Upgrade to Taffy 0.4

[nicoburns]

Objective

• Enables support for Display::Block
• Enables support for Overflow::Hidden
• Allows for cleaner integration with text, image and other content layout.
• Unblocks WIP: Support scrolling (Overflow::Scroll) in bevy_ui #8104
• Unlocks the possibility of Bevy creating a custom layout tree over which Taffy operates.
• Enables Migrate to cosmic-text #8808 / Cosmic text #10193 to remove a Mutex around the font system.

Todo

• Fix rendering of text/images to account for padding/border on nodes (should size/position to content box rather than border box) In order get this into a mergeable state this PR instead zeroes out padding/border when syncing leaf node styles into Taffy to preserve the existing behaviour. Text and Images can't be given padding #6879 can be fixed in a followup PR.

Solution

• Update the version of Taffy
• Update code to work with the new version

Note: Taffy 0.4 has not yet been released. This PR is being created in advance of the release to ensure that there are no blockers to upgrading once the release occurs.

---

Changelog

• Bevy now supports the Display::Block and Overflow::Hidden styles.

[nicoburns]

@ickshonpe This PR fixes Taffy reserving space for padding for text and image nodes, but the text/image position is not offset by the top/left padding when actually rendering. Do you know where that change would need to be made? Taffy 0.4 outputs computed padding and border values.

[alice-i-cecile]

This is no longer blocked, as taffy 0.4 has been released.

[BD103]

We're getting some CI errors for the checks that run nightly, and they appear to be related to Taffy. Would updating to 0.4 fix this error?

error[E0277]: the trait bound `f32: From<f64>` is not satisfied
   --> /home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/taffy-0.3.18/src/style_helpers.rs:58:31
    |
58  |     repeated_tracks.push(flex(1.0));
    |                          ---- ^^^ the trait `From<f64>` is not implemented for `f32`, which is required by `{float}: Into<f32>`
    |                          |
    |                          required by a bound introduced by this call
    |
    = help: the following other types implement trait `From<T>`:
              <f32 as From<bool>>
              <f32 as From<f16>>
              <f32 as From<i16>>
              <f32 as From<i8>>
              <f32 as From<u16>>
              <f32 as From<u8>>
    = note: required for `f64` to implement `Into<f32>`
note: required by a bound in `flex`
   --> /home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/taffy-0.3.18/src/style_helpers.rs:100:12
    |
98  | pub fn flex<Input, Output>(flex_fraction: Input) -> Output
    |        ---- required by a bound in this function
99  | where
100 |     Input: Into<f32> + Copy,
    |            ^^^^^^^^^ required by this bound in `flex`

[nicoburns]

Taffy 0.4 release is unlikely to fix this as that code is unchanged between versions. We'll likely need to do a patch release. Or for rustc to fix their inference regression.

[alice-i-cecile]

Once there's docs for NodeMeasure this LGTM! Happy to see this finally make it in.

[alice-i-cecile]

@nicoburns the CI failures look related: could you take a look at the failures reported during the failed merge if this latest attempt fails?

[nicoburns]

Yep, just having lunch but will take a look after. Keen to get this merged so we can stop supporting Taffy 0.3!

[nicoburns]

@alice-i-cecile Passing checks now