1# Changelog
2
3## 0.10.1
4
5### Fixed
6
7- CSS Grid auto-repeat and minimum-size handling (#946)
8
9## 0.10.0
10
11The MSRV for this release is 1.71.
12
13### Support for `direction`
14
15The `direction` property is now supported, allowing for RTL layout of boxes in Block, Flexbox, and CSS Grid layout modes.
16
17### Support for floats
18
19The `float` and `clear` properties are now supported. Support consists of a general-purpose `FloatContext` in the `compute` module, and integration of float layout into Block layout. Block layout now also has a `BlockContext` that allows a `FloatContext` to be shared across an entire Block formatting context.
20
21Float support is feature flagged by the `float_layout` feature.
22
23### Support for parsing styles from CSS string (#929)
24
25All of Taffy's style types (except the top-level `Style` struct) now have `FromStr` implementations that parses the type from the CSS representation of that value (e.g. `30px` or `50%` for `LengthPercentage`. A future version of Taffy will likely add support for parsing `Style` from `;`-seperated CSS.
26
27CSS parsing is feature flagged by the `parse` feature.
28
29Additionally the `parse_faster` feature enables optimizations for faster parsing at the cost of pulling in proc-macro dependencies such as `syn`.
30
31### Changed
32
33- Make DetailedGridTracksInfo accessible from a public module (#899)
34- Add `TaffyTree::write_tree` method to debug print the tree into an arbitrary writer (#925)
35- The cache `set` and `set` APIs now take `&LayoutInput` rather than individual values (#933)
36
37### Fixed
38
39- Flexbox: apply gap even when there are auto margins (#938)
40
41## 0.9.3
42
43### Added
44
45- Added write_tree method to utils.
46
47## 0.9.2
48
49### Fixed
50
51- Fix wrong size propogation for absolute elements (#878)
52- Fix bounds check in CellOccupancyMatrix::last_of_type (#890)
53- Use doc_cfg instead of doc_auto_cfg (#868)
54
55### Changed
56
57- Upgraded grid dependency from 0.18 to 1.0 (#864)
58
59## 0.9.1
60
61### Fixed
62
63- Flexbox: don't apply cross-axis stretch alignment to children with auto margins (#861)
64
65## 0.9.0
66
67The MSRV for this release is 1.65.
68
69### Support for named grid lines and grid areas
70
71Taffy now supports named grid lines and areas.
72
73As these rely on arbitrary user-provided strings, Taffy's `Style` struct is now generic
74over a string-like type (via the `CheapCloneStr` trait). Additionally as the `grid` feature is optional,
75it has a `PhantomData` field of that type to make type inference work.
76
77### Changed
78
79- `PrintTree` and `RoundTree`: use `Layout` instead of `&Layout` (#849).
80- Renamed `TrackSizingFunction` to `GridTemplateComponent`
81- Renamed `NonRepeatedTrackSizingFunction` to `TrackSizingFunction`
82- The `Repeat` variant of `GridTemplateComponent` now contains a new `GridTemplateRepetition` struct, which allows
83  line names to be specifed in addition to tracks.
84- The way that grid styles are exposed in the low-level API is now a lot more generic with many associated types.
85
86### Added
87
88- `GridTemplateArea` struct and `Style::grid_template_areas` field
89- `Style::grid_template_column_names` and `Style::grid_template_row_names` fields. If non-empty, these
90  should have length of exactly one greater than the corresponding `grid_template_column`/`grid_template_rows` style.
91
92## 0.8.3
93
94### Fixed
95
96- Fix `serde` feature on 32bit targets (#845)
97
98## 0.8.2
99
100### Fixed
101
102- Fix: Calculate correct new grid size when expanding cell_occupancy_matrix in the negative direction (#843)
103
104## 0.8.1
105
106### Added
107
108- Impl `GridItemStyle` and `BlockContainerStyle` for `Style` (#832).
109
110## 0.8.0
111
112### Highlights
113
114**The big feature in this release is support for `calc()` values in the low-level API.**
115
116To use this API:
117
118- Implement the `resolve_calc_value` method when implementing the `LayoutPartialTree` trait.
119- Pass a type-erased pointer (`*const ()`) to constructors like `LengthPercentage::calc(...)`
120
121Taffy treats the pointer as an opaque value (excepting that it uses the low 3 bits as a tag) which it will
122pass to `LayoutPartialTree::resolve_calc_value` along with a percentage resolution basis when it needs to
123resolve the value.
124
125### Changed
126
127- The representation of many "size" types is now a tagged pointer than an enum. This is to enable `calc()`.
128  The effected types are `LengthPercentage`, `LengthPercentageAuto`, `Dimension`, `MinTrackSizingFunction`, and
129`MaxTrackSizingFunction` types.
130
131### Added
132
133- Special-case "compressible replaced elements" in grid sizing algorithm (#807)
134  This allows for more correct sizing of "replaced" elements such as images that are children
135  of flexbox or grid containers.
136
137### Fixed
138
139- Grid: Fix infinite loop due to float precision in grid layout maximise tracks step (#792)
140- Grid: Fix removed wrong addition, causing items to be misplaced. (#817)
141- Grid: Fix grid placement for items with fixed primary axis (#818)
142- Leaf layout: don't set available space to max-size (#819)
143
144## 0.7.7
145
146### Fixed
147
148- Add `#[inline]` annotation to some methods on `TaffyTree` (#802)
149- Add `TaffyTree::remove_children_range` method (#802)
150
151## 0.7.6
152
153### Fixed
154
155- Fix infinite loop due to float precision in grid layout maximise tracks step (#792)
156
157## 0.7.5
158
159### Fixed
160
161- Grid: only stretch auto tracks if content-alignment is stretch (#783)
162
163## 0.7.4
164
165### Fixed
166
167- Fix detailed grid info for empty grid (#782)
168
169## 0.7.3
170
171### Fixed
172
173- Make `TaffyTree::detailed_layout_info` take `&self` rather than `&mut self` (#779)
174
175## 0.7.2
176
177### Added
178
179- The ability to access computed track sizes and item positions of a CSS Grid layout (#772).
180  This information can be accessed using the `LayoutGridContainer::set_detailed_grid_info` method
181  in the low-level API or the `TaffyTree::detailed_layout_info` method in the high-level API.
182
183## 0.7.1
184
185### Fixed
186
187- Improve interaction of abspos children of block containers with margin collapsing (#760)
188
189### Added
190
191- Add `TaffyTree::unrounded_layout` getter (#765)
192
193### Removed
194
195- The `num-traits` dependency was removed (#761) (#762)
196
197## 0.7.0
198
199### Changed
200
201- BREAKING: The `cache_mut` method on the `LayoutPartialTree` trait has been replaced with a separate `CacheTree` trait. This allows
202  Taffy to be more easily used without caching or with a custom cache implementation.
203- BREAKING: the `TaffyTree::set_children` method now removes the children from their previous parent (if they have one).
204
205### Added
206
207- Helper methods to retrieve content-box sizes were added to `Layout`
208
209## 0.6.3
210
211### Fixes
212
213- Block: ignore margin collapsing when computing static position of abspos items (#747)
214
215## 0.6.2
216
217### Fixes
218
219- Fix: clamp indefinite available space by min- and max- size as appropriate (#742)
220
221## 0.6.1
222
223### Fixes
224
225- Fix calculation of `auto-fill`/`auto-fit` repetition count when container has a definite percentage size (#722)
226- Fix min-size style not affecting intrinsic sizes (#723)
227- Fix documentation of dirty and mark_dirty functions (#724)
228- Fix intrinsic size of scroll containers that have a small explicit flex-basis (#728)
229
230## 0.6.0
231
232### Highlights
233
234- The `Style` struct has been "traitified". This supports Taffy's integration in Servo and generally makes Taffy more flexible. The
235  `Style` struct still exists and implements the new traits so existing uses of Taffy will continue to work as before.
236- The `box-sizing` style is supported
237- Computed margins are output in `Layout`
238
239### Fixes
240
241- Fix `print_tree()` when rounding is disabled (#680)
242- Absolute Insets should be resolved against the container size minus border (#666)
243- Fix flooring hypothetical_main_size by computed min size (#689)
244- Fix flex line cross-size determination (#690)
245- Fix panics in the grid algorithm (#691)
246- Fix resolving flexible lengths (WPT css/flexbox-multiline-min-max test) (#692)
247- Fix wrapping when a max main size style is present (#694)
248- Fix case where Taffy allowed margins to collapse through an element when it shouldn't have (#695)
249
250### Added
251
252- Legacy text align (for laying out `<center>` and `<div align="..">`) is supported
253- Add `is_table` for block items (#701)
254- Impl `Debug` and `Clone` for `Cache` (#688)
255- Implement `Debug` and `PartialEq` for tree types (#697)
256
257## 0.5.2
258
259- Fix block stretch sizing (don't always apply stretch sizing to block containers) (#674)
260- Fix computation of intrinsic main size when it depends on a child's known cross size (#673)
261- Fix panic when GridLine 0 is specified (#671)
262- Docs: Document feature flags and scrape examples (#672)
263- Docs: Update cosmic-text example to cosmic-text 0.12 (#670)
264
265## 0.5.1
266
267- Fix: Clamp block item stretch widths by their min and max width (#664)
268- Fix: Auto margin computation in block layout (#663)
269
270## 0.5.0
271
272The changes in 0.5 are relatively small but the new measure function parameter is a breaking change so it requires a minor version bump.
273
274- Added: A `style: &Style` parameter has been added to measure functions.
275- Added: The `MaybeMath`, `MaybeResolve`, and `ResolveOrZero` traits have been made public.
276- Fix: use SizingMode::Inherent when sizing absolute children of flexbox nodes.
277
278## 0.4.4
279
280### Fixes
281
282- Content alignment (`align-content`/`justify-content`) behaviour was updated to match the latest spec (and Chrome 123+) (#635)
283- Ensure that root Flexbox nodes are floored by their padding-border (#651, #655)
284- Use grid area size not available space when applying aspect ratio to grid containers (#656)
285
286## 0.4.3
287
288### Fixes
289
290- Fix compilation error in `evenly_sized_tracks` style helper in recent versions of rustc caused by a change/regression in type
291  inference (#643). Note that 3rd-party code that call style helpers that take an `Into<f32>` parameter may still be affected by this issue,
292  but they should be able to fix on their side by clarifying the type passed in
293
294## 0.4.2
295
296- Fixed: single-line flex-container should clamp the line's cross-size (#638)
297- Reduced binary footprint of Taffy from around 300kb to around 150kb (#636)
298
299## 0.4.1
300
301- Fixed: CSS Grid track sizing not respecting growth limits in some circumstances (#624)
302
303## 0.4.0
304
305### Highlights
306
307- Support for CSS Block layout (`display: block`)
308- Support for the `overflow` property (+ `scrollbar_width` for `overflow: scroll`)
309- Improved measure function API
310- Completely refactored low-level API
311- Simplified module hierarchy (+ most types/functions are now exported from the crate root)
312- Expanded set of examples which better document integration with other layout systems (e.g. text layout)
313- Computed values for `padding` and `border` are now output into the `Layout` struct
314
315### Block layout
316
317Support 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.
318
319### Overflow property
320
321Support 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.
322
323- Overflow is settable indpendently in each axis.
324- `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.
325- `Hidden` and `Scroll` affect layout by changing the automatic minimum size of Flexbox and Grid children
326- `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`.
327
328### Measure function changes
329
330The "measure function" API for integrating Taffy with other measurement systems (such as text layout) has been changed to be more flexible
331and to interact better with borrow checking (you can now borrow external data in your measure function!).
332
333- There are no longer per-node measure functions.
334- There is now a single "global" measure function, and a per-node "context" of a user-defined type
335- The `Taffy` tree is now a generic `TaffyTree<T>` where `T` is the "context" type.
336- The measure function is now called for all leaf nodes (nodes without children). If you wish to maintain compatibility with the previous
337  behaviour then your measure function should return `Size::ZERO` for leaf nodes whose context is `None`.
338
339If you are not using measure functions, then the only change you will need to make is from:
340
341```rust
342let mut tree = Taffy::new();
343```
344
345to
346
347```rust
348let mut tree : TaffyTree<()> = TaffyTree::new();
349```
350
351And generally update any uses of `Taffy` in your codebase to `TaffyTree<()>`.
352
353If you are using measure functions then you will need to make some bigger (but straightforward) changes. The following Taffy 0.3 code:
354
355```rust
356let mut tree = Taffy::new();
357let leaf = tree.new_leaf_with_measure(
358  Style::DEFAULT,
359  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>| Size { width: 100.0, height: 200.0 }
360);
361tree.compute_layout(leaf, Size::MAX_CONTENT);
362```
363
364Should become something like the following with Taffy 0.4:
365
366```rust
367let mut tree : TaffyTree<Size> = TaffyTree::new();
368let leaf = tree.new_leaf_with_context(Style::DEFAULT, Size { width: 100.0, height: 200.0 });
369tree.compute_layout_with_measure(
370  leaf,
371  Size::MAX_CONTENT,
372  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>, node_id: NodeId, node_context: Option<Size>| {
373    node_context.unwrap_or(Size::ZERO)
374  }
375);
376```
377
378Note that:
379
380- 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).
381- If you don't need a context then you can use `()` for the context type
382- As the single "global" measure function passed to `compute_layout_with_measure` only needs to exist for the duration of a single layout run,
383  it can (mutably) borrow data from it's environment
384
385### Low-level API (`LayoutTree` trait) refactor
386
387The low-level API has been completely reworked:
388
389- The `LayoutTree` trait has been split into 5 smaller traits which live in the `taffy::tree:traits` module (along with their associated documentation)
390- The following methods have been removed from split `LayoutTree` traits entirely: `parent`, `is_childless`, `measure_node`, `needs_measure`, and `mark_dirty`.
391- `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`.
392- Support for running each layout algorithm individually on a single node via the following top-level functions:
393  - `compute_flexbox_layout`
394  - `compute_grid_layout`
395  - `compute_block_layout`
396  - `compute_leaf_layout`
397  - `compute_root_layout`
398  - `compute_hidden_layout`
399
400It 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
401improved 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).
402
403### Module hierarchy changes
404
405The 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`.
406
407Specific changes:
408
409- The `math` module has been made private
410- The `axis` module has been merged into the `geometry` module
411- The debug module is no longer public. The `print_tree` function is now accessible under `util`.
412- All types from the `node`, `data`, `layout`, `error` and `cache` modules have been moved to the  the `tree` module.
413- The `layout_flexbox()` function has been removed from the prelude. Use `taffy::compute_flexbox_layout` instead.
414
415### Many APIs have been renamed to replace `points` or `Points` with `length` or `Length`
416
417This new name better describes one-dimensional measure of space in some unspecified unit
418which is often unrelated to the PostScript point or the CSS `pt` unit.
419
420This also removes a misleading similarity with the 2D `Point`,
421whose components can have any unit and are not even necessarily absolute lengths.
422
423Example usage change:
424
425```diff
426 use taffy::prelude::*;
427
428 // …
429
430 let header_node = taffy
431     .new_leaf(
432         Style {
433-            size: Size { width: points(800.0), height: points(100.0) },
434+            size: Size { width: length(800.0), height: length(100.0) },
435             ..Default::default()
436         },
437     ).unwrap();
438```
439
440### Other Changes
441
442- The `Taffy` type was renamed to `TaffyTree` and made generic of a context parameter
443- The Flexbox algorithm has now been moved behind the `flexbox` feature. The `flexbox` feature is enabled by default.
444- The `justify_self` property has been moved behind the `grid` feature.
445- Fixed misspelling: `RunMode::PeformLayout` renamed into `RunMode::PerformLayout` (added missing `r`).
446- `serde` dependency has been made compatible with `no_std` environments
447- `slotmap` dependency has been made compatible with `no_std` environments
448- 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.
449- Added `total_node_count()` method to the `TaffyTree` which returns the total number of nodes in the tree.
450- Added `get_disjoint_node_context_mut()` method to the `TaffyTree`. This can be used to safely get multiple mutable borrows at the same time.
451
452## 0.3.19
453
454### Fixes
455
456- Fix compilation error in `evenly_sized_tracks` style helper in recent versions of rustc caused by a change/regression in type
457  inference (#643). Note that 3rd-party code that call style helpers that take an `Into<f32>` parameter may still be affected by this issue,
458  but they should be able to fix on their side by clarifying the type passed in
459
460## 0.3.18
461
462### Fixes
463
464- Fix computation of Flexbox automatic minimum size when grid or flexbox child has an explicit width/height style set (#576)
465
466## 0.3.17
467
468### Added
469
470- Added `total_node_count` method to the `Taffy` struct. Returns the total number of nodes in the tree.
471
472## 0.3.16
473
474### Fixes
475
476- Improve performance of flexbox columns
477
478## 0.3.15
479
480### Fixes
481
482- Fix justify-content and align-content when free space is negative (content overflows container) (#549) (#551)
483
484## 0.3.14
485
486### Fixes
487
488- 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)
489
490## 0.3.13
491
492### Fixes
493
494- Fix rounding accumulation bug (#521) (Fixes #501 and bevyengine/bevy#8911)
495- Flexbox: pass correct cross-axis available space when computing an item's intrinsic main size (#522)(Fixes bevyengine/bevy#9350)
496- Flexbox: Subtract child margin not parent margin when computing stretch-alignment known size
497- Grid: Make CSS Grid algorithm correctly apply max width/height and available space when it is the root node (#491)
498- Grid: Fix CSS Grid "auto track" / placement bugs #481
499  - Fix divide by zero when using grid_auto_rows/grid_auto_columns with zero negative implicit tracks
500  - Fix over counting of tracks (leading to incorrect container heights) when auto-placing in grids that contain negative implicit tracks.
501  - Fix axis conflation in auto-placement code when grid_auto_flow is column
502  - Fix assignment of auto track sizes when initializing negative implicit tracks
503- Leaf: Apply margins to leaf nodes when computing available space for measure functions
504- Leaf: Reserve space for padding/borders in nodes with measure functions (#497)
505  
506  **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.
507
508### Dependencies
509
510- Upgrade `grid` to `0.10`. This eliminates the transitive dependency on `no-std-compat`.
511
512## 0.3.12
513
514### Fixes
515
516- Fix caching issue when toggling `display:none` on and off
517
518## 0.3.11
519
520### Fixes
521
522- Fix exponential blowup when laying out trees containing nodes with min and max sizes.
523
524## 0.3.10
525
526### Fixes
527
528- Fix sizing of children when the available_space < min_size (#407)
529
530## 0.3.9
531
532### Fixes
533
534- 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)
535
536## 0.3.8
537
538### Fixes
539
540- Fix incorrect min-content size for `flex-wrap: wrap` nodes (bevyengine/bevy#8082)
541
542## 0.3.7
543
544### Fixes
545
546- Fix: Make `padding` and `border` floor node sizes (#372)
547- Fix: Prevent percentages contributing to min-content sizes (#388) (also fixes bevyengine/bevy#8017)
548
549## 0.3.6
550
551### Fixes
552
553- Fix: Ignore `align_content` when `flex_wrap` is set to `nowrap` (#383)
554
555## 0.3.5
556
557### Fixes
558
559- Fix `display: none` when it is set on a flexbox child (#380)
560- Fix `display: none` when it is set on a grid child (#381)
561
562## 0.3.4
563
564### Fixes
565
566- Fix `display: none` when it is set for the only node in the hierarchy (#377)
567
568## 0.3.3
569
570### Added
571
572- 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.
573
574### Fixes
575
576- Fixed rounding algorithm such that it never leaves gaps between adjacent nodes (#369)
577- Fixed compiling with the `grid` feature disabled (#370)
578- Fixed compiling with the `std` feature disabled
579
580## 0.3.2
581
582### Fixes
583
584- Allow partial nested values to be deserialized into a `Style` using the `serde` feature.
585
586## 0.3.1
587
588### Fixes
589
590- The `serde` feature now works when the `grid` feature is enabled
591
592## 0.3.0
593
594### Highlights
595
596- [CSS Grid algorithm support](#new-feature-css-grid)
597- [Style helper functions](#new-feature-style-helpers)
598
599See below for details of breaking changes.
600
601### New Feature: CSS Grid
602
603We 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`.
604
605#### Learning Resources
606
607Taffy 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:
608
609- [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.
610- [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.
611
612#### Supported Features & Properties
613
614In addition to the usual sizing/spacing properties (size, min_size, padding, margin, etc), the following Grid style properties are supported on Grid Containers:
615
616| Property                  | Explanation                                                                                    |
617| ---                       | ---                                                                                            |
618| [`grid-template-columns`] | The track sizing functions of the grid's explicit columns                                      |
619| [`grid-template-rows`]    | The track sizing functions of the grid's explicit rows                                         |
620| [`grid-auto-rows`]        | Track sizing functions for the grid's implicitly generated rows                                |
621| [`grid-auto-columns`]     | Track sizing functions for the grid's implicitly generated columns                             |
622| [`grid-auto-flow`]        | Whether auto-placed items are placed row-wise or column-wise. And sparsely or densely.         |
623| [`gap`]                   | The size of the vertical and horizontal gaps between grid rows/columns                         |
624| [`align-content`]         | Align grid tracks within the container in the inline (horizontal) axis                         |
625| [`justify-content`]       | Align grid tracks within the container in the block (vertical) axis                            |
626| [`align-items`]           | Align the child items within their grid areas in the inline (horizontal) axis                  |
627| [`justify-items`]         | Align the child items within their grid areas in the block (vertical) axis                     |
628
629And the following Grid style properties are supported on Grid Items (children):
630
631| Property                  | Explanation                                                                                    |
632| ---                       | ---                                                                                            |
633| [`grid-row`]              | The (row) grid line the item starts at (or a span)                                             |
634| [`grid-column`]           | The (column) grid line the item end at (or a span)                                             |
635| [`align-self`]            | Align the item within it's grid area in the inline (horizontal) axis. Overrides `align-items`. |
636| [`justify-self`]          | Align the item within it's grid area in the block (vertical) axis. Overrides `justify-items`.  |
637
638[`grid-template-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-columns
639[`grid-template-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-rows
640[`grid-auto-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-rows
641[`grid-auto-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-columns
642[`grid-auto-flow`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-flow
643[`gap`]: https://developer.mozilla.org/en-US/docs/Web/CSS/gap
644[`align-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align_content
645[`justify-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify_content
646[`align-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-items
647[`justify-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-items
648[`grid-row`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-row
649[`grid-column`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-column
650[`align-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-self
651[`justify-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-self
652
653The following properties and features are not currently supported:
654
655- Subgrids
656- Masonry grid layout
657- Named grid lines
658- Named areas: `grid-template-areas` and `grid-area`
659- `grid-template` or `grid` shorthand
660
661#### Example
662
663See [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:
664
665```bash
666cargo run --example grid_holy_grail --features grid
667```
668
669### New Feature: Style Helpers
670
671Ten 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.
672
673For example, instead of:
674
675```rust
676let size : Size<Dimension> = Size { width: Dimension::Points(100.0), height: Dimension::Percent(50.0) };
677```
678
679you can now write
680
681```rust
682let size : Size<Dimension> = Size { width: points(100.0), height: percent(50.0) };
683```
684
685And 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
686
687```rust
688let size : Size<Dimension> = points(100.0);
689```
690
691Available style helpers:
692
693<table>
694  <thead><tr><th>Type(s)</th><th colspan="2">Helpers that work with that type</th></tr></thead>
695  <tbody>
696    <tr>
697      <td rowspan="3"><code>LengthPercentage</code></td>
698      <td><code>zero()</code></td>
699      <td>Generates a <code>Points</code> variant with the value <code>0.0</code></td>
700    </tr>
701    <tr>
702      <td><code>points(val:&nbsp;f32)</code></td>
703      <td>Generates a <code>Points</code> variant with the specified value</td>
704    </tr>
705    <tr>
706      <td><code>percent(val:&nbsp;f32)</code></td>
707      <td>Generates a <code>Percent</code> variant with the specified value.<br />Note that the scale of 0-1 not 0-100.</td>
708    </tr>
709    <tr>
710      <td rowspan="2"><code>LengthPercentageAuto</code><br /><code>Dimension</code></td>
711      <td colspan="2"><i>All helpers from <code>LengthPercentage</code> and...</i></td>
712    </tr>
713    <tr>
714      <td><code>auto()</code></td>
715      <td>Generates an <code>Auto</code> variant</td>
716    </tr>
717    <tr>
718      <td rowspan="3"><code>MinTrackSizingFunction</code></td>
719      <td colspan="2"><i>All helpers from <code>LengthPercentageAuto</code>/<code>Dimension</code> and...</i></td>
720    </tr>
721    <tr>
722      <td><code>min_content()</code></td>
723      <td>Generates an <code>MinContent</code> variant</td>
724    </tr>
725      <tr>
726      <td><code>max_content()</code></td>
727      <td>Generates an <code>MinContent</code> variant</td>
728    </tr>
729    <tr>
730      <td rowspan="3"><code>MaxTrackSizingFunction</code></td>
731      <td colspan="2"><i>All helpers from <code>MinTrackSizingFunction</code> and...</i></td>
732    </tr>
733    <tr>
734      <td><code>fit_content(limit:&nbsp;LengthPercentage)</code></td>
735      <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>
736    </tr>
737      <tr>
738      <td><code>fr(fraction:&nbsp;f32)</code></td>
739      <td>Generates a <code>Fraction</code> (<code>fr</code>) variant with the specified flex fraction </td>
740    </tr>
741    <tr>
742      <td rowspan="3"><code>NonRepeatingTrackSizingFunction</code></td>
743      <td colspan="2"><i>All helpers from <code>MaxTrackSizingFunction</code> and...</i></td>
744    </tr>
745    <tr>
746      <td><code>minmax(min: MinTrackSizingFunction, max: MaxTrackSizingFunction)</code></td>
747      <td>Equivalent to CSS <code>minmax()</code> function.</td>
748    </tr>
749    <tr>
750      <td><code>flex(fraction:&nbsp;f32)</code></td>
751      <td>Equivalent to CSS <code>minmax(0px, 1fr)</code>. This is likely what you want if you want evenly sized rows/columns.</td>
752    </tr>
753    <tr>
754      <td rowspan="2"><code>TrackSizingFunction</code></td>
755      <td colspan="2"><i>All helpers from <code>NonRepeatingTrackSizingFunction</code> and...</i></td>
756    </tr>
757    <tr>
758      <td><code>repeat(rep: GridTrackRepetition, tracks: Vec&lt;TrackSizingFunction&gt;)</code></td>
759      <td>Equivalent to css <code>repeat()</code> function.</td>
760    </tr>
761    <tr>
762      <td><code>Vec&lt;TrackSizingFunction&gt;</code></td>
763      <td><code>evenly_sized_tracks(count:&nbsp;u16)</code></td>
764      <td>Equivalent to CSS <code>repeat(count, minmax(0px, 1fr)</code></td>
765    </tr>
766    <tr>
767      <td rowspan="3"><code>AvailableSpace</code></td>
768      <td><code>auto()</code></td>
769      <td>Generates an <code>Auto</code> variant</td>
770    </tr>
771    <tr>
772      <td><code>min_content()</code></td>
773      <td>Generates an <code>MinContent</code> variant</td>
774    </tr>
775      <tr>
776      <td><code>max_content()</code></td>
777      <td>Generates an <code>MinContent</code> variant</td>
778    </tr>
779    <tr>
780      <td><code>Size&lt;T&gt;</code></td>
781      <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>
782    </tr>
783    <tr>
784      <td><code>Rect&lt;T&gt;</code></td>
785      <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>
786    </tr>
787  </tbody>
788</table>
789
790### Breaking API changes
791
792#### Changes to alignment style types
793
794- `AlignContent` and `JustifyContent` has been merged.
795  - `JustifyContent` is now an alias of `AlignContent` and contains the `Stretch` variant.
796  - This variant will be *ignored* (falling back to `Start`) when applied Flexbox containers. It is valid value for Grid containers.
797- `AlignItems` and `AlignSelf` have been merged.
798  - The `Auto` variant of `AlignSelf` has been removed. You should now use `Option::None` if you wish to specify `AlignSelf::Auto`.
799  - `AlignSelf` is now an alias of `AlignItems`.
800  - `JustifyItems` and `JustifySelf` aliases have been added. These properties have no affect on Flexbox containers, but apply to Grid containers.
801- `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.
802
803#### Strict style types
804
805- New types `LengthPercentage` and `LengthPercentageAuto` have been added.
806  - `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.
807  - `LengthPercentageAuto` is currently identical to `Dimension` but will allow us to expand dimension in future to support values like `MinContent`, `MaxContent` and `FitContent`.
808- 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).
809
810#### Position properties renamed
811
812- 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)
813- 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`.
814
815#### Changes to `LayoutTree`
816
817- Added generic associated type to `LayoutTree` for a `ChildIter`, an iterator on the children of a given node.
818- 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.
819- 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.
820- Added `is_childless` method to `LayoutTree` for querying whether a node has no children.
821
822#### `AvailableSpace` has been moved
823
824The `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.
825
826### Fixes
827
828- Flexbox nodes sized under a min-content constraint now size correctly (#291)
829- Aspect ratio is now applied correctly in many circumstances
830- Absolutely positioned items now apply margins correctly
831- Min/max size are now applied correctly
832- Inset applied incorrectly to relatively positioned flexbox children when both `top` and `bottom` or `left` and `right` were specified (#348)
833- 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)
834
835### Removed
836
837- 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.
838- 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.
839- 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.
840
841## 0.2.2
842
843### Fixes
844
845- Border or padding on the horizontal axis could, in some cases, increase the height of nodes.
846
847## 0.2.1
848
849### Fixes
850
851- 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`.
852- `taffy::compute_layout` has been made public allowing Taffy to be used with custom storage (#263)
853
854## 0.2.0
855
856### New features
857
858#### Flexbox "gap" and `AlignContent::SpaceEvenly`
859
860The [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.
861
862Additionally 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)
863
864#### Debug module and cargo feature
865
866Two debugging features have been added:
867
868- `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.
869- A cargo feature `debug`. This enabled debug logging of the layout computation process itself (this is probably mainly useful for those working taffy itself).
870
871### Performance improvements
872
873A number of performance improvements have landed since taffy 0.1:
874
875- 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%.
876- 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!
877
878#### Benchmarks vs. Taffy 0.1
879
880| Benchmark                                 | Taffy 0.1 | Taffy 0.2 | % change (0.1 -> 0.2) |
881| ---                                       | ---       | ---       | ---                   |
882| wide/1_000 nodes (2-level hierarchy)      | 699.18 µs | 445.01 µs | -36.279%              |
883| wide/10_000 nodes (2-level hierarchy)     | 8.8244 ms | 7.1313 ms | -16.352%              |
884| wide/100_000 nodes (2-level hierarchy)    | 204.48 ms | 242.93 ms | +18.803%              |
885| deep/4000 nodes (12-level hierarchy))     | 5.2320 s  | 2.7363 ms | -99.947%              |
886| deep/10_000 nodes (14-level hierarchy)    | 75.207 s  | 6.9415 ms | -99.991%              |
887| deep/100_000 nodes (17-level hierarchy)   | -         | 102.72 ms | -                     |
888| deep/1_000_000 nodes (20-level hierarchy) | -         | 799.35 ms | -                     |
889
890(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
891
892As 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.
893
894However, 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.
895
896#### Benchmarks vs. [Yoga](https://github.com/facebook/yoga)
897
898Yoga 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.
899
900| Benchmark | Yoga | Taffy 0.2 |
901| --- | --- | --- |
902| yoga/10 nodes (1-level hierarchy) | 45.1670 µs | 33.297 ns |
903| yoga/100 nodes (2-level hierarchy) | 134.1250 µs | 336.53 ns |
904| yoga/1_000 nodes (3-level hierarchy) | 1.2221 ms | 3.8928 µs |
905| yoga/10_000 nodes (4-level hierarchy) | 13.8672 ms | 36.162 µs |
906| yoga/100_000 nodes (5-level hierarchy) | 141.5307 ms | 1.6404 ms |
907
908(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
909
910While 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!
911
912### Breaking API changes
913
914#### Node creation changes
915
916- `taffy::Node` is now unique only to the Taffy instance from which it was created.
917- Renamed `Taffy.new_node(..)` -> `Taffy.new_with_children(..)`
918- Renamed `Taffy.new_leaf()` -> `Taffy.new_leaf_with_measure()`
919- Added `taffy::node::Taffy.new_leaf()` which allows the creation of new leaf-nodes without having to supply a measure function
920
921#### Error handling/representation improvements
922
923- Renamed `taffy::Error` -> `taffy::error::TaffyError`
924- Replaced `taffy::error::InvalidChild` with a new `InvalidChild` variant of `taffy::error::TaffyError`
925- Replaced `taffy::error::InvalidNode` with a new `InvalidNode` variant of `taffy::error::TaffyError`
926- The following method new return `Err(TaffyError::ChildIndexOutOfBounds)` instead of panicking:
927  - `taffy::Taffy::remove_child_at_index`
928  - `taffy::Taffy::replace_child_at_index`
929  - `taffy::Taffy::child_at_index`
930- `Taffy::remove` now returns a `Result<usize, Error>`, to indicate if the operation was successful (and if it was, which ID was invalidated).
931
932#### Some uses of `Option<f32>` replaced with a new `AvailableSpace` enum
933
934A new enum `Taffy::layout::AvailableSpace` has been added.
935
936The definition looks like this:
937
938```rust
939/// The amount of space available to a node in a given axis
940pub enum AvailableSpace {
941    /// The amount of space available is the specified number of pixels
942    Definite(f32),
943    /// The amount of space available is indefinite and the node should be laid out under a min-content constraint
944    MinContent,
945    /// The amount of space available is indefinite and the node should be laid out under a max-content constraint
946    MaxContent,
947}
948```
949
950This 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`).
951
952And 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..
953
954#### Builder methods are now `const` where possible
955
956- Several convenience constants have been defined: notably `Style::DEFAULT`
957- `Size<f32>.zero()` is now `Size::<f32>::ZERO`
958- `Point<f32>.zero()` is now  `Point::<f32>::ZERO`
959- `Size::undefined()` is now `Size::NONE`
960
961#### Removals
962
963- 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%).
964- Removed `taffy::number::Number`. Use `Option<f32>` is used instead
965  - the associated public `MinMax` and `OrElse` traits have also been removed; these should never have been public
966- 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).
967
968### Fixes
969
970- Miscellaneous correctness fixes which align our implementation with Chrome:
971
972  - Nodes can only ever have one parent
973  - Fixed rounding of fractional values to follow latest Chrome - values are now rounded the same regardless of their position
974  - Fixed computing free space when using both `flex-grow` and a minimum size
975  - 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)
976  - `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
977- Taffy can now be vendored using `cargo-vendor` (README.md is now included in package).
978
979## 0.1.0
980
981### 0.1.0 Changed
982
983- the `order` field of `Layout` is now public, and describes the relative z-ordering of nodes
984- renamed crate from `stretch2` to `taffy`
985- updated to the latest version of all dependencies to reduce upstream pain caused by duplicate dependencies
986- renamed `stretch::node::Stretch` -> `taffy::node::Taffy`
987
988### 0.1.0 Fixed
989
990- fixed feature strategy for `alloc` and `std`: these can now be compiled together, with `std`'s types taking priority
991
992### 0.1.0 Removed
993
994- removed Javascript / Kotlin / Swift bindings
995  - the maintainer team lacks expertise to keep these working
996  - more serious refactors are planned, and this will be challenging to keep working through that process
997  - if you are interested in helping us maintain bindings to other languages, [get in touch](https://github.com/DioxusLabs/taffy/discussions)!
998- 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)
999- removed the `Direction` and `Overflow` structs, and the corresponding `direction` and `overflow` fields from `Style`
1000  - these had no effect in the current code base and were actively misleading
1001
1002## stretch2 0.4.3
1003
1004This is the final release of `stretch`: migrate to the crate named `taffy` for future fixes and features!
1005
1006These notes describe the differences between this release and `stretch` 0.3.2, the abandoned crate from which this library was forked.
1007
1008### Changed
1009
1010- updated [assorted dependencies](https://github.com/vislyhq/stretch/commit/a6491117379cea52dedc9584d892594a143e8cb0)
1011
1012### Fixed
1013
1014- fixed an exponential performance blow-up with deep nesting
1015- fixed percent height values, which were using parent width
1016- recomputing layout no longer moves children of non-zero-positioned parent
1017- fixed broken Swift bindings