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