1# Release Notes
2
3## Unreleased
4
5### Breaking
6
7Many APIs have been renamed to replace `points` or `Points` with `length` or `Length`.
8This new name better describes one-dimentional measure of space in some unspecified unit
9which is often unrelated to the PostScript point or the CSS `pt` unit.
10
11This also removes a misleading similarity with the 2D `Point`,
12whose components can have any unit and are not even necessarily absolute lengths.
13
14Example usage change:
15
16```diff
17 use taffy::prelude::*;
18
19 // …
20
21 let header_node = taffy
22     .new_leaf(
23         Style {
24-            size: Size { width: points(800.0), height: points(100.0) },
25+            size: Size { width: length(800.0), height: length(100.0) },
26             ..Default::default()
27         },
28     ).unwrap();
29```
30
31### Added
32
33- Support 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 inline, inline-block and float have *not* been implemented. The use case supported is block container nodes which contain block-level children.
34
35### Removed
36
37- `layout_flexbox()` has been removed from the prelude. Use `FlexboxAlgorithm::perform_layout()` instead.
38- The following methods have been removed from the `LayoutTree` trait: `parent`, `is_childless`, `layout`, `measure_node`, `needs_measure`, `cache_mut` and `mark_dirty`. These no longer need to be implemented in custom implementation of `LayoutTree`.
39
40### Changes
41
42- The Flexbox algorithm has now been moved behind the `flexbox` feature. The `flexbox` feature is enabled by default.
43- The `justify_self` property has been moved behind the `grid` feature.
44- `taffy::node::Node` has been replaced with `taffy::tree::NodeId`. This should make it much easier to implement the `LayoutTree` trait as the underlying type backing the node id now a `u64` rather than a `slotmap::DefaultKey`.
45- Module organisation changes:
46  - The `math` module has been made private
47  - The `axis` module has been merged into the `geometry` module
48  - The debug module is no longer public. The `print_tree` function is now accesible under `util`.
49  - All types from the `node`, `data`, `layout`, `error` and `cache` modules have been moved to the  the `tree` module.
50
51### Fixes
52
53- Fix divide by zero when using grid_auto_rows/grid_auto_columns with zero negative implicit tracks
54- Fix over counting of tracks (leading to incorrect container heights) when auto-placing in grids that contain negative implicit tracks.
55- Fix axis conflation in auto-placement code when grid_auto_flow is column
56- Fix assignment of auto track sizes when initializing negative implicit tracks
57
58## 0.3.11
59
60### Fixes
61
62- Fix exponential blowup when laying out trees containing nodes with min and max sizes.
63
64## 0.3.10
65
66### Fixes
67
68- Fix sizing of children when the available_space < min_size (#407)
69
70## 0.3.9
71
72### Fixes
73
74- 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)
75
76## 0.3.8
77
78### Fixes
79
80- Fix incorrect min-content size for `flex-wrap: wrap` nodes (bevyengine/bevy#8082)
81
82## 0.3.7
83
84### Fixes
85
86- Fix: Make `padding` and `border` floor node sizes (#372)
87- Fix: Prevent percentages contributing to min-content sizes (#388) (also fixes bevyengine/bevy#8017)
88
89## 0.3.6
90
91### Fixes
92
93- Fix: Ignore `align_content` when `flex_wrap` is set to `nowrap` (#383)
94
95## 0.3.5
96
97### Fixes
98
99- Fix `display: none` when it is set on a flexbox child (#380)
100- Fix `display: none` when it is set on a grid child (#381)
101
102## 0.3.4
103
104### Fixes
105
106- Fix `display: none` when it is set for the only node in the hierarchy (#377)
107
108## 0.3.3
109
110### Added
111
112- 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.
113
114### Fixes
115
116- Fixed rounding algorithm such that it never leaves gaps between adjacent nodes (#369)
117- Fixed compiling with the `grid` feature disabled (#370)
118- Fixed compiling with the `std` feature disabled
119
120## 0.3.2
121
122### Fixes
123
124- Allow partial nested values to be deserialized into a `Style` using the `serde` feature.
125
126## 0.3.1
127
128### Fixes
129
130- The `serde` feature now works when the `grid` feature is enabled
131
132## 0.3.0
133
134### Highlights
135
136- [CSS Grid algorithm support](#new-feature-css-grid)
137- [Style helper functions](#new-feature-style-helpers)
138
139See below for details of breaking changes.
140
141### New Feature: CSS Grid
142
143We 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`.
144
145#### Learning Resources
146
147Taffy 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:
148
149- [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.
150- [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 comphrehensive written explanation of the different Grid propertie and how they work.
151
152#### Supported Features & Properties
153
154In addition to the usual sizing/spacing proerties (size, min_size, padding, margin, etc), the following Grid style properties are supported on Grid Containers:
155
156| Property                  | Explanation                                                                                    |
157| ---                       | ---                                                                                            |
158| [`grid-template-columns`] | The track sizing functions of the grid's explicit columns                                      |
159| [`grid-template-rows`]    | The track sizing functions of the grid's explicit rows                                         |
160| [`grid-auto-rows`]        | Track sizing functions for the grid's implicitly generated rows                                |
161| [`grid-auto-columns`]     | Track sizing functions for the grid's implicitly generated columns                             |
162| [`grid-auto-flow`]        | Whether auto-placed items are placed row-wise or column-wise. And sparsely or densely.         |
163| [`gap`]                   | The size of the vertical and horizontal gaps between grid rows/columns                         |
164| [`align-content`]         | Align grid tracks within the container in the inline (horizontal) axis                         |
165| [`justify-content`]       | Align grid tracks within the container in the block (vertical) axis                            |
166| [`align-items`]           | Align the child items within their grid areas in the inline (horizontal) axis                  |
167| [`justify-items`]         | Align the child items within their grid areas in the block (vertical) axis                     |
168
169And the following Grid style properties are supported on Grid Items (children):
170
171| Property                  | Explanation                                                                                    |
172| ---                       | ---                                                                                            |
173| [`grid-row`]              | The (row) grid line the item starts at (or a span)                                             |
174| [`grid-column`]           | The (column) grid line the item end at (or a span)                                             |
175| [`align-self`]            | Align the item within it's grid area in the inline (horizontal) axis. Overrides `align-items`. |
176| [`justify-self`]          | Align the item within it's grid area in the block (vertical) axis. Overrides `justify-items`.  |
177
178[`grid-template-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-columns
179[`grid-template-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-rows
180[`grid-auto-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-rows
181[`grid-auto-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-columns
182[`grid-auto-flow`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-flow
183[`gap`]: https://developer.mozilla.org/en-US/docs/Web/CSS/gap
184[`align-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align_content
185[`justify-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify_content
186[`align-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-items
187[`justify-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-items
188[`grid-row`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-row
189[`grid-column`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-column
190[`align-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-self
191[`justify-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-self
192
193The following properties and features are not currently supported:
194
195- Subgrids
196- Masonry grid layout
197- Named grid lines
198- Named areas: `grid-template-areas` and `grid-area`
199- `grid-template` or `grid` shorthand
200
201#### Example
202
203See [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:
204
205```bash
206cargo run --example grid_holy_grail --features grid
207```
208
209### New Feature: Style Helpers
210
211Ten 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.
212
213For example, instead of:
214
215```rust
216let size : Size<Dimension> = Size { width: Dimension::Points(100.0), height: Dimension::Percent(50.0) };
217```
218
219you can now write
220
221```rust
222let size : Size<Dimension> = Size { width: points(100.0), height: percent(50.0) };
223```
224
225And 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
226
227```rust
228let size : Size<Dimension> = points(100.0);
229```
230
231Available style helpers:
232
233<table>
234  <thead><tr><th>Type(s)</th><th colspan="2">Helpers that work with that type</th></tr></thead>
235  <tbody>
236    <tr>
237      <td rowspan="3"><code>LengthPercentage</code></td>
238      <td><code>zero()</code></td>
239      <td>Generates a <code>Points</code> variant with the value <code>0.0</code></td>
240    </tr>
241    <tr>
242      <td><code>points(val:&nbsp;f32)</code></td>
243      <td>Generates a <code>Points</code> variant with the specified value</td>
244    </tr>
245    <tr>
246      <td><code>percent(val:&nbsp;f32)</code></td>
247      <td>Generates a <code>Percent</code> variant with the specified value.<br />Note that the scale of 0-1 not 0-100.</td>
248    </tr>
249    <tr>
250      <td rowspan="2"><code>LengthPercentageAuto</code><br /><code>Dimension</code></td>
251      <td colspan="2"><i>All helpers from <code>LengthPercentage</code> and...</i></td>
252    </tr>
253    <tr>
254      <td><code>auto()</code></td>
255      <td>Generates an <code>Auto</code> variant</td>
256    </tr>
257    <tr>
258      <td rowspan="3"><code>MinTrackSizingFunction</code></td>
259      <td colspan="2"><i>All helpers from <code>LengthPercentageAuto</code>/<code>Dimension</code> and...</i></td>
260    </tr>
261    <tr>
262      <td><code>min_content()</code></td>
263      <td>Generates an <code>MinContent</code> variant</td>
264    </tr>
265      <tr>
266      <td><code>max_content()</code></td>
267      <td>Generates an <code>MinContent</code> variant</td>
268    </tr>
269    <tr>
270      <td rowspan="3"><code>MaxTrackSizingFunction</code></td>
271      <td colspan="2"><i>All helpers from <code>MinTrackSizingFunction</code> and...</i></td>
272    </tr>
273    <tr>
274      <td><code>fit_content(limit:&nbsp;LengthPercentage)</code></td>
275      <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>
276    </tr>
277      <tr>
278      <td><code>fr(fraction:&nbsp;f32)</code></td>
279      <td>Generates a <code>Fraction</code> (<code>fr</code>) variant with the specified flex fraction </td>
280    </tr>
281    <tr>
282      <td rowspan="3"><code>NonRepeatingTrackSizingFunction</code></td>
283      <td colspan="2"><i>All helpers from <code>MaxTrackSizingFunction</code> and...</i></td>
284    </tr>
285    <tr>
286      <td><code>minmax(min: MinTrackSizingFunction, max: MaxTrackSizingFunction)</code></td>
287      <td>Equivalent to CSS <code>minmax()</code> function.</td>
288    </tr>
289    <tr>
290      <td><code>flex(fraction:&nbsp;f32)</code></td>
291      <td>Equivalent to CSS <code>minmax(0px, 1fr)</code>. This is likely what you want if you want evenly sized rows/columns.</td>
292    </tr>
293    <tr>
294      <td rowspan="2"><code>TrackSizingFunction</code></td>
295      <td colspan="2"><i>All helpers from <code>NonRepeatingTrackSizingFunction</code> and...</i></td>
296    </tr>
297    <tr>
298      <td><code>repeat(rep: GridTrackRepetition, tracks: Vec&lt;TrackSizingFunction&gt;)</code></td>
299      <td>Equivalent to css <code>repeat()</code> function.</td>
300    </tr>
301    <tr>
302      <td><code>Vec&lt;TrackSizingFunction&gt;</code></td>
303      <td><code>evenly_sized_tracks(count:&nbsp;u16)</code></td>
304      <td>Equivalent to CSS <code>repeat(count, minmax(0px, 1fr)</code></td>
305    </tr>
306    <tr>
307      <td rowspan="3"><code>AvailableSpace</code></td>
308      <td><code>auto()</code></td>
309      <td>Generates an <code>Auto</code> variant</td>
310    </tr>
311    <tr>
312      <td><code>min_content()</code></td>
313      <td>Generates an <code>MinContent</code> variant</td>
314    </tr>
315      <tr>
316      <td><code>max_content()</code></td>
317      <td>Generates an <code>MinContent</code> variant</td>
318    </tr>
319    <tr>
320      <td><code>Size&lt;T&gt;</code></td>
321      <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>
322    </tr>
323    <tr>
324      <td><code>Rect&lt;T&gt;</code></td>
325      <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>
326    </tr>
327  </tbody>
328</table>
329
330### Breaking API changes
331
332#### Changes to alignment style types
333
334- `AlignContent` and `JustifyContent` has been merged.
335  - `JustifyContent` is now an alias of `AlignContent` and contains the `Stretch` variant.
336  - This variant will be *ignored* (falling back to `Start`) when applied Flexbox containers. It is valid value for Grid containers.
337- `AlignItems` and `AlignSelf` have been merged.
338  - The `Auto` variant of `AlignSelf` has been removed. You should now use `Option::None` if you wish to specify `AlignSelf::Auto`.
339  - `AlignSelf` is now an alias of `AlignItems`.
340  - `JustifyItems` and `JustifySelf` aliases have been added. These properties have no affect on Flexbox containers, but apply to Grid containers.
341- `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.
342
343#### Strict style types
344
345- New types `LengthPercentage` and `LengthPercentageAuto` have been added.
346  - `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.
347  - `LengthPercentageAuto` is currently identical to `Dimension` but will allow us to expand dimension in future to support values like `MinContent`, `MaxContent` and `FitContent`.
348- 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).
349
350#### Position properties renamed
351
352- 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)
353- 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`.
354
355#### Changes to `LayoutTree`
356
357- Added generic associated type to `LayoutTree` for a `ChildIter`, an iterator on the children of a given node.
358- 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.
359- 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.
360- Added `is_childless` method to `LayoutTree` for querying whether a node has no children.
361
362#### `AvailableSpace` has been moved
363
364The `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.
365
366### Fixes
367
368- Flexbox nodes sized under a min-content constraint now size correctly (#291)
369- Aspect ratio is now applied correctly in many circumstances
370- Absolutely positioned items now apply margins correctly
371- Min/max size are now applied correctly
372- Inset applied incorrectly to relatively positioned flexbox children when both `top` and `bottom` or `left` and `right` were specified (#348)
373- 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)
374
375### Removed
376
377- 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.
378- 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.
379- 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.
380
381## 0.2.2
382
383### Fixes
384
385- Border or padding on the horizontal axis could, in some cases, increase the height of nodes.
386
387## 0.2.1
388
389### Fixes
390
391- 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`.
392- `taffy::compute_layout` has been made public allowing Taffy to be used with custom storage (#263)
393
394## 0.2.0
395
396### New features
397
398#### Flexbox "gap" and `AlignContent::SpaceEvenly`
399
400The [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.
401
402Additionally 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)
403
404#### Debug module and cargo feature
405
406Two debugging features have been added:
407
408- `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.
409- A cargo feature `debug`. This enabled debug logging of the layout computation process itself (this is probably mainly useful for those working taffy itself).
410
411### Performance improvements
412
413A number of performance improvements have landed since taffy 0.1:
414
415- 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%.
416- 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 chache slots to better match the actual usage patterns of the flexbox layout algorithm. This had a particularly dramatic effect on deep hierachies (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!
417
418#### Benchmarks vs. Taffy 0.1
419
420| Benchmark                                 | Taffy 0.1 | Taffy 0.2 | % change (0.1 -> 0.2) |
421| ---                                       | ---       | ---       | ---                   |
422| wide/1_000 nodes (2-level hierarchy)      | 699.18 µs | 445.01 µs | -36.279%              |
423| wide/10_000 nodes (2-level hierarchy)     | 8.8244 ms | 7.1313 ms | -16.352%              |
424| wide/100_000 nodes (2-level hierarchy)    | 204.48 ms | 242.93 ms | +18.803%              |
425| deep/4000 nodes (12-level hierarchy))     | 5.2320 s  | 2.7363 ms | -99.947%              |
426| deep/10_000 nodes (14-level hierarchy)    | 75.207 s  | 6.9415 ms | -99.991%              |
427| deep/100_000 nodes (17-level hierarchy)   | -         | 102.72 ms | -                     |
428| deep/1_000_000 nodes (20-level hierarchy) | -         | 799.35 ms | -                     |
429
430(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
431
432As 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.
433
434However, in the "deep" benchmarks we see dramatic improvements. The previous version of Taffy suffered from exponential blowup in the case of deeply nested hierachies. This has resulted in somewhat silly improvements like the 10,000 node (14-level) hierachy 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.
435
436#### Benchmarks vs. [Yoga](https://github.com/facebook/yoga)
437
438Yoga 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.
439
440| Benchmark | Yoga | Taffy 0.2 |
441| --- | --- | --- |
442| yoga/10 nodes (1-level hierarchy) | 45.1670 µs | 33.297 ns |
443| yoga/100 nodes (2-level hierarchy) | 134.1250 µs | 336.53 ns |
444| yoga/1_000 nodes (3-level hierarchy) | 1.2221 ms | 3.8928 µs |
445| yoga/10_000 nodes (4-level hierarchy) | 13.8672 ms | 36.162 µs |
446| yoga/100_000 nodes (5-level hierarchy) | 141.5307 ms | 1.6404 ms |
447
448(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
449
450While 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!
451
452### Breaking API changes
453
454#### Node creation changes
455
456- `taffy::Node` is now unique only to the Taffy instance from which it was created.
457- Renamed `Taffy.new_node(..)` -> `Taffy.new_with_children(..)`
458- Renamed `Taffy.new_leaf()` -> `Taffy.new_leaf_with_measure()`
459- Added `taffy::node::Taffy.new_leaf()` which allows the creation of new leaf-nodes without having to supply a measure function
460
461#### Error handling/representation improvements
462
463- Renamed `taffy::Error` -> `taffy::error::TaffyError`
464- Replaced `taffy::error::InvalidChild` with a new `InvalidChild` variant of `taffy::error::TaffyError`
465- Replaced `taffy::error::InvalidNode` with a new `InvalidNode` variant of `taffy::error::TaffyError`
466- The following method new return `Err(TaffyError::ChildIndexOutOfBounds)` instead of panicking:
467  - `taffy::Taffy::remove_child_at_index`
468  - `taffy::Taffy::replace_child_at_index`
469  - `taffy::Taffy::child_at_index`
470- `Taffy::remove` now returns a `Result<usize, Error>`, to indicate if the operation was sucessful (and if it was, which ID was invalidated).
471
472#### Some uses of `Option<f32>` replaced with a new `AvailableSpace` enum
473
474A new enum `Taffy::layout::AvailableSpace` has been added.
475
476The definition looks like this:
477
478```rust
479/// The amount of space available to a node in a given axis
480pub enum AvailableSpace {
481    /// The amount of space available is the specified number of pixels
482    Definite(f32),
483    /// The amount of space available is indefinite and the node should be laid out under a min-content constraint
484    MinContent,
485    /// The amount of space available is indefinite and the node should be laid out under a max-content constraint
486    MaxContent,
487}
488```
489
490This 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`).
491
492And 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..
493
494#### Builder methods are now `const` where possible
495
496- Several convenience constants have been defined: notably `Style::DEFAULT`
497- `Size<f32>.zero()` is now `Size::<f32>::ZERO`
498- `Point<f32>.zero()` is now  `Point::<f32>::ZERO`
499- `Size::undefined()` is now `Size::NONE`
500
501#### Removals
502
503- 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%).
504- Removed `taffy::number::Number`. Use `Option<f32>` is used instead
505  - the associated public `MinMax` and `OrElse` traits have also been removed; these should never have been public
506- 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).
507
508### Fixes
509
510- Miscellaneous correctness fixes which align our implementation with Chrome:
511
512  - Nodes can only ever have one parent
513  - Fixed rounding of fractional values to follow latest Chrome - values are now rounded the same regardless of their position
514  - Fixed computing free space when using both `flex-grow` and a minimum size
515  - 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)
516  - `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
517- Taffy can now be vendored using `cargo-vendor` (README.md is now included in package).
518
519## 0.1.0
520
521### 0.1.0 Changed
522
523- the `order` field of `Layout` is now public, and describes the relative z-ordering of nodes
524- renamed crate from `stretch2` to `taffy`
525- updated to the latest version of all dependencies to reduce upstream pain caused by duplicate dependencies
526- renamed `stretch::node::Strech` -> `taffy::node::Taffy`
527
528### 0.1.0 Fixed
529
530- fixed feature strategy for `alloc` and `std`: these can now be compiled together, with `std`'s types taking priority
531
532### 0.1.0 Removed
533
534- removed Javascript / Kotlin / Swift bindings
535  - the maintainer team lacks expertise to keep these working
536  - more serious refactors are planned, and this will be challenging to keep working through that process
537  - if you are interested in helping us maintain bindings to other languages, [get in touch](https://github.com/DioxusLabs/taffy/discussions)!
538- 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)
539- removed the `Direction` and `Overflow` structs, and the corresponding `direction` and `overflow` fields from `Style`
540  - these had no effect in the current code base and were actively misleading
541
542## stretch2 0.4.3
543
544This is the final release of `stretch`: migrate to the crate named `taffy` for future fixes and features!
545
546These notes describe the differences between this release and `stretch` 0.3.2, the abandoned crate from which this library was forked.
547
548### Changed
549
550- updated [assorted dependencies](https://github.com/vislyhq/stretch/commit/a6491117379cea52dedc9584d892594a143e8cb0)
551
552### Fixed
553
554- fixed an exponential performance blow-up with deep nesting
555- fixed percent height values, which were using parent width
556- recomputing layout no longer moves children of non-zero-positioned parent
557- fixed broken Swift bindings