Render a background for the open_window example (#175)

This PR adds code to render a basic gray background to the opened window in the `open_window` example.

This also helps making the example a bit more useful, since most users will want to render to their window.

And also it looks nicer. 🙂 

This is done using the `softbuffer` crate, in the same manner of the `open_parented` introduced in #172.

examples/open_window.rs

@@ -1,10 +1,13 @@
+use std::num::NonZeroU32;
 use std::time::Duration;
 
 use rtrb::{Consumer, RingBuffer};
 
 #[cfg(target_os = "macos")]
 use baseview::copy_to_clipboard;
-use baseview::{Event, EventStatus, MouseEvent, Window, WindowHandler, WindowScalePolicy};
+use baseview::{
+    Event, EventStatus, MouseEvent, PhySize, Window, WindowEvent, WindowHandler, WindowScalePolicy,
+};
 
 #[derive(Debug, Clone)]
 enum Message {
@@ -13,32 +16,48 @@ enum Message {
 
 struct OpenWindowExample {
     rx: Consumer<Message>,
+
+    ctx: softbuffer::Context,
+    surface: softbuffer::Surface,
+    current_size: PhySize,
+    damaged: bool,
 }
 
 impl WindowHandler for OpenWindowExample {
     fn on_frame(&mut self, _window: &mut Window) {
+        let mut buf = self.surface.buffer_mut().unwrap();
+        if self.damaged {
+            buf.fill(0xFFAAAAAA);
+            self.damaged = false;
+        }
+        buf.present().unwrap();
+
         while let Ok(message) = self.rx.pop() {
             println!("Message: {:?}", message);
         }
     }
 
     fn on_event(&mut self, _window: &mut Window, event: Event) -> EventStatus {
-        match event {
-            Event::Mouse(e) => {
-                println!("Mouse event: {:?}", e);
+        match &event {
+            #[cfg(target_os = "macos")]
+            Event::Mouse(MouseEvent::ButtonPressed { .. }) => copy_to_clipboard(&"This is a test!"),
+            Event::Window(WindowEvent::Resized(info)) => {
+                println!("Resized: {:?}", info);
+                let new_size = info.physical_size();
+                self.current_size = new_size;
 
-                #[cfg(target_os = "macos")]
-                match e {
-                    MouseEvent::ButtonPressed { .. } => {
-                        copy_to_clipboard(&"This is a test!")
-                    }
-                    _ => (),
+                if let (Some(width), Some(height)) =
+                    (NonZeroU32::new(new_size.width), NonZeroU32::new(new_size.height))
+                {
+                    self.surface.resize(width, height).unwrap();
+                    self.damaged = true;
                 }
             }
-            Event::Keyboard(e) => println!("Keyboard event: {:?}", e),
-            Event::Window(e) => println!("Window event: {:?}", e),
+            _ => {}
         }
 
+        log_event(&event);
+
         EventStatus::Captured
     }
 }
@@ -56,13 +75,27 @@ fn main() {
 
     let (mut tx, rx) = RingBuffer::new(128);
 
-    ::std::thread::spawn(move || loop {
-        ::std::thread::sleep(Duration::from_secs(5));
+    std::thread::spawn(move || loop {
+        std::thread::sleep(Duration::from_secs(5));
 
         if let Err(_) = tx.push(Message::Hello) {
             println!("Failed sending message");
         }
     });
 
-    Window::open_blocking(window_open_options, |_| OpenWindowExample { rx });
+    Window::open_blocking(window_open_options, |window| {
+        let ctx = unsafe { softbuffer::Context::new(window) }.unwrap();
+        let mut surface = unsafe { softbuffer::Surface::new(&ctx, window) }.unwrap();
+        surface.resize(NonZeroU32::new(512).unwrap(), NonZeroU32::new(512).unwrap()).unwrap();
+
+        OpenWindowExample { ctx, surface, rx, current_size: PhySize::new(512, 512), damaged: true }
+    });
+}
+
+fn log_event(event: &Event) {
+    match event {
+        Event::Mouse(e) => println!("Mouse event: {:?}", e),
+        Event::Keyboard(e) => println!("Keyboard event: {:?}", e),
+        Event::Window(e) => println!("Window event: {:?}", e),
+    }
 }