Merge #142

142: Make libm optional r=Ogeon a=Ogeon

I decided to do this to avoid having it as an unused dependency and also to hopefully be compatible with a future release of `num_traits`, where they seem to be planning the same kind of construct, judging by rust-num/num-traits#99. A transition to using `num_trait` for both cases will hopefully be seamless for the users after this.

I think this also fixes #116.

Co-authored-by: Erik Hedvall <erikwhedvall@gmail.com>

README.md

@@ -9,7 +9,7 @@ A Rust library that makes linear color calculations and conversion easy and acce
 
 [Released](https://docs.rs/palette/0.4.1/palette/)
 
-[Master branch](https://ogeon.github.io/docs/palette/master/palette/index.html).
+[Master branch](https://ogeon.github.io/docs/palette/master/palette/index.html)
 
 ## Cargo.toml Entries
 
@@ -31,6 +31,7 @@ These features are enabled by default:
 These features are disabled by default:
 
 * `"serializing"` - Enables color serializing and deserializing using `serde`.
+* `"libm"` - Makes it use the `libm` floating point math library. It's only for when the `"std"` feature is disabled.
 
 ### Without the standard library
 
@@ -40,6 +41,7 @@ Here is an example `Cargo.toml` entry for using palette on `#![no_std]`:
 [dependencies.palette]
 version = "0.4"
 default-features = false
+features = ["libm"] # Makes it use libm instead of std for float math
 ```
 
 ## It's Never "Just RGB"

no_std_test/Cargo.toml

@@ -14,4 +14,4 @@ default-features = false
 [dependencies.palette]
 path = "../palette"
 default-features = false
-features = ["named"]
+features = ["libm", "named"]

palette/Cargo.toml

@@ -16,17 +16,20 @@ build = "build/main.rs"
 default = ["named_from_str", "std"]
 named_from_str = ["named", "phf", "phf_codegen", "std"]
 named = []
-std = ["approx/std", "num-traits/std"]
 serializing = ["serde", "std"]
 
-#internal
-strict = []
+#ignore in feature test
+std = ["approx/std", "num-traits/std"]
+strict = [] # Only for CI internal testing
 
 [dependencies]
 palette_derive = {version = "0.4.1", path = "../palette_derive"}
 num-traits = {version = "0.2", default-features = false}
 approx = {version = "0.3", default-features = false}
-libm = "0.1"
+
+[dependencies.libm]
+version = "0.1"
+optional = true
 
 [dependencies.phf]
 version = "0.7"

palette/README.md

@@ -0,0 +1 @@
+../README.md

palette/src/float.rs

@@ -17,7 +17,9 @@ pub use self::no_std_float_trait::Float;
 
 #[cfg(not(feature = "std"))]
 mod no_std_float_trait {
+    #[cfg(feature = "libm")]
     extern crate libm;
+    #[cfg(feature = "libm")]
     use self::libm::{F32Ext, F64Ext};
 
     use core::{f32, f64};
@@ -61,6 +63,7 @@ mod no_std_float_trait {
         fn round(self) -> Self;
     }
 
+    #[cfg(feature = "libm")]
     impl Float for f32 {
         fn sqrt(self) -> f32 {
             F32Ext::cbrt(self)
@@ -85,6 +88,7 @@ mod no_std_float_trait {
         }
     }
 
+    #[cfg(feature = "libm")]
     impl Float for f64 {
         fn sqrt(self) -> f64 {
             F64Ext::sqrt(self)
@@ -108,4 +112,57 @@ mod no_std_float_trait {
             F64Ext::round(self)
         }
     }
+
+    #[cfg(not(feature = "libm"))]
+    impl Float for f32 {
+        fn sqrt(self) -> f32 {
+            panic!("need to select a float library for palette")
+        }
+        fn cbrt(self) -> f32 {
+            panic!("need to select a float library for palette")
+        }
+        fn powf(self, other: f32) -> f32 {
+            panic!("need to select a float library for palette")
+        }
+        fn sin(self) -> f32 {
+            panic!("need to select a float library for palette")
+        }
+        fn cos(self) -> f32 {
+            panic!("need to select a float library for palette")
+        }
+        fn atan2(self, other: f32) -> f32 {
+            panic!("need to select a float library for palette")
+        }
+        fn round(self) -> f32 {
+            panic!("need to select a float library for palette")
+        }
+    }
+
+    #[cfg(not(feature = "libm"))]
+    impl Float for f64 {
+        fn sqrt(self) -> f64 {
+            panic!("need to select a float library for palette")
+        }
+        fn cbrt(self) -> f64 {
+            panic!("need to select a float library for palette")
+        }
+        fn powf(self, other: f64) -> f64 {
+            panic!("need to select a float library for palette")
+        }
+        fn sin(self) -> f64 {
+            panic!("need to select a float library for palette")
+        }
+        fn cos(self) -> f64 {
+            panic!("need to select a float library for palette")
+        }
+        fn atan2(self, other: f64) -> f64 {
+            panic!("need to select a float library for palette")
+        }
+        fn round(self) -> f64 {
+            panic!("need to select a float library for palette")
+        }
+    }
 }
+
+#[cfg(not(any(feature = "std", feature = "libm")))]
+compile_error!("The palette crate needs a float library. Please enable the \"std\" or \"libm\" feature.");

scripts/test_features.sh

@@ -4,7 +4,7 @@ set -e
 features=""
 
 #Features that will always be activated
-required_features="strict"
+required_features="std strict"
 
 
 #Find features
@@ -14,7 +14,7 @@ current_dependency=""
 while read -r line || [[ -n "$line" ]]; do
 	if [[ "$line" == "[features]" ]]; then
 		walking_features=true
-	elif [[ $walking_features == true ]] && [[ "$line" == "#internal" ]]; then
+	elif [[ $walking_features == true ]] && [[ "$line" == "#ignore in feature test" ]]; then
 		walking_features=false
 	elif [[ $walking_features == true ]] && echo "$line" | grep -E "^\[.*\]" > /dev/null; then
 		walking_features=false