1# Release Notes
2
3## 0.3.1
4
5### Fixes
6
7- The `serde` feature now works when the `grid` feature is enabled
8
9## 0.3.0
10
11### Highlights
12
13- [CSS Grid algorithm support](#new-feature-css-grid)
14- [Style helper functions](#new-feature-style-helpers)
15
16See below for details of breaking changes.
17
18### New Feature: CSS Grid
19
20We 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`.
21
22#### Learning Resources
23
24Taffy 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:
25
26- [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.
27- [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 comphrehensive written explanation of the different Grid propertie and how they work.
28
29#### Supported Features & Properties
30
31In addition to the usual sizing/spacing proerties (size, min_size, padding, margin, etc), the following Grid style properties are supported on Grid Containers:
32
33| Property | Explanation |
34| --- | --- |
35| [`grid-template-columns`] | The track sizing functions of the grid's explicit columns |
36| [`grid-template-rows`] | The track sizing functions of the grid's explicit rows |
37| [`grid-auto-rows`] | Track sizing functions for the grid's implicitly generated rows |
38| [`grid-auto-columns`] | Track sizing functions for the grid's implicitly generated columns |
39| [`grid-auto-flow`] | Whether auto-placed items are placed row-wise or column-wise. And sparsely or densely. |
40| [`gap`] | The size of the vertical and horizontal gaps between grid rows/columns |
41| [`align-content`] | Align grid tracks within the container in the inline (horizontal) axis |
42| [`justify-content`] | Align grid tracks within the container in the block (vertical) axis |
43| [`align-items`] | Align the child items within their grid areas in the inline (horizontal) axis |
44| [`justify-items`] | Align the child items within their grid areas in the block (vertical) axis |
45
46And the following Grid style properties are supported on Grid Items (children):
47
48| Property | Explanation |
49| --- | --- |
50| [`grid-row`] | The (row) grid line the item starts at (or a span) |
51| [`grid-column`] | The (column) grid line the item end at (or a span) |
52| [`align-self`] | Align the item within it's grid area in the inline (horizontal) axis. Overrides `align-items`. |
53| [`justify-self`] | Align the item within it's grid area in the block (vertical) axis. Overrides `justify-items`. |
54
55[`grid-template-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-columns
56[`grid-template-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-rows
57[`grid-auto-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-rows
58[`grid-auto-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-columns
59[`grid-auto-flow`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-flow
60[`gap`]: https://developer.mozilla.org/en-US/docs/Web/CSS/gap
61[`align-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align_content
62[`justify-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify_content
63[`align-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-items
64[`justify-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-items
65[`grid-row`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-row
66[`grid-column`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-column
67[`align-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-self
68[`justify-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-self
69
70The following properties and features are not currently supported:
71
72- Subgrids
73- Masonry grid layout
74- Named grid lines
75- Named areas: `grid-template-areas` and `grid-area`
76- `grid-template` or `grid` shorthand
77
78#### Example
79
80See [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:
81
82```bash
83cargo run --example grid_holy_grail --features grid
84```
85
86### New Feature: Style Helpers
87
88Ten 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.
89
90For example, instead of:
91
92```rust
93let size : Size<Dimension> = Size { width: Dimension::Points(100.0), height: Dimension::Percent(50.0) };
94```
95
96you can now write
97
98```rust
99let size : Size<Dimension> = Size { width: points(100.0), height: percent(50.0) };
100```
101
102And 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
103
104```rust
105let size : Size<Dimension> = points(100.0);
106```
107
108Available style helpers:
109
110<table>
111 <thead><tr><th>Type(s)</th><th colspan="2">Helpers that work with that type</th></tr></thead>
112 <tbody>
113 <tr>
114 <td rowspan="3"><code>LengthPercentage</code></td>
115 <td><code>zero()</code></td>
116 <td>Generates a <code>Points</code> variant with the value <code>0.0</code></td>
117 </tr>
118 <tr>
119 <td><code>points(val: f32)</code></td>
120 <td>Generates a <code>Points</code> variant with the specified value</td>
121 </tr>
122 <tr>
123 <td><code>percent(val: f32)</code></td>
124 <td>Generates a <code>Percent</code> variant with the specified value.<br />Note that the scale of 0-1 not 0-100.</td>
125 </tr>
126 <tr>
127 <td rowspan="2"><code>LengthPercentageAuto</code><br /><code>Dimension</code></td>
128 <td colspan="2"><i>All helpers from <code>LengthPercentage</code> and...</i></td>
129 </tr>
130 <tr>
131 <td><code>auto()</code></td>
132 <td>Generates an <code>Auto</code> variant</td>
133 </tr>
134 <tr>
135 <td rowspan="3"><code>MinTrackSizingFunction</code></td>
136 <td colspan="2"><i>All helpers from <code>LengthPercentageAuto</code>/<code>Dimension</code> and...</i></td>
137 </tr>
138 <tr>
139 <td><code>min_content()</code></td>
140 <td>Generates an <code>MinContent</code> variant</td>
141 </tr>
142 <tr>
143 <td><code>max_content()</code></td>
144 <td>Generates an <code>MinContent</code> variant</td>
145 </tr>
146 <tr>
147 <td rowspan="3"><code>MaxTrackSizingFunction</code></td>
148 <td colspan="2"><i>All helpers from <code>MinTrackSizingFunction</code> and...</i></td>
149 </tr>
150 <tr>
151 <td><code>fit_content(limit: LengthPercentage)</code></td>
152 <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>
153 </tr>
154 <tr>
155 <td><code>fr(fraction: f32)</code></td>
156 <td>Generates a <code>Fraction</code> (<code>fr</code>) variant with the specified flex fraction </td>
157 </tr>
158 <tr>
159 <td rowspan="3"><code>NonRepeatingTrackSizingFunction</code></td>
160 <td colspan="2"><i>All helpers from <code>MaxTrackSizingFunction</code> and...</i></td>
161 </tr>
162 <tr>
163 <td><code>minmax(min: MinTrackSizingFunction, max: MaxTrackSizingFunction)</code></td>
164 <td>Equivalent to CSS <code>minmax()</code> function.</td>
165 </tr>
166 <tr>
167 <td><code>flex(fraction: f32)</code></td>
168 <td>Equivalent to CSS <code>minmax(0px, 1fr)</code>. This is likely what you want if you want evenly sized rows/columns.</td>
169 </tr>
170 <tr>
171 <td rowspan="2"><code>TrackSizingFunction</code></td>
172 <td colspan="2"><i>All helpers from <code>NonRepeatingTrackSizingFunction</code> and...</i></td>
173 </tr>
174 <tr>
175 <td><code>repeat(rep: GridTrackRepetition, tracks: Vec<TrackSizingFunction>)</code></td>
176 <td>Equivalent to css <code>repeat()</code> function.</td>
177 </tr>
178 <tr>
179 <td><code>Vec<TrackSizingFunction></code></td>
180 <td><code>evenly_sized_tracks(count: u16)</code></td>
181 <td>Equivalent to CSS <code>repeat(count, minmax(0px, 1fr)</code></td>
182 </tr>
183 <tr>
184 <td rowspan="3"><code>AvailableSpace</code></td>
185 <td><code>auto()</code></td>
186 <td>Generates an <code>Auto</code> variant</td>
187 </tr>
188 <tr>
189 <td><code>min_content()</code></td>
190 <td>Generates an <code>MinContent</code> variant</td>
191 </tr>
192 <tr>
193 <td><code>max_content()</code></td>
194 <td>Generates an <code>MinContent</code> variant</td>
195 </tr>
196 <tr>
197 <td><code>Size<T></code></td>
198 <td colspan="2">Any helper that works for <code>T</code> will also work for <code>Size<T></code> and will set both <code>width</code> and <code>height</code> to that value</td>
199 </tr>
200 <tr>
201 <td><code>Rect<T></code></td>
202 <td colspan="2">Any helper that works for <code>T</code> will also work for <code>Rect<T></code> and will set <code>top</code>, <code>left</code>, <code>bottom</code>, and <code>right</code> to that value</td>
203 </tr>
204 </tbody>
205</table>
206
207### Breaking API changes
208
209#### Changes to alignment style types
210
211- `AlignContent` and `JustifyContent` has been merged.
212 - `JustifyContent` is now an alias of `AlignContent` and contains the `Stretch` variant.
213 - This variant will be *ignored* (falling back to `Start`) when applied Flexbox containers. It is valid value for Grid containers.
214- `AlignItems` and `AlignSelf` have been merged.
215 - The `Auto` variant of `AlignSelf` has been removed. You should now use `Option::None` if you wish to specify `AlignSelf::Auto`.
216 - `AlignSelf` is now an alias of `AlignItems`.
217 - `JustifyItems` and `JustifySelf` aliases have been added. These properties have no affect on Flexbox containers, but apply to Grid containers.
218- `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.
219
220#### Strict style types
221
222- New types `LengthPercentage` and `LengthPercentageAuto` have been added.
223 - `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.
224 - `LengthPercentageAuto` is currently identical to `Dimension` but will allow us to expand dimension in future to support values like `MinContent`, `MaxContent` and `FitContent`.
225- 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).
226
227#### Position properties renamed
228
229- 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)
230- 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`.
231
232#### Changes to `LayoutTree`
233
234- Added generic associated type to `LayoutTree` for a `ChildIter`, an iterator on the children of a given node.
235- 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.
236- 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.
237- Added `is_childless` method to `LayoutTree` for querying whether a node has no children.
238
239#### `AvailableSpace` has been moved
240
241The `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.
242
243### Fixes
244
245- Flexbox nodes sized under a min-content constraint now size correctly (#291)
246- Aspect ratio is now applied correctly in many circumstances
247- Absolutely positioned items now apply margins correctly
248- Min/max size are now applied correctly
249- Inset applied incorrectly to relatively positioned flexbox children when both `top` and `bottom` or `left` and `right` were specified (#348)
250- 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)
251
252### Removed
253
254- 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.
255- 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.
256- 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.
257
258## 0.2.2
259
260### Fixes
261
262- Border or padding on the horizontal axis could, in some cases, increase the height of nodes.
263
264## 0.2.1
265
266### Fixes
267
268- 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`.
269- `taffy::compute_layout` has been made public allowing Taffy to be used with custom storage (#263)
270
271## 0.2.0
272
273### New features
274
275#### Flexbox "gap" and `AlignContent::SpaceEvenly`
276
277The [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.
278
279Additionally 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)
280
281#### Debug module and cargo feature
282
283Two debugging features have been added:
284
285- `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.
286- A cargo feature `debug`. This enabled debug logging of the layout computation process itself (this is probably mainly useful for those working taffy itself).
287
288### Performance improvements
289
290A number of performance improvements have landed since taffy 0.1:
291
292- 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%.
293- 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 chache slots to better match the actual usage patterns of the flexbox layout algorithm. This had a particularly dramatic effect on deep hierachies (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!
294
295#### Benchmarks vs. Taffy 0.1
296
297| Benchmark | Taffy 0.1 | Taffy 0.2 | % change (0.1 -> 0.2) |
298| --- | --- | --- | --- |
299| wide/1_000 nodes (2-level hierarchy) | 699.18 µs | 445.01 µs | -36.279% |
300| wide/10_000 nodes (2-level hierarchy) | 8.8244 ms | 7.1313 ms | -16.352% |
301| wide/100_000 nodes (2-level hierarchy) | 204.48 ms | 242.93 ms | +18.803% |
302| deep/4000 nodes (12-level hierarchy)) | 5.2320 s | 2.7363 ms | -99.947% |
303| deep/10_000 nodes (14-level hierarchy) | 75.207 s | 6.9415 ms | -99.991% |
304| deep/100_000 nodes (17-level hierarchy) | - | 102.72 ms | - |
305| deep/1_000_000 nodes (20-level hierarchy) | - | 799.35 ms | - |
306
307(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
308
309As 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.
310
311However, in the "deep" benchmarks we see dramatic improvements. The previous version of Taffy suffered from exponential blowup in the case of deeply nested hierachies. This has resulted in somewhat silly improvements like the 10,000 node (14-level) hierachy 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.
312
313#### Benchmarks vs. [Yoga](https://github.com/facebook/yoga)
314
315Yoga 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.
316
317| Benchmark | Yoga | Taffy 0.2 |
318| --- | --- | --- |
319| yoga/10 nodes (1-level hierarchy) | 45.1670 µs | 33.297 ns |
320| yoga/100 nodes (2-level hierarchy) | 134.1250 µs | 336.53 ns |
321| yoga/1_000 nodes (3-level hierarchy) | 1.2221 ms | 3.8928 µs |
322| yoga/10_000 nodes (4-level hierarchy) | 13.8672 ms | 36.162 µs |
323| yoga/100_000 nodes (5-level hierarchy) | 141.5307 ms | 1.6404 ms |
324
325(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
326
327While 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!
328
329### Breaking API changes
330
331#### Node creation changes
332
333- `taffy::Node` is now unique only to the Taffy instance from which it was created.
334- Renamed `Taffy.new_node(..)` -> `Taffy.new_with_children(..)`
335- Renamed `Taffy.new_leaf()` -> `Taffy.new_leaf_with_measure()`
336- Added `taffy::node::Taffy.new_leaf()` which allows the creation of new leaf-nodes without having to supply a measure function
337
338#### Error handling/representation improvements
339
340- Renamed `taffy::Error` -> `taffy::error::TaffyError`
341- Replaced `taffy::error::InvalidChild` with a new `InvalidChild` variant of `taffy::error::TaffyError`
342- Replaced `taffy::error::InvalidNode` with a new `InvalidNode` variant of `taffy::error::TaffyError`
343- The following method new return `Err(TaffyError::ChildIndexOutOfBounds)` instead of panicking:
344 - `taffy::Taffy::remove_child_at_index`
345 - `taffy::Taffy::replace_child_at_index`
346 - `taffy::Taffy::child_at_index`
347- `Taffy::remove` now returns a `Result<usize, Error>`, to indicate if the operation was sucessful (and if it was, which ID was invalidated).
348
349#### Some uses of `Option<f32>` replaced with a new `AvailableSpace` enum
350
351A new enum `Taffy::layout::AvailableSpace` has been added.
352
353The definition looks like this:
354
355```rust
356/// The amount of space available to a node in a given axis
357pub enum AvailableSpace {
358 /// The amount of space available is the specified number of pixels
359 Definite(f32),
360 /// The amount of space available is indefinite and the node should be laid out under a min-content constraint
361 MinContent,
362 /// The amount of space available is indefinite and the node should be laid out under a max-content constraint
363 MaxContent,
364}
365```
366
367This 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`).
368
369And 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..
370
371#### Builder methods are now `const` where possible
372
373- Several convenience constants have been defined: notably `Style::DEFAULT`
374- `Size<f32>.zero()` is now `Size::<f32>::ZERO`
375- `Point<f32>.zero()` is now `Point::<f32>::ZERO`
376- `Size::undefined()` is now `Size::NONE`
377
378#### Removals
379
380- 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%).
381- Removed `taffy::number::Number`. Use `Option<f32>` is used instead
382 - the associated public `MinMax` and `OrElse` traits have also been removed; these should never have been public
383- 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).
384
385### Fixes
386
387- Miscellaneous correctness fixes which align our implementation with Chrome:
388
389 - Nodes can only ever have one parent
390 - Fixed rounding of fractional values to follow latest Chrome - values are now rounded the same regardless of their position
391 - Fixed computing free space when using both `flex-grow` and a minimum size
392 - 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)
393 - `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
394- Taffy can now be vendored using `cargo-vendor` (README.md is now included in package).
395
396## 0.1.0
397
398### 0.1.0 Changed
399
400- the `order` field of `Layout` is now public, and describes the relative z-ordering of nodes
401- renamed crate from `stretch2` to `taffy`
402- updated to the latest version of all dependencies to reduce upstream pain caused by duplicate dependencies
403- renamed `stretch::node::Strech` -> `taffy::node::Taffy`
404
405### 0.1.0 Fixed
406
407- fixed feature strategy for `alloc` and `std`: these can now be compiled together, with `std`'s types taking priority
408
409### 0.1.0 Removed
410
411- removed Javascript / Kotlin / Swift bindings
412 - the maintainer team lacks expertise to keep these working
413 - more serious refactors are planned, and this will be challenging to keep working through that process
414 - if you are interested in helping us maintain bindings to other languages, [get in touch](https://github.com/DioxusLabs/taffy/discussions)!
415- 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)
416- removed the `Direction` and `Overflow` structs, and the corresponding `direction` and `overflow` fields from `Style`
417 - these had no effect in the current code base and were actively misleading
418
419## stretch2 0.4.3
420
421This is the final release of `stretch`: migrate to the crate named `taffy` for future fixes and features!
422
423These notes describe the differences between this release and `stretch` 0.3.2, the abandoned crate from which this library was forked.
424
425### Changed
426
427- updated [assorted dependencies](https://github.com/vislyhq/stretch/commit/a6491117379cea52dedc9584d892594a143e8cb0)
428
429### Fixed
430
431- fixed an exponential performance blow-up with deep nesting
432- fixed percent height values, which were using parent width
433- recomputing layout no longer moves children of non-zero-positioned parent
434- fixed broken Swift bindings
RELEASES.md
Release Notes
0.3.1
Fixes
- The
serde feature now works when the grid feature is enabled
0.3.0
Highlights
See below for details of breaking changes.
New Feature: CSS Grid
We 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.
Learning Resources
Taffy 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:
- CSS Grid Garden. This is an interactive tutorial/game that allows you to learn the essential parts of CSS Grid in a fun engaging way.
- A Complete Guide To CSS Grid by CSS Tricks. This is detailed guide with illustrations and comphrehensive written explanation of the different Grid propertie and how they work.
Supported Features & Properties
In addition to the usual sizing/spacing proerties (size, min_size, padding, margin, etc), the following Grid style properties are supported on Grid Containers:
| Property | Explanation |
grid-template-columns | The track sizing functions of the grid's explicit columns |
grid-template-rows | The track sizing functions of the grid's explicit rows |
grid-auto-rows | Track sizing functions for the grid's implicitly generated rows |
grid-auto-columns | Track sizing functions for the grid's implicitly generated columns |
grid-auto-flow | Whether auto-placed items are placed row-wise or column-wise. And sparsely or densely. |
gap | The size of the vertical and horizontal gaps between grid rows/columns |
align-content | Align grid tracks within the container in the inline (horizontal) axis |
justify-content | Align grid tracks within the container in the block (vertical) axis |
align-items | Align the child items within their grid areas in the inline (horizontal) axis |
justify-items | Align the child items within their grid areas in the block (vertical) axis |
And the following Grid style properties are supported on Grid Items (children):
| Property | Explanation |
grid-row | The (row) grid line the item starts at (or a span) |
grid-column | The (column) grid line the item end at (or a span) |
align-self | Align the item within it's grid area in the inline (horizontal) axis. Overrides align-items. |
justify-self | Align the item within it's grid area in the block (vertical) axis. Overrides justify-items. |
The following properties and features are not currently supported:
- Subgrids
- Masonry grid layout
- Named grid lines
- Named areas:
grid-template-areas and grid-area
grid-template or grid shorthand
Example
See examples/grid_holy_grail.rs for an example using Taffy to implement the so-called Holy Grail Layout. If you want to run this example, the don't forget the enable the CSS Grid cargo feature:
cargo run --example grid_holy_grail --features grid
New Feature: Style Helpers
Ten 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.
For example, instead of:
let size : Size<Dimension> = Size { width: Dimension::Points(100.0), height: Dimension::Percent(50.0) };
you can now write
let size : Size<Dimension> = Size { width: points(100.0), height: percent(50.0) };
And 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
let size : Size<Dimension> = points(100.0);
Available style helpers:
<table>
<thead><tr><th>Type(s)</th><th colspan="2">Helpers that work with that type</th></tr></thead>
<tbody>
<tr>
<td rowspan="3"><code>LengthPercentage</code></td>
<td><code>zero()</code></td>
<td>Generates a <code>Points</code> variant with the value <code>0.0</code></td>
</tr>
<tr>
<td><code>points(val: f32)</code></td>
<td>Generates a <code>Points</code> variant with the specified value</td>
</tr>
<tr>
<td><code>percent(val: f32)</code></td>
<td>Generates a <code>Percent</code> variant with the specified value.<br />Note that the scale of 0-1 not 0-100.</td>
</tr>
<tr>
<td rowspan="2"><code>LengthPercentageAuto</code><br /><code>Dimension</code></td>
<td colspan="2"><i>All helpers from <code>LengthPercentage</code> and...</i></td>
</tr>
<tr>
<td><code>auto()</code></td>
<td>Generates an <code>Auto</code> variant</td>
</tr>
<tr>
<td rowspan="3"><code>MinTrackSizingFunction</code></td>
<td colspan="2"><i>All helpers from <code>LengthPercentageAuto</code>/<code>Dimension</code> and...</i></td>
</tr>
<tr>
<td><code>min_content()</code></td>
<td>Generates an <code>MinContent</code> variant</td>
</tr>
<tr>
<td><code>max_content()</code></td>
<td>Generates an <code>MinContent</code> variant</td>
</tr>
<tr>
<td rowspan="3"><code>MaxTrackSizingFunction</code></td>
<td colspan="2"><i>All helpers from <code>MinTrackSizingFunction</code> and...</i></td>
</tr>
<tr>
<td><code>fit_content(limit: LengthPercentage)</code></td>
<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>
</tr>
<tr>
<td><code>fr(fraction: f32)</code></td>
<td>Generates a <code>Fraction</code> (<code>fr</code>) variant with the specified flex fraction </td>
</tr>
<tr>
<td rowspan="3"><code>NonRepeatingTrackSizingFunction</code></td>
<td colspan="2"><i>All helpers from <code>MaxTrackSizingFunction</code> and...</i></td>
</tr>
<tr>
<td><code>minmax(min: MinTrackSizingFunction, max: MaxTrackSizingFunction)</code></td>
<td>Equivalent to CSS <code>minmax()</code> function.</td>
</tr>
<tr>
<td><code>flex(fraction: f32)</code></td>
<td>Equivalent to CSS <code>minmax(0px, 1fr)</code>. This is likely what you want if you want evenly sized rows/columns.</td>
</tr>
<tr>
<td rowspan="2"><code>TrackSizingFunction</code></td>
<td colspan="2"><i>All helpers from <code>NonRepeatingTrackSizingFunction</code> and...</i></td>
</tr>
<tr>
<td><code>repeat(rep: GridTrackRepetition, tracks: Vec<TrackSizingFunction>)</code></td>
<td>Equivalent to css <code>repeat()</code> function.</td>
</tr>
<tr>
<td><code>Vec<TrackSizingFunction></code></td>
<td><code>evenly_sized_tracks(count: u16)</code></td>
<td>Equivalent to CSS <code>repeat(count, minmax(0px, 1fr)</code></td>
</tr>
<tr>
<td rowspan="3"><code>AvailableSpace</code></td>
<td><code>auto()</code></td>
<td>Generates an <code>Auto</code> variant</td>
</tr>
<tr>
<td><code>min_content()</code></td>
<td>Generates an <code>MinContent</code> variant</td>
</tr>
<tr>
<td><code>max_content()</code></td>
<td>Generates an <code>MinContent</code> variant</td>
</tr>
<tr>
<td><code>Size<T></code></td>
<td colspan="2">Any helper that works for <code>T</code> will also work for <code>Size<T></code> and will set both <code>width</code> and <code>height</code> to that value</td>
</tr>
<tr>
<td><code>Rect<T></code></td>
<td colspan="2">Any helper that works for <code>T</code> will also work for <code>Rect<T></code> and will set <code>top</code>, <code>left</code>, <code>bottom</code>, and <code>right</code> to that value</td>
</tr>
</tbody>
</table>
Breaking API changes
Changes to alignment style types
AlignContent and JustifyContent has been merged.
JustifyContent is now an alias of AlignContent and contains the Stretch variant.
- This variant will be ignored (falling back to
Start) when applied Flexbox containers. It is valid value for Grid containers.
AlignItems and AlignSelf have been merged.
- The
Auto variant of AlignSelf has been removed. You should now use Option::None if you wish to specify AlignSelf::Auto.
AlignSelf is now an alias of AlignItems.
JustifyItems and JustifySelf aliases have been added. These properties have no affect on Flexbox containers, but apply to Grid containers.
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.
Strict style types
- New types
LengthPercentage and LengthPercentageAuto have been added.
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.
LengthPercentageAuto is currently identical to Dimension but will allow us to expand dimension in future to support values like MinContent, MaxContent and FitContent.
- 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).
Position properties renamed
- The
position property is now renamed to inset and is now in line with CSS inset specs
- The
position_type property is now renamed to position and is now in line with CSS position specs. The PositionType enum has been similarly renamed to Position.
Changes to LayoutTree
- Added generic associated type to
LayoutTree for a ChildIter, an iterator on the children of a given node.
- 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.
- 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.
- Added
is_childless method to LayoutTree for querying whether a node has no children.
AvailableSpace has been moved
The 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.
Fixes
- Flexbox nodes sized under a min-content constraint now size correctly (#291)
- Aspect ratio is now applied correctly in many circumstances
- Absolutely positioned items now apply margins correctly
- Min/max size are now applied correctly
- Inset applied incorrectly to relatively positioned flexbox children when both
top and bottom or left and right were specified (#348)
- 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)
Removed
- 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.
- 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.
- 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.
0.2.2
Fixes
- Border or padding on the horizontal axis could, in some cases, increase the height of nodes.
0.2.1
Fixes
- 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.
taffy::compute_layout has been made public allowing Taffy to be used with custom storage (#263)
0.2.0
New features
Flexbox "gap" and AlignContent::SpaceEvenly
The gap property is now supported on flex containers. This can make it much easier to create even spacing or "gutters" between nodes.
Additionally 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)
Debug module and cargo feature
Two debugging features have been added:
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.
- A cargo feature
debug. This enabled debug logging of the layout computation process itself (this is probably mainly useful for those working taffy itself).
Performance improvements
A number of performance improvements have landed since taffy 0.1:
- 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%.
- 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 chache slots to better match the actual usage patterns of the flexbox layout algorithm. This had a particularly dramatic effect on deep hierachies (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!
Benchmarks vs. Taffy 0.1
| Benchmark | Taffy 0.1 | Taffy 0.2 | % change (0.1 -> 0.2) |
| wide/1_000 nodes (2-level hierarchy) | 699.18 µs | 445.01 µs | -36.279% |
| wide/10_000 nodes (2-level hierarchy) | 8.8244 ms | 7.1313 ms | -16.352% |
| wide/100_000 nodes (2-level hierarchy) | 204.48 ms | 242.93 ms | +18.803% |
| deep/4000 nodes (12-level hierarchy)) | 5.2320 s | 2.7363 ms | -99.947% |
| deep/10_000 nodes (14-level hierarchy) | 75.207 s | 6.9415 ms | -99.991% |
| deep/100_000 nodes (17-level hierarchy) | - | 102.72 ms | - |
| deep/1_000_000 nodes (20-level hierarchy) | - | 799.35 ms | - |
(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
As 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.
However, in the "deep" benchmarks we see dramatic improvements. The previous version of Taffy suffered from exponential blowup in the case of deeply nested hierachies. This has resulted in somewhat silly improvements like the 10,000 node (14-level) hierachy 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.
Benchmarks vs. Yoga
Yoga 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.
| Benchmark | Yoga | Taffy 0.2 |
| yoga/10 nodes (1-level hierarchy) | 45.1670 µs | 33.297 ns |
| yoga/100 nodes (2-level hierarchy) | 134.1250 µs | 336.53 ns |
| yoga/1_000 nodes (3-level hierarchy) | 1.2221 ms | 3.8928 µs |
| yoga/10_000 nodes (4-level hierarchy) | 13.8672 ms | 36.162 µs |
| yoga/100_000 nodes (5-level hierarchy) | 141.5307 ms | 1.6404 ms |
(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
While 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!
Breaking API changes
Node creation changes
taffy::Node is now unique only to the Taffy instance from which it was created.
- Renamed
Taffy.new_node(..) -> Taffy.new_with_children(..)
- Renamed
Taffy.new_leaf() -> Taffy.new_leaf_with_measure()
- Added
taffy::node::Taffy.new_leaf() which allows the creation of new leaf-nodes without having to supply a measure function
Error handling/representation improvements
- Renamed
taffy::Error -> taffy::error::TaffyError
- Replaced
taffy::error::InvalidChild with a new InvalidChild variant of taffy::error::TaffyError
- Replaced
taffy::error::InvalidNode with a new InvalidNode variant of taffy::error::TaffyError
- The following method new return
Err(TaffyError::ChildIndexOutOfBounds) instead of panicking:
taffy::Taffy::remove_child_at_index
taffy::Taffy::replace_child_at_index
taffy::Taffy::child_at_index
Taffy::remove now returns a Result<usize, Error>, to indicate if the operation was sucessful (and if it was, which ID was invalidated).
Some uses of Option<f32> replaced with a new AvailableSpace enum
A new enum Taffy::layout::AvailableSpace has been added.
The definition looks like this:
/// The amount of space available to a node in a given axis
pub enum AvailableSpace {
/// The amount of space available is the specified number of pixels
Definite(f32),
/// The amount of space available is indefinite and the node should be laid out under a min-content constraint
MinContent,
/// The amount of space available is indefinite and the node should be laid out under a max-content constraint
MaxContent,
}
This 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).
And a different instance of it is passed as a new second parameter to MeasureFunc. MeasureFuncs 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..
Builder methods are now const where possible
- Several convenience constants have been defined: notably
Style::DEFAULT
Size<f32>.zero() is now Size::<f32>::ZERO
Point<f32>.zero() is now Point::<f32>::ZERO
Size::undefined() is now Size::NONE
Removals
- 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%).
- Removed
taffy::number::Number. Use Option<f32> is used instead
- the associated public
MinMax and OrElse traits have also been removed; these should never have been public
- 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).
Fixes
0.1.0
0.1.0 Changed
- the
order field of Layout is now public, and describes the relative z-ordering of nodes
- renamed crate from
stretch2 to taffy
- updated to the latest version of all dependencies to reduce upstream pain caused by duplicate dependencies
- renamed
stretch::node::Strech -> taffy::node::Taffy
0.1.0 Fixed
- fixed feature strategy for
alloc and std: these can now be compiled together, with std's types taking priority
0.1.0 Removed
- removed Javascript / Kotlin / Swift bindings
- the maintainer team lacks expertise to keep these working
- more serious refactors are planned, and this will be challenging to keep working through that process
- if you are interested in helping us maintain bindings to other languages, get in touch!
- 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)
- removed the
Direction and Overflow structs, and the corresponding direction and overflow fields from Style
- these had no effect in the current code base and were actively misleading
stretch2 0.4.3
This is the final release of stretch: migrate to the crate named taffy for future fixes and features!
These notes describe the differences between this release and stretch 0.3.2, the abandoned crate from which this library was forked.
Changed
Fixed
- fixed an exponential performance blow-up with deep nesting
- fixed percent height values, which were using parent width
- recomputing layout no longer moves children of non-zero-positioned parent
- fixed broken Swift bindings