document wgpu feature flags

wgpu/src/lib.rs

@@ -25,6 +25,8 @@
 #![deny(unused_results)]
 #![forbid(unsafe_code)]
 #![forbid(rust_2018_idioms)]
+#![cfg_attr(docsrs, feature(doc_cfg))]
+
 pub mod defaults;
 pub mod settings;
 pub mod triangle;

wgpu/src/widget.rs

@@ -37,6 +37,7 @@ pub use slider::Slider;
 pub use text_input::TextInput;
 
 #[cfg(feature = "canvas")]
+#[cfg_attr(docsrs, doc(cfg(feature = "canvas")))]
 pub mod canvas;
 
 #[cfg(feature = "canvas")]

wgpu/src/widget/canvas/frame.rs

@@ -172,6 +172,7 @@ impl Frame {
     ///
     /// [`Text`]: struct.Text.html
     /// [`Frame`]: struct.Frame.html
+    /// [`Canvas`]: struct.Canvas.html
     pub fn fill_text(&mut self, text: Text) {
         use std::f32;