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