1# Changelog
2
3## 0.11.0
4
5The MSRV for this release is 1.71.
6
7### Implemented safe alignment keywords (#952)
8
9Taffy now implements [safe alignment](https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Properties/align-items#safe) (in addition to unsafe alignment).
10
11The alignment style types are now structs consisting of an `AlignmentKeyword` and an `AlignmentSafety` modifier. For most users this will mean changing from using enum variants like `AlignContent::Start` to associated constants like `AlignContent::START`.
12
13This change applies to the `AlignContent`, `JustifyContent`, `AlignItems`, `JustifyItems`, `AlignSelf`, and `JustifySelf` types.
14
15### Fixed
16
17- Grid: resolve item percentages against grid area rather than grid container (#960)
18
19## 0.10.1
20
21### Fixed
22
23- CSS Grid auto-repeat and minimum-size handling (#946)
24
25## 0.10.0
26
27The MSRV for this release is 1.71.
28
29### Support for `direction`
30
31The `direction` property is now supported, allowing for RTL layout of boxes in Block, Flexbox, and CSS Grid layout modes.
32
33### Support for floats
34
35The `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.
36
37Float support is feature flagged by the `float_layout` feature.
38
39### Support for parsing styles from CSS string (#929)
40
41All 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.
42
43CSS parsing is feature flagged by the `parse` feature.
44
45Additionally the `parse_faster` feature enables optimizations for faster parsing at the cost of pulling in proc-macro dependencies such as `syn`.
46
47### Changed
48
49- Make DetailedGridTracksInfo accessible from a public module (#899)
50- Add `TaffyTree::write_tree` method to debug print the tree into an arbitrary writer (#925)
51- The cache `set` and `set` APIs now take `&LayoutInput` rather than individual values (#933)
52
53### Fixed
54
55- Flexbox: apply gap even when there are auto margins (#938)
56
57## 0.9.3
58
59### Added
60
61- Added write_tree method to utils.
62
63## 0.9.2
64
65### Fixed
66
67- Fix wrong size propogation for absolute elements (#878)
68- Fix bounds check in CellOccupancyMatrix::last_of_type (#890)
69- Use doc_cfg instead of doc_auto_cfg (#868)
70
71### Changed
72
73- Upgraded grid dependency from 0.18 to 1.0 (#864)
74
75## 0.9.1
76
77### Fixed
78
79- Flexbox: don't apply cross-axis stretch alignment to children with auto margins (#861)
80
81## 0.9.0
82
83The MSRV for this release is 1.65.
84
85### Support for named grid lines and grid areas
86
87Taffy now supports named grid lines and areas.
88
89As these rely on arbitrary user-provided strings, Taffy's `Style` struct is now generic
90over a string-like type (via the `CheapCloneStr` trait). Additionally as the `grid` feature is optional,
91it has a `PhantomData` field of that type to make type inference work.
92
93### Changed
94
95- `PrintTree` and `RoundTree`: use `Layout` instead of `&Layout` (#849).
96- Renamed `TrackSizingFunction` to `GridTemplateComponent`
97- Renamed `NonRepeatedTrackSizingFunction` to `TrackSizingFunction`
98- The `Repeat` variant of `GridTemplateComponent` now contains a new `GridTemplateRepetition` struct, which allows
99  line names to be specifed in addition to tracks.
100- The way that grid styles are exposed in the low-level API is now a lot more generic with many associated types.
101
102### Added
103
104- `GridTemplateArea` struct and `Style::grid_template_areas` field
105- `Style::grid_template_column_names` and `Style::grid_template_row_names` fields. If non-empty, these
106  should have length of exactly one greater than the corresponding `grid_template_column`/`grid_template_rows` style.
107
108## 0.8.3
109
110### Fixed
111
112- Fix `serde` feature on 32bit targets (#845)
113
114## 0.8.2
115
116### Fixed
117
118- Fix: Calculate correct new grid size when expanding cell_occupancy_matrix in the negative direction (#843)
119
120## 0.8.1
121
122### Added
123
124- Impl `GridItemStyle` and `BlockContainerStyle` for `Style` (#832).
125
126## 0.8.0
127
128### Highlights
129
130**The big feature in this release is support for `calc()` values in the low-level API.**
131
132To use this API:
133
134- Implement the `resolve_calc_value` method when implementing the `LayoutPartialTree` trait.
135- Pass a type-erased pointer (`*const ()`) to constructors like `LengthPercentage::calc(...)`
136
137Taffy treats the pointer as an opaque value (excepting that it uses the low 3 bits as a tag) which it will
138pass to `LayoutPartialTree::resolve_calc_value` along with a percentage resolution basis when it needs to
139resolve the value.
140
141### Changed
142
143- The representation of many "size" types is now a tagged pointer than an enum. This is to enable `calc()`.
144  The effected types are `LengthPercentage`, `LengthPercentageAuto`, `Dimension`, `MinTrackSizingFunction`, and
145`MaxTrackSizingFunction` types.
146
147### Added
148
149- Special-case "compressible replaced elements" in grid sizing algorithm (#807)
150  This allows for more correct sizing of "replaced" elements such as images that are children
151  of flexbox or grid containers.
152
153### Fixed
154
155- Grid: Fix infinite loop due to float precision in grid layout maximise tracks step (#792)
156- Grid: Fix removed wrong addition, causing items to be misplaced. (#817)
157- Grid: Fix grid placement for items with fixed primary axis (#818)
158- Leaf layout: don't set available space to max-size (#819)
159
160## 0.7.7
161
162### Fixed
163
164- Add `#[inline]` annotation to some methods on `TaffyTree` (#802)
165- Add `TaffyTree::remove_children_range` method (#802)
166
167## 0.7.6
168
169### Fixed
170
171- Fix infinite loop due to float precision in grid layout maximise tracks step (#792)
172
173## 0.7.5
174
175### Fixed
176
177- Grid: only stretch auto tracks if content-alignment is stretch (#783)
178
179## 0.7.4
180
181### Fixed
182
183- Fix detailed grid info for empty grid (#782)
184
185## 0.7.3
186
187### Fixed
188
189- Make `TaffyTree::detailed_layout_info` take `&self` rather than `&mut self` (#779)
190
191## 0.7.2
192
193### Added
194
195- The ability to access computed track sizes and item positions of a CSS Grid layout (#772).
196  This information can be accessed using the `LayoutGridContainer::set_detailed_grid_info` method
197  in the low-level API or the `TaffyTree::detailed_layout_info` method in the high-level API.
198
199## 0.7.1
200
201### Fixed
202
203- Improve interaction of abspos children of block containers with margin collapsing (#760)
204
205### Added
206
207- Add `TaffyTree::unrounded_layout` getter (#765)
208
209### Removed
210
211- The `num-traits` dependency was removed (#761) (#762)
212
213## 0.7.0
214
215### Changed
216
217- BREAKING: The `cache_mut` method on the `LayoutPartialTree` trait has been replaced with a separate `CacheTree` trait. This allows
218  Taffy to be more easily used without caching or with a custom cache implementation.
219- BREAKING: the `TaffyTree::set_children` method now removes the children from their previous parent (if they have one).
220
221### Added
222
223- Helper methods to retrieve content-box sizes were added to `Layout`
224
225## 0.6.3
226
227### Fixes
228
229- Block: ignore margin collapsing when computing static position of abspos items (#747)
230
231## 0.6.2
232
233### Fixes
234
235- Fix: clamp indefinite available space by min- and max- size as appropriate (#742)
236
237## 0.6.1
238
239### Fixes
240
241- Fix calculation of `auto-fill`/`auto-fit` repetition count when container has a definite percentage size (#722)
242- Fix min-size style not affecting intrinsic sizes (#723)
243- Fix documentation of dirty and mark_dirty functions (#724)
244- Fix intrinsic size of scroll containers that have a small explicit flex-basis (#728)
245
246## 0.6.0
247
248### Highlights
249
250- The `Style` struct has been "traitified". This supports Taffy's integration in Servo and generally makes Taffy more flexible. The
251  `Style` struct still exists and implements the new traits so existing uses of Taffy will continue to work as before.
252- The `box-sizing` style is supported
253- Computed margins are output in `Layout`
254
255### Fixes
256
257- Fix `print_tree()` when rounding is disabled (#680)
258- Absolute Insets should be resolved against the container size minus border (#666)
259- Fix flooring hypothetical_main_size by computed min size (#689)
260- Fix flex line cross-size determination (#690)
261- Fix panics in the grid algorithm (#691)
262- Fix resolving flexible lengths (WPT css/flexbox-multiline-min-max test) (#692)
263- Fix wrapping when a max main size style is present (#694)
264- Fix case where Taffy allowed margins to collapse through an element when it shouldn't have (#695)
265
266### Added
267
268- Legacy text align (for laying out `<center>` and `<div align="..">`) is supported
269- Add `is_table` for block items (#701)
270- Impl `Debug` and `Clone` for `Cache` (#688)
271- Implement `Debug` and `PartialEq` for tree types (#697)
272
273## 0.5.2
274
275- Fix block stretch sizing (don't always apply stretch sizing to block containers) (#674)
276- Fix computation of intrinsic main size when it depends on a child's known cross size (#673)
277- Fix panic when GridLine 0 is specified (#671)
278- Docs: Document feature flags and scrape examples (#672)
279- Docs: Update cosmic-text example to cosmic-text 0.12 (#670)
280
281## 0.5.1
282
283- Fix: Clamp block item stretch widths by their min and max width (#664)
284- Fix: Auto margin computation in block layout (#663)
285
286## 0.5.0
287
288The changes in 0.5 are relatively small but the new measure function parameter is a breaking change so it requires a minor version bump.
289
290- Added: A `style: &Style` parameter has been added to measure functions.
291- Added: The `MaybeMath`, `MaybeResolve`, and `ResolveOrZero` traits have been made public.
292- Fix: use SizingMode::Inherent when sizing absolute children of flexbox nodes.
293
294## 0.4.4
295
296### Fixes
297
298- Content alignment (`align-content`/`justify-content`) behaviour was updated to match the latest spec (and Chrome 123+) (#635)
299- Ensure that root Flexbox nodes are floored by their padding-border (#651, #655)
300- Use grid area size not available space when applying aspect ratio to grid containers (#656)
301
302## 0.4.3
303
304### Fixes
305
306- Fix compilation error in `evenly_sized_tracks` style helper in recent versions of rustc caused by a change/regression in type
307  inference (#643). Note that 3rd-party code that call style helpers that take an `Into<f32>` parameter may still be affected by this issue,
308  but they should be able to fix on their side by clarifying the type passed in
309
310## 0.4.2
311
312- Fixed: single-line flex-container should clamp the line's cross-size (#638)
313- Reduced binary footprint of Taffy from around 300kb to around 150kb (#636)
314
315## 0.4.1
316
317- Fixed: CSS Grid track sizing not respecting growth limits in some circumstances (#624)
318
319## 0.4.0
320
321### Highlights
322
323- Support for CSS Block layout (`display: block`)
324- Support for the `overflow` property (+ `scrollbar_width` for `overflow: scroll`)
325- Improved measure function API
326- Completely refactored low-level API
327- Simplified module hierarchy (+ most types/functions are now exported from the crate root)
328- Expanded set of examples which better document integration with other layout systems (e.g. text layout)
329- Computed values for `padding` and `border` are now output into the `Layout` struct
330
331### Block layout
332
333Support 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.
334
335### Overflow property
336
337Support 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.
338
339- Overflow is settable indpendently in each axis.
340- `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.
341- `Hidden` and `Scroll` affect layout by changing the automatic minimum size of Flexbox and Grid children
342- `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`.
343
344### Measure function changes
345
346The "measure function" API for integrating Taffy with other measurement systems (such as text layout) has been changed to be more flexible
347and to interact better with borrow checking (you can now borrow external data in your measure function!).
348
349- There are no longer per-node measure functions.
350- There is now a single "global" measure function, and a per-node "context" of a user-defined type
351- The `Taffy` tree is now a generic `TaffyTree<T>` where `T` is the "context" type.
352- The measure function is now called for all leaf nodes (nodes without children). If you wish to maintain compatibility with the previous
353  behaviour then your measure function should return `Size::ZERO` for leaf nodes whose context is `None`.
354
355If you are not using measure functions, then the only change you will need to make is from:
356
357```rust
358let mut tree = Taffy::new();
359```
360
361to
362
363```rust
364let mut tree : TaffyTree<()> = TaffyTree::new();
365```
366
367And generally update any uses of `Taffy` in your codebase to `TaffyTree<()>`.
368
369If you are using measure functions then you will need to make some bigger (but straightforward) changes. The following Taffy 0.3 code:
370
371```rust
372let mut tree = Taffy::new();
373let leaf = tree.new_leaf_with_measure(
374  Style::DEFAULT,
375  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>| Size { width: 100.0, height: 200.0 }
376);
377tree.compute_layout(leaf, Size::MAX_CONTENT);
378```
379
380Should become something like the following with Taffy 0.4:
381
382```rust
383let mut tree : TaffyTree<Size> = TaffyTree::new();
384let leaf = tree.new_leaf_with_context(Style::DEFAULT, Size { width: 100.0, height: 200.0 });
385tree.compute_layout_with_measure(
386  leaf,
387  Size::MAX_CONTENT,
388  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>, node_id: NodeId, node_context: Option<Size>| {
389    node_context.unwrap_or(Size::ZERO)
390  }
391);
392```
393
394Note that:
395
396- 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).
397- If you don't need a context then you can use `()` for the context type
398- As the single "global" measure function passed to `compute_layout_with_measure` only needs to exist for the duration of a single layout run,
399  it can (mutably) borrow data from it's environment
400
401### Low-level API (`LayoutTree` trait) refactor
402
403The low-level API has been completely reworked:
404
405- The `LayoutTree` trait has been split into 5 smaller traits which live in the `taffy::tree:traits` module (along with their associated documentation)
406- The following methods have been removed from split `LayoutTree` traits entirely: `parent`, `is_childless`, `measure_node`, `needs_measure`, and `mark_dirty`.
407- `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`.
408- Support for running each layout algorithm individually on a single node via the following top-level functions:
409  - `compute_flexbox_layout`
410  - `compute_grid_layout`
411  - `compute_block_layout`
412  - `compute_leaf_layout`
413  - `compute_root_layout`
414  - `compute_hidden_layout`
415
416It 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
417improved 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).
418
419### Module hierarchy changes
420
421The 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`.
422
423Specific changes:
424
425- The `math` module has been made private
426- The `axis` module has been merged into the `geometry` module
427- The debug module is no longer public. The `print_tree` function is now accessible under `util`.
428- All types from the `node`, `data`, `layout`, `error` and `cache` modules have been moved to the  the `tree` module.
429- The `layout_flexbox()` function has been removed from the prelude. Use `taffy::compute_flexbox_layout` instead.
430
431### Many APIs have been renamed to replace `points` or `Points` with `length` or `Length`
432
433This new name better describes one-dimensional measure of space in some unspecified unit
434which is often unrelated to the PostScript point or the CSS `pt` unit.
435
436This also removes a misleading similarity with the 2D `Point`,
437whose components can have any unit and are not even necessarily absolute lengths.
438
439Example usage change:
440
441```diff
442 use taffy::prelude::*;
443
444 // …
445
446 let header_node = taffy
447     .new_leaf(
448         Style {
449-            size: Size { width: points(800.0), height: points(100.0) },
450+            size: Size { width: length(800.0), height: length(100.0) },
451             ..Default::default()
452         },
453     ).unwrap();
454```
455
456### Other Changes
457
458- The `Taffy` type was renamed to `TaffyTree` and made generic of a context parameter
459- The Flexbox algorithm has now been moved behind the `flexbox` feature. The `flexbox` feature is enabled by default.
460- The `justify_self` property has been moved behind the `grid` feature.
461- Fixed misspelling: `RunMode::PeformLayout` renamed into `RunMode::PerformLayout` (added missing `r`).
462- `serde` dependency has been made compatible with `no_std` environments
463- `slotmap` dependency has been made compatible with `no_std` environments
464- 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.
465- Added `total_node_count()` method to the `TaffyTree` which returns the total number of nodes in the tree.
466- Added `get_disjoint_node_context_mut()` method to the `TaffyTree`. This can be used to safely get multiple mutable borrows at the same time.
467
468## 0.3.19
469
470### Fixes
471
472- Fix compilation error in `evenly_sized_tracks` style helper in recent versions of rustc caused by a change/regression in type
473  inference (#643). Note that 3rd-party code that call style helpers that take an `Into<f32>` parameter may still be affected by this issue,
474  but they should be able to fix on their side by clarifying the type passed in
475
476## 0.3.18
477
478### Fixes
479
480- Fix computation of Flexbox automatic minimum size when grid or flexbox child has an explicit width/height style set (#576)
481
482## 0.3.17
483
484### Added
485
486- Added `total_node_count` method to the `Taffy` struct. Returns the total number of nodes in the tree.
487
488## 0.3.16
489
490### Fixes
491
492- Improve performance of flexbox columns
493
494## 0.3.15
495
496### Fixes
497
498- Fix justify-content and align-content when free space is negative (content overflows container) (#549) (#551)
499
500## 0.3.14
501
502### Fixes
503
504- 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)
505
506## 0.3.13
507
508### Fixes
509
510- Fix rounding accumulation bug (#521) (Fixes #501 and bevyengine/bevy#8911)
511- Flexbox: pass correct cross-axis available space when computing an item's intrinsic main size (#522)(Fixes bevyengine/bevy#9350)
512- Flexbox: Subtract child margin not parent margin when computing stretch-alignment known size
513- Grid: Make CSS Grid algorithm correctly apply max width/height and available space when it is the root node (#491)
514- Grid: Fix CSS Grid "auto track" / placement bugs #481
515  - Fix divide by zero when using grid_auto_rows/grid_auto_columns with zero negative implicit tracks
516  - Fix over counting of tracks (leading to incorrect container heights) when auto-placing in grids that contain negative implicit tracks.
517  - Fix axis conflation in auto-placement code when grid_auto_flow is column
518  - Fix assignment of auto track sizes when initializing negative implicit tracks
519- Leaf: Apply margins to leaf nodes when computing available space for measure functions
520- Leaf: Reserve space for padding/borders in nodes with measure functions (#497)
521  
522  **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.
523
524### Dependencies
525
526- Upgrade `grid` to `0.10`. This eliminates the transitive dependency on `no-std-compat`.
527
528## 0.3.12
529
530### Fixes
531
532- Fix caching issue when toggling `display:none` on and off
533
534## 0.3.11
535
536### Fixes
537
538- Fix exponential blowup when laying out trees containing nodes with min and max sizes.
539
540## 0.3.10
541
542### Fixes
543
544- Fix sizing of children when the available_space < min_size (#407)
545
546## 0.3.9
547
548### Fixes
549
550- 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)
551
552## 0.3.8
553
554### Fixes
555
556- Fix incorrect min-content size for `flex-wrap: wrap` nodes (bevyengine/bevy#8082)
557
558## 0.3.7
559
560### Fixes
561
562- Fix: Make `padding` and `border` floor node sizes (#372)
563- Fix: Prevent percentages contributing to min-content sizes (#388) (also fixes bevyengine/bevy#8017)
564
565## 0.3.6
566
567### Fixes
568
569- Fix: Ignore `align_content` when `flex_wrap` is set to `nowrap` (#383)
570
571## 0.3.5
572
573### Fixes
574
575- Fix `display: none` when it is set on a flexbox child (#380)
576- Fix `display: none` when it is set on a grid child (#381)
577
578## 0.3.4
579
580### Fixes
581
582- Fix `display: none` when it is set for the only node in the hierarchy (#377)
583
584## 0.3.3
585
586### Added
587
588- 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.
589
590### Fixes
591
592- Fixed rounding algorithm such that it never leaves gaps between adjacent nodes (#369)
593- Fixed compiling with the `grid` feature disabled (#370)
594- Fixed compiling with the `std` feature disabled
595
596## 0.3.2
597
598### Fixes
599
600- Allow partial nested values to be deserialized into a `Style` using the `serde` feature.
601
602## 0.3.1
603
604### Fixes
605
606- The `serde` feature now works when the `grid` feature is enabled
607
608## 0.3.0
609
610### Highlights
611
612- [CSS Grid algorithm support](#new-feature-css-grid)
613- [Style helper functions](#new-feature-style-helpers)
614
615See below for details of breaking changes.
616
617### New Feature: CSS Grid
618
619We 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`.
620
621#### Learning Resources
622
623Taffy 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:
624
625- [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.
626- [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.
627
628#### Supported Features & Properties
629
630In addition to the usual sizing/spacing properties (size, min_size, padding, margin, etc), the following Grid style properties are supported on Grid Containers:
631
632| Property                  | Explanation                                                                                    |
633| ---                       | ---                                                                                            |
634| [`grid-template-columns`] | The track sizing functions of the grid's explicit columns                                      |
635| [`grid-template-rows`]    | The track sizing functions of the grid's explicit rows                                         |
636| [`grid-auto-rows`]        | Track sizing functions for the grid's implicitly generated rows                                |
637| [`grid-auto-columns`]     | Track sizing functions for the grid's implicitly generated columns                             |
638| [`grid-auto-flow`]        | Whether auto-placed items are placed row-wise or column-wise. And sparsely or densely.         |
639| [`gap`]                   | The size of the vertical and horizontal gaps between grid rows/columns                         |
640| [`align-content`]         | Align grid tracks within the container in the inline (horizontal) axis                         |
641| [`justify-content`]       | Align grid tracks within the container in the block (vertical) axis                            |
642| [`align-items`]           | Align the child items within their grid areas in the inline (horizontal) axis                  |
643| [`justify-items`]         | Align the child items within their grid areas in the block (vertical) axis                     |
644
645And the following Grid style properties are supported on Grid Items (children):
646
647| Property                  | Explanation                                                                                    |
648| ---                       | ---                                                                                            |
649| [`grid-row`]              | The (row) grid line the item starts at (or a span)                                             |
650| [`grid-column`]           | The (column) grid line the item end at (or a span)                                             |
651| [`align-self`]            | Align the item within it's grid area in the inline (horizontal) axis. Overrides `align-items`. |
652| [`justify-self`]          | Align the item within it's grid area in the block (vertical) axis. Overrides `justify-items`.  |
653
654[`grid-template-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-columns
655[`grid-template-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-rows
656[`grid-auto-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-rows
657[`grid-auto-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-columns
658[`grid-auto-flow`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-flow
659[`gap`]: https://developer.mozilla.org/en-US/docs/Web/CSS/gap
660[`align-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align_content
661[`justify-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify_content
662[`align-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-items
663[`justify-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-items
664[`grid-row`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-row
665[`grid-column`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-column
666[`align-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-self
667[`justify-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-self
668
669The following properties and features are not currently supported:
670
671- Subgrids
672- Masonry grid layout
673- Named grid lines
674- Named areas: `grid-template-areas` and `grid-area`
675- `grid-template` or `grid` shorthand
676
677#### Example
678
679See [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:
680
681```bash
682cargo run --example grid_holy_grail --features grid
683```
684
685### New Feature: Style Helpers
686
687Ten 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.
688
689For example, instead of:
690
691```rust
692let size : Size<Dimension> = Size { width: Dimension::Points(100.0), height: Dimension::Percent(50.0) };
693```
694
695you can now write
696
697```rust
698let size : Size<Dimension> = Size { width: points(100.0), height: percent(50.0) };
699```
700
701And 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
702
703```rust
704let size : Size<Dimension> = points(100.0);
705```
706
707Available style helpers:
708
709<table>
710  <thead><tr><th>Type(s)</th><th colspan="2">Helpers that work with that type</th></tr></thead>
711  <tbody>
712    <tr>
713      <td rowspan="3"><code>LengthPercentage</code></td>
714      <td><code>zero()</code></td>
715      <td>Generates a <code>Points</code> variant with the value <code>0.0</code></td>
716    </tr>
717    <tr>
718      <td><code>points(val:&nbsp;f32)</code></td>
719      <td>Generates a <code>Points</code> variant with the specified value</td>
720    </tr>
721    <tr>
722      <td><code>percent(val:&nbsp;f32)</code></td>
723      <td>Generates a <code>Percent</code> variant with the specified value.<br />Note that the scale of 0-1 not 0-100.</td>
724    </tr>
725    <tr>
726      <td rowspan="2"><code>LengthPercentageAuto</code><br /><code>Dimension</code></td>
727      <td colspan="2"><i>All helpers from <code>LengthPercentage</code> and...</i></td>
728    </tr>
729    <tr>
730      <td><code>auto()</code></td>
731      <td>Generates an <code>Auto</code> variant</td>
732    </tr>
733    <tr>
734      <td rowspan="3"><code>MinTrackSizingFunction</code></td>
735      <td colspan="2"><i>All helpers from <code>LengthPercentageAuto</code>/<code>Dimension</code> and...</i></td>
736    </tr>
737    <tr>
738      <td><code>min_content()</code></td>
739      <td>Generates an <code>MinContent</code> variant</td>
740    </tr>
741      <tr>
742      <td><code>max_content()</code></td>
743      <td>Generates an <code>MinContent</code> variant</td>
744    </tr>
745    <tr>
746      <td rowspan="3"><code>MaxTrackSizingFunction</code></td>
747      <td colspan="2"><i>All helpers from <code>MinTrackSizingFunction</code> and...</i></td>
748    </tr>
749    <tr>
750      <td><code>fit_content(limit:&nbsp;LengthPercentage)</code></td>
751      <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>
752    </tr>
753      <tr>
754      <td><code>fr(fraction:&nbsp;f32)</code></td>
755      <td>Generates a <code>Fraction</code> (<code>fr</code>) variant with the specified flex fraction </td>
756    </tr>
757    <tr>
758      <td rowspan="3"><code>NonRepeatingTrackSizingFunction</code></td>
759      <td colspan="2"><i>All helpers from <code>MaxTrackSizingFunction</code> and...</i></td>
760    </tr>
761    <tr>
762      <td><code>minmax(min: MinTrackSizingFunction, max: MaxTrackSizingFunction)</code></td>
763      <td>Equivalent to CSS <code>minmax()</code> function.</td>
764    </tr>
765    <tr>
766      <td><code>flex(fraction:&nbsp;f32)</code></td>
767      <td>Equivalent to CSS <code>minmax(0px, 1fr)</code>. This is likely what you want if you want evenly sized rows/columns.</td>
768    </tr>
769    <tr>
770      <td rowspan="2"><code>TrackSizingFunction</code></td>
771      <td colspan="2"><i>All helpers from <code>NonRepeatingTrackSizingFunction</code> and...</i></td>
772    </tr>
773    <tr>
774      <td><code>repeat(rep: GridTrackRepetition, tracks: Vec&lt;TrackSizingFunction&gt;)</code></td>
775      <td>Equivalent to css <code>repeat()</code> function.</td>
776    </tr>
777    <tr>
778      <td><code>Vec&lt;TrackSizingFunction&gt;</code></td>
779      <td><code>evenly_sized_tracks(count:&nbsp;u16)</code></td>
780      <td>Equivalent to CSS <code>repeat(count, minmax(0px, 1fr)</code></td>
781    </tr>
782    <tr>
783      <td rowspan="3"><code>AvailableSpace</code></td>
784      <td><code>auto()</code></td>
785      <td>Generates an <code>Auto</code> variant</td>
786    </tr>
787    <tr>
788      <td><code>min_content()</code></td>
789      <td>Generates an <code>MinContent</code> variant</td>
790    </tr>
791      <tr>
792      <td><code>max_content()</code></td>
793      <td>Generates an <code>MinContent</code> variant</td>
794    </tr>
795    <tr>
796      <td><code>Size&lt;T&gt;</code></td>
797      <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>
798    </tr>
799    <tr>
800      <td><code>Rect&lt;T&gt;</code></td>
801      <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>
802    </tr>
803  </tbody>
804</table>
805
806### Breaking API changes
807
808#### Changes to alignment style types
809
810- `AlignContent` and `JustifyContent` has been merged.
811  - `JustifyContent` is now an alias of `AlignContent` and contains the `Stretch` variant.
812  - This variant will be *ignored* (falling back to `Start`) when applied Flexbox containers. It is valid value for Grid containers.
813- `AlignItems` and `AlignSelf` have been merged.
814  - The `Auto` variant of `AlignSelf` has been removed. You should now use `Option::None` if you wish to specify `AlignSelf::Auto`.
815  - `AlignSelf` is now an alias of `AlignItems`.
816  - `JustifyItems` and `JustifySelf` aliases have been added. These properties have no affect on Flexbox containers, but apply to Grid containers.
817- `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.
818
819#### Strict style types
820
821- New types `LengthPercentage` and `LengthPercentageAuto` have been added.
822  - `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.
823  - `LengthPercentageAuto` is currently identical to `Dimension` but will allow us to expand dimension in future to support values like `MinContent`, `MaxContent` and `FitContent`.
824- 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).
825
826#### Position properties renamed
827
828- 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)
829- 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`.
830
831#### Changes to `LayoutTree`
832
833- Added generic associated type to `LayoutTree` for a `ChildIter`, an iterator on the children of a given node.
834- 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.
835- 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.
836- Added `is_childless` method to `LayoutTree` for querying whether a node has no children.
837
838#### `AvailableSpace` has been moved
839
840The `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.
841
842### Fixes
843
844- Flexbox nodes sized under a min-content constraint now size correctly (#291)
845- Aspect ratio is now applied correctly in many circumstances
846- Absolutely positioned items now apply margins correctly
847- Min/max size are now applied correctly
848- Inset applied incorrectly to relatively positioned flexbox children when both `top` and `bottom` or `left` and `right` were specified (#348)
849- 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)
850
851### Removed
852
853- 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.
854- 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.
855- 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.
856
857## 0.2.2
858
859### Fixes
860
861- Border or padding on the horizontal axis could, in some cases, increase the height of nodes.
862
863## 0.2.1
864
865### Fixes
866
867- 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`.
868- `taffy::compute_layout` has been made public allowing Taffy to be used with custom storage (#263)
869
870## 0.2.0
871
872### New features
873
874#### Flexbox "gap" and `AlignContent::SpaceEvenly`
875
876The [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.
877
878Additionally 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)
879
880#### Debug module and cargo feature
881
882Two debugging features have been added:
883
884- `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.
885- A cargo feature `debug`. This enabled debug logging of the layout computation process itself (this is probably mainly useful for those working taffy itself).
886
887### Performance improvements
888
889A number of performance improvements have landed since taffy 0.1:
890
891- 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%.
892- 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!
893
894#### Benchmarks vs. Taffy 0.1
895
896| Benchmark                                 | Taffy 0.1 | Taffy 0.2 | % change (0.1 -> 0.2) |
897| ---                                       | ---       | ---       | ---                   |
898| wide/1_000 nodes (2-level hierarchy)      | 699.18 µs | 445.01 µs | -36.279%              |
899| wide/10_000 nodes (2-level hierarchy)     | 8.8244 ms | 7.1313 ms | -16.352%              |
900| wide/100_000 nodes (2-level hierarchy)    | 204.48 ms | 242.93 ms | +18.803%              |
901| deep/4000 nodes (12-level hierarchy))     | 5.2320 s  | 2.7363 ms | -99.947%              |
902| deep/10_000 nodes (14-level hierarchy)    | 75.207 s  | 6.9415 ms | -99.991%              |
903| deep/100_000 nodes (17-level hierarchy)   | -         | 102.72 ms | -                     |
904| deep/1_000_000 nodes (20-level hierarchy) | -         | 799.35 ms | -                     |
905
906(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
907
908As 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.
909
910However, 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.
911
912#### Benchmarks vs. [Yoga](https://github.com/facebook/yoga)
913
914Yoga 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.
915
916| Benchmark | Yoga | Taffy 0.2 |
917| --- | --- | --- |
918| yoga/10 nodes (1-level hierarchy) | 45.1670 µs | 33.297 ns |
919| yoga/100 nodes (2-level hierarchy) | 134.1250 µs | 336.53 ns |
920| yoga/1_000 nodes (3-level hierarchy) | 1.2221 ms | 3.8928 µs |
921| yoga/10_000 nodes (4-level hierarchy) | 13.8672 ms | 36.162 µs |
922| yoga/100_000 nodes (5-level hierarchy) | 141.5307 ms | 1.6404 ms |
923
924(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
925
926While 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!
927
928### Breaking API changes
929
930#### Node creation changes
931
932- `taffy::Node` is now unique only to the Taffy instance from which it was created.
933- Renamed `Taffy.new_node(..)` -> `Taffy.new_with_children(..)`
934- Renamed `Taffy.new_leaf()` -> `Taffy.new_leaf_with_measure()`
935- Added `taffy::node::Taffy.new_leaf()` which allows the creation of new leaf-nodes without having to supply a measure function
936
937#### Error handling/representation improvements
938
939- Renamed `taffy::Error` -> `taffy::error::TaffyError`
940- Replaced `taffy::error::InvalidChild` with a new `InvalidChild` variant of `taffy::error::TaffyError`
941- Replaced `taffy::error::InvalidNode` with a new `InvalidNode` variant of `taffy::error::TaffyError`
942- The following method new return `Err(TaffyError::ChildIndexOutOfBounds)` instead of panicking:
943  - `taffy::Taffy::remove_child_at_index`
944  - `taffy::Taffy::replace_child_at_index`
945  - `taffy::Taffy::child_at_index`
946- `Taffy::remove` now returns a `Result<usize, Error>`, to indicate if the operation was successful (and if it was, which ID was invalidated).
947
948#### Some uses of `Option<f32>` replaced with a new `AvailableSpace` enum
949
950A new enum `Taffy::layout::AvailableSpace` has been added.
951
952The definition looks like this:
953
954```rust
955/// The amount of space available to a node in a given axis
956pub enum AvailableSpace {
957    /// The amount of space available is the specified number of pixels
958    Definite(f32),
959    /// The amount of space available is indefinite and the node should be laid out under a min-content constraint
960    MinContent,
961    /// The amount of space available is indefinite and the node should be laid out under a max-content constraint
962    MaxContent,
963}
964```
965
966This 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`).
967
968And 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..
969
970#### Builder methods are now `const` where possible
971
972- Several convenience constants have been defined: notably `Style::DEFAULT`
973- `Size<f32>.zero()` is now `Size::<f32>::ZERO`
974- `Point<f32>.zero()` is now  `Point::<f32>::ZERO`
975- `Size::undefined()` is now `Size::NONE`
976
977#### Removals
978
979- 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%).
980- Removed `taffy::number::Number`. Use `Option<f32>` is used instead
981  - the associated public `MinMax` and `OrElse` traits have also been removed; these should never have been public
982- 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).
983
984### Fixes
985
986- Miscellaneous correctness fixes which align our implementation with Chrome:
987
988  - Nodes can only ever have one parent
989  - Fixed rounding of fractional values to follow latest Chrome - values are now rounded the same regardless of their position
990  - Fixed computing free space when using both `flex-grow` and a minimum size
991  - 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)
992  - `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
993- Taffy can now be vendored using `cargo-vendor` (README.md is now included in package).
994
995## 0.1.0
996
997### 0.1.0 Changed
998
999- the `order` field of `Layout` is now public, and describes the relative z-ordering of nodes
1000- renamed crate from `stretch2` to `taffy`
1001- updated to the latest version of all dependencies to reduce upstream pain caused by duplicate dependencies
1002- renamed `stretch::node::Stretch` -> `taffy::node::Taffy`
1003
1004### 0.1.0 Fixed
1005
1006- fixed feature strategy for `alloc` and `std`: these can now be compiled together, with `std`'s types taking priority
1007
1008### 0.1.0 Removed
1009
1010- removed Javascript / Kotlin / Swift bindings
1011  - the maintainer team lacks expertise to keep these working
1012  - more serious refactors are planned, and this will be challenging to keep working through that process
1013  - if you are interested in helping us maintain bindings to other languages, [get in touch](https://github.com/DioxusLabs/taffy/discussions)!
1014- 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)
1015- removed the `Direction` and `Overflow` structs, and the corresponding `direction` and `overflow` fields from `Style`
1016  - these had no effect in the current code base and were actively misleading
1017
1018## stretch2 0.4.3
1019
1020This is the final release of `stretch`: migrate to the crate named `taffy` for future fixes and features!
1021
1022These notes describe the differences between this release and `stretch` 0.3.2, the abandoned crate from which this library was forked.
1023
1024### Changed
1025
1026- updated [assorted dependencies](https://github.com/vislyhq/stretch/commit/a6491117379cea52dedc9584d892594a143e8cb0)
1027
1028### Fixed
1029
1030- fixed an exponential performance blow-up with deep nesting
1031- fixed percent height values, which were using parent width
1032- recomputing layout no longer moves children of non-zero-positioned parent
1033- fixed broken Swift bindings