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