Implement revamped RedrawRequested on Web (#1301)

* Implement revamped `RedrawRequested` on Web

* Add `web` example

Cargo.toml

@@ -117,3 +117,6 @@ package = "stdweb"
 version = "=0.4.20"
 optional = true
 features = ["experimental_features_which_may_break_on_minor_version_bumps"]
+
+[target.'cfg(target_arch = "wasm32")'.dev-dependencies]
+console_log = "0.1"

examples/web.rs

@@ -0,0 +1,72 @@
+use winit::{
+    event::{Event, WindowEvent},
+    event_loop::{ControlFlow, EventLoop},
+    window::WindowBuilder,
+};
+
+pub fn main() {
+    let event_loop = EventLoop::new();
+
+    let window = WindowBuilder::new()
+        .with_title("A fantastic window!")
+        .build(&event_loop)
+        .unwrap();
+
+    #[cfg(feature = "web-sys")]
+    {
+        use winit::platform::web::WindowExtWebSys;
+
+        let canvas = window.canvas();
+
+        let window = web_sys::window().unwrap();
+        let document = window.document().unwrap();
+        let body = document.body().unwrap();
+
+        body.append_child(&canvas)
+            .expect("Append canvas to HTML body");
+    }
+
+    #[cfg(feature = "stdweb")]
+    {
+        use std_web::web::INode;
+        use winit::platform::web::WindowExtStdweb;
+
+        let canvas = window.canvas();
+
+        let document = std_web::web::document();
+        let body: std_web::web::Node = document.body().expect("Get HTML body").into();
+
+        body.append_child(&canvas);
+    }
+
+    event_loop.run(move |event, _, control_flow| {
+        #[cfg(feature = "web-sys")]
+        log::debug!("{:?}", event);
+
+        #[cfg(feature = "stdweb")]
+        std_web::console!(log, "%s", format!("{:?}", event));
+
+        match event {
+            Event::WindowEvent {
+                event: WindowEvent::CloseRequested,
+                window_id,
+            } if window_id == window.id() => *control_flow = ControlFlow::Exit,
+            Event::MainEventsCleared => {
+                window.request_redraw();
+            }
+            _ => *control_flow = ControlFlow::Wait,
+        }
+    });
+}
+
+#[cfg(feature = "web-sys")]
+mod wasm {
+    use wasm_bindgen::prelude::*;
+
+    #[wasm_bindgen(start)]
+    pub fn run() {
+        console_log::init_with_level(log::Level::Debug);
+
+        super::main();
+    }
+}

src/platform_impl/web/event_loop/runner.rs

@@ -1,5 +1,5 @@
 use super::{backend, state::State};
-use crate::event::{Event, StartCause, WindowEvent};
+use crate::event::{Event, StartCause};
 use crate::event_loop as root;
 use crate::window::WindowId;
 
@@ -127,18 +127,15 @@ impl<T: 'static> Shared<T> {
         if !event_is_start {
             self.handle_event(event, &mut control);
         }
+        self.handle_event(Event::MainEventsCleared, &mut control);
+
         // Collect all of the redraw events to avoid double-locking the RefCell
         let redraw_events: Vec<WindowId> = self.0.redraw_pending.borrow_mut().drain().collect();
         for window_id in redraw_events {
-            self.handle_event(
+            self.handle_event(Event::RedrawRequested(window_id), &mut control);
-                Event::WindowEvent {
-                    window_id,
-                    event: WindowEvent::RedrawRequested,
-                },
-                &mut control,
-            );
         }
-        self.handle_event(Event::EventsCleared, &mut control);
+        self.handle_event(Event::RedrawEventsCleared, &mut control);
+
         self.apply_control_flow(control);
         // If the event loop is closed, it has been closed this iteration and now the closing
         // event should be emitted