Deprecate window creation with stale event loop

Creating window when event loop is not running generally doesn't work,
since a bunch of events and sync OS requests can't be processed. This
is also an issue on e.g. Android, since window can't be created outside
event loop easily.

Thus deprecate the window creation when event loop is not running,
as well as other resource creation to running event loop.

Given that all the examples use the bad pattern of creating the window
when event loop is not running and also most example existence is
questionable, since they show single thing and the majority of their
code is window/event loop initialization, they wore merged into
a single example 'window.rs' example that showcases very simple
application using winit.

Fixes #3399.

examples/x11_embed.rs

@@ -1,70 +1,62 @@
 //! A demonstration of embedding a winit window in an existing X11 application.
+use std::error::Error;
 
 #[cfg(x11_platform)]
-#[path = "util/fill.rs"]
-mod fill;
-
-#[cfg(x11_platform)]
-mod imple {
-    use super::fill;
+fn main() -> Result<(), Box<dyn Error>> {
     use simple_logger::SimpleLogger;
+
     use winit::{
         event::{Event, WindowEvent},
         event_loop::EventLoop,
-        platform::x11::WindowBuilderExtX11,
+        platform::x11::WindowAttributesExtX11,
         window::Window,
     };
 
-    pub(super) fn entry() -> Result<(), Box<dyn std::error::Error>> {
-        // First argument should be a 32-bit X11 window ID.
-        let parent_window_id = std::env::args()
-            .nth(1)
-            .ok_or("Expected a 32-bit X11 window ID as the first argument.")?
-            .parse::<u32>()?;
+    #[path = "util/fill.rs"]
+    mod fill;
 
-        SimpleLogger::new().init().unwrap();
-        let event_loop = EventLoop::new()?;
+    // First argument should be a 32-bit X11 window ID.
+    let parent_window_id = std::env::args()
+        .nth(1)
+        .ok_or("Expected a 32-bit X11 window ID as the first argument.")?
+        .parse::<u32>()?;
 
-        let window = Window::builder()
-            .with_title("An embedded window!")
-            .with_inner_size(winit::dpi::LogicalSize::new(128.0, 128.0))
-            .with_embed_parent_window(parent_window_id)
-            .build(&event_loop)
-            .unwrap();
+    SimpleLogger::new().init().unwrap();
+    let event_loop = EventLoop::new()?;
+
+    let mut window = None;
+    event_loop.run(move |event, event_loop| match event {
+        Event::Resumed => {
+            let window_attributes = Window::default_attributes()
+                .with_title("An embedded window!")
+                .with_inner_size(winit::dpi::LogicalSize::new(128.0, 128.0))
+                .with_embed_parent_window(parent_window_id);
+
+            window = Some(event_loop.create_window(window_attributes).unwrap());
+        }
+        Event::WindowEvent { event, .. } => {
+            let window = window.as_ref().unwrap();
 
-        event_loop.run(move |event, elwt| {
             match event {
-                Event::WindowEvent {
-                    event: WindowEvent::CloseRequested,
-                    window_id,
-                } if window_id == window.id() => elwt.exit(),
-                Event::AboutToWait => {
-                    window.request_redraw();
-                }
-                Event::WindowEvent {
-                    event: WindowEvent::RedrawRequested,
-                    ..
-                } => {
-                    // Notify the windowing system that we'll be presenting to the window.
+                WindowEvent::CloseRequested => event_loop.exit(),
+                WindowEvent::RedrawRequested => {
                     window.pre_present_notify();
-                    fill::fill_window(&window);
+                    fill::fill_window(window);
                 }
                 _ => (),
             }
-        })?;
+        }
+        Event::AboutToWait => {
+            window.as_ref().unwrap().request_redraw();
+        }
+        _ => (),
+    })?;
 
-        Ok(())
-    }
+    Ok(())
 }
 
 #[cfg(not(x11_platform))]
-mod imple {
-    pub(super) fn entry() -> Result<(), Box<dyn std::error::Error>> {
-        println!("This example is only supported on X11 platforms.");
-        Ok(())
-    }
-}
-
-fn main() -> Result<(), Box<dyn std::error::Error>> {
-    imple::entry()
+fn main() -> Result<(), Box<dyn Error>> {
+    println!("This example is only supported on X11 platforms.");
+    Ok(())
 }