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