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