1# Changelog
2
3## 0.6.3
4
5### Fixes
6
7- Block: ignore margin collapsing when computing static position of abspos items (#747)
8
9## 0.6.2
10
11### Fixes
12
13- Fix: clamp indefinite available space by min- and max- size as appropriate (#742)
14
15## 0.6.1
16
17### Fixes
18
19- Fix calculation of `auto-fill`/`auto-fit` repetition count when container has a definite percentage size (#722)
20- Fix min-size style not affecting intrinsic sizes (#723)
21- Fix documentation of dirty and mark_dirty functions (#724)
22- Fix intrinsic size of scroll containers that have a small explicit flex-basis (#728)
23
24## 0.6.0
25
26### Highlights
27
28- The `Style` struct has been "traitified". This supports Taffy's integration in Servo and generally makes Taffy more flexible. The
29  `Style` struct still exists and implements the new traits so existing uses of Taffy will continue to work as before.
30- The `box-sizing` style is supported
31- Computed margins are output in `Layout`
32
33### Fixes
34
35- Fix `print_tree()` when rounding is disabled (#680)
36- Absolute Insets should be resolved against the container size minus border (#666)
37- Fix flooring hypothetical_main_size by computed min size (#689)
38- Fix flex line cross-size determination (#690)
39- Fix panics in the grid algorithm (#691)
40- Fix resolving flexible lengths (WPT css/flexbox-multiline-min-max test) (#692)
41- Fix wrapping when a max main size style is present (#694)
42- Fix case where Taffy allowed margins to collapse through an element when it shouldn't have (#695)
43
44### Added
45
46- Legacy text align (for laying out `<center>` and `<div align="..">`) is supported
47- Add `is_table` for block items (#701)
48- Impl `Debug` and `Clone` for `Cache` (#688)
49- Implement `Debug` and `PartialEq` for tree types (#697)
50
51## 0.5.2
52
53- Fix block stretch sizing (don't always apply stretch sizing to block containers) (#674)
54- Fix computation of intrinsic main size when it depends on a child's known cross size (#673)
55- Fix panic when GridLine 0 is specified (#671)
56- Docs: Document feature flags and scrape examples (#672)
57- Docs: Update cosmic-text example to cosmic-text 0.12 (#670)
58
59## 0.5.1
60
61- Fix: Clamp block item stretch widths by their min and max width (#664)
62- Fix: Auto margin computation in block layout (#663)
63
64## 0.5.0
65
66The changes in 0.5 are relatively small but the new measure function parameter is a breaking change so it requires a minor version bump.
67
68- Added: A `style: &Style` parameter has been added to measure functions.
69- Added: The `MaybeMath`, `MaybeResolve`, and `ResolveOrZero` traits have been made public.
70- Fix: use SizingMode::Inherent when sizing absolute children of flexbox nodes.
71
72## 0.4.4
73
74### Fixes
75
76- Content alignment (`align-content`/`justify-content`) behaviour was updated to match the latest spec (and Chrome 123+) (#635)
77- Ensure that root Flexbox nodes are floored by their padding-border (#651, #655)
78- Use grid area size not available space when applying aspect ratio to grid containers (#656)
79
80## 0.4.3
81
82### Fixes
83
84- Fix compilation error in `evenly_sized_tracks` style helper in recent versions of rustc caused by a change/regression in type
85  inference (#643). Note that 3rd-party code that call style helpers that take an `Into<f32>` parameter may still be affected by this issue,
86  but they should be able to fix on their side by clarifying the type passed in
87
88## 0.4.2
89
90- Fixed: single-line flex-container should clamp the line's cross-size (#638)
91- Reduced binary footprint of Taffy from around 300kb to around 150kb (#636)
92
93## 0.4.1
94
95- Fixed: CSS Grid track sizing not respecting growth limits in some circumstances (#624)
96
97## 0.4.0
98
99### Highlights
100
101- Support for CSS Block layout (`display: block`)
102- Support for the `overflow` property (+ `scrollbar_width` for `overflow: scroll`)
103- Improved measure function API
104- Completely refactored low-level API
105- Simplified module hierarchy (+ most types/functions are now exported from the crate root)
106- Expanded set of examples which better document integration with other layout systems (e.g. text layout)
107- Computed values for `padding` and `border` are now output into the `Layout` struct
108
109### Block layout
110
111Support 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.
112
113### Overflow property
114
115Support 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.
116
117- Overflow is settable indpendently in each axis.
118- `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.
119- `Hidden` and `Scroll` affect layout by changing the automatic minimum size of Flexbox and Grid children
120- `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`.
121
122### Measure function changes
123
124The "measure function" API for integrating Taffy with other measurement systems (such as text layout) has been changed to be more flexible
125and to interact better with borrow checking (you can now borrow external data in your measure function!).
126
127- There are no longer per-node measure functions.
128- There is now a single "global" measure function, and a per-node "context" of a user-defined type
129- The `Taffy` tree is now a generic `TaffyTree<T>` where `T` is the "context" type.
130- The measure function is now called for all leaf nodes (nodes without children). If you wish to maintain compatibility with the previous
131  behaviour then your measure function should return `Size::ZERO` for leaf nodes whose context is `None`.
132
133If you are not using measure functions, then the only change you will need to make is from:
134
135```rust
136let mut tree = Taffy::new();
137```
138
139to
140
141```rust
142let mut tree : TaffyTree<()> = TaffyTree::new();
143```
144
145And generally update any uses of `Taffy` in your codebase to `TaffyTree<()>`.
146
147If you are using measure functions then you will need to make some bigger (but straightforward) changes. The following Taffy 0.3 code:
148
149```rust
150let mut tree = Taffy::new();
151let leaf = tree.new_leaf_with_measure(
152  Style::DEFAULT,
153  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>| Size { width: 100.0, height: 200.0 }
154);
155tree.compute_layout(leaf, Size::MAX_CONTENT);
156```
157
158Should become something like the following with Taffy 0.4:
159
160```rust
161let mut tree : TaffyTree<Size> = TaffyTree::new();
162let leaf = tree.new_leaf_with_context(Style::DEFAULT, Size { width: 100.0, height: 200.0 });
163tree.compute_layout_with_measure(
164  leaf,
165  Size::MAX_CONTENT,
166  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>, node_id: NodeId, node_context: Option<Size>| {
167    node_context.unwrap_or(Size::ZERO)
168  }
169);
170```
171
172Note that:
173
174- 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).
175- If you don't need a context then you can use `()` for the context type
176- As the single "global" measure function passed to `compute_layout_with_measure` only needs to exist for the duration of a single layout run,
177  it can (mutably) borrow data from it's environment
178
179### Low-level API (`LayoutTree` trait) refactor
180
181The low-level API has been completely reworked:
182
183- The `LayoutTree` trait has been split into 5 smaller traits which live in the `taffy::tree:traits` module (along with their associated documentation)
184- The following methods have been removed from split `LayoutTree` traits entirely: `parent`, `is_childless`, `measure_node`, `needs_measure`, and `mark_dirty`.
185- `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`.
186- Support for running each layout algorithm individually on a single node via the following top-level functions:
187  - `compute_flexbox_layout`
188  - `compute_grid_layout`
189  - `compute_block_layout`
190  - `compute_leaf_layout`
191  - `compute_root_layout`
192  - `compute_hidden_layout`
193
194It 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
195improved 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).
196
197### Module hierarchy changes
198
199The 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`.
200
201Specific changes:
202
203- The `math` module has been made private
204- The `axis` module has been merged into the `geometry` module
205- The debug module is no longer public. The `print_tree` function is now accessible under `util`.
206- All types from the `node`, `data`, `layout`, `error` and `cache` modules have been moved to the  the `tree` module.
207- The `layout_flexbox()` function has been removed from the prelude. Use `taffy::compute_flexbox_layout` instead.
208
209### Many APIs have been renamed to replace `points` or `Points` with `length` or `Length`
210
211This new name better describes one-dimensional measure of space in some unspecified unit
212which is often unrelated to the PostScript point or the CSS `pt` unit.
213
214This also removes a misleading similarity with the 2D `Point`,
215whose components can have any unit and are not even necessarily absolute lengths.
216
217Example usage change:
218
219```diff
220 use taffy::prelude::*;
221
222 // …
223
224 let header_node = taffy
225     .new_leaf(
226         Style {
227-            size: Size { width: points(800.0), height: points(100.0) },
228+            size: Size { width: length(800.0), height: length(100.0) },
229             ..Default::default()
230         },
231     ).unwrap();
232```
233
234### Other Changes
235
236- The `Taffy` type was renamed to `TaffyTree` and made generic of a context parameter
237- The Flexbox algorithm has now been moved behind the `flexbox` feature. The `flexbox` feature is enabled by default.
238- The `justify_self` property has been moved behind the `grid` feature.
239- Fixed misspelling: `RunMode::PeformLayout` renamed into `RunMode::PerformLayout` (added missing `r`).
240- `serde` dependency has been made compatible with `no_std` environments
241- `slotmap` dependency has been made compatible with `no_std` environments
242- 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.
243- Added `total_node_count()` method to the `TaffyTree` which returns the total number of nodes in the tree.
244- Added `get_disjoint_node_context_mut()` method to the `TaffyTree`. This can be used to safely get multiple mutable borrows at the same time.
245
246## 0.3.19
247
248### Fixes
249
250- Fix compilation error in `evenly_sized_tracks` style helper in recent versions of rustc caused by a change/regression in type
251  inference (#643). Note that 3rd-party code that call style helpers that take an `Into<f32>` parameter may still be affected by this issue,
252  but they should be able to fix on their side by clarifying the type passed in
253
254## 0.3.18
255
256### Fixes
257
258- Fix computation of Flexbox automatic minimum size when grid or flexbox child has an explicit width/height style set (#576)
259
260## 0.3.17
261
262### Added
263
264- Added `total_node_count` method to the `Taffy` struct. Returns the total number of nodes in the tree.
265
266## 0.3.16
267
268### Fixes
269
270- Improve performance of flexbox columns
271
272## 0.3.15
273
274### Fixes
275
276- Fix justify-content and align-content when free space is negative (content overflows container) (#549) (#551)
277
278## 0.3.14
279
280### Fixes
281
282- 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)
283
284## 0.3.13
285
286### Fixes
287
288- Fix rounding accumulation bug (#521) (Fixes #501 and bevyengine/bevy#8911)
289- Flexbox: pass correct cross-axis available space when computing an item's intrinsic main size (#522)(Fixes bevyengine/bevy#9350)
290- Flexbox: Subtract child margin not parent margin when computing stretch-alignment known size
291- Grid: Make CSS Grid algorithm correctly apply max width/height and available space when it is the root node (#491)
292- Grid: Fix CSS Grid "auto track" / placement bugs #481
293  - Fix divide by zero when using grid_auto_rows/grid_auto_columns with zero negative implicit tracks
294  - Fix over counting of tracks (leading to incorrect container heights) when auto-placing in grids that contain negative implicit tracks.
295  - Fix axis conflation in auto-placement code when grid_auto_flow is column
296  - Fix assignment of auto track sizes when initializing negative implicit tracks
297- Leaf: Apply margins to leaf nodes when computing available space for measure functions
298- Leaf: Reserve space for padding/borders in nodes with measure functions (#497)
299  
300  **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.
301
302### Dependencies
303
304- Upgrade `grid` to `0.10`. This eliminates the transitive dependency on `no-std-compat`.
305
306## 0.3.12
307
308### Fixes
309
310- Fix caching issue when toggling `display:none` on and off
311
312## 0.3.11
313
314### Fixes
315
316- Fix exponential blowup when laying out trees containing nodes with min and max sizes.
317
318## 0.3.10
319
320### Fixes
321
322- Fix sizing of children when the available_space < min_size (#407)
323
324## 0.3.9
325
326### Fixes
327
328- 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)
329
330## 0.3.8
331
332### Fixes
333
334- Fix incorrect min-content size for `flex-wrap: wrap` nodes (bevyengine/bevy#8082)
335
336## 0.3.7
337
338### Fixes
339
340- Fix: Make `padding` and `border` floor node sizes (#372)
341- Fix: Prevent percentages contributing to min-content sizes (#388) (also fixes bevyengine/bevy#8017)
342
343## 0.3.6
344
345### Fixes
346
347- Fix: Ignore `align_content` when `flex_wrap` is set to `nowrap` (#383)
348
349## 0.3.5
350
351### Fixes
352
353- Fix `display: none` when it is set on a flexbox child (#380)
354- Fix `display: none` when it is set on a grid child (#381)
355
356## 0.3.4
357
358### Fixes
359
360- Fix `display: none` when it is set for the only node in the hierarchy (#377)
361
362## 0.3.3
363
364### Added
365
366- 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.
367
368### Fixes
369
370- Fixed rounding algorithm such that it never leaves gaps between adjacent nodes (#369)
371- Fixed compiling with the `grid` feature disabled (#370)
372- Fixed compiling with the `std` feature disabled
373
374## 0.3.2
375
376### Fixes
377
378- Allow partial nested values to be deserialized into a `Style` using the `serde` feature.
379
380## 0.3.1
381
382### Fixes
383
384- The `serde` feature now works when the `grid` feature is enabled
385
386## 0.3.0
387
388### Highlights
389
390- [CSS Grid algorithm support](#new-feature-css-grid)
391- [Style helper functions](#new-feature-style-helpers)
392
393See below for details of breaking changes.
394
395### New Feature: CSS Grid
396
397We 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`.
398
399#### Learning Resources
400
401Taffy 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:
402
403- [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.
404- [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.
405
406#### Supported Features & Properties
407
408In addition to the usual sizing/spacing properties (size, min_size, padding, margin, etc), the following Grid style properties are supported on Grid Containers:
409
410| Property                  | Explanation                                                                                    |
411| ---                       | ---                                                                                            |
412| [`grid-template-columns`] | The track sizing functions of the grid's explicit columns                                      |
413| [`grid-template-rows`]    | The track sizing functions of the grid's explicit rows                                         |
414| [`grid-auto-rows`]        | Track sizing functions for the grid's implicitly generated rows                                |
415| [`grid-auto-columns`]     | Track sizing functions for the grid's implicitly generated columns                             |
416| [`grid-auto-flow`]        | Whether auto-placed items are placed row-wise or column-wise. And sparsely or densely.         |
417| [`gap`]                   | The size of the vertical and horizontal gaps between grid rows/columns                         |
418| [`align-content`]         | Align grid tracks within the container in the inline (horizontal) axis                         |
419| [`justify-content`]       | Align grid tracks within the container in the block (vertical) axis                            |
420| [`align-items`]           | Align the child items within their grid areas in the inline (horizontal) axis                  |
421| [`justify-items`]         | Align the child items within their grid areas in the block (vertical) axis                     |
422
423And the following Grid style properties are supported on Grid Items (children):
424
425| Property                  | Explanation                                                                                    |
426| ---                       | ---                                                                                            |
427| [`grid-row`]              | The (row) grid line the item starts at (or a span)                                             |
428| [`grid-column`]           | The (column) grid line the item end at (or a span)                                             |
429| [`align-self`]            | Align the item within it's grid area in the inline (horizontal) axis. Overrides `align-items`. |
430| [`justify-self`]          | Align the item within it's grid area in the block (vertical) axis. Overrides `justify-items`.  |
431
432[`grid-template-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-columns
433[`grid-template-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-rows
434[`grid-auto-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-rows
435[`grid-auto-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-columns
436[`grid-auto-flow`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-flow
437[`gap`]: https://developer.mozilla.org/en-US/docs/Web/CSS/gap
438[`align-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align_content
439[`justify-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify_content
440[`align-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-items
441[`justify-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-items
442[`grid-row`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-row
443[`grid-column`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-column
444[`align-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-self
445[`justify-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-self
446
447The following properties and features are not currently supported:
448
449- Subgrids
450- Masonry grid layout
451- Named grid lines
452- Named areas: `grid-template-areas` and `grid-area`
453- `grid-template` or `grid` shorthand
454
455#### Example
456
457See [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:
458
459```bash
460cargo run --example grid_holy_grail --features grid
461```
462
463### New Feature: Style Helpers
464
465Ten 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.
466
467For example, instead of:
468
469```rust
470let size : Size<Dimension> = Size { width: Dimension::Points(100.0), height: Dimension::Percent(50.0) };
471```
472
473you can now write
474
475```rust
476let size : Size<Dimension> = Size { width: points(100.0), height: percent(50.0) };
477```
478
479And 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
480
481```rust
482let size : Size<Dimension> = points(100.0);
483```
484
485Available style helpers:
486
487<table>
488  <thead><tr><th>Type(s)</th><th colspan="2">Helpers that work with that type</th></tr></thead>
489  <tbody>
490    <tr>
491      <td rowspan="3"><code>LengthPercentage</code></td>
492      <td><code>zero()</code></td>
493      <td>Generates a <code>Points</code> variant with the value <code>0.0</code></td>
494    </tr>
495    <tr>
496      <td><code>points(val:&nbsp;f32)</code></td>
497      <td>Generates a <code>Points</code> variant with the specified value</td>
498    </tr>
499    <tr>
500      <td><code>percent(val:&nbsp;f32)</code></td>
501      <td>Generates a <code>Percent</code> variant with the specified value.<br />Note that the scale of 0-1 not 0-100.</td>
502    </tr>
503    <tr>
504      <td rowspan="2"><code>LengthPercentageAuto</code><br /><code>Dimension</code></td>
505      <td colspan="2"><i>All helpers from <code>LengthPercentage</code> and...</i></td>
506    </tr>
507    <tr>
508      <td><code>auto()</code></td>
509      <td>Generates an <code>Auto</code> variant</td>
510    </tr>
511    <tr>
512      <td rowspan="3"><code>MinTrackSizingFunction</code></td>
513      <td colspan="2"><i>All helpers from <code>LengthPercentageAuto</code>/<code>Dimension</code> and...</i></td>
514    </tr>
515    <tr>
516      <td><code>min_content()</code></td>
517      <td>Generates an <code>MinContent</code> variant</td>
518    </tr>
519      <tr>
520      <td><code>max_content()</code></td>
521      <td>Generates an <code>MinContent</code> variant</td>
522    </tr>
523    <tr>
524      <td rowspan="3"><code>MaxTrackSizingFunction</code></td>
525      <td colspan="2"><i>All helpers from <code>MinTrackSizingFunction</code> and...</i></td>
526    </tr>
527    <tr>
528      <td><code>fit_content(limit:&nbsp;LengthPercentage)</code></td>
529      <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>
530    </tr>
531      <tr>
532      <td><code>fr(fraction:&nbsp;f32)</code></td>
533      <td>Generates a <code>Fraction</code> (<code>fr</code>) variant with the specified flex fraction </td>
534    </tr>
535    <tr>
536      <td rowspan="3"><code>NonRepeatingTrackSizingFunction</code></td>
537      <td colspan="2"><i>All helpers from <code>MaxTrackSizingFunction</code> and...</i></td>
538    </tr>
539    <tr>
540      <td><code>minmax(min: MinTrackSizingFunction, max: MaxTrackSizingFunction)</code></td>
541      <td>Equivalent to CSS <code>minmax()</code> function.</td>
542    </tr>
543    <tr>
544      <td><code>flex(fraction:&nbsp;f32)</code></td>
545      <td>Equivalent to CSS <code>minmax(0px, 1fr)</code>. This is likely what you want if you want evenly sized rows/columns.</td>
546    </tr>
547    <tr>
548      <td rowspan="2"><code>TrackSizingFunction</code></td>
549      <td colspan="2"><i>All helpers from <code>NonRepeatingTrackSizingFunction</code> and...</i></td>
550    </tr>
551    <tr>
552      <td><code>repeat(rep: GridTrackRepetition, tracks: Vec&lt;TrackSizingFunction&gt;)</code></td>
553      <td>Equivalent to css <code>repeat()</code> function.</td>
554    </tr>
555    <tr>
556      <td><code>Vec&lt;TrackSizingFunction&gt;</code></td>
557      <td><code>evenly_sized_tracks(count:&nbsp;u16)</code></td>
558      <td>Equivalent to CSS <code>repeat(count, minmax(0px, 1fr)</code></td>
559    </tr>
560    <tr>
561      <td rowspan="3"><code>AvailableSpace</code></td>
562      <td><code>auto()</code></td>
563      <td>Generates an <code>Auto</code> variant</td>
564    </tr>
565    <tr>
566      <td><code>min_content()</code></td>
567      <td>Generates an <code>MinContent</code> variant</td>
568    </tr>
569      <tr>
570      <td><code>max_content()</code></td>
571      <td>Generates an <code>MinContent</code> variant</td>
572    </tr>
573    <tr>
574      <td><code>Size&lt;T&gt;</code></td>
575      <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>
576    </tr>
577    <tr>
578      <td><code>Rect&lt;T&gt;</code></td>
579      <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>
580    </tr>
581  </tbody>
582</table>
583
584### Breaking API changes
585
586#### Changes to alignment style types
587
588- `AlignContent` and `JustifyContent` has been merged.
589  - `JustifyContent` is now an alias of `AlignContent` and contains the `Stretch` variant.
590  - This variant will be *ignored* (falling back to `Start`) when applied Flexbox containers. It is valid value for Grid containers.
591- `AlignItems` and `AlignSelf` have been merged.
592  - The `Auto` variant of `AlignSelf` has been removed. You should now use `Option::None` if you wish to specify `AlignSelf::Auto`.
593  - `AlignSelf` is now an alias of `AlignItems`.
594  - `JustifyItems` and `JustifySelf` aliases have been added. These properties have no affect on Flexbox containers, but apply to Grid containers.
595- `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.
596
597#### Strict style types
598
599- New types `LengthPercentage` and `LengthPercentageAuto` have been added.
600  - `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.
601  - `LengthPercentageAuto` is currently identical to `Dimension` but will allow us to expand dimension in future to support values like `MinContent`, `MaxContent` and `FitContent`.
602- 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).
603
604#### Position properties renamed
605
606- 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)
607- 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`.
608
609#### Changes to `LayoutTree`
610
611- Added generic associated type to `LayoutTree` for a `ChildIter`, an iterator on the children of a given node.
612- 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.
613- 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.
614- Added `is_childless` method to `LayoutTree` for querying whether a node has no children.
615
616#### `AvailableSpace` has been moved
617
618The `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.
619
620### Fixes
621
622- Flexbox nodes sized under a min-content constraint now size correctly (#291)
623- Aspect ratio is now applied correctly in many circumstances
624- Absolutely positioned items now apply margins correctly
625- Min/max size are now applied correctly
626- Inset applied incorrectly to relatively positioned flexbox children when both `top` and `bottom` or `left` and `right` were specified (#348)
627- 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)
628
629### Removed
630
631- 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.
632- 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.
633- 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.
634
635## 0.2.2
636
637### Fixes
638
639- Border or padding on the horizontal axis could, in some cases, increase the height of nodes.
640
641## 0.2.1
642
643### Fixes
644
645- 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`.
646- `taffy::compute_layout` has been made public allowing Taffy to be used with custom storage (#263)
647
648## 0.2.0
649
650### New features
651
652#### Flexbox "gap" and `AlignContent::SpaceEvenly`
653
654The [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.
655
656Additionally 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)
657
658#### Debug module and cargo feature
659
660Two debugging features have been added:
661
662- `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.
663- A cargo feature `debug`. This enabled debug logging of the layout computation process itself (this is probably mainly useful for those working taffy itself).
664
665### Performance improvements
666
667A number of performance improvements have landed since taffy 0.1:
668
669- 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%.
670- 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!
671
672#### Benchmarks vs. Taffy 0.1
673
674| Benchmark                                 | Taffy 0.1 | Taffy 0.2 | % change (0.1 -> 0.2) |
675| ---                                       | ---       | ---       | ---                   |
676| wide/1_000 nodes (2-level hierarchy)      | 699.18 µs | 445.01 µs | -36.279%              |
677| wide/10_000 nodes (2-level hierarchy)     | 8.8244 ms | 7.1313 ms | -16.352%              |
678| wide/100_000 nodes (2-level hierarchy)    | 204.48 ms | 242.93 ms | +18.803%              |
679| deep/4000 nodes (12-level hierarchy))     | 5.2320 s  | 2.7363 ms | -99.947%              |
680| deep/10_000 nodes (14-level hierarchy)    | 75.207 s  | 6.9415 ms | -99.991%              |
681| deep/100_000 nodes (17-level hierarchy)   | -         | 102.72 ms | -                     |
682| deep/1_000_000 nodes (20-level hierarchy) | -         | 799.35 ms | -                     |
683
684(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
685
686As 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.
687
688However, 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.
689
690#### Benchmarks vs. [Yoga](https://github.com/facebook/yoga)
691
692Yoga 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.
693
694| Benchmark | Yoga | Taffy 0.2 |
695| --- | --- | --- |
696| yoga/10 nodes (1-level hierarchy) | 45.1670 µs | 33.297 ns |
697| yoga/100 nodes (2-level hierarchy) | 134.1250 µs | 336.53 ns |
698| yoga/1_000 nodes (3-level hierarchy) | 1.2221 ms | 3.8928 µs |
699| yoga/10_000 nodes (4-level hierarchy) | 13.8672 ms | 36.162 µs |
700| yoga/100_000 nodes (5-level hierarchy) | 141.5307 ms | 1.6404 ms |
701
702(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
703
704While 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!
705
706### Breaking API changes
707
708#### Node creation changes
709
710- `taffy::Node` is now unique only to the Taffy instance from which it was created.
711- Renamed `Taffy.new_node(..)` -> `Taffy.new_with_children(..)`
712- Renamed `Taffy.new_leaf()` -> `Taffy.new_leaf_with_measure()`
713- Added `taffy::node::Taffy.new_leaf()` which allows the creation of new leaf-nodes without having to supply a measure function
714
715#### Error handling/representation improvements
716
717- Renamed `taffy::Error` -> `taffy::error::TaffyError`
718- Replaced `taffy::error::InvalidChild` with a new `InvalidChild` variant of `taffy::error::TaffyError`
719- Replaced `taffy::error::InvalidNode` with a new `InvalidNode` variant of `taffy::error::TaffyError`
720- The following method new return `Err(TaffyError::ChildIndexOutOfBounds)` instead of panicking:
721  - `taffy::Taffy::remove_child_at_index`
722  - `taffy::Taffy::replace_child_at_index`
723  - `taffy::Taffy::child_at_index`
724- `Taffy::remove` now returns a `Result<usize, Error>`, to indicate if the operation was successful (and if it was, which ID was invalidated).
725
726#### Some uses of `Option<f32>` replaced with a new `AvailableSpace` enum
727
728A new enum `Taffy::layout::AvailableSpace` has been added.
729
730The definition looks like this:
731
732```rust
733/// The amount of space available to a node in a given axis
734pub enum AvailableSpace {
735    /// The amount of space available is the specified number of pixels
736    Definite(f32),
737    /// The amount of space available is indefinite and the node should be laid out under a min-content constraint
738    MinContent,
739    /// The amount of space available is indefinite and the node should be laid out under a max-content constraint
740    MaxContent,
741}
742```
743
744This 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`).
745
746And 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..
747
748#### Builder methods are now `const` where possible
749
750- Several convenience constants have been defined: notably `Style::DEFAULT`
751- `Size<f32>.zero()` is now `Size::<f32>::ZERO`
752- `Point<f32>.zero()` is now  `Point::<f32>::ZERO`
753- `Size::undefined()` is now `Size::NONE`
754
755#### Removals
756
757- 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%).
758- Removed `taffy::number::Number`. Use `Option<f32>` is used instead
759  - the associated public `MinMax` and `OrElse` traits have also been removed; these should never have been public
760- 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).
761
762### Fixes
763
764- Miscellaneous correctness fixes which align our implementation with Chrome:
765
766  - Nodes can only ever have one parent
767  - Fixed rounding of fractional values to follow latest Chrome - values are now rounded the same regardless of their position
768  - Fixed computing free space when using both `flex-grow` and a minimum size
769  - 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)
770  - `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
771- Taffy can now be vendored using `cargo-vendor` (README.md is now included in package).
772
773## 0.1.0
774
775### 0.1.0 Changed
776
777- the `order` field of `Layout` is now public, and describes the relative z-ordering of nodes
778- renamed crate from `stretch2` to `taffy`
779- updated to the latest version of all dependencies to reduce upstream pain caused by duplicate dependencies
780- renamed `stretch::node::Stretch` -> `taffy::node::Taffy`
781
782### 0.1.0 Fixed
783
784- fixed feature strategy for `alloc` and `std`: these can now be compiled together, with `std`'s types taking priority
785
786### 0.1.0 Removed
787
788- removed Javascript / Kotlin / Swift bindings
789  - the maintainer team lacks expertise to keep these working
790  - more serious refactors are planned, and this will be challenging to keep working through that process
791  - if you are interested in helping us maintain bindings to other languages, [get in touch](https://github.com/DioxusLabs/taffy/discussions)!
792- 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)
793- removed the `Direction` and `Overflow` structs, and the corresponding `direction` and `overflow` fields from `Style`
794  - these had no effect in the current code base and were actively misleading
795
796## stretch2 0.4.3
797
798This is the final release of `stretch`: migrate to the crate named `taffy` for future fixes and features!
799
800These notes describe the differences between this release and `stretch` 0.3.2, the abandoned crate from which this library was forked.
801
802### Changed
803
804- updated [assorted dependencies](https://github.com/vislyhq/stretch/commit/a6491117379cea52dedc9584d892594a143e8cb0)
805
806### Fixed
807
808- fixed an exponential performance blow-up with deep nesting
809- fixed percent height values, which were using parent width
810- recomputing layout no longer moves children of non-zero-positioned parent
811- fixed broken Swift bindings