1# Changelog
2
3## 0.12.0
4
5The MSRV for this release is 1.71.
6
7### Block: support for `align-content` (#959)
8
9Block containers now implement `align_content` along the block axis for their in-flow children.
10
11### More correct caching logic
12
13- The cache key now includes the axis, parent size, and available space, and ignores available space in an axis when a known dimension is set there. This is a performance hit (~10% in common cases, ~60% in pathalogically ones) but is necessary for correctness. It does also enable early-return optimizations (in cases where only the horizontal size is needed, which can allow that performance to be recouped in some cases (#911)
14
15### Fixed
16
17- Flexbox: fall back to safe `align-self` of `start` on absolute-position overflow (#958)
18- Block: derive definite height from `aspect-ratio` at final layout. A block container with `aspect-ratio` and an automatic height now becomes definite when its width is filled/stretched, so children's percentage heights resolve correctly and the ratio is preserved (#965)
19
20## 0.11.0
21
22The MSRV for this release is 1.71.
23
24### Implemented safe alignment keywords (#952)
25
26Taffy now implements [safe alignment](https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Properties/align-items#safe) (in addition to unsafe alignment).
27
28The 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`.
29
30This change applies to the `AlignContent`, `JustifyContent`, `AlignItems`, `JustifyItems`, `AlignSelf`, and `JustifySelf` types.
31
32### Fixed
33
34- Grid: resolve item percentages against grid area rather than grid container (#960)
35
36## 0.10.1
37
38### Fixed
39
40- CSS Grid auto-repeat and minimum-size handling (#946)
41
42## 0.10.0
43
44The MSRV for this release is 1.71.
45
46### Support for `direction`
47
48The `direction` property is now supported, allowing for RTL layout of boxes in Block, Flexbox, and CSS Grid layout modes.
49
50### Support for floats
51
52The `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.
53
54Float support is feature flagged by the `float_layout` feature.
55
56### Support for parsing styles from CSS string (#929)
57
58All 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.
59
60CSS parsing is feature flagged by the `parse` feature.
61
62Additionally the `parse_faster` feature enables optimizations for faster parsing at the cost of pulling in proc-macro dependencies such as `syn`.
63
64### Changed
65
66- Make DetailedGridTracksInfo accessible from a public module (#899)
67- Add `TaffyTree::write_tree` method to debug print the tree into an arbitrary writer (#925)
68- The cache `set` and `set` APIs now take `&LayoutInput` rather than individual values (#933)
69
70### Fixed
71
72- Flexbox: apply gap even when there are auto margins (#938)
73
74## 0.9.3
75
76### Added
77
78- Added write_tree method to utils.
79
80## 0.9.2
81
82### Fixed
83
84- Fix wrong size propogation for absolute elements (#878)
85- Fix bounds check in CellOccupancyMatrix::last_of_type (#890)
86- Use doc_cfg instead of doc_auto_cfg (#868)
87
88### Changed
89
90- Upgraded grid dependency from 0.18 to 1.0 (#864)
91
92## 0.9.1
93
94### Fixed
95
96- Flexbox: don't apply cross-axis stretch alignment to children with auto margins (#861)
97
98## 0.9.0
99
100The MSRV for this release is 1.65.
101
102### Support for named grid lines and grid areas
103
104Taffy now supports named grid lines and areas.
105
106As these rely on arbitrary user-provided strings, Taffy's `Style` struct is now generic
107over a string-like type (via the `CheapCloneStr` trait). Additionally as the `grid` feature is optional,
108it has a `PhantomData` field of that type to make type inference work.
109
110### Changed
111
112- `PrintTree` and `RoundTree`: use `Layout` instead of `&Layout` (#849).
113- Renamed `TrackSizingFunction` to `GridTemplateComponent`
114- Renamed `NonRepeatedTrackSizingFunction` to `TrackSizingFunction`
115- The `Repeat` variant of `GridTemplateComponent` now contains a new `GridTemplateRepetition` struct, which allows
116  line names to be specifed in addition to tracks.
117- The way that grid styles are exposed in the low-level API is now a lot more generic with many associated types.
118
119### Added
120
121- `GridTemplateArea` struct and `Style::grid_template_areas` field
122- `Style::grid_template_column_names` and `Style::grid_template_row_names` fields. If non-empty, these
123  should have length of exactly one greater than the corresponding `grid_template_column`/`grid_template_rows` style.
124
125## 0.8.3
126
127### Fixed
128
129- Fix `serde` feature on 32bit targets (#845)
130
131## 0.8.2
132
133### Fixed
134
135- Fix: Calculate correct new grid size when expanding cell_occupancy_matrix in the negative direction (#843)
136
137## 0.8.1
138
139### Added
140
141- Impl `GridItemStyle` and `BlockContainerStyle` for `Style` (#832).
142
143## 0.8.0
144
145### Highlights
146
147**The big feature in this release is support for `calc()` values in the low-level API.**
148
149To use this API:
150
151- Implement the `resolve_calc_value` method when implementing the `LayoutPartialTree` trait.
152- Pass a type-erased pointer (`*const ()`) to constructors like `LengthPercentage::calc(...)`
153
154Taffy treats the pointer as an opaque value (excepting that it uses the low 3 bits as a tag) which it will
155pass to `LayoutPartialTree::resolve_calc_value` along with a percentage resolution basis when it needs to
156resolve the value.
157
158### Changed
159
160- The representation of many "size" types is now a tagged pointer than an enum. This is to enable `calc()`.
161  The effected types are `LengthPercentage`, `LengthPercentageAuto`, `Dimension`, `MinTrackSizingFunction`, and
162`MaxTrackSizingFunction` types.
163
164### Added
165
166- Special-case "compressible replaced elements" in grid sizing algorithm (#807)
167  This allows for more correct sizing of "replaced" elements such as images that are children
168  of flexbox or grid containers.
169
170### Fixed
171
172- Grid: Fix infinite loop due to float precision in grid layout maximise tracks step (#792)
173- Grid: Fix removed wrong addition, causing items to be misplaced. (#817)
174- Grid: Fix grid placement for items with fixed primary axis (#818)
175- Leaf layout: don't set available space to max-size (#819)
176
177## 0.7.7
178
179### Fixed
180
181- Add `#[inline]` annotation to some methods on `TaffyTree` (#802)
182- Add `TaffyTree::remove_children_range` method (#802)
183
184## 0.7.6
185
186### Fixed
187
188- Fix infinite loop due to float precision in grid layout maximise tracks step (#792)
189
190## 0.7.5
191
192### Fixed
193
194- Grid: only stretch auto tracks if content-alignment is stretch (#783)
195
196## 0.7.4
197
198### Fixed
199
200- Fix detailed grid info for empty grid (#782)
201
202## 0.7.3
203
204### Fixed
205
206- Make `TaffyTree::detailed_layout_info` take `&self` rather than `&mut self` (#779)
207
208## 0.7.2
209
210### Added
211
212- The ability to access computed track sizes and item positions of a CSS Grid layout (#772).
213  This information can be accessed using the `LayoutGridContainer::set_detailed_grid_info` method
214  in the low-level API or the `TaffyTree::detailed_layout_info` method in the high-level API.
215
216## 0.7.1
217
218### Fixed
219
220- Improve interaction of abspos children of block containers with margin collapsing (#760)
221
222### Added
223
224- Add `TaffyTree::unrounded_layout` getter (#765)
225
226### Removed
227
228- The `num-traits` dependency was removed (#761) (#762)
229
230## 0.7.0
231
232### Changed
233
234- BREAKING: The `cache_mut` method on the `LayoutPartialTree` trait has been replaced with a separate `CacheTree` trait. This allows
235  Taffy to be more easily used without caching or with a custom cache implementation.
236- BREAKING: the `TaffyTree::set_children` method now removes the children from their previous parent (if they have one).
237
238### Added
239
240- Helper methods to retrieve content-box sizes were added to `Layout`
241
242## 0.6.3
243
244### Fixes
245
246- Block: ignore margin collapsing when computing static position of abspos items (#747)
247
248## 0.6.2
249
250### Fixes
251
252- Fix: clamp indefinite available space by min- and max- size as appropriate (#742)
253
254## 0.6.1
255
256### Fixes
257
258- Fix calculation of `auto-fill`/`auto-fit` repetition count when container has a definite percentage size (#722)
259- Fix min-size style not affecting intrinsic sizes (#723)
260- Fix documentation of dirty and mark_dirty functions (#724)
261- Fix intrinsic size of scroll containers that have a small explicit flex-basis (#728)
262
263## 0.6.0
264
265### Highlights
266
267- The `Style` struct has been "traitified". This supports Taffy's integration in Servo and generally makes Taffy more flexible. The
268  `Style` struct still exists and implements the new traits so existing uses of Taffy will continue to work as before.
269- The `box-sizing` style is supported
270- Computed margins are output in `Layout`
271
272### Fixes
273
274- Fix `print_tree()` when rounding is disabled (#680)
275- Absolute Insets should be resolved against the container size minus border (#666)
276- Fix flooring hypothetical_main_size by computed min size (#689)
277- Fix flex line cross-size determination (#690)
278- Fix panics in the grid algorithm (#691)
279- Fix resolving flexible lengths (WPT css/flexbox-multiline-min-max test) (#692)
280- Fix wrapping when a max main size style is present (#694)
281- Fix case where Taffy allowed margins to collapse through an element when it shouldn't have (#695)
282
283### Added
284
285- Legacy text align (for laying out `<center>` and `<div align="..">`) is supported
286- Add `is_table` for block items (#701)
287- Impl `Debug` and `Clone` for `Cache` (#688)
288- Implement `Debug` and `PartialEq` for tree types (#697)
289
290## 0.5.2
291
292- Fix block stretch sizing (don't always apply stretch sizing to block containers) (#674)
293- Fix computation of intrinsic main size when it depends on a child's known cross size (#673)
294- Fix panic when GridLine 0 is specified (#671)
295- Docs: Document feature flags and scrape examples (#672)
296- Docs: Update cosmic-text example to cosmic-text 0.12 (#670)
297
298## 0.5.1
299
300- Fix: Clamp block item stretch widths by their min and max width (#664)
301- Fix: Auto margin computation in block layout (#663)
302
303## 0.5.0
304
305The changes in 0.5 are relatively small but the new measure function parameter is a breaking change so it requires a minor version bump.
306
307- Added: A `style: &Style` parameter has been added to measure functions.
308- Added: The `MaybeMath`, `MaybeResolve`, and `ResolveOrZero` traits have been made public.
309- Fix: use SizingMode::Inherent when sizing absolute children of flexbox nodes.
310
311## 0.4.4
312
313### Fixes
314
315- Content alignment (`align-content`/`justify-content`) behaviour was updated to match the latest spec (and Chrome 123+) (#635)
316- Ensure that root Flexbox nodes are floored by their padding-border (#651, #655)
317- Use grid area size not available space when applying aspect ratio to grid containers (#656)
318
319## 0.4.3
320
321### Fixes
322
323- Fix compilation error in `evenly_sized_tracks` style helper in recent versions of rustc caused by a change/regression in type
324  inference (#643). Note that 3rd-party code that call style helpers that take an `Into<f32>` parameter may still be affected by this issue,
325  but they should be able to fix on their side by clarifying the type passed in
326
327## 0.4.2
328
329- Fixed: single-line flex-container should clamp the line's cross-size (#638)
330- Reduced binary footprint of Taffy from around 300kb to around 150kb (#636)
331
332## 0.4.1
333
334- Fixed: CSS Grid track sizing not respecting growth limits in some circumstances (#624)
335
336## 0.4.0
337
338### Highlights
339
340- Support for CSS Block layout (`display: block`)
341- Support for the `overflow` property (+ `scrollbar_width` for `overflow: scroll`)
342- Improved measure function API
343- Completely refactored low-level API
344- Simplified module hierarchy (+ most types/functions are now exported from the crate root)
345- Expanded set of examples which better document integration with other layout systems (e.g. text layout)
346- Computed values for `padding` and `border` are now output into the `Layout` struct
347
348### Block layout
349
350Support 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.
351
352### Overflow property
353
354Support 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.
355
356- Overflow is settable indpendently in each axis.
357- `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.
358- `Hidden` and `Scroll` affect layout by changing the automatic minimum size of Flexbox and Grid children
359- `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`.
360
361### Measure function changes
362
363The "measure function" API for integrating Taffy with other measurement systems (such as text layout) has been changed to be more flexible
364and to interact better with borrow checking (you can now borrow external data in your measure function!).
365
366- There are no longer per-node measure functions.
367- There is now a single "global" measure function, and a per-node "context" of a user-defined type
368- The `Taffy` tree is now a generic `TaffyTree<T>` where `T` is the "context" type.
369- The measure function is now called for all leaf nodes (nodes without children). If you wish to maintain compatibility with the previous
370  behaviour then your measure function should return `Size::ZERO` for leaf nodes whose context is `None`.
371
372If you are not using measure functions, then the only change you will need to make is from:
373
374```rust
375let mut tree = Taffy::new();
376```
377
378to
379
380```rust
381let mut tree : TaffyTree<()> = TaffyTree::new();
382```
383
384And generally update any uses of `Taffy` in your codebase to `TaffyTree<()>`.
385
386If you are using measure functions then you will need to make some bigger (but straightforward) changes. The following Taffy 0.3 code:
387
388```rust
389let mut tree = Taffy::new();
390let leaf = tree.new_leaf_with_measure(
391  Style::DEFAULT,
392  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>| Size { width: 100.0, height: 200.0 }
393);
394tree.compute_layout(leaf, Size::MAX_CONTENT);
395```
396
397Should become something like the following with Taffy 0.4:
398
399```rust
400let mut tree : TaffyTree<Size> = TaffyTree::new();
401let leaf = tree.new_leaf_with_context(Style::DEFAULT, Size { width: 100.0, height: 200.0 });
402tree.compute_layout_with_measure(
403  leaf,
404  Size::MAX_CONTENT,
405  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>, node_id: NodeId, node_context: Option<Size>| {
406    node_context.unwrap_or(Size::ZERO)
407  }
408);
409```
410
411Note that:
412
413- 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).
414- If you don't need a context then you can use `()` for the context type
415- As the single "global" measure function passed to `compute_layout_with_measure` only needs to exist for the duration of a single layout run,
416  it can (mutably) borrow data from it's environment
417
418### Low-level API (`LayoutTree` trait) refactor
419
420The low-level API has been completely reworked:
421
422- The `LayoutTree` trait has been split into 5 smaller traits which live in the `taffy::tree:traits` module (along with their associated documentation)
423- The following methods have been removed from split `LayoutTree` traits entirely: `parent`, `is_childless`, `measure_node`, `needs_measure`, and `mark_dirty`.
424- `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`.
425- Support for running each layout algorithm individually on a single node via the following top-level functions:
426  - `compute_flexbox_layout`
427  - `compute_grid_layout`
428  - `compute_block_layout`
429  - `compute_leaf_layout`
430  - `compute_root_layout`
431  - `compute_hidden_layout`
432
433It 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
434improved 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).
435
436### Module hierarchy changes
437
438The 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`.
439
440Specific changes:
441
442- The `math` module has been made private
443- The `axis` module has been merged into the `geometry` module
444- The debug module is no longer public. The `print_tree` function is now accessible under `util`.
445- All types from the `node`, `data`, `layout`, `error` and `cache` modules have been moved to the  the `tree` module.
446- The `layout_flexbox()` function has been removed from the prelude. Use `taffy::compute_flexbox_layout` instead.
447
448### Many APIs have been renamed to replace `points` or `Points` with `length` or `Length`
449
450This new name better describes one-dimensional measure of space in some unspecified unit
451which is often unrelated to the PostScript point or the CSS `pt` unit.
452
453This also removes a misleading similarity with the 2D `Point`,
454whose components can have any unit and are not even necessarily absolute lengths.
455
456Example usage change:
457
458```diff
459 use taffy::prelude::*;
460
461 // …
462
463 let header_node = taffy
464     .new_leaf(
465         Style {
466-            size: Size { width: points(800.0), height: points(100.0) },
467+            size: Size { width: length(800.0), height: length(100.0) },
468             ..Default::default()
469         },
470     ).unwrap();
471```
472
473### Other Changes
474
475- The `Taffy` type was renamed to `TaffyTree` and made generic of a context parameter
476- The Flexbox algorithm has now been moved behind the `flexbox` feature. The `flexbox` feature is enabled by default.
477- The `justify_self` property has been moved behind the `grid` feature.
478- Fixed misspelling: `RunMode::PeformLayout` renamed into `RunMode::PerformLayout` (added missing `r`).
479- `serde` dependency has been made compatible with `no_std` environments
480- `slotmap` dependency has been made compatible with `no_std` environments
481- 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.
482- Added `total_node_count()` method to the `TaffyTree` which returns the total number of nodes in the tree.
483- Added `get_disjoint_node_context_mut()` method to the `TaffyTree`. This can be used to safely get multiple mutable borrows at the same time.
484
485## 0.3.19
486
487### Fixes
488
489- Fix compilation error in `evenly_sized_tracks` style helper in recent versions of rustc caused by a change/regression in type
490  inference (#643). Note that 3rd-party code that call style helpers that take an `Into<f32>` parameter may still be affected by this issue,
491  but they should be able to fix on their side by clarifying the type passed in
492
493## 0.3.18
494
495### Fixes
496
497- Fix computation of Flexbox automatic minimum size when grid or flexbox child has an explicit width/height style set (#576)
498
499## 0.3.17
500
501### Added
502
503- Added `total_node_count` method to the `Taffy` struct. Returns the total number of nodes in the tree.
504
505## 0.3.16
506
507### Fixes
508
509- Improve performance of flexbox columns
510
511## 0.3.15
512
513### Fixes
514
515- Fix justify-content and align-content when free space is negative (content overflows container) (#549) (#551)
516
517## 0.3.14
518
519### Fixes
520
521- 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)
522
523## 0.3.13
524
525### Fixes
526
527- Fix rounding accumulation bug (#521) (Fixes #501 and bevyengine/bevy#8911)
528- Flexbox: pass correct cross-axis available space when computing an item's intrinsic main size (#522)(Fixes bevyengine/bevy#9350)
529- Flexbox: Subtract child margin not parent margin when computing stretch-alignment known size
530- Grid: Make CSS Grid algorithm correctly apply max width/height and available space when it is the root node (#491)
531- Grid: Fix CSS Grid "auto track" / placement bugs #481
532  - Fix divide by zero when using grid_auto_rows/grid_auto_columns with zero negative implicit tracks
533  - Fix over counting of tracks (leading to incorrect container heights) when auto-placing in grids that contain negative implicit tracks.
534  - Fix axis conflation in auto-placement code when grid_auto_flow is column
535  - Fix assignment of auto track sizes when initializing negative implicit tracks
536- Leaf: Apply margins to leaf nodes when computing available space for measure functions
537- Leaf: Reserve space for padding/borders in nodes with measure functions (#497)
538  
539  **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.
540
541### Dependencies
542
543- Upgrade `grid` to `0.10`. This eliminates the transitive dependency on `no-std-compat`.
544
545## 0.3.12
546
547### Fixes
548
549- Fix caching issue when toggling `display:none` on and off
550
551## 0.3.11
552
553### Fixes
554
555- Fix exponential blowup when laying out trees containing nodes with min and max sizes.
556
557## 0.3.10
558
559### Fixes
560
561- Fix sizing of children when the available_space < min_size (#407)
562
563## 0.3.9
564
565### Fixes
566
567- 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)
568
569## 0.3.8
570
571### Fixes
572
573- Fix incorrect min-content size for `flex-wrap: wrap` nodes (bevyengine/bevy#8082)
574
575## 0.3.7
576
577### Fixes
578
579- Fix: Make `padding` and `border` floor node sizes (#372)
580- Fix: Prevent percentages contributing to min-content sizes (#388) (also fixes bevyengine/bevy#8017)
581
582## 0.3.6
583
584### Fixes
585
586- Fix: Ignore `align_content` when `flex_wrap` is set to `nowrap` (#383)
587
588## 0.3.5
589
590### Fixes
591
592- Fix `display: none` when it is set on a flexbox child (#380)
593- Fix `display: none` when it is set on a grid child (#381)
594
595## 0.3.4
596
597### Fixes
598
599- Fix `display: none` when it is set for the only node in the hierarchy (#377)
600
601## 0.3.3
602
603### Added
604
605- 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.
606
607### Fixes
608
609- Fixed rounding algorithm such that it never leaves gaps between adjacent nodes (#369)
610- Fixed compiling with the `grid` feature disabled (#370)
611- Fixed compiling with the `std` feature disabled
612
613## 0.3.2
614
615### Fixes
616
617- Allow partial nested values to be deserialized into a `Style` using the `serde` feature.
618
619## 0.3.1
620
621### Fixes
622
623- The `serde` feature now works when the `grid` feature is enabled
624
625## 0.3.0
626
627### Highlights
628
629- [CSS Grid algorithm support](#new-feature-css-grid)
630- [Style helper functions](#new-feature-style-helpers)
631
632See below for details of breaking changes.
633
634### New Feature: CSS Grid
635
636We 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`.
637
638#### Learning Resources
639
640Taffy 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:
641
642- [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.
643- [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.
644
645#### Supported Features & Properties
646
647In addition to the usual sizing/spacing properties (size, min_size, padding, margin, etc), the following Grid style properties are supported on Grid Containers:
648
649| Property                  | Explanation                                                                                    |
650| ---                       | ---                                                                                            |
651| [`grid-template-columns`] | The track sizing functions of the grid's explicit columns                                      |
652| [`grid-template-rows`]    | The track sizing functions of the grid's explicit rows                                         |
653| [`grid-auto-rows`]        | Track sizing functions for the grid's implicitly generated rows                                |
654| [`grid-auto-columns`]     | Track sizing functions for the grid's implicitly generated columns                             |
655| [`grid-auto-flow`]        | Whether auto-placed items are placed row-wise or column-wise. And sparsely or densely.         |
656| [`gap`]                   | The size of the vertical and horizontal gaps between grid rows/columns                         |
657| [`align-content`]         | Align grid tracks within the container in the inline (horizontal) axis                         |
658| [`justify-content`]       | Align grid tracks within the container in the block (vertical) axis                            |
659| [`align-items`]           | Align the child items within their grid areas in the inline (horizontal) axis                  |
660| [`justify-items`]         | Align the child items within their grid areas in the block (vertical) axis                     |
661
662And the following Grid style properties are supported on Grid Items (children):
663
664| Property                  | Explanation                                                                                    |
665| ---                       | ---                                                                                            |
666| [`grid-row`]              | The (row) grid line the item starts at (or a span)                                             |
667| [`grid-column`]           | The (column) grid line the item end at (or a span)                                             |
668| [`align-self`]            | Align the item within it's grid area in the inline (horizontal) axis. Overrides `align-items`. |
669| [`justify-self`]          | Align the item within it's grid area in the block (vertical) axis. Overrides `justify-items`.  |
670
671[`grid-template-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-columns
672[`grid-template-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-template-rows
673[`grid-auto-rows`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-rows
674[`grid-auto-columns`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-columns
675[`grid-auto-flow`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-flow
676[`gap`]: https://developer.mozilla.org/en-US/docs/Web/CSS/gap
677[`align-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align_content
678[`justify-content`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify_content
679[`align-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-items
680[`justify-items`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-items
681[`grid-row`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-row
682[`grid-column`]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-column
683[`align-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/align-self
684[`justify-self`]: https://developer.mozilla.org/en-US/docs/Web/CSS/justify-self
685
686The following properties and features are not currently supported:
687
688- Subgrids
689- Masonry grid layout
690- Named grid lines
691- Named areas: `grid-template-areas` and `grid-area`
692- `grid-template` or `grid` shorthand
693
694#### Example
695
696See [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:
697
698```bash
699cargo run --example grid_holy_grail --features grid
700```
701
702### New Feature: Style Helpers
703
704Ten 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.
705
706For example, instead of:
707
708```rust
709let size : Size<Dimension> = Size { width: Dimension::Points(100.0), height: Dimension::Percent(50.0) };
710```
711
712you can now write
713
714```rust
715let size : Size<Dimension> = Size { width: points(100.0), height: percent(50.0) };
716```
717
718And 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
719
720```rust
721let size : Size<Dimension> = points(100.0);
722```
723
724Available style helpers:
725
726<table>
727  <thead><tr><th>Type(s)</th><th colspan="2">Helpers that work with that type</th></tr></thead>
728  <tbody>
729    <tr>
730      <td rowspan="3"><code>LengthPercentage</code></td>
731      <td><code>zero()</code></td>
732      <td>Generates a <code>Points</code> variant with the value <code>0.0</code></td>
733    </tr>
734    <tr>
735      <td><code>points(val:&nbsp;f32)</code></td>
736      <td>Generates a <code>Points</code> variant with the specified value</td>
737    </tr>
738    <tr>
739      <td><code>percent(val:&nbsp;f32)</code></td>
740      <td>Generates a <code>Percent</code> variant with the specified value.<br />Note that the scale of 0-1 not 0-100.</td>
741    </tr>
742    <tr>
743      <td rowspan="2"><code>LengthPercentageAuto</code><br /><code>Dimension</code></td>
744      <td colspan="2"><i>All helpers from <code>LengthPercentage</code> and...</i></td>
745    </tr>
746    <tr>
747      <td><code>auto()</code></td>
748      <td>Generates an <code>Auto</code> variant</td>
749    </tr>
750    <tr>
751      <td rowspan="3"><code>MinTrackSizingFunction</code></td>
752      <td colspan="2"><i>All helpers from <code>LengthPercentageAuto</code>/<code>Dimension</code> and...</i></td>
753    </tr>
754    <tr>
755      <td><code>min_content()</code></td>
756      <td>Generates an <code>MinContent</code> variant</td>
757    </tr>
758      <tr>
759      <td><code>max_content()</code></td>
760      <td>Generates an <code>MinContent</code> variant</td>
761    </tr>
762    <tr>
763      <td rowspan="3"><code>MaxTrackSizingFunction</code></td>
764      <td colspan="2"><i>All helpers from <code>MinTrackSizingFunction</code> and...</i></td>
765    </tr>
766    <tr>
767      <td><code>fit_content(limit:&nbsp;LengthPercentage)</code></td>
768      <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>
769    </tr>
770      <tr>
771      <td><code>fr(fraction:&nbsp;f32)</code></td>
772      <td>Generates a <code>Fraction</code> (<code>fr</code>) variant with the specified flex fraction </td>
773    </tr>
774    <tr>
775      <td rowspan="3"><code>NonRepeatingTrackSizingFunction</code></td>
776      <td colspan="2"><i>All helpers from <code>MaxTrackSizingFunction</code> and...</i></td>
777    </tr>
778    <tr>
779      <td><code>minmax(min: MinTrackSizingFunction, max: MaxTrackSizingFunction)</code></td>
780      <td>Equivalent to CSS <code>minmax()</code> function.</td>
781    </tr>
782    <tr>
783      <td><code>flex(fraction:&nbsp;f32)</code></td>
784      <td>Equivalent to CSS <code>minmax(0px, 1fr)</code>. This is likely what you want if you want evenly sized rows/columns.</td>
785    </tr>
786    <tr>
787      <td rowspan="2"><code>TrackSizingFunction</code></td>
788      <td colspan="2"><i>All helpers from <code>NonRepeatingTrackSizingFunction</code> and...</i></td>
789    </tr>
790    <tr>
791      <td><code>repeat(rep: GridTrackRepetition, tracks: Vec&lt;TrackSizingFunction&gt;)</code></td>
792      <td>Equivalent to css <code>repeat()</code> function.</td>
793    </tr>
794    <tr>
795      <td><code>Vec&lt;TrackSizingFunction&gt;</code></td>
796      <td><code>evenly_sized_tracks(count:&nbsp;u16)</code></td>
797      <td>Equivalent to CSS <code>repeat(count, minmax(0px, 1fr)</code></td>
798    </tr>
799    <tr>
800      <td rowspan="3"><code>AvailableSpace</code></td>
801      <td><code>auto()</code></td>
802      <td>Generates an <code>Auto</code> variant</td>
803    </tr>
804    <tr>
805      <td><code>min_content()</code></td>
806      <td>Generates an <code>MinContent</code> variant</td>
807    </tr>
808      <tr>
809      <td><code>max_content()</code></td>
810      <td>Generates an <code>MinContent</code> variant</td>
811    </tr>
812    <tr>
813      <td><code>Size&lt;T&gt;</code></td>
814      <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>
815    </tr>
816    <tr>
817      <td><code>Rect&lt;T&gt;</code></td>
818      <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>
819    </tr>
820  </tbody>
821</table>
822
823### Breaking API changes
824
825#### Changes to alignment style types
826
827- `AlignContent` and `JustifyContent` has been merged.
828  - `JustifyContent` is now an alias of `AlignContent` and contains the `Stretch` variant.
829  - This variant will be *ignored* (falling back to `Start`) when applied Flexbox containers. It is valid value for Grid containers.
830- `AlignItems` and `AlignSelf` have been merged.
831  - The `Auto` variant of `AlignSelf` has been removed. You should now use `Option::None` if you wish to specify `AlignSelf::Auto`.
832  - `AlignSelf` is now an alias of `AlignItems`.
833  - `JustifyItems` and `JustifySelf` aliases have been added. These properties have no affect on Flexbox containers, but apply to Grid containers.
834- `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.
835
836#### Strict style types
837
838- New types `LengthPercentage` and `LengthPercentageAuto` have been added.
839  - `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.
840  - `LengthPercentageAuto` is currently identical to `Dimension` but will allow us to expand dimension in future to support values like `MinContent`, `MaxContent` and `FitContent`.
841- 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).
842
843#### Position properties renamed
844
845- 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)
846- 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`.
847
848#### Changes to `LayoutTree`
849
850- Added generic associated type to `LayoutTree` for a `ChildIter`, an iterator on the children of a given node.
851- 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.
852- 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.
853- Added `is_childless` method to `LayoutTree` for querying whether a node has no children.
854
855#### `AvailableSpace` has been moved
856
857The `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.
858
859### Fixes
860
861- Flexbox nodes sized under a min-content constraint now size correctly (#291)
862- Aspect ratio is now applied correctly in many circumstances
863- Absolutely positioned items now apply margins correctly
864- Min/max size are now applied correctly
865- Inset applied incorrectly to relatively positioned flexbox children when both `top` and `bottom` or `left` and `right` were specified (#348)
866- 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)
867
868### Removed
869
870- 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.
871- 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.
872- 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.
873
874## 0.2.2
875
876### Fixes
877
878- Border or padding on the horizontal axis could, in some cases, increase the height of nodes.
879
880## 0.2.1
881
882### Fixes
883
884- 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`.
885- `taffy::compute_layout` has been made public allowing Taffy to be used with custom storage (#263)
886
887## 0.2.0
888
889### New features
890
891#### Flexbox "gap" and `AlignContent::SpaceEvenly`
892
893The [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.
894
895Additionally 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)
896
897#### Debug module and cargo feature
898
899Two debugging features have been added:
900
901- `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.
902- A cargo feature `debug`. This enabled debug logging of the layout computation process itself (this is probably mainly useful for those working taffy itself).
903
904### Performance improvements
905
906A number of performance improvements have landed since taffy 0.1:
907
908- 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%.
909- 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!
910
911#### Benchmarks vs. Taffy 0.1
912
913| Benchmark                                 | Taffy 0.1 | Taffy 0.2 | % change (0.1 -> 0.2) |
914| ---                                       | ---       | ---       | ---                   |
915| wide/1_000 nodes (2-level hierarchy)      | 699.18 µs | 445.01 µs | -36.279%              |
916| wide/10_000 nodes (2-level hierarchy)     | 8.8244 ms | 7.1313 ms | -16.352%              |
917| wide/100_000 nodes (2-level hierarchy)    | 204.48 ms | 242.93 ms | +18.803%              |
918| deep/4000 nodes (12-level hierarchy))     | 5.2320 s  | 2.7363 ms | -99.947%              |
919| deep/10_000 nodes (14-level hierarchy)    | 75.207 s  | 6.9415 ms | -99.991%              |
920| deep/100_000 nodes (17-level hierarchy)   | -         | 102.72 ms | -                     |
921| deep/1_000_000 nodes (20-level hierarchy) | -         | 799.35 ms | -                     |
922
923(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
924
925As 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.
926
927However, 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.
928
929#### Benchmarks vs. [Yoga](https://github.com/facebook/yoga)
930
931Yoga 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.
932
933| Benchmark | Yoga | Taffy 0.2 |
934| --- | --- | --- |
935| yoga/10 nodes (1-level hierarchy) | 45.1670 µs | 33.297 ns |
936| yoga/100 nodes (2-level hierarchy) | 134.1250 µs | 336.53 ns |
937| yoga/1_000 nodes (3-level hierarchy) | 1.2221 ms | 3.8928 µs |
938| yoga/10_000 nodes (4-level hierarchy) | 13.8672 ms | 36.162 µs |
939| yoga/100_000 nodes (5-level hierarchy) | 141.5307 ms | 1.6404 ms |
940
941(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))
942
943While 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!
944
945### Breaking API changes
946
947#### Node creation changes
948
949- `taffy::Node` is now unique only to the Taffy instance from which it was created.
950- Renamed `Taffy.new_node(..)` -> `Taffy.new_with_children(..)`
951- Renamed `Taffy.new_leaf()` -> `Taffy.new_leaf_with_measure()`
952- Added `taffy::node::Taffy.new_leaf()` which allows the creation of new leaf-nodes without having to supply a measure function
953
954#### Error handling/representation improvements
955
956- Renamed `taffy::Error` -> `taffy::error::TaffyError`
957- Replaced `taffy::error::InvalidChild` with a new `InvalidChild` variant of `taffy::error::TaffyError`
958- Replaced `taffy::error::InvalidNode` with a new `InvalidNode` variant of `taffy::error::TaffyError`
959- The following method new return `Err(TaffyError::ChildIndexOutOfBounds)` instead of panicking:
960  - `taffy::Taffy::remove_child_at_index`
961  - `taffy::Taffy::replace_child_at_index`
962  - `taffy::Taffy::child_at_index`
963- `Taffy::remove` now returns a `Result<usize, Error>`, to indicate if the operation was successful (and if it was, which ID was invalidated).
964
965#### Some uses of `Option<f32>` replaced with a new `AvailableSpace` enum
966
967A new enum `Taffy::layout::AvailableSpace` has been added.
968
969The definition looks like this:
970
971```rust
972/// The amount of space available to a node in a given axis
973pub enum AvailableSpace {
974    /// The amount of space available is the specified number of pixels
975    Definite(f32),
976    /// The amount of space available is indefinite and the node should be laid out under a min-content constraint
977    MinContent,
978    /// The amount of space available is indefinite and the node should be laid out under a max-content constraint
979    MaxContent,
980}
981```
982
983This 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`).
984
985And 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..
986
987#### Builder methods are now `const` where possible
988
989- Several convenience constants have been defined: notably `Style::DEFAULT`
990- `Size<f32>.zero()` is now `Size::<f32>::ZERO`
991- `Point<f32>.zero()` is now  `Point::<f32>::ZERO`
992- `Size::undefined()` is now `Size::NONE`
993
994#### Removals
995
996- 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%).
997- Removed `taffy::number::Number`. Use `Option<f32>` is used instead
998  - the associated public `MinMax` and `OrElse` traits have also been removed; these should never have been public
999- 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).
1000
1001### Fixes
1002
1003- Miscellaneous correctness fixes which align our implementation with Chrome:
1004
1005  - Nodes can only ever have one parent
1006  - Fixed rounding of fractional values to follow latest Chrome - values are now rounded the same regardless of their position
1007  - Fixed computing free space when using both `flex-grow` and a minimum size
1008  - 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)
1009  - `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
1010- Taffy can now be vendored using `cargo-vendor` (README.md is now included in package).
1011
1012## 0.1.0
1013
1014### 0.1.0 Changed
1015
1016- the `order` field of `Layout` is now public, and describes the relative z-ordering of nodes
1017- renamed crate from `stretch2` to `taffy`
1018- updated to the latest version of all dependencies to reduce upstream pain caused by duplicate dependencies
1019- renamed `stretch::node::Stretch` -> `taffy::node::Taffy`
1020
1021### 0.1.0 Fixed
1022
1023- fixed feature strategy for `alloc` and `std`: these can now be compiled together, with `std`'s types taking priority
1024
1025### 0.1.0 Removed
1026
1027- removed Javascript / Kotlin / Swift bindings
1028  - the maintainer team lacks expertise to keep these working
1029  - more serious refactors are planned, and this will be challenging to keep working through that process
1030  - if you are interested in helping us maintain bindings to other languages, [get in touch](https://github.com/DioxusLabs/taffy/discussions)!
1031- 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)
1032- removed the `Direction` and `Overflow` structs, and the corresponding `direction` and `overflow` fields from `Style`
1033  - these had no effect in the current code base and were actively misleading
1034
1035## stretch2 0.4.3
1036
1037This is the final release of `stretch`: migrate to the crate named `taffy` for future fixes and features!
1038
1039These notes describe the differences between this release and `stretch` 0.3.2, the abandoned crate from which this library was forked.
1040
1041### Changed
1042
1043- updated [assorted dependencies](https://github.com/vislyhq/stretch/commit/a6491117379cea52dedc9584d892594a143e8cb0)
1044
1045### Fixed
1046
1047- fixed an exponential performance blow-up with deep nesting
1048- fixed percent height values, which were using parent width
1049- recomputing layout no longer moves children of non-zero-positioned parent
1050- fixed broken Swift bindings