On wasm, provide intradoc-link for spawn() function in EventLoop docs (#3178)

src/event_loop.rs

@@ -224,14 +224,22 @@ impl<T> EventLoop<T> {
     ///   (that Rust doesn't see) that will also mean that the rest of the function is never executed
     ///   and any values not passed to this function will *not* be dropped.
     ///
-    ///   Web applications are recommended to use `spawn()` instead of `run()` to avoid the need
+    ///   Web applications are recommended to use
+    #[cfg_attr(
+        wasm_platform,
+        doc = "[`EventLoopExtWebSys::spawn()`][crate::platform::web::EventLoopExtWebSys::spawn()]"
+    )]
+    #[cfg_attr(not(wasm_platform), doc = "`EventLoopExtWebSys::spawn()`")]
+    ///   [^1] instead of [`run()`] to avoid the need
     ///   for the Javascript exception trick, and to make it clearer that the event loop runs
     ///   asynchronously (via the browser's own, internal, event loop) and doesn't block the
     ///   current thread of execution like it does on other platforms.
     ///
     ///   This function won't be available with `target_feature = "exception-handling"`.
     ///
-    /// [`set_control_flow()`]: EventLoopWindowTarget::set_control_flow
+    /// [`set_control_flow()`]: EventLoopWindowTarget::set_control_flow()
+    /// [`run()`]: Self::run()
+    /// [^1]: `EventLoopExtWebSys::spawn()` is only available on WASM.
     #[inline]
     #[cfg(not(all(wasm_platform, target_feature = "exception-handling")))]
     pub fn run<F>(self, event_handler: F) -> Result<(), EventLoopError>

src/lib.rs

@@ -26,16 +26,36 @@
 //! window or a key getting pressed while the window is focused. Devices can generate
 //! [`DeviceEvent`]s, which contain unfiltered event data that isn't specific to a certain window.
 //! Some user activity, like mouse movement, can generate both a [`WindowEvent`] *and* a
-//! [`DeviceEvent`]. You can also create and handle your own custom [`UserEvent`]s, if desired.
+//! [`DeviceEvent`]. You can also create and handle your own custom [`Event::UserEvent`]s, if desired.
 //!
-//! You can retrieve events by calling [`EventLoop::run`][event_loop_run]. This function will
+//! You can retrieve events by calling [`EventLoop::run()`]. This function will
 //! dispatch events for every [`Window`] that was created with that particular [`EventLoop`], and
-//! will run until [`exit()`] is used, at which point [`Event`]`::`[`LoopExiting`].
+//! will run until [`exit()`] is used, at which point [`Event::LoopExiting`].
 //!
 //! Winit no longer uses a `EventLoop::poll_events() -> impl Iterator<Event>`-based event loop
 //! model, since that can't be implemented properly on some platforms (e.g web, iOS) and works poorly on
 //! most other platforms. However, this model can be re-implemented to an extent with
-//! [`EventLoopExtPumpEvents::pump_events`]. See that method's documentation for more reasons about why
+#![cfg_attr(
+    any(
+        windows_platform,
+        macos_platform,
+        android_platform,
+        x11_platform,
+        wayland_platform
+    ),
+    doc = "[`EventLoopExtPumpEvents::pump_events()`][platform::pump_events::EventLoopExtPumpEvents::pump_events()]"
+)]
+#![cfg_attr(
+    not(any(
+        windows_platform,
+        macos_platform,
+        android_platform,
+        x11_platform,
+        wayland_platform
+    )),
+    doc = "`EventLoopExtPumpEvents::pump_events()`"
+)]
+//! [^1]. See that method's documentation for more reasons about why
 //! it's discouraged, beyond compatibility reasons.
 //!
 //!
@@ -92,8 +112,8 @@
 //! });
 //! ```
 //!
-//! [`Event`]`::`[`WindowEvent`] has a [`WindowId`] member. In multi-window environments, it should be
+//! [`WindowEvent`] has a [`WindowId`] member. In multi-window environments, it should be
-//! compared to the value returned by [`Window::id()`][window_id_fn] to determine which [`Window`]
+//! compared to the value returned by [`Window::id()`] to determine which [`Window`]
 //! dispatched the event.
 //!
 //! # Drawing on the window
@@ -101,7 +121,7 @@
 //! Winit doesn't directly provide any methods for drawing on a [`Window`]. However it allows you to
 //! retrieve the raw handle of the window and display (see the [`platform`] module and/or the
 //! [`raw_window_handle`] and [`raw_display_handle`] methods), which in turn allows
-//!  you to create an OpenGL/Vulkan/DirectX/Metal/etc. context that can be used to render graphics.
+//! you to create an OpenGL/Vulkan/DirectX/Metal/etc. context that can be used to render graphics.
 //!
 //! Note that many platforms will display garbage data in the window's client area if the
 //! application doesn't render anything to the window by the time the desktop compositor is ready to
@@ -110,9 +130,8 @@
 //! window visible only once you're ready to render into it.
 //!
 //! [`EventLoop`]: event_loop::EventLoop
-//! [`EventLoopExtPumpEvents::pump_events`]: ./platform/pump_events/trait.EventLoopExtPumpEvents.html#tymethod.pump_events
 //! [`EventLoop::new()`]: event_loop::EventLoop::new
-//! [event_loop_run]: event_loop::EventLoop::run
+//! [`EventLoop::run()`]: event_loop::EventLoop::run
 //! [`exit()`]: event_loop::EventLoopWindowTarget::exit
 //! [`Window`]: window::Window
 //! [`WindowId`]: window::WindowId
@@ -120,15 +139,14 @@
 //! [window_new]: window::Window::new
 //! [window_builder_new]: window::WindowBuilder::new
 //! [window_builder_build]: window::WindowBuilder::build
-//! [window_id_fn]: window::Window::id
+//! [`Window::id()`]: window::Window::id
-//! [`Event`]: event::Event
 //! [`WindowEvent`]: event::WindowEvent
 //! [`DeviceEvent`]: event::DeviceEvent
-//! [`UserEvent`]: event::Event::UserEvent
+//! [`Event::UserEvent`]: event::Event::UserEvent
-//! [`LoopExiting`]: event::Event::LoopExiting
+//! [`Event::LoopExiting`]: event::Event::LoopExiting
-//! [`platform`]: platform
 //! [`raw_window_handle`]: ./window/struct.Window.html#method.raw_window_handle
 //! [`raw_display_handle`]: ./window/struct.Window.html#method.raw_display_handle
+//! [^1]: `EventLoopExtPumpEvents::pump_events()` is only available on Windows, macOS, Android, X11 and Wayland.
 
 #![deny(rust_2018_idioms)]
 #![deny(rustdoc::broken_intra_doc_links)]

src/platform/run_on_demand.rs

@@ -35,9 +35,9 @@ pub trait EventLoopExtRunOnDemand {
     /// See the [`set_control_flow()`] docs on how to change the event loop's behavior.
     ///
     /// # Caveats
-    /// - This extension isn't available on all platforms, since it's not always possible to
+    /// - This extension isn't available on all platforms, since it's not always possible to return
-    ///   return to the caller (specifically this is impossible on iOS and Web - though with
+    ///   to the caller (specifically this is impossible on iOS and Web - though with the Web
-    ///   the Web backend it is possible to use `spawn()` more than once instead).
+    ///   backend it is possible to use `EventLoopExtWebSys::spawn()`[^1] more than once instead).
     /// - No [`Window`] state can be carried between separate runs of the event loop.
     ///
     /// You are strongly encouraged to use [`EventLoop::run()`] for portability, unless you specifically need
@@ -57,8 +57,13 @@ pub trait EventLoopExtRunOnDemand {
     ///   on an event loop that is internal to the browser itself.
     /// - **iOS:** It's not possible to stop and start an `NSApplication` repeatedly on iOS.
     ///
-    /// [`exit()`]: EventLoopWindowTarget::exit
+    #[cfg_attr(
-    /// [`set_control_flow()`]: EventLoopWindowTarget::set_control_flow
+        not(wasm_platform),
+        doc = "[^1]: `spawn()` is only available on `wasm` platforms."
+    )]
+    ///
+    /// [`exit()`]: EventLoopWindowTarget::exit()
+    /// [`set_control_flow()`]: EventLoopWindowTarget::set_control_flow()
     fn run_on_demand<F>(&mut self, event_handler: F) -> Result<(), EventLoopError>
     where
         F: FnMut(Event<Self::UserEvent>, &EventLoopWindowTarget<Self::UserEvent>);

src/platform/web.rs

@@ -109,13 +109,28 @@ pub trait EventLoopExtWebSys {
 
     /// Initializes the winit event loop.
     ///
-    /// Unlike `run`, this returns immediately, and doesn't throw an exception in order to
+    /// Unlike
-    /// satisfy its `!` return type.
+    #[cfg_attr(
+        all(wasm_platform, target_feature = "exception-handling"),
+        doc = "`run()`"
+    )]
+    #[cfg_attr(
+        not(all(wasm_platform, target_feature = "exception-handling")),
+        doc = "[`run()`]"
+    )]
+    /// [^1], this returns immediately, and doesn't throw an exception in order to
+    /// satisfy its [`!`] return type.
     ///
     /// Once the event loop has been destroyed, it's possible to reinitialize another event loop
     /// by calling this function again. This can be useful if you want to recreate the event loop
     /// while the WebAssembly module is still loaded. For example, this can be used to recreate the
     /// event loop when switching between tabs on a single page application.
+    ///
+    #[cfg_attr(
+        not(all(wasm_platform, target_feature = "exception-handling")),
+        doc = "[`run()`]: EventLoop::run()"
+    )]
+    /// [^1]: `run()` is _not_ available on WASM when the target supports `exception-handling`.
     fn spawn<F>(self, event_handler: F)
     where
         F: 'static + FnMut(Event<Self::UserEvent>, &EventLoopWindowTarget<Self::UserEvent>);