feat: Add a feature that allows piet to be used in no_std environments

.github/workflows/ci.yml

@@ -63,6 +63,12 @@ jobs:
           command: clippy
           args: --manifest-path=piet/Cargo.toml --all-targets --all-features -- -D warnings
 
+      - name: cargo clippy piet with no default features
+        uses: actions-rs/cargo@v1
+        with:
+          command: clippy
+          args: --manifest-path=piet/Cargo.toml --all-targets --no-default-features --features libm -- -D warnings
+
       - name: cargo clippy piet-cairo
         uses: actions-rs/cargo@v1
         with:
@@ -103,6 +109,12 @@ jobs:
           command: test
           args: --manifest-path=piet/Cargo.toml --all-features
 
+      - name: cargo test piet with no default features
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
+          args: --manifest-path=piet/Cargo.toml --no-default-features --features libm
+
       - name: cargo test piet-cairo
         uses: actions-rs/cargo@v1
         with:
@@ -233,6 +245,12 @@ jobs:
           command: test
           args: --manifest-path=piet/Cargo.toml --all-features
 
+      - name: cargo test piet with no default features
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
+          args: --manifest-path=piet/Cargo.toml --no-default-features --features libm
+
       - name: cargo test piet-cairo
         uses: actions-rs/cargo@v1
         with:

piet-svg/src/text.rs

@@ -1,5 +1,7 @@
 //! Text functionality for Piet svg backend
 
+#![allow(clippy::arc_with_non_send_sync)]
+
 use std::{
     collections::HashSet,
     fs, io,

piet/Cargo.toml

@@ -13,17 +13,22 @@ include = ["src/**/*", "Cargo.toml", "snapshots/resources/*"]
 
 [dependencies]
 image = { version = "0.24.5", optional = true, default-features = false }
-kurbo = "0.9"
+kurbo = { version = "0.9", default-features = false }
 pico-args = { version = "0.4.2", optional = true }
 png = { version = "0.17.7", optional = true }
 os_info = { version = "3.6.0", optional = true, default-features = false }
 unic-bidi = "0.9.0"
 
 [features]
-samples = ["pico-args", "png", "os_info"]
+default = ["std"]
+std = ["kurbo/std"]
+libm = ["kurbo/libm"]
+
+samples = ["pico-args", "png", "os_info", "std"]
 
 # passing on all the image features. AVIF is not supported because it does not
 # support decoding, and thats al we use `Image` for.
+image = ["dep:image", "std"]
 image_png = ["image/png", "image"]
 jpeg = ["image/jpeg", "image"]
 jpeg_rayon = ["image/jpeg_rayon", "image"]

piet/src/color.rs

@@ -1,6 +1,6 @@
 //! A simple representation of color
 
-use std::fmt::{Debug, Formatter};
+use core::fmt::{Debug, Formatter};
 
 /// A datatype representing color.
 ///
@@ -138,7 +138,7 @@ impl Color {
                 3. * d * d * (t - 4. / 29.)
             }
         }
-        let th = h * (std::f64::consts::PI / 180.);
+        let th = h * (core::f64::consts::PI / 180.);
         let a = c * th.cos();
         let b = c * th.sin();
         let ll = (L + 16.) * (1. / 116.);
@@ -341,13 +341,13 @@ const fn hex_from_ascii_byte(b: u8) -> Result<u8, u8> {
 }
 
 impl Debug for Color {
-    fn fmt(&self, f: &mut Formatter) -> std::fmt::Result {
+    fn fmt(&self, f: &mut Formatter) -> core::fmt::Result {
         write!(f, "#{:08x}", self.as_rgba_u32())
     }
 }
 
-impl std::fmt::Display for ColorParseError {
-    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+impl core::fmt::Display for ColorParseError {
+    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
         match self {
             ColorParseError::WrongSize(n) => write!(f, "Input string has invalid length {n}"),
             ColorParseError::NotHex { idx, byte } => {
@@ -357,6 +357,7 @@ impl std::fmt::Display for ColorParseError {
     }
 }
 
+#[cfg(feature = "std")]
 impl std::error::Error for ColorParseError {}
 #[cfg(test)]
 mod tests {

piet/src/error.rs

@@ -1,6 +1,6 @@
 //! The common error type for piet operations.
 
-use std::fmt;
+use core::fmt;
 
 /// An error that can occur while rendering 2D graphics.
 #[derive(Debug)]
@@ -17,6 +17,7 @@ pub enum Error {
     /// A stack pop failed.
     StackUnbalance,
     /// The backend failed unexpectedly.
+    #[cfg(feature = "std")]
     BackendError(Box<dyn std::error::Error>),
     /// A font could not be found.
     MissingFont,
@@ -40,6 +41,7 @@ impl fmt::Display for Error {
                 "This functionality is not yet implemented for this backend"
             ),
             Error::MissingFeature(feature) => write!(f, "Missing feature '{feature}'"),
+            #[cfg(feature = "std")]
             Error::BackendError(e) => {
                 write!(f, "Backend error: ")?;
                 e.fmt(f)
@@ -50,8 +52,10 @@ impl fmt::Display for Error {
     }
 }
 
+#[cfg(feature = "std")]
 impl std::error::Error for Error {}
 
+#[cfg(feature = "std")]
 impl From<Box<dyn std::error::Error>> for Error {
     fn from(e: Box<dyn std::error::Error>) -> Error {
         Error::BackendError(e)

piet/src/font.rs

@@ -1,6 +1,6 @@
 //! Font families, weights, etcetera
 
-use std::sync::Arc;
+use alloc::sync::Arc;
 
 /// A reference to a font family.
 ///

piet/src/gradient.rs

@@ -20,8 +20,10 @@
 //!
 //! [unit square]: https://en.wikipedia.org/wiki/Unit_square
 
-use std::borrow::Cow;
-use std::hash::{Hash, Hasher};
+use alloc::borrow::{Cow, ToOwned};
+use alloc::vec::Vec;
+
+use core::hash::{Hash, Hasher};
 
 use kurbo::{Point, Rect, Size, Vec2};
 

piet/src/image.rs

@@ -14,11 +14,11 @@
 
 //! Types for working with images
 
+use alloc::sync::Arc;
 #[cfg(feature = "image")]
 use std::error::Error;
 #[cfg(feature = "image")]
 use std::path::Path;
-use std::sync::Arc;
 
 use crate::kurbo::Size;
 use crate::util::unpremul;
@@ -205,8 +205,8 @@ impl ImageBuf {
     }
 }
 
-impl std::fmt::Debug for ImageBuf {
-    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+impl core::fmt::Debug for ImageBuf {
+    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
         f.debug_struct("ImageBuf")
             .field("size", &self.pixels.len())
             .field("width", &self.width)

piet/src/lib.rs

@@ -23,6 +23,9 @@
 
 #![warn(missing_docs)]
 #![deny(clippy::trivially_copy_pass_by_ref, rustdoc::broken_intra_doc_links)]
+#![cfg_attr(not(feature = "std"), no_std)]
+
+extern crate alloc;
 
 pub use kurbo;
 

piet/src/null_renderer.rs

@@ -1,7 +1,7 @@
 //! A render context that does nothing.
 
-use std::borrow::Cow;
-use std::ops::RangeBounds;
+use alloc::borrow::Cow;
+use core::ops::RangeBounds;
 
 use kurbo::{Affine, Point, Rect, Shape, Size};
 
@@ -223,7 +223,7 @@ impl IntoBrush<NullRenderContext> for NullBrush {
         &'b self,
         _piet: &mut NullRenderContext,
         _bbox: impl FnOnce() -> Rect,
-    ) -> std::borrow::Cow<'b, NullBrush> {
+    ) -> Cow<'b, NullBrush> {
         Cow::Borrowed(self)
     }
 }

piet/src/render_context.rs

@@ -1,6 +1,6 @@
 //! The main render context trait.
 
-use std::borrow::Cow;
+use alloc::borrow::{Cow, ToOwned};
 
 use kurbo::{Affine, Point, Rect, Shape};
 

piet/src/shapes.rs

@@ -1,6 +1,6 @@
 //! Options for drawing paths.
 
-use std::rc::Rc;
+use alloc::rc::Rc;
 
 /// Options for drawing stroked lines.
 ///
@@ -229,7 +229,7 @@ impl Default for LineJoin {
     }
 }
 
-impl std::ops::Deref for StrokeDash {
+impl core::ops::Deref for StrokeDash {
     type Target = [f64];
     fn deref(&self) -> &Self::Target {
         self.alloc.as_deref().unwrap_or(self.slice)

piet/src/text.rs

@@ -1,6 +1,7 @@
 //! Traits for fonts and text handling.
 
-use std::ops::{Range, RangeBounds};
+use alloc::vec::Vec;
+use core::ops::{Deref, Range, RangeBounds};
 
 use crate::kurbo::{Point, Rect, Size};
 use crate::{Color, Error, FontFamily, FontStyle, FontWeight};
@@ -122,7 +123,7 @@ pub trait TextStorage: 'static {
     fn as_str(&self) -> &str;
 }
 
-impl std::ops::Deref for dyn TextStorage {
+impl Deref for dyn TextStorage {
     type Target = str;
     fn deref(&self) -> &Self::Target {
         self.as_str()
@@ -570,31 +571,31 @@ impl From<FontStyle> for TextAttribute {
     }
 }
 
-impl TextStorage for std::sync::Arc<str> {
+impl TextStorage for alloc::sync::Arc<str> {
     fn as_str(&self) -> &str {
         self
     }
 }
 
-impl TextStorage for std::rc::Rc<str> {
+impl TextStorage for alloc::rc::Rc<str> {
     fn as_str(&self) -> &str {
         self
     }
 }
 
-impl TextStorage for String {
+impl TextStorage for alloc::string::String {
     fn as_str(&self) -> &str {
         self.as_str()
     }
 }
 
-impl TextStorage for std::sync::Arc<String> {
+impl TextStorage for alloc::sync::Arc<alloc::string::String> {
     fn as_str(&self) -> &str {
         self
     }
 }
 
-impl TextStorage for std::rc::Rc<String> {
+impl TextStorage for alloc::rc::Rc<alloc::string::String> {
     fn as_str(&self) -> &str {
         self
     }

piet/src/util.rs

@@ -1,6 +1,8 @@
 //! Code useful for multiple backends
 
-use std::ops::{Bound, Range, RangeBounds};
+use alloc::vec;
+use alloc::vec::Vec;
+use core::ops::{Bound, Range, RangeBounds};
 
 use crate::kurbo::{Rect, Size};
 use crate::{Color, Error, FontFamily, FontStyle, FontWeight, LineMetric, TextAttribute};
@@ -143,7 +145,7 @@ pub fn compute_blurred_rect(rect: Rect, radius: f64, stride: usize, buf: &mut [u
 // See https://raphlinus.github.io/audio/2018/09/05/sigmoid.html for a little
 // explanation of this approximation to the erf function.
 fn compute_erf7(x: f64) -> f64 {
-    let x = x * std::f64::consts::FRAC_2_SQRT_PI;
+    let x = x * core::f64::consts::FRAC_2_SQRT_PI;
     let xx = x * x;
     let x = x + (0.24295 + (0.03395 + 0.0104 * xx) * xx) * (x * xx);
     x / (1.0 + x * x).sqrt()
@@ -290,6 +292,7 @@ pub fn image_buffer_to_tightly_packed(
 #[cfg(test)]
 mod tests {
     use super::*;
+    use alloc::string::ToString;
 
     #[test]
     fn test_count_until_utf16() {