1# Release Notes
2
3## 0.3.0-alpha2 (unreleased)
4
5### Changed
6
7- `experimental_grid` feature named to just `grid`
8- `grid` feature enabled by default
9- `GridPlacement::Line` now stores a `GridLine` newtype wrapper around an `i16` rather than a raw `i16`. If you are using the style helpers then this change will not affect you.
10- *BREAKING:* `Position` is now renamed to `Inset` and is now in line with [CSS inset specs](https://developer.mozilla.org/en-US/docs/Web/CSS/inset)
11- *BREAKING:* `PositionType` is now renamed to `Position` and is now in line with [CSS position specs](https://developer.mozilla.org/en-US/docs/Web/CSS/position)
12
13### Fixes
14
15- Flexbox nodes sized under a min-content constraint now size correctly (#291)
16
17### Removed
18
19- 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.
20- 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.
21- 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.
22
23## 0.3.0-alpha1
24
25This is the first in a series of planned alpha releases to allow users of Taffy to try out the new CSS Grid layout mode in advance of a stable release. We hope that by marking this is alpha release we are clearly communicating that this a pre-release and that the implementation is not yet of production quality. But we never-the-less encourage you to try it out. Feedback is welcome, and bug reports for the Grid implementation are being accepted as of this release.
26
27~**Note: CSS Grid support must be enabled using the `experimental_grid` feature. For the time being this feature is not enabled by default.**~ From `0.3.0-alpha2`, the CSS Grid feature is now enabled by default.
28
29### New Feature: CSS Grid (Experimental)
30
31We very excited to report that we have an initial version of the CSS Grid layout available. This is in addition to the existing Flexbox layout support, and the two modes interoperate (although this interaction has not been extensively tested). You can set a node to use Grid layout by setting the `display` property to `Display::Grid`.
32
33#### Learning Resources
34
35Taffy 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:
36
37- [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.
38- [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.
39
40#### Supported Features & Properties
41
42In addition to the usual sizing/spacing proerties (size, min_size, padding, margin, etc), the following Grid style properties are supported on Grid Containers:
43
44| Property                  | Explanation                                                                                    |
45| ---                       | ---                                                                                            |
46| [`grid-template-columns`] | The track sizing functions of the grid's explicit columns                                      |
47| [`grid-template-rows`]    | The track sizing functions of the grid's explicit rows                                         |
48| [`grid-auto-rows`]        | Track sizing functions for the grid's implicitly generated rows                                |
49| [`grid-auto-columns`]     | Track sizing functions for the grid's implicitly generated columns                             |
50| [`grid-auto-flow`]        | Whether auto-placed items are placed row-wise or column-wise. And sparsely or densely.         |
51| [`gap`]                   | The size of the vertical and horizontal gaps between grid rows/columns                         |
52| [`align-content`]         | Align grid tracks within the container in the inline (horizontal) axis                         |
53| [`justify-content`]       | Align grid tracks within the container in the block (vertical) axis                            |
54| [`align-items`]           | Align the child items within their grid areas in the inline (horizontal) axis                  |
55| [`justify-items`]         | Align the child items within their grid areas in the block (vertical) axis                     |
56
57And the following Grid style properties are supported on Grid Items (children):
58
59| Property                  | Explanation                                                                                    |
60| ---                       | ---                                                                                            |
61| [`grid-row`]              | The (row) grid line the item starts at (or a span)                                             |
62| [`grid-column`]           | The (column) grid line the item end at (or a span)                                             |
63| [`align-self`]            | Align the item within it's grid area in the inline (horizontal) axis. Overrides `align-items`. |
64| [`justify-self`]          | Align the item within it's grid area in the block (vertical) axis. Overrides `justify-items`.  |
65
66[`grid-template-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-columns
67[`grid-template-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-rows
68[`grid-auto-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-rows
69[`grid-auto-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-columns
70[`grid-auto-flow`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-flow
71[`gap`]: https://developer.mozilla.org/en-US/docs/Web/CSS/gap
72[`align-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align_content
73[`justify-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify_content
74[`align-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-items
75[`justify-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-items
76[`grid-row`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-row
77[`grid-column`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-column
78[`align-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-self
79[`justify-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-self
80
81The following properties and features are not yet supported, but are planned for the near future:
82
83- Baseline alignment
84- `fit-content()` with a percentage argument.
85- `repeat()` with integer repetition (but users of Taffy can just expand these definition manually)
86
87The following properties and features are not supported, and there are no immediate plans to implement them:
88
89- Subgrids
90- Named grid lines
91- Named areas: `grid-template-areas` and `grid-area`
92- `grid-template` or `grid` shorthand
93
94#### Example
95
96See [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:
97
98```bash
99cargo run --example grid_holy_grail --features grid
100```
101
102### New Feature: Style Helpers
103
104Ten 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.
105
106For example, instead of:
107
108```rust
109let size : Size<Dimension> = Size { width: Dimension::Points(100.0), height: Dimension::Percent(50.0) };
110```
111
112you can now write
113
114```rust
115let size : Size<Dimension> = Size { width: points(100.0), height: percent(50.0) };
116```
117
118And 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
119
120```rust
121let size : Size<Dimension> = points(100.0);
122```
123
124The following functions work for `Dimension`, `LengthPercentageAuto`, `LengthPercentage`, `AvailableSpace` and for Grid track sizing functions
125
126- `points(f32)` - Generates a `Points` variant with the specified value
127- `zero()` - Generates a `Points` variant with the value `0.0`.
128
129The following functions work for `Dimension`, `LengthPercentageAuto`, `LengthPercentage` and for Grid track sizing functions
130
131- `percent(f32)` - Generates a `Percent` value
132- `auto()` - Generates an `Auto` variant
133
134The following functions work for `AvailableSpace` and grid track sizing functions:
135
136- `min_content()` - Generates an `MinContent` variant
137- `max_content()` - Generates an `MaxContent` variant
138
139The following functions currently work only for grid track sizing functions:
140
141- `flex(f32)` - Genrates a `Flex` variant with the specified flex fraction
142- `fit_content(LengthPercentage)` - Generates a `FitContent` variant with the specified limit. Nest `points` or `percent` inside this function to specified the limit.
143- `minmax(MinTrackSizingFunction, MaxTrackSizingFunction)` - Generates a track sizing function with different min and max sizing functions. Nest `points`, `percent`, `auto`, `min_content`, `max_content`, or `flex` to specify the min and max functions.
144- `repeat(GridTrackRepetition, Vec<TrackSizingFunction>)` - Genereate an auto-repeating track definition.
145
146### Breaking API changes
147
148#### Changes to alignment style types
149
150- `AlignContent` and `JustifyContent` has been merged.
151  - `JustifyContent` is now an alias of `AlignContent` and contains the `Stretch` variant.
152  - This variant will be *ignored* (falling back to `Start`) when applied Flexbox containers. It is valid value for Grid containers.
153- `AlignItems` and `AlignSelf` have been merged.
154  - The `Auto` variant of `AlignSelf` has been removed. You should now use `Option::None` if you wish to specify `AlignSelf::Auto`.
155  - `AlignSelf` is now an alias of `AlignItems`.
156  - `JustifyItems` and `JustifySelf` aliases have been added. These properties have no affect on Flexbox containers, but apply to Grid containers.
157- `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.
158
159#### Strict style types
160
161- New types `LengthPercentage` and `LengthPercentageAuto` have been added.
162  - `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.
163  - `LengthPercentageAuto` is currently identical to `Dimension` but will allow us to expand dimension in future to support values like `MinContent`, `MaxContent` and `FitContent`.
164- 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).
165
166#### Changes to `LayoutTree`
167
168- Added generic associated type to `LayoutTree` for a `ChildIter`, an iterator on the children of a given node.
169- 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.
170- 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.
171- Added `is_childless` method to `LayoutTree` for querying whether a node has no children.
172
173#### `AvailableSpace` has been moved
174
175The `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.
176
177### Fixes
178
179- 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)
180
181## 0.2.2
182
183### Fixes
184
185- Border or padding on the horizontal axis could, in some cases, increase the height of nodes.
186
187## 0.2.1
188
189### Fixes
190
191- 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`.
192- `taffy::compute_layout` has been made public allowing Taffy to be used with custom storage (#263)
193
194## 0.2.0
195
196### New features
197
198#### Flexbox "gap" and `AlignContent::SpaceEvenly`
199
200The [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.
201
202Additionally 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)
203
204#### Debug module and cargo feature
205
206Two debugging features have been added:
207
208- `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.
209- A cargo feature `debug`. This enabled debug logging of the layout computation process itself (this is probably mainly useful for those working taffy itself).
210
211### Performance improvements
212
213A number of performance improvements have landed since taffy 0.1:
214
215- 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%.
216- 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!
217
218#### Benchmarks vs. Taffy 0.1
219
220| Benchmark | Taffy 0.1 | Taffy 0.2 | % change (0.1 -> 0.2) |
221| --- | --- | --- | --- |
222| wide/1_000 nodes (2-level hierarchy) | 3.5458 µs | 4.3571 µs | +23.333% |
223| wide/10_000 nodes (2-level hierarchy) | 36.418 µs | 42.967 µs | +17.357% |
224| wide/100_000 nodes (2-level hierarchy) | 1.8275 ms | 3.9096 ms | +112.26% |
225| deep/4000 nodes (12-level hierarchy)) | 5.1845 s | 15.318 µs | -100.000% |
226| deep/10_000 nodes (14-level hierarchy) | 75.978 s | 40.315 µs | -100.000% |
227| deep/100_000 nodes (17-level hierarchy) | - | 2.7644 ms| - |
228| deep/1_000_000 nodes (20-level hierarchy) | - | 1.2130 s| - |
229
230(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
231
232As 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.
233
234However, 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.
235
236#### Benchmarks vs. [Yoga](https://github.com/facebook/yoga)
237
238Yoga 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.
239
240| Benchmark | Yoga | Taffy 0.2 |
241| --- | --- | --- |
242| yoga/10 nodes (1-level hierarchy) | 45.1670 µs | 33.297 ns |
243| yoga/100 nodes (2-level hierarchy) | 134.1250 µs | 336.53 ns |
244| yoga/1_000 nodes (3-level hierarchy) | 1.2221 ms | 3.8928 µs |
245| yoga/10_000 nodes (4-level hierarchy) | 13.8672 ms | 36.162 µs |
246| yoga/100_000 nodes (5-level hierarchy) | 141.5307 ms | 1.6404 ms |
247
248(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
249
250While 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!
251
252### Breaking API changes
253
254#### Node creation changes
255
256- `taffy::Node` is now unique only to the Taffy instance from which it was created.
257- Renamed `Taffy.new_node(..)` -> `Taffy.new_with_children(..)`
258- Renamed `Taffy.new_leaf()` -> `Taffy.new_leaf_with_measure()`
259- Added `taffy::node::Taffy.new_leaf()` which allows the creation of new leaf-nodes without having to supply a measure function
260
261#### Error handling/representation improvements
262
263- Renamed `taffy::Error` -> `taffy::error::TaffyError`
264- Replaced `taffy::error::InvalidChild` with a new `InvalidChild` variant of `taffy::error::TaffyError`
265- Replaced `taffy::error::InvalidNode` with a new `InvalidNode` variant of `taffy::error::TaffyError`
266- The following method new return `Err(TaffyError::ChildIndexOutOfBounds)` instead of panicking:
267  - `taffy::Taffy::remove_child_at_index`
268  - `taffy::Taffy::replace_child_at_index`
269  - `taffy::Taffy::child_at_index`
270- `Taffy::remove` now returns a `Result<usize, Error>`, to indicate if the operation was sucessful (and if it was, which ID was invalidated).
271
272#### Some uses of `Option<f32>` replaced with a new `AvailableSpace` enum
273
274A new enum `Taffy::layout::AvailableSpace` has been added.
275
276The definition looks like this:
277
278```rust
279/// The amount of space available to a node in a given axis
280pub enum AvailableSpace {
281    /// The amount of space available is the specified number of pixels
282    Definite(f32),
283    /// The amount of space available is indefinite and the node should be laid out under a min-content constraint
284    MinContent,
285    /// The amount of space available is indefinite and the node should be laid out under a max-content constraint
286    MaxContent,
287}
288```
289
290This 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`).
291
292And 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..
293
294#### Builder methods are now `const` where possible
295
296- Several convenience constants have been defined: notably `Style::DEFAULT`
297- `Size<f32>.zero()` is now `Size::<f32>::ZERO`
298- `Point<f32>.zero()` is now  `Point::<f32>::ZERO`
299- `Size::undefined()` is now `Size::NONE`
300
301#### Removals
302
303- 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%).
304- Removed `taffy::number::Number`. Use `Option<f32>` is used instead
305  - the associated public `MinMax` and `OrElse` traits have also been removed; these should never have been public
306- 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).
307
308### Fixes
309
310- Miscellaneous correctness fixes which align our implementation with Chrome:
311
312  - Nodes can only ever have one parent
313  - Fixed rounding of fractional values to follow latest Chrome - values are now rounded the same regardless of their position
314  - Fixed computing free space when using both `flex-grow` and a minimum size
315  - 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)
316  - `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
317- Taffy can now be vendored using `cargo-vendor` (README.md is now included in package).
318
319## 0.1.0
320
321### 0.1.0 Changed
322
323- the `order` field of `Layout` is now public, and describes the relative z-ordering of nodes
324- renamed crate from `stretch2` to `taffy`
325- updated to the latest version of all dependencies to reduce upstream pain caused by duplicate dependencies
326- renamed `stretch::node::Strech` -> `taffy::node::Taffy`
327
328### 0.1.0 Fixed
329
330- fixed feature strategy for `alloc` and `std`: these can now be compiled together, with `std`'s types taking priority
331
332### 0.1.0 Removed
333
334- removed Javascript / Kotlin / Swift bindings
335  - the maintainer team lacks expertise to keep these working
336  - more serious refactors are planned, and this will be challenging to keep working through that process
337  - if you are interested in helping us maintain bindings to other languages, [get in touch](https://github.com/DioxusLabs/taffy/discussions)!
338- 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)
339- removed the `Direction` and `Overflow` structs, and the corresponding `direction` and `overflow` fields from `Style`
340  - these had no effect in the current code base and were actively misleading
341
342## stretch2 0.4.3
343
344This is the final release of `stretch`: migrate to the crate named `taffy` for future fixes and features!
345
346These notes describe the differences between this release and `stretch` 0.3.2, the abandoned crate from which this library was forked.
347
348### Changed
349
350- updated [assorted dependencies](https://github.com/vislyhq/stretch/commit/a6491117379cea52dedc9584d892594a143e8cb0)
351
352### Fixed
353
354- fixed an exponential performance blow-up with deep nesting
355- fixed percent height values, which were using parent width
356- recomputing layout no longer moves children of non-zero-positioned parent
357- fixed broken Swift bindings