored using `cargo-vendor` (README.md is now included in package).
812
813## 0.1.0
814
815### 0.1.0 Changed
816
817- the `order` field of `Layout` is now public, and describes the relative z-ordering of nodes
818- renamed crate from `stretch2` to `taffy`
819- updated to the latest version of all dependencies to reduce upstream pain caused by duplicate dependencies
820- renamed `stretch::node::Stretch` -> `taffy::node::Taffy`
821
822### 0.1.0 Fixed
823
824- fixed feature strategy for `alloc` and `std`: these can now be compiled together, with `std`'s types taking priority
825
826### 0.1.0 Removed
827
828- removed Javascript / Kotlin / Swift bindings
829  - the maintainer team lacks expertise to keep these working
830  - more serious refactors are planned, and this will be challenging to keep working through that process
831  - if you are interested in helping us maintain bindings to other languages, [get in touch](https://github.com/DioxusLabs/taffy/discussions)!
832- 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)
833- removed the `Direction` and `Overflow` structs, and the corresponding `direction` and `overflow` fields from `Style`
834  - these had no effect in the current code base and were actively misleading
835
836## stretch2 0.4.3
837
838This is the final release of `stretch`: migrate to the crate named `taffy` for future fixes and features!
839
840These notes describe the differences between this release and `stretch` 0.3.2, the abandoned crate from which this library was forked.
841
842### Changed
843
844- updated [assorted dependencies](https://github.com/vislyhq/stretch/commit/a6491117379cea52dedc9584d892594a143e8cb0)
845
846### Fixed
847
848- fixed an exponential performance blow-up with deep nesting
849- fixed percent height values, which were using parent width
850- recomputing layout no longer moves children of non-zero-positioned parent
851- fixed broken Swift bindings