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