1# Release Notes
2
3## 0.3.13
4
5### Fixes
6
7- Fix rounding accumulation bug (#521) (Fixes #501 and bevyengine/bevy#8911)
8- Flexbox: pass correct cross-axis available space when computing an item's intrinsic main size (#522)(Fixes bevyengine/bevy#9350)
9- Flexbox: Subtract child margin not parent margin when computing stretch-alignment known size
10- Grid: Make CSS Grid algorithm correctly apply max width/height and available space when it is the root node (#491)
11- Grid: Fix CSS Grid "auto track" / placement bugs #481
12  - Fix divide by zero when using grid_auto_rows/grid_auto_columns with zero negative implicit tracks
13  - Fix over counting of tracks (leading to incorrect container heights) when auto-placing in grids that contain negative implicit tracks.
14  - Fix axis conflation in auto-placement code when grid_auto_flow is column
15  - Fix assignment of auto track sizes when initializing negative implicit tracks
16- Leaf: Apply margins to leaf nodes when computing available space for measure functions
17- Leaf: Reserve space for padding/borders in nodes with measure functions (#497)
18  
19  **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.
20
21### Dependencies
22
23- Upgrade `grid` to `0.10`. This eliminates the transitive dependency on `no-std-compat`.
24
25## 0.3.12
26
27### Fixes
28
29- Fix caching issue when toggling `display:none` on and off
30
31## 0.3.11
32
33### Fixes
34
35- Fix exponential blowup when laying out trees containing nodes with min and max sizes.
36
37## 0.3.10
38
39### Fixes
40
41- Fix sizing of children when the available_space < min_size (#407)
42
43## 0.3.9
44
45### Fixes
46
47- 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)
48
49## 0.3.8
50
51### Fixes
52
53- Fix incorrect min-content size for `flex-wrap: wrap` nodes (bevyengine/bevy#8082)
54
55## 0.3.7
56
57### Fixes
58
59- Fix: Make `padding` and `border` floor node sizes (#372)
60- Fix: Prevent percentages contributing to min-content sizes (#388) (also fixes bevyengine/bevy#8017)
61
62## 0.3.6
63
64### Fixes
65
66- Fix: Ignore `align_content` when `flex_wrap` is set to `nowrap` (#383)
67
68## 0.3.5
69
70### Fixes
71
72- Fix `display: none` when it is set on a flexbox child (#380)
73- Fix `display: none` when it is set on a grid child (#381)
74
75## 0.3.4
76
77### Fixes
78
79- Fix `display: none` when it is set for the only node in the hierarchy (#377)
80
81## 0.3.3
82
83### Added
84
85- 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.
86
87### Fixes
88
89- Fixed rounding algorithm such that it never leaves gaps between adjacent nodes (#369)
90- Fixed compiling with the `grid` feature disabled (#370)
91- Fixed compiling with the `std` feature disabled
92
93## 0.3.2
94
95### Fixes
96
97- Allow partial nested values to be deserialized into a `Style` using the `serde` feature.
98
99## 0.3.1
100
101### Fixes
102
103- The `serde` feature now works when the `grid` feature is enabled
104
105## 0.3.0
106
107### Highlights
108
109- [CSS Grid algorithm support](#new-feature-css-grid)
110- [Style helper functions](#new-feature-style-helpers)
111
112See below for details of breaking changes.
113
114### New Feature: CSS Grid
115
116We 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`.
117
118#### Learning Resources
119
120Taffy 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:
121
122- [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.
123- [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.
124
125#### Supported Features & Properties
126
127In addition to the usual sizing/spacing proerties (size, min_size, padding, margin, etc), the following Grid style properties are supported on Grid Containers:
128
129| Property                  | Explanation                                                                                    |
130| ---                       | ---                                                                                            |
131| [`grid-template-columns`] | The track sizing functions of the grid's explicit columns                                      |
132| [`grid-template-rows`]    | The track sizing functions of the grid's explicit rows                                         |
133| [`grid-auto-rows`]        | Track sizing functions for the grid's implicitly generated rows                                |
134| [`grid-auto-columns`]     | Track sizing functions for the grid's implicitly generated columns                             |
135| [`grid-auto-flow`]        | Whether auto-placed items are placed row-wise or column-wise. And sparsely or densely.         |
136| [`gap`]                   | The size of the vertical and horizontal gaps between grid rows/columns                         |
137| [`align-content`]         | Align grid tracks within the container in the inline (horizontal) axis                         |
138| [`justify-content`]       | Align grid tracks within the container in the block (vertical) axis                            |
139| [`align-items`]           | Align the child items within their grid areas in the inline (horizontal) axis                  |
140| [`justify-items`]         | Align the child items within their grid areas in the block (vertical) axis                     |
141
142And the following Grid style properties are supported on Grid Items (children):
143
144| Property                  | Explanation                                                                                    |
145| ---                       | ---                                                                                            |
146| [`grid-row`]              | The (row) grid line the item starts at (or a span)                                             |
147| [`grid-column`]           | The (column) grid line the item end at (or a span)                                             |
148| [`align-self`]            | Align the item within it's grid area in the inline (horizontal) axis. Overrides `align-items`. |
149| [`justify-self`]          | Align the item within it's grid area in the block (vertical) axis. Overrides `justify-items`.  |
150
151[`grid-template-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-columns
152[`grid-template-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-rows
153[`grid-auto-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-rows
154[`grid-auto-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-columns
155[`grid-auto-flow`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-flow
156[`gap`]: https://developer.mozilla.org/en-US/docs/Web/CSS/gap
157[`align-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align_content
158[`justify-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify_content
159[`align-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-items
160[`justify-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-items
161[`grid-row`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-row
162[`grid-column`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-column
163[`align-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-self
164[`justify-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-self
165
166The following properties and features are not currently supported:
167
168- Subgrids
169- Masonry grid layout
170- Named grid lines
171- Named areas: `grid-template-areas` and `grid-area`
172- `grid-template` or `grid` shorthand
173
174#### Example
175
176See [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:
177
178```bash
179cargo run --example grid_holy_grail --features grid
180```
181
182### New Feature: Style Helpers
183
184Ten 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.
185
186For example, instead of:
187
188```rust
189let size : Size<Dimension> = Size { width: Dimension::Points(100.0), height: Dimension::Percent(50.0) };
190```
191
192you can now write
193
194```rust
195let size : Size<Dimension> = Size { width: points(100.0), height: percent(50.0) };
196```
197
198And 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
199
200```rust
201let size : Size<Dimension> = points(100.0);
202```
203
204Available style helpers:
205
206<table>
207  <thead><tr><th>Type(s)</th><th colspan="2">Helpers that work with that type</th></tr></thead>
208  <tbody>
209    <tr>
210      <td rowspan="3"><code>LengthPercentage</code></td>
211      <td><code>zero()</code></td>
212      <td>Generates a <code>Points</code> variant with the value <code>0.0</code></td>
213    </tr>
214    <tr>
215      <td><code>points(val:&nbsp;f32)</code></td>
216      <td>Generates a <code>Points</code> variant with the specified value</td>
217    </tr>
218    <tr>
219      <td><code>percent(val:&nbsp;f32)</code></td>
220      <td>Generates a <code>Percent</code> variant with the specified value.<br />Note that the scale of 0-1 not 0-100.</td>
221    </tr>
222    <tr>
223      <td rowspan="2"><code>LengthPercentageAuto</code><br /><code>Dimension</code></td>
224      <td colspan="2"><i>All helpers from <code>LengthPercentage</code> and...</i></td>
225    </tr>
226    <tr>
227      <td><code>auto()</code></td>
228      <td>Generates an <code>Auto</code> variant</td>
229    </tr>
230    <tr>
231      <td rowspan="3"><code>MinTrackSizingFunction</code></td>
232      <td colspan="2"><i>All helpers from <code>LengthPercentageAuto</code>/<code>Dimension</code> and...</i></td>
233    </tr>
234    <tr>
235      <td><code>min_content()</code></td>
236      <td>Generates an <code>MinContent</code> variant</td>
237    </tr>
238      <tr>
239      <td><code>max_content()</code></td>
240      <td>Generates an <code>MinContent</code> variant</td>
241    </tr>
242    <tr>
243      <td rowspan="3"><code>MaxTrackSizingFunction</code></td>
244      <td colspan="2"><i>All helpers from <code>MinTrackSizingFunction</code> and...</i></td>
245    </tr>
246    <tr>
247      <td><code>fit_content(limit:&nbsp;LengthPercentage)</code></td>
248      <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>
249    </tr>
250      <tr>
251      <td><code>fr(fraction:&nbsp;f32)</code></td>
252      <td>Generates a <code>Fraction</code> (<code>fr</code>) variant with the specified flex fraction </td>
253    </tr>
254    <tr>
255      <td rowspan="3"><code>NonRepeatingTrackSizingFunction</code></td>
256      <td colspan="2"><i>All helpers from <code>MaxTrackSizingFunction</code> and...</i></td>
257    </tr>
258    <tr>
259      <td><code>minmax(min: MinTrackSizingFunction, max: MaxTrackSizingFunction)</code></td>
260      <td>Equivalent to CSS <code>minmax()</code> function.</td>
261    </tr>
262    <tr>
263      <td><code>flex(fraction:&nbsp;f32)</code></td>
264      <td>Equivalent to CSS <code>minmax(0px, 1fr)</code>. This is likely what you want if you want evenly sized rows/columns.</td>
265    </tr>
266    <tr>
267      <td rowspan="2"><code>TrackSizingFunction</code></td>
268      <td colspan="2"><i>All helpers from <code>NonRepeatingTrackSizingFunction</code> and...</i></td>
269    </tr>
270    <tr>
271      <td><code>repeat(rep: GridTrackRepetition, tracks: Vec&lt;TrackSizingFunction&gt;)</code></td>
272      <td>Equivalent to css <code>repeat()</code> function.</td>
273    </tr>
274    <tr>
275      <td><code>Vec&lt;TrackSizingFunction&gt;</code></td>
276      <td><code>evenly_sized_tracks(count:&nbsp;u16)</code></td>
277      <td>Equivalent to CSS <code>repeat(count, minmax(0px, 1fr)</code></td>
278    </tr>
279    <tr>
280      <td rowspan="3"><code>AvailableSpace</code></td>
281      <td><code>auto()</code></td>
282      <td>Generates an <code>Auto</code> variant</td>
283    </tr>
284    <tr>
285      <td><code>min_content()</code></td>
286      <td>Generates an <code>MinContent</code> variant</td>
287    </tr>
288      <tr>
289      <td><code>max_content()</code></td>
290      <td>Generates an <code>MinContent</code> variant</td>
291    </tr>
292    <tr>
293      <td><code>Size&lt;T&gt;</code></td>
294      <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>
295    </tr>
296    <tr>
297      <td><code>Rect&lt;T&gt;</code></td>
298      <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>
299    </tr>
300  </tbody>
301</table>
302
303### Breaking API changes
304
305#### Changes to alignment style types
306
307- `AlignContent` and `JustifyContent` has been merged.
308  - `JustifyContent` is now an alias of `AlignContent` and contains the `Stretch` variant.
309  - This variant will be *ignored* (falling back to `Start`) when applied Flexbox containers. It is valid value for Grid containers.
310- `AlignItems` and `AlignSelf` have been merged.
311  - The `Auto` variant of `AlignSelf` has been removed. You should now use `Option::None` if you wish to specify `AlignSelf::Auto`.
312  - `AlignSelf` is now an alias of `AlignItems`.
313  - `JustifyItems` and `JustifySelf` aliases have been added. These properties have no affect on Flexbox containers, but apply to Grid containers.
314- `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.
315
316#### Strict style types
317
318- New types `LengthPercentage` and `LengthPercentageAuto` have been added.
319  - `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.
320  - `LengthPercentageAuto` is currently identical to `Dimension` but will allow us to expand dimension in future to support values like `MinContent`, `MaxContent` and `FitContent`.
321- 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).
322
323#### Position properties renamed
324
325- 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)
326- 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`.
327
328#### Changes to `LayoutTree`
329
330- Added generic associated type to `LayoutTree` for a `ChildIter`, an iterator on the children of a given node.
331- 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.
332- 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.
333- Added `is_childless` method to `LayoutTree` for querying whether a node has no children.
334
335#### `AvailableSpace` has been moved
336
337The `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.
338
339### Fixes
340
341- Flexbox nodes sized under a min-content constraint now size correctly (#291)
342- Aspect ratio is now applied correctly in many circumstances
343- Absolutely positioned items now apply margins correctly
344- Min/max size are now applied correctly
345- Inset applied incorrectly to relatively positioned flexbox children when both `top` and `bottom` or `left` and `right` were specified (#348)
346- 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)
347
348### Removed
349
350- 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.
351- 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.
352- 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.
353
354## 0.2.2
355
356### Fixes
357
358- Border or padding on the horizontal axis could, in some cases, increase the height of nodes.
359
360## 0.2.1
361
362### Fixes
363
364- 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`.
365- `taffy::compute_layout` has been made public allowing Taffy to be used with custom storage (#263)
366
367## 0.2.0
368
369### New features
370
371#### Flexbox "gap" and `AlignContent::SpaceEvenly`
372
373The [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.
374
375Additionally 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)
376
377#### Debug module and cargo feature
378
379Two debugging features have been added:
380
381- `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.
382- A cargo feature `debug`. This enabled debug logging of the layout computation process itself (this is probably mainly useful for those working taffy itself).
383
384### Performance improvements
385
386A number of performance improvements have landed since taffy 0.1:
387
388- 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%.
389- 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!
390
391#### Benchmarks vs. Taffy 0.1
392
393| Benchmark                                 | Taffy 0.1 | Taffy 0.2 | % change (0.1 -> 0.2) |
394| ---                                       | ---       | ---       | ---                   |
395| wide/1_000 nodes (2-level hierarchy)      | 699.18 µs | 445.01 µs | -36.279%              |
396| wide/10_000 nodes (2-level hierarchy)     | 8.8244 ms | 7.1313 ms | -16.352%              |
397| wide/100_000 nodes (2-level hierarchy)    | 204.48 ms | 242.93 ms | +18.803%              |
398| deep/4000 nodes (12-level hierarchy))     | 5.2320 s  | 2.7363 ms | -99.947%              |
399| deep/10_000 nodes (14-level hierarchy)    | 75.207 s  | 6.9415 ms | -99.991%              |
400| deep/100_000 nodes (17-level hierarchy)   | -         | 102.72 ms | -                     |
401| deep/1_000_000 nodes (20-level hierarchy) | -         | 799.35 ms | -                     |
402
403(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
404
405As 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.
406
407However, 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.
408
409#### Benchmarks vs. [Yoga](https://github.com/facebook/yoga)
410
411Yoga 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.
412
413| Benchmark | Yoga | Taffy 0.2 |
414| --- | --- | --- |
415| yoga/10 nodes (1-level hierarchy) | 45.1670 µs | 33.297 ns |
416| yoga/100 nodes (2-level hierarchy) | 134.1250 µs | 336.53 ns |
417| yoga/1_000 nodes (3-level hierarchy) | 1.2221 ms | 3.8928 µs |
418| yoga/10_000 nodes (4-level hierarchy) | 13.8672 ms | 36.162 µs |
419| yoga/100_000 nodes (5-level hierarchy) | 141.5307 ms | 1.6404 ms |
420
421(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
422
423While 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!
424
425### Breaking API changes
426
427#### Node creation changes
428
429- `taffy::Node` is now unique only to the Taffy instance from which it was created.
430- Renamed `Taffy.new_node(..)` -> `Taffy.new_with_children(..)`
431- Renamed `Taffy.new_leaf()` -> `Taffy.new_leaf_with_measure()`
432- Added `taffy::node::Taffy.new_leaf()` which allows the creation of new leaf-nodes without having to supply a measure function
433
434#### Error handling/representation improvements
435
436- Renamed `taffy::Error` -> `taffy::error::TaffyError`
437- Replaced `taffy::error::InvalidChild` with a new `InvalidChild` variant of `taffy::error::TaffyError`
438- Replaced `taffy::error::InvalidNode` with a new `InvalidNode` variant of `taffy::error::TaffyError`
439- The following method new return `Err(TaffyError::ChildIndexOutOfBounds)` instead of panicking:
440  - `taffy::Taffy::remove_child_at_index`
441  - `taffy::Taffy::replace_child_at_index`
442  - `taffy::Taffy::child_at_index`
443- `Taffy::remove` now returns a `Result<usize, Error>`, to indicate if the operation was sucessful (and if it was, which ID was invalidated).
444
445#### Some uses of `Option<f32>` replaced with a new `AvailableSpace` enum
446
447A new enum `Taffy::layout::AvailableSpace` has been added.
448
449The definition looks like this:
450
451```rust
452/// The amount of space available to a node in a given axis
453pub enum AvailableSpace {
454    /// The amount of space available is the specified number of pixels
455    Definite(f32),
456    /// The amount of space available is indefinite and the node should be laid out under a min-content constraint
457    MinContent,
458    /// The amount of space available is indefinite and the node should be laid out under a max-content constraint
459    MaxContent,
460}
461```
462
463This 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`).
464
465And 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..
466
467#### Builder methods are now `const` where possible
468
469- Several convenience constants have been defined: notably `Style::DEFAULT`
470- `Size<f32>.zero()` is now `Size::<f32>::ZERO`
471- `Point<f32>.zero()` is now  `Point::<f32>::ZERO`
472- `Size::undefined()` is now `Size::NONE`
473
474#### Removals
475
476- 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%).
477- Removed `taffy::number::Number`. Use `Option<f32>` is used instead
478  - the associated public `MinMax` and `OrElse` traits have also been removed; these should never have been public
479- 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).
480
481### Fixes
482
483- Miscellaneous correctness fixes which align our implementation with Chrome:
484
485  - Nodes can only ever have one parent
486  - Fixed rounding of fractional values to follow latest Chrome - values are now rounded the same regardless of their position
487  - Fixed computing free space when using both `flex-grow` and a minimum size
488  - 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)
489  - `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
490- Taffy can now be vendored using `cargo-vendor` (README.md is now included in package).
491
492## 0.1.0
493
494### 0.1.0 Changed
495
496- the `order` field of `Layout` is now public, and describes the relative z-ordering of nodes
497- renamed crate from `stretch2` to `taffy`
498- updated to the latest version of all dependencies to reduce upstream pain caused by duplicate dependencies
499- renamed `stretch::node::Strech` -> `taffy::node::Taffy`
500
501### 0.1.0 Fixed
502
503- fixed feature strategy for `alloc` and `std`: these can now be compiled together, with `std`'s types taking priority
504
505### 0.1.0 Removed
506
507- removed Javascript / Kotlin / Swift bindings
508  - the maintainer team lacks expertise to keep these working
509  - more serious refactors are planned, and this will be challenging to keep working through that process
510  - if you are interested in helping us maintain bindings to other languages, [get in touch](https://github.com/DioxusLabs/taffy/discussions)!
511- 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)
512- removed the `Direction` and `Overflow` structs, and the corresponding `direction` and `overflow` fields from `Style`
513  - these had no effect in the current code base and were actively misleading
514
515## stretch2 0.4.3
516
517This is the final release of `stretch`: migrate to the crate named `taffy` for future fixes and features!
518
519These notes describe the differences between this release and `stretch` 0.3.2, the abandoned crate from which this library was forked.
520
521### Changed
522
523- updated [assorted dependencies](https://github.com/vislyhq/stretch/commit/a6491117379cea52dedc9584d892594a143e8cb0)
524
525### Fixed
526
527- fixed an exponential performance blow-up with deep nesting
528- fixed percent height values, which were using parent width
529- recomputing layout no longer moves children of non-zero-positioned parent
530- fixed broken Swift bindings