Migrate from LegacyColor to bevy_color::Color

[alice-i-cecile]

Objective

• As part of the migration process we need to a) see the end effect of the migration on user ergonomics b) check for serious perf regressions c) actually migrate the code
• To accomplish this, I'm going to attempt to migrate all of the remaining user-facing usages of LegacyColor in one PR, being careful to keep a clean commit history.
• Fixes bevy_color migration plan #12056.

Solution

I've chosen to use the polymorphic Color type as our standard user-facing API.

• Migrate bevy_gizmos.
• Take impl Into<Color> in all bevy_gizmos APIs
• Migrate sprites
• Migrate UI
• Migrate ColorMaterial
• Migrate MaterialMesh2D
• Migrate fog
• Migrate lights
• Migrate StandardMaterial
• Migrate wireframes
• Migrate clear color
• Migrate text
• Migrate gltf loader
• Register color types for reflection
• Remove LegacyColor
• Make sure CI passes

Incidental improvements to ease migration:

• added Color::srgba_u8, Color::srgba_from_array and friends
• added set_alpha, is_fully_transparent and is_fully_opaque to the Alpha trait
• add and immediately deprecate (lol) Color::rgb and friends in favor of more explicit and consistent Color::srgb
• standardized on white and black for most example text colors
• added vector field traits to LinearRgba: Add, Sub, AddAssign, SubAssign, Mul<f32> and Div<f32>. Multiplications and divisions do not scale alpha. Add and Sub have been cut from this PR.
• added LinearRgba and Srgba RED/GREEN/BLUE
• added LinearRgba_to_f32_array and LinearRgba::to_u32

Migration Guide

Bevy's color types have changed! Wherever you used a bevy::render::Color, a bevy::color::Color is used instead.

These are quite similar! Both are enums storing a color in a specific color space (or to be more precise, using a specific color model). However, each of the different color models now has its own type.

TODO...

• Color::rgba, Color::rgb, Color::rbga_u8, Color::rgb_u8, Color::rgb_from_array are now Color::srgba, Color::srgb, Color::srgba_u8, Color::srgb_u8 and Color::srgb_from_array.
• Color::set_a and Color::a is now Color::set_alpha and Color::alpha. These are part of the Alpha trait in bevy_color.
• Color::is_fully_transparent is now part of the Alpha trait in bevy_color
• Color::r, Color::set_r, Color::with_r and the equivalents for g, b h, s and l have been removed due to causing silent relatively expensive conversions. Convert your Color into the desired color space, perform your operations there, and then convert it back into a polymorphic Color enum.
• Color::hex is now Srgba::hex. Call .into or construct a Color::Srgba variant manually to convert it.
• WireframeMaterial, ExtractedUiNode, ExtractedDirectionalLight, ExtractedPointLight, ExtractedSpotLight and ExtractedSprite now store a LinearRgba, rather than a polymorphic Color
• Color::rgb_linear and Color::rgba_linear are now Color::linear_rgb and Color::linear_rgba
• The various CSS color constants are no longer stored directly on Color. Instead, they're defined in the Srgba color space, and accessed via bevy::color::palettes::css. Call .into() on them to convert them into a Color for quick debugging use, and consider using the much prettier tailwind palette for prototyping.
• The LIME_GREEN color has been renamed to LIMEGREEN to comply with the standard naming.
• Vector field arithmetic operations on Color (add, subtract, multiply and divide by a f32) have been removed. Instead, convert your colors into LinearRgba space, and perform your operations explicitly there. This is particularly relevant when working with emissive or HDR colors, whose color channel values are routinely outside of the ordinary 0 to 1 range.
• Color::as_linear_rgba_f32 has been removed. Call LinearRgba::to_f32_array instead, converting if needed.
• Color::as_linear_rgba_u32 has been removed. Call LinearRgba::to_u32 instead, converting if needed.
• Several other color conversion methods to transform LCH or HSL colors into float arrays or Vec types have been removed. Please reimplement these externally or open a PR to re-add them if you found them particularly useful.
• Various methods on Color such as rgb or hsl to convert the color into a specific color space have been removed. Convert into LinearRgba, then to the color space of your choice.
• Various implicitly-converting color value methods on Color such as r, g, b or h have been removed. Please convert it into the color space of your choice, then check these properties.
• Color no longer implements AsBindGroup. Store a LinearRgba internally instead to avoid conversion costs.

[bushrat011899]

Looking good so far!

[bushrat011899]

Might need to do some performance testing to confirm, but we probably need to go back over the various From implementations an annotate them with #[inline]. I'm not sure how good the Rust compiler is at inlining these tiny functions.

[alice-i-cecile]

Yeah agreed. I want to do perf testing towards the end of this process.