Add no_std support

.github/workflows/ci.yml

@@ -50,7 +50,11 @@ jobs:
     - run: cargo build --verbose
     - run: cargo build --verbose --target wasm32-unknown-unknown
       env:
-        RUSTFLAGS: --cfg=web_sys_unstable_apis 
+        RUSTFLAGS: --cfg=web_sys_unstable_apis
+    - run: cargo build --verbose --no-default-features
+    - run: cargo build --verbose --target wasm32-unknown-unknown --no-default-features
+      env:
+        RUSTFLAGS: --cfg=web_sys_unstable_apis
     - run: cargo test --verbose
     - run: (cd examples/hello && cargo build --features glutin_winit)
     - run: (cd examples/hello && cargo build --target wasm32-unknown-unknown)

Cargo.toml

@@ -19,28 +19,47 @@ targets = [
   "x86_64-pc-windows-msvc",
   "i686-unknown-linux-gnu",
   "i686-pc-windows-msvc",
-  "wasm32-unknown-unknown"
+  "wasm32-unknown-unknown",
 ]
 
 [lib]
 name = "glow"
 path = "src/lib.rs"
 
 [dependencies]
-log = { version = "0.4.16", optional = true }
+log = { version = "0.4.16", optional = true, default-features = false }
 
 [features]
+default = ["std"]
+std = [
+  "log/std",
+  "wasm_bindgen/std",
+  "web_sys/std",
+  "js_sys/std",
+  "slotmap/std",
+]
 debug_trace_calls = []
 debug_automatic_glGetError = []
 
-[target.'cfg(target_arch = "wasm32")'.dependencies]
-js-sys = "~0.3"
-wasm-bindgen = "~0.2"
-slotmap = "1"
+[target.'cfg(target_arch = "wasm32")'.dependencies.js_sys]
+version = "~0.3"
+package = "js-sys"
+default-features = false
+
+[target.'cfg(target_arch = "wasm32")'.dependencies.wasm_bindgen]
+version = "~0.2"
+package = "wasm-bindgen"
+default-features = false
+
+[target.'cfg(target_arch = "wasm32")'.dependencies.slotmap]
+version = "1"
+package = "slotmap"
+default-features = false
 
 [target.'cfg(target_arch = "wasm32")'.dependencies.web_sys]
-version = "~0.3.60"
+version = "~0.3.77"
 package = "web-sys"
+default-features = false
 features = [
   "Document",
   "Element",

README.md

@@ -22,6 +22,30 @@ cargo build
 cargo build --target wasm32-unknown-unknown
 ```
 
+## `no_std` support
+
+`no_std` support can be enabled by compiling with `--no-default-features` to
+disable `std` support. For example:
+
+```toml
+[dependencies]
+glow = { version = "0.16", default-features = false }
+```
+
+To support both `std` and `no_std` builds in project, you can use the following
+in your `Cargo.toml`:
+
+```toml
+[features]
+default = ["std", "other features"]
+
+std = ["glow/std"]
+other_features = []
+
+[dependencies]
+glow = { version = "0.16", default-features = false }
+```
+
 ## License
 
 This project is licensed under any one of [Apache License, Version

examples/hello/src/main.rs

@@ -1,6 +1,8 @@
+#[cfg(any(target_arch = "wasm32", feature = "glutin_winit", feature = "sdl2"))]
 use glow::*;
 
 fn main() {
+    #[cfg(any(target_arch = "wasm32", feature = "glutin_winit", feature = "sdl2"))]
     unsafe {
         // Create a context from a WebGL2 context on wasm32 targets
         #[cfg(target_arch = "wasm32")]
@@ -27,6 +29,8 @@ fn main() {
         // Create a context from a glutin window on non-wasm32 targets
         #[cfg(feature = "glutin_winit")]
         let (gl, gl_surface, gl_context, shader_version, _window, event_loop) = {
+            use core::num::NonZeroU32;
+
             use glutin::{
                 config::{ConfigTemplateBuilder, GlConfig},
                 context::{ContextApi, ContextAttributesBuilder, NotCurrentGlContext},
@@ -35,7 +39,6 @@ fn main() {
             };
             use glutin_winit::{DisplayBuilder, GlWindow};
             use raw_window_handle::HasRawWindowHandle;
-            use std::num::NonZeroU32;
 
             let event_loop = winit::event_loop::EventLoopBuilder::new().build().unwrap();
             let window_builder = winit::window::WindowBuilder::new()