Change color type to use f32 values internally (#9820)

* Change Color type to be f32 internally but no other changes

* Add missing clamp

* Add round function as we're not on MSRV 1.90+

* Prepare for being able to switch between u8s and f32s

* [autofix.ci] apply automated fixes

* Fix Display impl

* Add feature flag for 8-bit color values. Name to be bikeshed

* Fix brighter-darker test

* Update test screenshot

* Remove unused Float trait import

* Add cfg thing for not(cbindgen)

* Change Channel to float in cbindgen

* Change the cpp color type for uint8_t for now

* Opt cpp into 8-bit-color

* Switch feature around

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

Author: expenses

api/cpp/cbindgen.rs

@@ -234,6 +234,7 @@ fn default_config() -> cbindgen::Config {
             // therefore it is ok to reinterpret_cast
             ("MenuEntryModel".into(), "std::shared_ptr<slint::Model<MenuEntry>>".into()),
             ("Coord".into(), "float".into()),
+            ("Channel".into(), "uint8_t".into()),
         ]
         .iter()
         .cloned()
@@ -397,6 +398,7 @@ fn gen_corelib(
         "MenuEntryModel",
         "MenuEntryArg",
         "Coord",
+        "Channel",
         "LogicalRect",
         "LogicalPoint",
         "LogicalPosition",

internal/core/Cargo.toml

@@ -74,6 +74,7 @@ unstable-wgpu-27 = ["dep:wgpu-27"]
 
 tr = ["dep:tr"]
 
+32-bit-color = []
 default = ["std", "unicode"]
 
 shared-parley = ["shared-fontique", "dep:parley", "dep:skrifa"]