Add examples/window_pump_events

A minimal example of an application based on an external event loop that
calls `pump_events` for each iteration of the external loop.

examples/window_pump_events.rs

@@ -0,0 +1,70 @@
+#![allow(clippy::single_match)]
+
+// Limit this example to only compatible platforms.
+#[cfg(any(
+    windows_platform,
+    macos_platform,
+    x11_platform,
+    wayland_platform,
+    android_platform,
+))]
+fn main() -> std::process::ExitCode {
+    use std::{process::ExitCode, thread::sleep, time::Duration};
+
+    use simple_logger::SimpleLogger;
+    use winit::{
+        event::{Event, WindowEvent},
+        event_loop::EventLoop,
+        platform::pump_events::{EventLoopExtPumpEvents, PumpStatus},
+        window::WindowBuilder,
+    };
+
+    #[path = "util/fill.rs"]
+    mod fill;
+
+    let mut event_loop = EventLoop::new();
+
+    SimpleLogger::new().init().unwrap();
+    let window = WindowBuilder::new()
+        .with_title("A fantastic window!")
+        .build(&event_loop)
+        .unwrap();
+
+    'main: loop {
+        let status = event_loop.pump_events(|event, _, control_flow| {
+            if let Event::WindowEvent { event, .. } = &event {
+                // Print only Window events to reduce noise
+                println!("{event:?}");
+            }
+
+            match event {
+                Event::WindowEvent {
+                    event: WindowEvent::CloseRequested,
+                    window_id,
+                } if window_id == window.id() => control_flow.set_exit(),
+                Event::MainEventsCleared => {
+                    window.request_redraw();
+                }
+                Event::RedrawRequested(_) => {
+                    fill::fill_window(&window);
+                }
+                _ => (),
+            }
+        });
+        if let PumpStatus::Exit(exit_code) = status {
+            break 'main ExitCode::from(exit_code as u8);
+        }
+
+        // Sleep for 1/60 second to simulate application work
+        //
+        // Since `pump_events` doesn't block it will be important to
+        // throttle the loop in the app somehow.
+        println!("Update()");
+        sleep(Duration::from_millis(16));
+    }
+}
+
+#[cfg(any(ios_platform, wasm_platform, orbital_platform))]
+fn main() {
+    println!("This platform doesn't support pump_events.");
+}