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