Changelog

0.10.1

Fixed

CSS Grid auto-repeat and minimum-size handling (#946)

0.10.0

The MSRV for this release is 1.71.

Support for `direction`

The direction property is now supported, allowing for RTL layout of boxes in Block, Flexbox, and CSS Grid layout modes.

Support for floats

The 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.

Float support is feature flagged by the float_layout feature.

Support for parsing styles from CSS string (#929)

All 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.

CSS parsing is feature flagged by the parse feature.

Additionally the parse_faster feature enables optimizations for faster parsing at the cost of pulling in proc-macro dependencies such as syn.

Changed

Make DetailedGridTracksInfo accessible from a public module (#899)
Add TaffyTree::write_tree method to debug print the tree into an arbitrary writer (#925)
The cache set and set APIs now take &LayoutInput rather than individual values (#933)

Fixed

Flexbox: apply gap even when there are auto margins (#938)

0.9.3

Added

Added write_tree method to utils.

0.9.2

Fixed

Fix wrong size propogation for absolute elements (#878)
Fix bounds check in CellOccupancyMatrix::last_of_type (#890)
Use doc_cfg instead of doc_auto_cfg (#868)

Changed

Upgraded grid dependency from 0.18 to 1.0 (#864)

0.9.1

Fixed

Flexbox: don't apply cross-axis stretch alignment to children with auto margins (#861)

0.9.0

The MSRV for this release is 1.65.

Support for named grid lines and grid areas

Taffy now supports named grid lines and areas.

As these rely on arbitrary user-provided strings, Taffy's Style struct is now generic over a string-like type (via the CheapCloneStr trait). Additionally as the grid feature is optional, it has a PhantomData field of that type to make type inference work.

Changed

PrintTree and RoundTree: use Layout instead of &Layout (#849).
Renamed TrackSizingFunction to GridTemplateComponent
Renamed NonRepeatedTrackSizingFunction to TrackSizingFunction
The Repeat variant of GridTemplateComponent now contains a new GridTemplateRepetition struct, which allows line names to be specifed in addition to tracks.
The way that grid styles are exposed in the low-level API is now a lot more generic with many associated types.

Added

GridTemplateArea struct and Style::grid_template_areas field
Style::grid_template_column_names and Style::grid_template_row_names fields. If non-empty, these should have length of exactly one greater than the corresponding grid_template_column/grid_template_rows style.

0.8.3

Fixed

Fix serde feature on 32bit targets (#845)

0.8.2

Fixed

Fix: Calculate correct new grid size when expanding cell_occupancy_matrix in the negative direction (#843)

0.8.1

Added

Impl GridItemStyle and BlockContainerStyle for Style (#832).

0.8.0

Highlights

The big feature in this release is support for calc() values in the low-level API.

To use this API:

Implement the resolve_calc_value method when implementing the LayoutPartialTree trait.
Pass a type-erased pointer (*const ()) to constructors like LengthPercentage::calc(...)

Taffy treats the pointer as an opaque value (excepting that it uses the low 3 bits as a tag) which it will pass to LayoutPartialTree::resolve_calc_value along with a percentage resolution basis when it needs to resolve the value.

Changed

The representation of many "size" types is now a tagged pointer than an enum. This is to enable calc(). The effected types are LengthPercentage, LengthPercentageAuto, Dimension, MinTrackSizingFunction, and MaxTrackSizingFunction types.

Added

Special-case "compressible replaced elements" in grid sizing algorithm (#807) This allows for more correct sizing of "replaced" elements such as images that are children of flexbox or grid containers.

Fixed

Grid: Fix infinite loop due to float precision in grid layout maximise tracks step (#792)
Grid: Fix removed wrong addition, causing items to be misplaced. (#817)
Grid: Fix grid placement for items with fixed primary axis (#818)
Leaf layout: don't set available space to max-size (#819)

0.7.7

Fixed

Add #[inline] annotation to some methods on TaffyTree (#802)
Add TaffyTree::remove_children_range method (#802)

0.7.6

Fixed

Fix infinite loop due to float precision in grid layout maximise tracks step (#792)

0.7.5

Fixed

Grid: only stretch auto tracks if content-alignment is stretch (#783)

0.7.4

Fixed

Fix detailed grid info for empty grid (#782)

0.7.3

Fixed

Make TaffyTree::detailed_layout_info take &self rather than &mut self (#779)

0.7.2

Added

The ability to access computed track sizes and item positions of a CSS Grid layout (#772). This information can be accessed using the LayoutGridContainer::set_detailed_grid_info method in the low-level API or the TaffyTree::detailed_layout_info method in the high-level API.

0.7.1

Fixed

Improve interaction of abspos children of block containers with margin collapsing (#760)

Added

Add TaffyTree::unrounded_layout getter (#765)

Removed

The num-traits dependency was removed (#761) (#762)

0.7.0

Changed

BREAKING: The cache_mut method on the LayoutPartialTree trait has been replaced with a separate CacheTree trait. This allows Taffy to be more easily used without caching or with a custom cache implementation.
BREAKING: the TaffyTree::set_children method now removes the children from their previous parent (if they have one).

Added

Helper methods to retrieve content-box sizes were added to Layout

0.6.3

Fixes

Block: ignore margin collapsing when computing static position of abspos items (#747)

0.6.2

Fixes

Fix: clamp indefinite available space by min- and max- size as appropriate (#742)

0.6.1

Fixes

Fix calculation of auto-fill/auto-fit repetition count when container has a definite percentage size (#722)
Fix min-size style not affecting intrinsic sizes (#723)
Fix documentation of dirty and mark_dirty functions (#724)
Fix intrinsic size of scroll containers that have a small explicit flex-basis (#728)

0.6.0

Highlights

The Style struct has been "traitified". This supports Taffy's integration in Servo and generally makes Taffy more flexible. The Style struct still exists and implements the new traits so existing uses of Taffy will continue to work as before.
The box-sizing style is supported
Computed margins are output in Layout

Fixes

Fix print_tree() when rounding is disabled (#680)
Absolute Insets should be resolved against the container size minus border (#666)
Fix flooring hypothetical_main_size by computed min size (#689)
Fix flex line cross-size determination (#690)
Fix panics in the grid algorithm (#691)
Fix resolving flexible lengths (WPT css/flexbox-multiline-min-max test) (#692)
Fix wrapping when a max main size style is present (#694)
Fix case where Taffy allowed margins to collapse through an element when it shouldn't have (#695)

Added

Legacy text align (for laying out <center> and <div align="..">) is supported
Add is_table for block items (#701)
Impl Debug and Clone for Cache (#688)
Implement Debug and PartialEq for tree types (#697)

0.5.2

Fix block stretch sizing (don't always apply stretch sizing to block containers) (#674)
Fix computation of intrinsic main size when it depends on a child's known cross size (#673)
Fix panic when GridLine 0 is specified (#671)
Docs: Document feature flags and scrape examples (#672)
Docs: Update cosmic-text example to cosmic-text 0.12 (#670)

0.5.1

Fix: Clamp block item stretch widths by their min and max width (#664)
Fix: Auto margin computation in block layout (#663)

0.5.0

The changes in 0.5 are relatively small but the new measure function parameter is a breaking change so it requires a minor version bump.

Added: A style: &Style parameter has been added to measure functions.
Added: The MaybeMath, MaybeResolve, and ResolveOrZero traits have been made public.
Fix: use SizingMode::Inherent when sizing absolute children of flexbox nodes.

0.4.4

Fixes

Content alignment (align-content/justify-content) behaviour was updated to match the latest spec (and Chrome 123+) (#635)
Ensure that root Flexbox nodes are floored by their padding-border (#651, #655)
Use grid area size not available space when applying aspect ratio to grid containers (#656)

0.4.3

Fixes

Fix compilation error in evenly_sized_tracks style helper in recent versions of rustc caused by a change/regression in type inference (#643). Note that 3rd-party code that call style helpers that take an Into<f32> parameter may still be affected by this issue, but they should be able to fix on their side by clarifying the type passed in

0.4.2

Fixed: single-line flex-container should clamp the line's cross-size (#638)
Reduced binary footprint of Taffy from around 300kb to around 150kb (#636)

0.4.1

Fixed: CSS Grid track sizing not respecting growth limits in some circumstances (#624)

0.4.0

Highlights

Support for CSS Block layout (display: block)
Support for the overflow property (+ scrollbar_width for overflow: scroll)
Improved measure function API
Completely refactored low-level API
Simplified module hierarchy (+ most types/functions are now exported from the crate root)
Expanded set of examples which better document integration with other layout systems (e.g. text layout)
Computed values for padding and border are now output into the Layout struct

Block layout

Support for CSS Block layout 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.

Overflow property

Support 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.

Overflow is settable indpendently in each axis.
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.
Hidden and Scroll affect layout by changing the automatic minimum size of Flexbox and Grid children
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.

Measure function changes

The "measure function" API for integrating Taffy with other measurement systems (such as text layout) has been changed to be more flexible and to interact better with borrow checking (you can now borrow external data in your measure function!).

There are no longer per-node measure functions.
There is now a single "global" measure function, and a per-node "context" of a user-defined type
The Taffy tree is now a generic TaffyTree<T> where T is the "context" type.
The measure function is now called for all leaf nodes (nodes without children). If you wish to maintain compatibility with the previous behaviour then your measure function should return Size::ZERO for leaf nodes whose context is None.

If you are not using measure functions, then the only change you will need to make is from:

let mut tree = Taffy::new();

let mut tree : TaffyTree<()> = TaffyTree::new();

And generally update any uses of Taffy in your codebase to TaffyTree<()>.

If you are using measure functions then you will need to make some bigger (but straightforward) changes. The following Taffy 0.3 code:

let mut tree = Taffy::new();
let leaf = tree.new_leaf_with_measure(
  Style::DEFAULT,
  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>| Size { width: 100.0, height: 200.0 }
);
tree.compute_layout(leaf, Size::MAX_CONTENT);

Should become something like the following with Taffy 0.4:

let mut tree : TaffyTree<Size> = TaffyTree::new();
let leaf = tree.new_leaf_with_context(Style::DEFAULT, Size { width: 100.0, height: 200.0 });
tree.compute_layout_with_measure(
  leaf,
  Size::MAX_CONTENT,
  |known_dimensions: Size<Option<f32>>, available_space: Size<AvailableSpace>, node_id: NodeId, node_context: Option<Size>| {
    node_context.unwrap_or(Size::ZERO)
  }
);

Note that:

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).
If you don't need a context then you can use () for the context type
As the single "global" measure function passed to compute_layout_with_measure only needs to exist for the duration of a single layout run, it can (mutably) borrow data from it's environment

Low-level API (`LayoutTree` trait) refactor

The low-level API has been completely reworked:

The LayoutTree trait has been split into 5 smaller traits which live in the taffy::tree:traits module (along with their associated documentation)
The following methods have been removed from split LayoutTree traits entirely: parent, is_childless, measure_node, needs_measure, and mark_dirty.
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.
Support for running each layout algorithm individually on a single node via the following top-level functions:
- compute_flexbox_layout
- compute_grid_layout
- compute_block_layout
- compute_leaf_layout
- compute_root_layout
- compute_hidden_layout

It 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 improved both the documentation and have added examples using the new API, both of which are linked to from the main documentation page.

Module hierarchy changes

The 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.

Specific changes:

The math module has been made private
The axis module has been merged into the geometry module
The debug module is no longer public. The print_tree function is now accessible under util.
All types from the node, data, layout, error and cache modules have been moved to the the tree module.
The layout_flexbox() function has been removed from the prelude. Use taffy::compute_flexbox_layout instead.

Many APIs have been renamed to replace `points` or `Points` with `length` or `Length`

This new name better describes one-dimensional measure of space in some unspecified unit which is often unrelated to the PostScript point or the CSS pt unit.

This also removes a misleading similarity with the 2D Point, whose components can have any unit and are not even necessarily absolute lengths.

Example usage change:

 use taffy::prelude::*;

 // …

 let header_node = taffy
     .new_leaf(
         Style {
-            size: Size { width: points(800.0), height: points(100.0) },
+            size: Size { width: length(800.0), height: length(100.0) },
             ..Default::default()
         },
     ).unwrap();

Other Changes

The Taffy type was renamed to TaffyTree and made generic of a context parameter
The Flexbox algorithm has now been moved behind the flexbox feature. The flexbox feature is enabled by default.
The justify_self property has been moved behind the grid feature.
Fixed misspelling: RunMode::PeformLayout renamed into RunMode::PerformLayout (added missing r).
serde dependency has been made compatible with no_std environments
slotmap dependency has been made compatible with no_std environments
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.
Added total_node_count() method to the TaffyTree which returns the total number of nodes in the tree.
Added get_disjoint_node_context_mut() method to the TaffyTree. This can be used to safely get multiple mutable borrows at the same time.

0.3.19

Fixes

Fix compilation error in evenly_sized_tracks style helper in recent versions of rustc caused by a change/regression in type inference (#643). Note that 3rd-party code that call style helpers that take an Into<f32> parameter may still be affected by this issue, but they should be able to fix on their side by clarifying the type passed in

0.3.18

Fixes

Fix computation of Flexbox automatic minimum size when grid or flexbox child has an explicit width/height style set (#576)

0.3.17

Added

Added total_node_count method to the Taffy struct. Returns the total number of nodes in the tree.

0.3.16

Fixes

Improve performance of flexbox columns

0.3.15

Fixes

Fix justify-content and align-content when free space is negative (content overflows container) (#549) (#551)

0.3.14

Fixes

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)

0.3.13

Fixes

Fix rounding accumulation bug (#521) (Fixes #501 and bevyengine/bevy#8911)
Flexbox: pass correct cross-axis available space when computing an item's intrinsic main size (#522)(Fixes bevyengine/bevy#9350)
Flexbox: Subtract child margin not parent margin when computing stretch-alignment known size
Grid: Make CSS Grid algorithm correctly apply max width/height and available space when it is the root node (#491)
Grid: Fix CSS Grid "auto track" / placement bugs #481
- Fix divide by zero when using grid_auto_rows/grid_auto_columns with zero negative implicit tracks
- Fix over counting of tracks (leading to incorrect container heights) when auto-placing in grids that contain negative implicit tracks.
- Fix axis conflation in auto-placement code when grid_auto_flow is column
- Fix assignment of auto track sizes when initializing negative implicit tracks
Leaf: Apply margins to leaf nodes when computing available space for measure functions
Leaf: Reserve space for padding/borders in nodes with measure functions (#497)

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.

Dependencies

Upgrade grid to 0.10. This eliminates the transitive dependency on no-std-compat.

0.3.12

Fixes

Fix caching issue when toggling display:none on and off

0.3.11

Fixes

Fix exponential blowup when laying out trees containing nodes with min and max sizes.

0.3.10

Fixes

Fix sizing of children when the available_space < min_size (#407)

0.3.9

Fixes

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)

0.3.8

Fixes

Fix incorrect min-content size for flex-wrap: wrap nodes (bevyengine/bevy#8082)

0.3.7

Fixes

Fix: Make padding and border floor node sizes (#372)
Fix: Prevent percentages contributing to min-content sizes (#388) (also fixes bevyengine/bevy#8017)

0.3.6

Fixes

Fix: Ignore align_content when flex_wrap is set to nowrap (#383)

0.3.5

Fixes

Fix display: none when it is set on a flexbox child (#380)
Fix display: none when it is set on a grid child (#381)

0.3.4

Fixes

Fix display: none when it is set for the only node in the hierarchy (#377)

0.3.3

Added

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.

Fixes

Fixed rounding algorithm such that it never leaves gaps between adjacent nodes (#369)
Fixed compiling with the grid feature disabled (#370)
Fixed compiling with the std feature disabled

0.3.2

Fixes

Allow partial nested values to be deserialized into a Style using the serde feature.

0.3.1

Fixes

The serde feature now works when the grid feature is enabled

0.3.0

See below for details of breaking changes.

New Feature: CSS Grid

We 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.

Learning Resources

Taffy 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:

CSS Grid Garden. This is an interactive tutorial/game that allows you to learn the essential parts of CSS Grid in a fun engaging way.
A Complete Guide To CSS Grid by CSS Tricks. This is detailed guide with illustrations and comprehensive written explanation of the different Grid properties and how they work.

Supported Features & Properties

In addition to the usual sizing/spacing properties (size, min_size, padding, margin, etc), the following Grid style properties are supported on Grid Containers:

Property	Explanation
`grid-template-columns`	The track sizing functions of the grid's explicit columns
`grid-template-rows`	The track sizing functions of the grid's explicit rows
`grid-auto-rows`	Track sizing functions for the grid's implicitly generated rows
`grid-auto-columns`	Track sizing functions for the grid's implicitly generated columns
`grid-auto-flow`	Whether auto-placed items are placed row-wise or column-wise. And sparsely or densely.
`gap`	The size of the vertical and horizontal gaps between grid rows/columns
`align-content`	Align grid tracks within the container in the inline (horizontal) axis
`justify-content`	Align grid tracks within the container in the block (vertical) axis
`align-items`	Align the child items within their grid areas in the inline (horizontal) axis
`justify-items`	Align the child items within their grid areas in the block (vertical) axis

And the following Grid style properties are supported on Grid Items (children):

Property	Explanation
`grid-row`	The (row) grid line the item starts at (or a span)
`grid-column`	The (column) grid line the item end at (or a span)
`align-self`	Align the item within it's grid area in the inline (horizontal) axis. Overrides `align-items`.
`justify-self`	Align the item within it's grid area in the block (vertical) axis. Overrides `justify-items`.

The following properties and features are not currently supported:

Subgrids
Masonry grid layout
Named grid lines
Named areas: grid-template-areas and grid-area
grid-template or grid shorthand

Example

See examples/grid_holy_grail.rs for an example using Taffy to implement the so-called Holy Grail Layout. If you want to run this example, the don't forget the enable the CSS Grid cargo feature:

cargo run --example grid_holy_grail --features grid

New Feature: Style Helpers

Ten 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.

For example, instead of:

let size : Size<Dimension> = Size { width: Dimension::Points(100.0), height: Dimension::Percent(50.0) };

you can now write

let size : Size<Dimension> = Size { width: points(100.0), height: percent(50.0) };

And 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

let size : Size<Dimension> = points(100.0);

Available style helpers:

Type(s)	Helpers that work with that type
`LengthPercentage`	`zero()`	Generates a `Points` variant with the value `0.0`
	`points(val: f32)`	Generates a `Points` variant with the specified value
	`percent(val: f32)`	Generates a `Percent` variant with the specified value. Note that the scale of 0-1 not 0-100.
`LengthPercentageAuto` `Dimension`	All helpers from `LengthPercentage` and...
`LengthPercentageAuto` `Dimension`	`auto()`	Generates an `Auto` variant
`MinTrackSizingFunction`	All helpers from `LengthPercentageAuto`/`Dimension` and...
	`min_content()`	Generates an `MinContent` variant
	`max_content()`	Generates an `MinContent` variant
`MaxTrackSizingFunction`	All helpers from `MinTrackSizingFunction` and...
	`fit_content(limit: LengthPercentage)`	Generates a `FitContent` variant with the specified limit. Nest the `points` or `percent` helper inside this function to specified the limit.
	`fr(fraction: f32)`	Generates a `Fraction` (`fr`) variant with the specified flex fraction
`NonRepeatingTrackSizingFunction`	All helpers from `MaxTrackSizingFunction` and...
	`minmax(min: MinTrackSizingFunction, max: MaxTrackSizingFunction)`	Equivalent to CSS `minmax()` function.
	`flex(fraction: f32)`	Equivalent to CSS `minmax(0px, 1fr)`. This is likely what you want if you want evenly sized rows/columns.
`TrackSizingFunction`	All helpers from `NonRepeatingTrackSizingFunction` and...
`TrackSizingFunction`	`repeat(rep: GridTrackRepetition, tracks: Vec<TrackSizingFunction>)`	Equivalent to css `repeat()` function.
`Vec<TrackSizingFunction>`	`evenly_sized_tracks(count: u16)`	Equivalent to CSS `repeat(count, minmax(0px, 1fr)`
`AvailableSpace`	`auto()`	Generates an `Auto` variant
	`min_content()`	Generates an `MinContent` variant
	`max_content()`	Generates an `MinContent` variant
`Size<T>`	Any helper that works for `T` will also work for `Size<T>` and will set both `width` and `height` to that value
`Rect<T>`	Any helper that works for `T` will also work for `Rect<T>` and will set `top`, `left`, `bottom`, and `right` to that value

Breaking API changes

Changes to alignment style types

AlignContent and JustifyContent has been merged.
- JustifyContent is now an alias of AlignContent and contains the Stretch variant.
- This variant will be ignored (falling back to Start) when applied Flexbox containers. It is valid value for Grid containers.
AlignItems and AlignSelf have been merged.
- The Auto variant of AlignSelf has been removed. You should now use Option::None if you wish to specify AlignSelf::Auto.
- AlignSelf is now an alias of AlignItems.
- JustifyItems and JustifySelf aliases have been added. These properties have no affect on Flexbox containers, but apply to Grid containers.
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.

Strict style types

New types LengthPercentage and LengthPercentageAuto have been added.
- 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.
- LengthPercentageAuto is currently identical to Dimension but will allow us to expand dimension in future to support values like MinContent, MaxContent and FitContent.
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).

Position properties renamed

The position property is now renamed to inset and is now in line with CSS inset specs
The position_type property is now renamed to position and is now in line with CSS position specs. The PositionType enum has been similarly renamed to Position.

Changes to `LayoutTree`

Added generic associated type to LayoutTree for a ChildIter, an iterator on the children of a given node.
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.
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.
Added is_childless method to LayoutTree for querying whether a node has no children.

`AvailableSpace` has been moved

The 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.

Fixes

Flexbox nodes sized under a min-content constraint now size correctly (#291)
Aspect ratio is now applied correctly in many circumstances
Absolutely positioned items now apply margins correctly
Min/max size are now applied correctly
Inset applied incorrectly to relatively positioned flexbox children when both top and bottom or left and right were specified (#348)
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)

Removed

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.
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.
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.

0.2.2

Fixes

Border or padding on the horizontal axis could, in some cases, increase the height of nodes.

0.2.1

Fixes

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.
taffy::compute_layout has been made public allowing Taffy to be used with custom storage (#263)

0.2.0

New features

Flexbox "gap" and `AlignContent::SpaceEvenly`

The gap property is now supported on flex containers. This can make it much easier to create even spacing or "gutters" between nodes.

Additionally 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)

Debug module and cargo feature

Two debugging features have been added:

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.
A cargo feature debug. This enabled debug logging of the layout computation process itself (this is probably mainly useful for those working taffy itself).

Performance improvements

A number of performance improvements have landed since taffy 0.1:

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%.
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!

Benchmarks vs. Taffy 0.1

Benchmark	Taffy 0.1	Taffy 0.2	% change (0.1 -> 0.2)
wide/1_000 nodes (2-level hierarchy)	699.18 µs	445.01 µs	-36.279%
wide/10_000 nodes (2-level hierarchy)	8.8244 ms	7.1313 ms	-16.352%
wide/100_000 nodes (2-level hierarchy)	204.48 ms	242.93 ms	+18.803%
deep/4000 nodes (12-level hierarchy))	5.2320 s	2.7363 ms	-99.947%
deep/10_000 nodes (14-level hierarchy)	75.207 s	6.9415 ms	-99.991%
deep/100_000 nodes (17-level hierarchy)	-	102.72 ms	-
deep/1_000_000 nodes (20-level hierarchy)	-	799.35 ms	-

(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))

As 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.

However, 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.

Benchmarks vs. Yoga

Yoga 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.

Benchmark	Yoga	Taffy 0.2
yoga/10 nodes (1-level hierarchy)	45.1670 µs	33.297 ns
yoga/100 nodes (2-level hierarchy)	134.1250 µs	336.53 ns
yoga/1_000 nodes (3-level hierarchy)	1.2221 ms	3.8928 µs
yoga/10_000 nodes (4-level hierarchy)	13.8672 ms	36.162 µs
yoga/100_000 nodes (5-level hierarchy)	141.5307 ms	1.6404 ms

(note that the table above contains multiple different units (milliseconds vs. microseconds vs. nanoseconds))

While 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!

Breaking API changes

Node creation changes

taffy::Node is now unique only to the Taffy instance from which it was created.
Renamed Taffy.new_node(..) -> Taffy.new_with_children(..)
Renamed Taffy.new_leaf() -> Taffy.new_leaf_with_measure()
Added taffy::node::Taffy.new_leaf() which allows the creation of new leaf-nodes without having to supply a measure function

Error handling/representation improvements

Renamed taffy::Error -> taffy::error::TaffyError
Replaced taffy::error::InvalidChild with a new InvalidChild variant of taffy::error::TaffyError
Replaced taffy::error::InvalidNode with a new InvalidNode variant of taffy::error::TaffyError
The following method new return Err(TaffyError::ChildIndexOutOfBounds) instead of panicking:
- taffy::Taffy::remove_child_at_index
- taffy::Taffy::replace_child_at_index
- taffy::Taffy::child_at_index
Taffy::remove now returns a Result<usize, Error>, to indicate if the operation was successful (and if it was, which ID was invalidated).

Some uses of `Option<f32>` replaced with a new `AvailableSpace` enum

A new enum Taffy::layout::AvailableSpace has been added.

The definition looks like this:

/// The amount of space available to a node in a given axis
pub enum AvailableSpace {
    /// The amount of space available is the specified number of pixels
    Definite(f32),
    /// The amount of space available is indefinite and the node should be laid out under a min-content constraint
    MinContent,
    /// The amount of space available is indefinite and the node should be laid out under a max-content constraint
    MaxContent,
}

This 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).

And a different instance of it is passed as a new second parameter to MeasureFunc. MeasureFuncs 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..

Builder methods are now `const` where possible

Several convenience constants have been defined: notably Style::DEFAULT
Size<f32>.zero() is now Size::<f32>::ZERO
Point<f32>.zero() is now Point::<f32>::ZERO
Size::undefined() is now Size::NONE

Removals

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%).
Removed taffy::number::Number. Use Option<f32> is used instead
- the associated public MinMax and OrElse traits have also been removed; these should never have been public
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).

Fixes

Miscellaneous correctness fixes which align our implementation with Chrome:
- Nodes can only ever have one parent
- Fixed rounding of fractional values to follow latest Chrome - values are now rounded the same regardless of their position
- Fixed computing free space when using both flex-grow and a minimum size
- 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
- 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
Taffy can now be vendored using cargo-vendor (README.md is now included in package).

0.1.0

0.1.0 Changed

the order field of Layout is now public, and describes the relative z-ordering of nodes
renamed crate from stretch2 to taffy
updated to the latest version of all dependencies to reduce upstream pain caused by duplicate dependencies
renamed stretch::node::Stretch -> taffy::node::Taffy

0.1.0 Fixed

fixed feature strategy for alloc and std: these can now be compiled together, with std's types taking priority

0.1.0 Removed

removed Javascript / Kotlin / Swift bindings
- the maintainer team lacks expertise to keep these working
- more serious refactors are planned, and this will be challenging to keep working through that process
- if you are interested in helping us maintain bindings to other languages, get in touch!
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)
removed the Direction and Overflow structs, and the corresponding direction and overflow fields from Style
- these had no effect in the current code base and were actively misleading

stretch2 0.4.3

This is the final release of stretch: migrate to the crate named taffy for future fixes and features!

These notes describe the differences between this release and stretch 0.3.2, the abandoned crate from which this library was forked.

Changed

updated assorted dependencies

Fixed

fixed an exponential performance blow-up with deep nesting
fixed percent height values, which were using parent width
recomputing layout no longer moves children of non-zero-positioned parent
fixed broken Swift bindings

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Changelog

0.10.1

Fixed

0.10.0

Support for direction

Support for floats

Support for parsing styles from CSS string (#929)

Changed

Fixed

0.9.3

Added

0.9.2

Fixed

Changed

0.9.1

Fixed

0.9.0

Support for named grid lines and grid areas

Changed

Added

0.8.3

Fixed

0.8.2

Fixed

0.8.1

Added

0.8.0

Highlights

Changed

Added

Fixed

0.7.7

Fixed

0.7.6

Fixed

0.7.5

Fixed

0.7.4

Fixed

0.7.3

Fixed

0.7.2

Added

0.7.1

Fixed

Added

Removed

0.7.0

Changed

Added

0.6.3

Fixes

0.6.2

Fixes

0.6.1

Fixes

0.6.0

Highlights

Fixes

Added

0.5.2

0.5.1

0.5.0

0.4.4

Fixes

0.4.3

Fixes

0.4.2

0.4.1

0.4.0

Highlights

Block layout

Overflow property

Measure function changes

Support for `direction`

Low-level API (`LayoutTree` trait) refactor

Many APIs have been renamed to replace `points` or `Points` with `length` or `Length`

Changes to `LayoutTree`

`AvailableSpace` has been moved