1# Changelog
2
3## 0.9.1
4
5### Fixed
6
7- Flexbox: don't apply cross-axis stretch alignment to children with auto margins (#861)
8
9## 0.9.0
10
11### Support for named grid lines and grid areas
12
13Taffy now supports named grid lines and areas.
14
15As these rely on arbitrary user-provided strings, Taffy's `Style` struct is now generic
16over a string-like type (via the `CheapCloneStr` trait). Additionally as the `grid` feature is optional,
17it has a `PhantomData` field of that type to make type inference work.
18
19### Changed
20
21- `PrintTree` and `RoundTree`: use `Layout` instead of `&Layout` (#849).
22- Renamed `TrackSizingFunction` to `GridTemplateComponent`
23- Renamed `NonRepeatedTrackSizingFunction` to `TrackSizingFunction`
24- The `Repeat` variant of `GridTemplateComponent` now contains a new `GridTemplateRepetition` struct, which allows
25  line names to be specifed in addition to tracks.
26- The way that grid styles are exposed in the low-level API is now a lot more generic with many associated types.
27
28### Added
29
30- `GridTemplateArea` struct and `Style::grid_template_areas` field
31- `Style::grid_template_column_names` and `Style::grid_template_row_names` fields. If non-empty, these
32  should have length of exactly one greater than the corresponding `grid_template_column`/`grid_template_rows` style.
33
34## 0.8.3
35
36### Fixed
37
38- Fix `serde` feature on 32bit targets (#845)
39
40## 0.8.2
41
42### Fixed
43
44- Fix: Calculate correct new grid size when expanding cell_occupancy_matrix in the negative direction (#843)
45
46## 0.8.1
47
48### Added
49
50- Impl `GridItemStyle` and `BlockContainerStyle` for `Style` (#832).
51
52## 0.8.0
53
54### Highlights
55
56**The big feature in this release is support for `calc()` values in the low-level API.**
57
58To use this API:
59
60- Implement the `resolve_calc_value` method when implementing the `LayoutPartialTree` trait.
61- Pass a type-erased pointer (`*const ()`) to constructors like `LengthPercentage::calc(...)`
62
63Taffy treats the pointer as an opaque value (excepting that it uses the low 3 bits as a tag) which it will
64pass to `LayoutPartialTree::resolve_calc_value` along with a percentage resolution basis when it needs to
65resolve the value.
66
67### Changed
68
69- The representation of many "size" types is now a tagged pointer than an enum. This is to enable `calc()`.
70  The effected types are `LengthPercentage`, `LengthPercentageAuto`, `Dimension`, `MinTrackSizingFunction`, and
71`MaxTrackSizingFunction` types.
72
73### Added
74
75- Special-case "compressible replaced elements" in grid sizing algorithm (#807)
76  This allows for more correct sizing of "replaced" elements such as images that are children
77  of flexbox or grid containers.
78
79### Fixed
80
81- Grid: Fix infinite loop due to float precision in grid layout maximise tracks step (#792)
82- Grid: Fix removed wrong addition, causing items to be misplaced. (#817)
83- Grid: Fix grid placement for items with fixed primary axis (#818)
84- Leaf layout: don't set available space to max-size (#819)
85
86## 0.7.7
87
88### Fixed
89
90- Add `#[inline]` annotation to some methods on `TaffyTree` (#802)
91- Add `TaffyTree::remove_children_range` method (#802)
92
93## 0.7.6
94
95### Fixed
96
97- Fix infinite loop due to float precision in grid layout maximise tracks step (#792)
98
99## 0.7.5
100
101### Fixed
102
103- Grid: only stretch auto tracks if content-alignment is stretch (#783)
104
105## 0.7.4
106
107### Fixed
108
109- Fix detailed grid info for empty grid (#782)
110
111## 0.7.3
112
113### Fixed
114
115- Make `TaffyTree::detailed_layout_info` take `&self` rather than `&mut self` (#779)
116
117## 0.7.2
118
119### Added
120
121- The ability to access computed track sizes and item positions of a CSS Grid layout (#772).
122  This information can be accessed using the `LayoutGridContainer::set_detailed_grid_info` method
123  in the low-level API or the `TaffyTree::detailed_layout_info` method in the high-level API.
124
125## 0.7.1
126
127### Fixed
128
129- Improve interaction of abspos children of block containers with margin collapsing (#760)
130
131### Added
132
133- Add `TaffyTree::unrounded_layout` getter (#765)
134
135### Removed
136
137- The `num-traits` dependency was removed (#761) (#762)
138
139## 0.7.0
140
141### Changed
142
143- BREAKING: The `cache_mut` method on the `LayoutPartialTree` trait has been replaced with a separate `CacheTree` trait. This allows
144  Taffy to be more easily used without caching or with a custom cache implementation.
145- BREAKING: the `TaffyTree::set_children` method now removes the children from their previous parent (if they have one).
146
147### Added
148
149- Helper methods to retrieve content-box sizes were added to `Layout`
150
151## 0.6.3
152
153### Fixes
154
155- Block: ignore margin collapsing when computing static position of abspos items (#747)
156
157## 0.6.2
158
159### Fixes
160
161- Fix: clamp indefinite available space by min- and max- size as appropriate (#742)
162
163## 0.6.1
164
165### Fixes
166
167- Fix calculation of `auto-fill`/`auto-fit` repetition count when container has a definite percentage size (#722)
168- Fix min-size style not affecting intrinsic sizes (#723)
169- Fix documentation of dirty and mark_dirty functions (#724)
170- Fix intrinsic size of scroll containers that have a small explicit flex-basis (#728)
171
172## 0.6.0
173
174### Highlights
175
176- The `Style` struct has been "traitified". This supports Taffy's integration in Servo and generally makes Taffy more flexible. The
177  `Style` struct still exists and implements the new traits so existing uses of Taffy will continue to work as before.
178- The `box-sizing` style is supported
179- Computed margins are output in `Layout`
180
181### Fixes
182
183- Fix `print_tree()` when rounding is disabled (#680)
184- Absolute Insets should be resolved against the container size minus border (#666)
185- Fix flooring hypothetical_main_size by computed min size (#689)
186- Fix flex line cross-size determination (#690)
187- Fix panics in the grid algorithm (#691)
188- Fix resolving flexible lengths (WPT css/flexbox-multiline-min-max test) (#692)
189- Fix wrapping when a max main size style is present (#694)
190- Fix case where Taffy allowed margins to collapse through an element when it shouldn't have (#695)
191
192### Added
193
194- Legacy text align (for laying out `<center>` and `<div align="..">`) is supported
195- Add `is_table` for block items (#701)
196- Impl `Debug` and `Clone` for `Cache` (#688)
197- Implement `Debug` and `PartialEq` for tree types (#697)
198
199## 0.5.2
200
201- Fix block stretch sizing (don't always apply stretch sizing to block containers) (#674)
202- Fix computation of intrinsic main size when it depends on a child's known cross size (#673)
203- Fix panic when GridLine 0 is specified (#671)
204- Docs: Document feature flags and scrape examples (#672)
205- Docs: Update cosmic-text example to cosmic-text 0.12 (#670)
206
207## 0.5.1
208
209- Fix: Clamp block item stretch widths by their min and max width (#664)
210- Fix: Auto margin computation in block layout (#663)
211
212## 0.5.0
213
214The changes in 0.5 are relatively small but the new measure function parameter is a breaking change so it requires a minor version bump.
215
216- Added: A `style: &Style` parameter has been added to measure functions.
217- Added: The `MaybeMath`, `MaybeResolve`, and `ResolveOrZero` traits have been made public.
218- Fix: use SizingMode::Inherent when sizing absolute children of flexbox nodes.
219
220## 0.4.4
221
222### Fixes
223
224- Content alignment (`align-content`/`justify-content`) behaviour was updated to match the latest spec (and Chrome 123+) (#635)
225- Ensure that root Flexbox nodes are floored by their padding-border (#651, #655)
226- Use grid area size not available space when applying aspect ratio to grid containers (#656)
227
228## 0.4.3
229
230### Fixes
231
232- Fix compilation error in `evenly_sized_tracks` style helper in recent versions of rustc caused by a change/regression in type
233  inference (#643). Note that 3rd-party code that call style helpers that take an `Into<f32>` parameter may still be affected by this issue,
234  but they should be able to fix on their side by clarifying the type passed in
235
236## 0.4.2
237
238- Fixed: single-line flex-container should clamp the line's cross-size (#638)
239- Reduced binary footprint of Taffy from around 300kb to around 150kb (#636)
240
241## 0.4.1
242
243- Fixed: CSS Grid track sizing not respecting growth limits in some circumstances (#624)
244
245## 0.4.0
246
247### Highlights
248
249- Support for CSS Block layout (`display: block`)
250- Support for the `overflow` property (+ `scrollbar_width` for `overflow: scroll`)
251- Improved measure function API
252- Completely refactored low-level API
253- Simplified module hierarchy (+ most types/functions are now exported from the crate root)
254- Expanded set of examples which better document integration with other layout systems (e.g. text layout)
255- Computed values for `padding` and `border` are now output into the `Layout` struct
256
257### Block layout
258
259Support for [CSS Block layout](https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Flow_Layout/Block_and_Inline_Layout_in_Normal_Flow#elements_participating_in_a_block_formatting_context) has been added. This can be used via the new `Display::Block` variant of the `Display` enum. Note that  full flow layout: inline, inline-block and float layout have *not* been implemented. The use case supported is block container nodes which contain block-level children.
260
261### Overflow property
262
263Support has been added for a new `overflow` style property with `Visible`, `Clip`, `Hidden`, and `Scroll` values (`Auto` is not currently implemented). Additionally a `scrollbar_width` property has been added to control the size of scrollbars for nodes with `Overflow::Scroll` set.
264
265- Overflow is settable indpendently in each axis.
266- `Visible` and `Clip` will produce layouts equivalent to the Taffy 0.3. `Clip` will affect the new `content_size` output by restricting it to the available space.
267- `Hidden` and `Scroll` affect layout by changing the automatic minimum size of Flexbox and Grid children
268- `Scroll` additionally reserves `scrollbar_width` pixels for a scrollbar in the opposite axis to which scrolling is enabled. `Scroll` with `scrollbar_width` set to zero is equivalent to `Hidden`.
269
270### Measure function changes
271
272The "measure function" API for integrating Taffy with other measurement systems (such as text layout) has been changed to be more flexible
273and to interact better with borrow checking (you can now borrow external data in your measure function!).
274
275- There are no longer per-node measure functions.
276- There is now a single "global" measure function, and a per-node "context" of a user-defined type
277- The `Taffy` tree is now a generic `TaffyTree<T>` where `T` is the "context" type.
278- The measure function is now called for all leaf nodes (nodes without children). If you wish to maintain compatibility with the previous
279  behaviour then your measure function should return `Size::ZERO` for leaf nodes whose context is `None`.
280
281If you are not using measure functions, then the only change you will need to make is from:
282
283```rust
284let mut tree = Taffy::new();
285```
286
287to
288
289```rust
290let mut tree : TaffyTree<()> = TaffyTree::new();
291```
292
293And generally update any uses of `Taffy` in your codebase to `TaffyTree<()>`.
294
295If you are using measure functions then you will need to make some bigger (but straightforward) changes. The following Taffy 0.3 code:
296
297```rust
298let mut tree = Taffy::new();
299let leaf = tree.new_leaf_with_measure(
300  Style::DEFAULT,
301  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>| Size { width: 100.0, height: 200.0 }
302);
303tree.compute_layout(leaf, Size::MAX_CONTENT);
304```
305
306Should become something like the following with Taffy 0.4:
307
308```rust
309let mut tree : TaffyTree<Size> = TaffyTree::new();
310let leaf = tree.new_leaf_with_context(Style::DEFAULT, Size { width: 100.0, height: 200.0 });
311tree.compute_layout_with_measure(
312  leaf,
313  Size::MAX_CONTENT,
314  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>, node_id: NodeId, node_context: Option<Size>| {
315    node_context.unwrap_or(Size::ZERO)
316  }
317);
318```
319
320Note that:
321
322- You can choose any type instead of `Size` in the above example. This includes your own custom type (which can be an enum or a trait object).
323- If you don't need a context then you can use `()` for the context type
324- As the single "global" measure function passed to `compute_layout_with_measure` only needs to exist for the duration of a single layout run,
325  it can (mutably) borrow data from it's environment
326
327### Low-level API (`LayoutTree` trait) refactor
328
329The low-level API has been completely reworked:
330
331- The `LayoutTree` trait has been split into 5 smaller traits which live in the `taffy::tree:traits` module (along with their associated documentation)
332- The following methods have been removed from split `LayoutTree` traits entirely: `parent`, `is_childless`, `measure_node`, `needs_measure`, and `mark_dirty`.
333- `taffy::node::Node` has been replaced with `taffy::NodeId`. This should make it much easier to implement the low-level traits as the underlying type backing the node id now a `u64` rather than a `slotmap::DefaultKey`.
334- Support for running each layout algorithm individually on a single node via the following top-level functions:
335  - `compute_flexbox_layout`
336  - `compute_grid_layout`
337  - `compute_block_layout`
338  - `compute_leaf_layout`
339  - `compute_root_layout`
340  - `compute_hidden_layout`
341
342It is believed that nobody was previously using the low-level API so we are not providing a migration guide. However, along with the refactor we have greatly
343improved both the documentation and have added examples using the new API, both of which are linked to from the [main documentation page](https://docs.rs/taffy).
344
345### Module hierarchy changes
346
347The specific changes are detailed below. However for most users the most significant change will be that almost all types are now re-exported from the root module. This means that module specific imports like `use taffy::layout::Layout` can now in almost all cases be replaced with the simpler `use taffy::Layout`.
348
349Specific changes:
350
351- The `math` module has been made private
352- The `axis` module has been merged into the `geometry` module
353- The debug module is no longer public. The `print_tree` function is now accessible under `util`.
354- All types from the `node`, `data`, `layout`, `error` and `cache` modules have been moved to the  the `tree` module.
355- The `layout_flexbox()` function has been removed from the prelude. Use `taffy::compute_flexbox_layout` instead.
356
357### Many APIs have been renamed to replace `points` or `Points` with `length` or `Length`
358
359This new name better describes one-dimensional measure of space in some unspecified unit
360which is often unrelated to the PostScript point or the CSS `pt` unit.
361
362This also removes a misleading similarity with the 2D `Point`,
363whose components can have any unit and are not even necessarily absolute lengths.
364
365Example usage change:
366
367```diff
368 use taffy::prelude::*;
369
370 // …
371
372 let header_node = taffy
373     .new_leaf(
374         Style {
375-            size: Size { width: points(800.0), height: points(100.0) },
376+            size: Size { width: length(800.0), height: length(100.0) },
377             ..Default::default()
378         },
379     ).unwrap();
380```
381
382### Other Changes
383
384- The `Taffy` type was renamed to `TaffyTree` and made generic of a context parameter
385- The Flexbox algorithm has now been moved behind the `flexbox` feature. The `flexbox` feature is enabled by default.
386- The `justify_self` property has been moved behind the `grid` feature.
387- Fixed misspelling: `RunMode::PeformLayout` renamed into `RunMode::PerformLayout` (added missing `r`).
388- `serde` dependency has been made compatible with `no_std` environments
389- `slotmap` dependency has been made compatible with `no_std` environments
390- Added `insert_child_at_index()` method to the `TaffyTree`. This can be used to insert a child node at any position instead of just the end.
391- Added `total_node_count()` method to the `TaffyTree` which returns the total number of nodes in the tree.
392- Added `get_disjoint_node_context_mut()` method to the `TaffyTree`. This can be used to safely get multiple mutable borrows at the same time.
393
394## 0.3.19
395
396### Fixes
397
398- Fix compilation error in `evenly_sized_tracks` style helper in recent versions of rustc caused by a change/regression in type
399  inference (#643). Note that 3rd-party code that call style helpers that take an `Into<f32>` parameter may still be affected by this issue,
400  but they should be able to fix on their side by clarifying the type passed in
401
402## 0.3.18
403
404### Fixes
405
406- Fix computation of Flexbox automatic minimum size when grid or flexbox child has an explicit width/height style set (#576)
407
408## 0.3.17
409
410### Added
411
412- Added `total_node_count` method to the `Taffy` struct. Returns the total number of nodes in the tree.
413
414## 0.3.16
415
416### Fixes
417
418- Improve performance of flexbox columns
419
420## 0.3.15
421
422### Fixes
423
424- Fix justify-content and align-content when free space is negative (content overflows container) (#549) (#551)
425
426## 0.3.14
427
428### Fixes
429
430- Flex: Fix issue where constraints were not being propagated, causing nodes with inherent aspect-ratio (typically images) to not apply that aspect-ratio (#545) (Fixes bevyengine/bevy#9841)
431
432## 0.3.13
433
434### Fixes
435
436- Fix rounding accumulation bug (#521) (Fixes #501 and bevyengine/bevy#8911)
437- Flexbox: pass correct cross-axis available space when computing an item's intrinsic main size (#522)(Fixes bevyengine/bevy#9350)
438- Flexbox: Subtract child margin not parent margin when computing stretch-alignment known size
439- Grid: Make CSS Grid algorithm correctly apply max width/height and available space when it is the root node (#491)
440- Grid: Fix CSS Grid "auto track" / placement bugs #481
441  - Fix divide by zero when using grid_auto_rows/grid_auto_columns with zero negative implicit tracks
442  - Fix over counting of tracks (leading to incorrect container heights) when auto-placing in grids that contain negative implicit tracks.
443  - Fix axis conflation in auto-placement code when grid_auto_flow is column
444  - Fix assignment of auto track sizes when initializing negative implicit tracks
445- Leaf: Apply margins to leaf nodes when computing available space for measure functions
446- Leaf: Reserve space for padding/borders in nodes with measure functions (#497)
447  
448  **NOTE: This has the potential to break layouts relying on the old behaviour.** However, such layouts would be relying on a style having no effect, so it is judged that such layouts are unlikely to exist in the wild. If this turns out not to be true then this fix will be reverted on the 0.3.x branch.
449
450### Dependencies
451
452- Upgrade `grid` to `0.10`. This eliminates the transitive dependency on `no-std-compat`.
453
454## 0.3.12
455
456### Fixes
457
458- Fix caching issue when toggling `display:none` on and off
459
460## 0.3.11
461
462### Fixes
463
464- Fix exponential blowup when laying out trees containing nodes with min and max sizes.
465
466## 0.3.10
467
468### Fixes
469
470- Fix sizing of children when the available_space < min_size (#407)
471
472## 0.3.9
473
474### Fixes
475
476- Fix caching bug where a cached result would sometimes be incorrectly used when the amount of available space increased (bevyengine/bevy#8111) and (bevyengine/bevy#8124)
477
478## 0.3.8
479
480### Fixes
481
482- Fix incorrect min-content size for `flex-wrap: wrap` nodes (bevyengine/bevy#8082)
483
484## 0.3.7
485
486### Fixes
487
488- Fix: Make `padding` and `border` floor node sizes (#372)
489- Fix: Prevent percentages contributing to min-content sizes (#388) (also fixes bevyengine/bevy#8017)
490
491## 0.3.6
492
493### Fixes
494
495- Fix: Ignore `align_content` when `flex_wrap` is set to `nowrap` (#383)
496
497## 0.3.5
498
499### Fixes
500
501- Fix `display: none` when it is set on a flexbox child (#380)
502- Fix `display: none` when it is set on a grid child (#381)
503
504## 0.3.4
505
506### Fixes
507
508- Fix `display: none` when it is set for the only node in the hierarchy (#377)
509
510## 0.3.3
511
512### Added
513
514- Added `enable_rounding` and `disable_rounding` methods to the `Taffy` struct which enable consumers of Taffy to obtain unrounded `f32` values for the computed layouts if they want them. Rounding remains enabled by default.
515
516### Fixes
517
518- Fixed rounding algorithm such that it never leaves gaps between adjacent nodes (#369)
519- Fixed compiling with the `grid` feature disabled (#370)
520- Fixed compiling with the `std` feature disabled
521
522## 0.3.2
523
524### Fixes
525
526- Allow partial nested values to be deserialized into a `Style` using the `serde` feature.
527
528## 0.3.1
529
530### Fixes
531
532- The `serde` feature now works when the `grid` feature is enabled
533
534## 0.3.0
535
536### Highlights
537
538- [CSS Grid algorithm support](#new-feature-css-grid)
539- [Style helper functions](#new-feature-style-helpers)
540
541See below for details of breaking changes.
542
543### New Feature: CSS Grid
544
545We 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`.
546
547#### Learning Resources
548
549Taffy 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:
550
551- [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.
552- [A Complete Guide To CSS Grid](https://css-tricks.com/snippets/css/complete-guide-grid/) by CSS Tricks. This is detailed guide with illustrations and comprehensive written explanation of the different Grid properties and how they work.
553
554#### Supported Features & Properties
555
556In addition to the usual sizing/spacing properties (size, min_size, padding, margin, etc), the following Grid style properties are supported on Grid Containers:
557
558| Property                  | Explanation                                                                                    |
559| ---                       | ---                                                                                            |
560| [`grid-template-columns`] | The track sizing functions of the grid's explicit columns                                      |
561| [`grid-template-rows`]    | The track sizing functions of the grid's explicit rows                                         |
562| [`grid-auto-rows`]        | Track sizing functions for the grid's implicitly generated rows                                |
563| [`grid-auto-columns`]     | Track sizing functions for the grid's implicitly generated columns                             |
564| [`grid-auto-flow`]        | Whether auto-placed items are placed row-wise or column-wise. And sparsely or densely.         |
565| [`gap`]                   | The size of the vertical and horizontal gaps between grid rows/columns                         |
566| [`align-content`]         | Align grid tracks within the container in the inline (horizontal) axis                         |
567| [`justify-content`]       | Align grid tracks within the container in the block (vertical) axis                            |
568| [`align-items`]           | Align the child items within their grid areas in the inline (horizontal) axis                  |
569| [`justify-items`]         | Align the child items within their grid areas in the block (vertical) axis                     |
570
571And the following Grid style properties are supported on Grid Items (children):
572
573| Property                  | Explanation                                                                                    |
574| ---                       | ---                                                                                            |
575| [`grid-row`]              | The (row) grid line the item starts at (or a span)                                             |
576| [`grid-column`]           | The (column) grid line the item end at (or a span)                                             |
577| [`align-self`]            | Align the item within it's grid area in the inline (horizontal) axis. Overrides `align-items`. |
578| [`justify-self`]          | Align the item within it's grid area in the block (vertical) axis. Overrides `justify-items`.  |
579
580[`grid-template-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-columns
581[`grid-template-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-rows
582[`grid-auto-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-rows
583[`grid-auto-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-columns
584[`grid-auto-flow`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-flow
585[`gap`]: https://developer.mozilla.org/en-US/docs/Web/CSS/gap
586[`align-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align_content
587[`justify-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify_content
588[`align-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-items
589[`justify-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-items
590[`grid-row`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-row
591[`grid-column`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-column
592[`align-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-self
593[`justify-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-self
594
595The following properties and features are not currently supported:
596
597- Subgrids
598- Masonry grid layout
599- Named grid lines
600- Named areas: `grid-template-areas` and `grid-area`
601- `grid-template` or `grid` shorthand
602
603#### Example
604
605See [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:
606
607```bash
608cargo run --example grid_holy_grail --features grid
609```
610
611### New Feature: Style Helpers
612
613Ten 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.
614
615For example, instead of:
616
617```rust
618let size : Size<Dimension> = Size { width: Dimension::Points(100.0), height: Dimension::Percent(50.0) };
619```
620
621you can now write
622
623```rust
624let size : Size<Dimension> = Size { width: points(100.0), height: percent(50.0) };
625```
626
627And 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
628
629```rust
630let size : Size<Dimension> = points(100.0);
631```
632
633Available style helpers:
634
635<table>
636  <thead><tr><th>Type(s)</th><th colspan="2">Helpers that work with that type</th></tr></thead>
637  <tbody>
638    <tr>
639      <td rowspan="3"><code>LengthPercentage</code></td>
640      <td><code>zero()</code></td>
641      <td>Generates a <code>Points</code> variant with the value <code>0.0</code></td>
642    </tr>
643    <tr>
644      <td><code>points(val:&nbsp;f32)</code></td>
645      <td>Generates a <code>Points</code> variant with the specified value</td>
646    </tr>
647    <tr>
648      <td><code>percent(val:&nbsp;f32)</code></td>
649      <td>Generates a <code>Percent</code> variant with the specified value.<br />Note that the scale of 0-1 not 0-100.</td>
650    </tr>
651    <tr>
652      <td rowspan="2"><code>LengthPercentageAuto</code><br /><code>Dimension</code></td>
653      <td colspan="2"><i>All helpers from <code>LengthPercentage</code> and...</i></td>
654    </tr>
655    <tr>
656      <td><code>auto()</code></td>
657      <td>Generates an <code>Auto</code> variant</td>
658    </tr>
659    <tr>
660      <td rowspan="3"><code>MinTrackSizingFunction</code></td>
661      <td colspan="2"><i>All helpers from <code>LengthPercentageAuto</code>/<code>Dimension</code> and...</i></td>
662    </tr>
663    <tr>
664      <td><code>min_content()</code></td>
665      <td>Generates an <code>MinContent</code> variant</td>
666    </tr>
667      <tr>
668      <td><code>max_content()</code></td>
669      <td>Generates an <code>MinContent</code> variant</td>
670    </tr>
671    <tr>
672      <td rowspan="3"><code>MaxTrackSizingFunction</code></td>
673      <td colspan="2"><i>All helpers from <code>MinTrackSizingFunction</code> and...</i></td>
674    </tr>
675    <tr>
676      <td><code>fit_content(limit:&nbsp;LengthPercentage)</code></td>
677      <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>
678    </tr>
679      <tr>
680      <td><code>fr(fraction:&nbsp;f32)</code></td>
681      <td>Generates a <code>Fraction</code> (<code>fr</code>) variant with the specified flex fraction </td>
682    </tr>
683    <tr>
684      <td rowspan="3"><code>NonRepeatingTrackSizingFunction</code></td>
685      <td colspan="2"><i>All helpers from <code>MaxTrackSizingFunction</code> and...</i></td>
686    </tr>
687    <tr>
688      <td><code>minmax(min: MinTrackSizingFunction, max: MaxTrackSizingFunction)</code></td>
689      <td>Equivalent to CSS <code>minmax()</code> function.</td>
690    </tr>
691    <tr>
692      <td><code>flex(fraction:&nbsp;f32)</code></td>
693      <td>Equivalent to CSS <code>minmax(0px, 1fr)</code>. This is likely what you want if you want evenly sized rows/columns.</td>
694    </tr>
695    <tr>
696      <td rowspan="2"><code>TrackSizingFunction</code></td>
697      <td colspan="2"><i>All helpers from <code>NonRepeatingTrackSizingFunction</code> and...</i></td>
698    </tr>
699    <tr>
700      <td><code>repeat(rep: GridTrackRepetition, tracks: Vec&lt;TrackSizingFunction&gt;)</code></td>
701      <td>Equivalent to css <code>repeat()</code> function.</td>
702    </tr>
703    <tr>
704      <td><code>Vec&lt;TrackSizingFunction&gt;</code></td>
705      <td><code>evenly_sized_tracks(count:&nbsp;u16)</code></td>
706      <td>Equivalent to CSS <code>repeat(count, minmax(0px, 1fr)</code></td>
707    </tr>
708    <tr>
709      <td rowspan="3"><code>AvailableSpace</code></td>
710      <td><code>auto()</code></td>
711      <td>Generates an <code>Auto</code> variant</td>
712    </tr>
713    <tr>
714      <td><code>min_content()</code></td>
715      <td>Generates an <code>MinContent</code> variant</td>
716    </tr>
717      <tr>
718      <td><code>max_content()</code></td>
719      <td>Generates an <code>MinContent</code> variant</td>
720    </tr>
721    <tr>
722      <td><code>Size&lt;T&gt;</code></td>
723      <td colspan="2">Any helper that works for <code>T</code> will also work for <code>Size&lt;T&gt;</code> and will set both <code>width</code> and <code>height</code> to that value</td>
724    </tr>
725    <tr>
726      <td><code>Rect&lt;T&gt;</code></td>
727      <td colspan="2">Any helper that works for <code>T</code> will also work for <code>Rect&lt;T&gt;</code> and will set <code>top</code>, <code>left</code>, <code>bottom</code>, and <code>right</code> to that value</td>
728    </tr>
729  </tbody>
730</table>
731
732### Breaking API changes
733
734#### Changes to alignment style types
735
736- `AlignContent` and `JustifyContent` has been merged.
737  - `JustifyContent` is now an alias of `AlignContent` and contains the `Stretch` variant.
738  - This variant will be *ignored* (falling back to `Start`) when applied Flexbox containers. It is valid value for Grid containers.
739- `AlignItems` and `AlignSelf` have been merged.
740  - The `Auto` variant of `AlignSelf` has been removed. You should now use `Option::None` if you wish to specify `AlignSelf::Auto`.
741  - `AlignSelf` is now an alias of `AlignItems`.
742  - `JustifyItems` and `JustifySelf` aliases have been added. These properties have no affect on Flexbox containers, but apply to Grid containers.
743- `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.
744
745#### Strict style types
746
747- New types `LengthPercentage` and `LengthPercentageAuto` have been added.
748  - `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.
749  - `LengthPercentageAuto` is currently identical to `Dimension` but will allow us to expand dimension in future to support values like `MinContent`, `MaxContent` and `FitContent`.
750- 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).
751
752#### Position properties renamed
753
754- 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)
755- 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`.
756
757#### Changes to `LayoutTree`
758
759- Added generic associated type to `LayoutTree` for a `ChildIter`, an iterator on the children of a given node.
760- 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.
761- 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.
762- Added `is_childless` method to `LayoutTree` for querying whether a node has no children.
763
764#### `AvailableSpace` has been moved
765
766The `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.
767
768### Fixes
769
770- Flexbox nodes sized under a min-content constraint now size correctly (#291)
771- Aspect ratio is now applied correctly in many circumstances
772- Absolutely positioned items now apply margins correctly
773- Min/max size are now applied correctly
774- Inset applied incorrectly to relatively positioned flexbox children when both `top` and `bottom` or `left` and `right` were specified (#348)
775- 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)
776
777### Removed
778
779- 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.
780- 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.
781- 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.
782
783## 0.2.2
784
785### Fixes
786
787- Border or padding on the horizontal axis could, in some cases, increase the height of nodes.
788
789## 0.2.1
790
791### Fixes
792
793- 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`.
794- `taffy::compute_layout` has been made public allowing Taffy to be used with custom storage (#263)
795
796## 0.2.0
797
798### New features
799
800#### Flexbox "gap" and `AlignContent::SpaceEvenly`
801
802The [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.
803
804Additionally 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)
805
806#### Debug module and cargo feature
807
808Two debugging features have been added:
809
810- `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.
811- A cargo feature `debug`. This enabled debug logging of the layout computation process itself (this is probably mainly useful for those working taffy itself).
812
813### Performance improvements
814
815A number of performance improvements have landed since taffy 0.1:
816
817- 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%.
818- Secondly, the caching implementation was improved by upping the number of cache slots from 2 to 4 and tweaking how computed results are allocated to cache slots to better match the actual usage patterns of the flexbox layout algorithm. This had a particularly dramatic effect on deep hierarchies (which often involve recomputing the same results repeatedly), fixing the exponential blowup that was previously exhibited on these trees and improving performance by over 1000x in some cases!
819
820#### Benchmarks vs. Taffy 0.1
821
822| Benchmark                                 | Taffy 0.1 | Taffy 0.2 | % change (0.1 -> 0.2) |
823| ---                                       | ---       | ---       | ---                   |
824| wide/1_000 nodes (2-level hierarchy)      | 699.18 µs | 445.01 µs | -36.279%              |
825| wide/10_000 nodes (2-level hierarchy)     | 8.8244 ms | 7.1313 ms | -16.352%              |
826| wide/100_000 nodes (2-level hierarchy)    | 204.48 ms | 242.93 ms | +18.803%              |
827| deep/4000 nodes (12-level hierarchy))     | 5.2320 s  | 2.7363 ms | -99.947%              |
828| deep/10_000 nodes (14-level hierarchy)    | 75.207 s  | 6.9415 ms | -99.991%              |
829| deep/100_000 nodes (17-level hierarchy)   | -         | 102.72 ms | -                     |
830| deep/1_000_000 nodes (20-level hierarchy) | -         | 799.35 ms | -                     |
831
832(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
833
834As 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.
835
836However, in the "deep" benchmarks we see dramatic improvements. The previous version of Taffy suffered from exponential blowup in the case of deeply nested hierarchies. This has resulted in somewhat silly improvements like the 10,000 node (14-level) hierarchy where Taffy 0.2 is a full 1 million times faster than Taffy 0.1. We've also included results with larger numbers of nodes (although you're unlikely to need that many) to demonstrate that this scalability continues up to even deeper levels of nesting.
837
838#### Benchmarks vs. [Yoga](https://github.com/facebook/yoga)
839
840Yoga 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.
841
842| Benchmark | Yoga | Taffy 0.2 |
843| --- | --- | --- |
844| yoga/10 nodes (1-level hierarchy) | 45.1670 µs | 33.297 ns |
845| yoga/100 nodes (2-level hierarchy) | 134.1250 µs | 336.53 ns |
846| yoga/1_000 nodes (3-level hierarchy) | 1.2221 ms | 3.8928 µs |
847| yoga/10_000 nodes (4-level hierarchy) | 13.8672 ms | 36.162 µs |
848| yoga/100_000 nodes (5-level hierarchy) | 141.5307 ms | 1.6404 ms |
849
850(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
851
852While 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!
853
854### Breaking API changes
855
856#### Node creation changes
857
858- `taffy::Node` is now unique only to the Taffy instance from which it was created.
859- Renamed `Taffy.new_node(..)` -> `Taffy.new_with_children(..)`
860- Renamed `Taffy.new_leaf()` -> `Taffy.new_leaf_with_measure()`
861- Added `taffy::node::Taffy.new_leaf()` which allows the creation of new leaf-nodes without having to supply a measure function
862
863#### Error handling/representation improvements
864
865- Renamed `taffy::Error` -> `taffy::error::TaffyError`
866- Replaced `taffy::error::InvalidChild` with a new `InvalidChild` variant of `taffy::error::TaffyError`
867- Replaced `taffy::error::InvalidNode` with a new `InvalidNode` variant of `taffy::error::TaffyError`
868- The following method new return `Err(TaffyError::ChildIndexOutOfBounds)` instead of panicking:
869  - `taffy::Taffy::remove_child_at_index`
870  - `taffy::Taffy::replace_child_at_index`
871  - `taffy::Taffy::child_at_index`
872- `Taffy::remove` now returns a `Result<usize, Error>`, to indicate if the operation was successful (and if it was, which ID was invalidated).
873
874#### Some uses of `Option<f32>` replaced with a new `AvailableSpace` enum
875
876A new enum `Taffy::layout::AvailableSpace` has been added.
877
878The definition looks like this:
879
880```rust
881/// The amount of space available to a node in a given axis
882pub enum AvailableSpace {
883    /// The amount of space available is the specified number of pixels
884    Definite(f32),
885    /// The amount of space available is indefinite and the node should be laid out under a min-content constraint
886    MinContent,
887    /// The amount of space available is indefinite and the node should be laid out under a max-content constraint
888    MaxContent,
889}
890```
891
892This 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`).
893
894And 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..
895
896#### Builder methods are now `const` where possible
897
898- Several convenience constants have been defined: notably `Style::DEFAULT`
899- `Size<f32>.zero()` is now `Size::<f32>::ZERO`
900- `Point<f32>.zero()` is now  `Point::<f32>::ZERO`
901- `Size::undefined()` is now `Size::NONE`
902
903#### Removals
904
905- 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%).
906- Removed `taffy::number::Number`. Use `Option<f32>` is used instead
907  - the associated public `MinMax` and `OrElse` traits have also been removed; these should never have been public
908- 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).
909
910### Fixes
911
912- Miscellaneous correctness fixes which align our implementation with Chrome:
913
914  - Nodes can only ever have one parent
915  - Fixed rounding of fractional values to follow latest Chrome - values are now rounded the same regardless of their position
916  - Fixed computing free space when using both `flex-grow` and a minimum size
917  - 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)
918  - `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
919- Taffy can now be vendored using `cargo-vendor` (README.md is now included in package).
920
921## 0.1.0
922
923### 0.1.0 Changed
924
925- the `order` field of `Layout` is now public, and describes the relative z-ordering of nodes
926- renamed crate from `stretch2` to `taffy`
927- updated to the latest version of all dependencies to reduce upstream pain caused by duplicate dependencies
928- renamed `stretch::node::Stretch` -> `taffy::node::Taffy`
929
930### 0.1.0 Fixed
931
932- fixed feature strategy for `alloc` and `std`: these can now be compiled together, with `std`'s types taking priority
933
934### 0.1.0 Removed
935
936- removed Javascript / Kotlin / Swift bindings
937  - the maintainer team lacks expertise to keep these working
938  - more serious refactors are planned, and this will be challenging to keep working through that process
939  - if you are interested in helping us maintain bindings to other languages, [get in touch](https://github.com/DioxusLabs/taffy/discussions)!
940- 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)
941- removed the `Direction` and `Overflow` structs, and the corresponding `direction` and `overflow` fields from `Style`
942  - these had no effect in the current code base and were actively misleading
943
944## stretch2 0.4.3
945
946This is the final release of `stretch`: migrate to the crate named `taffy` for future fixes and features!
947
948These notes describe the differences between this release and `stretch` 0.3.2, the abandoned crate from which this library was forked.
949
950### Changed
951
952- updated [assorted dependencies](https://github.com/vislyhq/stretch/commit/a6491117379cea52dedc9584d892594a143e8cb0)
953
954### Fixed
955
956- fixed an exponential performance blow-up with deep nesting
957- fixed percent height values, which were using parent width
958- recomputing layout no longer moves children of non-zero-positioned parent
959- fixed broken Swift bindings