Added functional open_parented example (#172)

This PR adds a simple example that allows to test and showcase the `Window::open_parented` method.

That example first creates a parent window using `Window::open_blocking`, and then creates a smaller child window using `Window::open_parented`.

Both window's handlers log all of their events to the console, in a similar fashion to the `open_window` example.

Both windows actually do rendering (unlike the `open_window` example for now): the parent fills its window with a grey backround, and the child fills its window with a red background.

This example also uses the `softbuffer` crate to perform the rendering, which allows testing it in a more portable manner and in the simplest use case possible, without having to involve OpenGL or any 3D rendering pipeline at all.

Cargo.toml

@@ -40,3 +40,4 @@ uuid = { version = "0.8", features = ["v4"] }
 
 [dev-dependencies]
 rtrb = "0.2"
+softbuffer = "0.3.4"

examples/open_parented.rs

@@ -0,0 +1,141 @@
+use baseview::{
+    Event, EventStatus, PhySize, Window, WindowEvent, WindowHandle, WindowHandler,
+    WindowScalePolicy,
+};
+use std::num::NonZeroU32;
+
+struct ParentWindowHandler {
+    ctx: softbuffer::Context,
+    surface: softbuffer::Surface,
+    current_size: PhySize,
+    damaged: bool,
+
+    child_window: Option<WindowHandle>,
+}
+
+impl ParentWindowHandler {
+    pub fn new(window: &mut Window) -> Self {
+        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();
+
+        let window_open_options = baseview::WindowOpenOptions {
+            title: "baseview child".into(),
+            size: baseview::Size::new(256.0, 256.0),
+            scale: WindowScalePolicy::SystemScaleFactor,
+
+            // TODO: Add an example that uses the OpenGL context
+            #[cfg(feature = "opengl")]
+            gl_config: None,
+        };
+        let child_window =
+            Window::open_parented(window, window_open_options, ChildWindowHandler::new);
+
+        // TODO: no way to query physical size initially?
+        Self {
+            ctx,
+            surface,
+            current_size: PhySize::new(512, 512),
+            damaged: true,
+            child_window: Some(child_window),
+        }
+    }
+}
+
+impl WindowHandler for ParentWindowHandler {
+    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();
+    }
+
+    fn on_event(&mut self, _window: &mut Window, event: Event) -> EventStatus {
+        match event {
+            Event::Window(WindowEvent::Resized(info)) => {
+                println!("Parent Resized: {:?}", info);
+                let new_size = info.physical_size();
+                self.current_size = new_size;
+
+                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::Mouse(e) => println!("Parent Mouse event: {:?}", e),
+            Event::Keyboard(e) => println!("Parent Keyboard event: {:?}", e),
+            Event::Window(e) => println!("Parent Window event: {:?}", e),
+        }
+
+        EventStatus::Captured
+    }
+}
+
+struct ChildWindowHandler {
+    ctx: softbuffer::Context,
+    surface: softbuffer::Surface,
+    current_size: PhySize,
+    damaged: bool,
+}
+
+impl ChildWindowHandler {
+    pub fn new(window: &mut Window) -> Self {
+        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();
+
+        // TODO: no way to query physical size initially?
+        Self { ctx, surface, current_size: PhySize::new(256, 256), damaged: true }
+    }
+}
+
+impl WindowHandler for ChildWindowHandler {
+    fn on_frame(&mut self, _window: &mut Window) {
+        let mut buf = self.surface.buffer_mut().unwrap();
+        if self.damaged {
+            buf.fill(0xFFAA0000);
+            self.damaged = false;
+        }
+        buf.present().unwrap();
+    }
+
+    fn on_event(&mut self, _window: &mut Window, event: Event) -> EventStatus {
+        match event {
+            Event::Window(WindowEvent::Resized(info)) => {
+                println!("Child Resized: {:?}", info);
+                let new_size = info.physical_size();
+                self.current_size = new_size;
+
+                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::Mouse(e) => println!("Child Mouse event: {:?}", e),
+            Event::Keyboard(e) => println!("Child Keyboard event: {:?}", e),
+            Event::Window(e) => println!("Child Window event: {:?}", e),
+        }
+
+        EventStatus::Captured
+    }
+}
+
+fn main() {
+    let window_open_options = baseview::WindowOpenOptions {
+        title: "baseview".into(),
+        size: baseview::Size::new(512.0, 512.0),
+        scale: WindowScalePolicy::SystemScaleFactor,
+
+        // TODO: Add an example that uses the OpenGL context
+        #[cfg(feature = "opengl")]
+        gl_config: None,
+    };
+
+    Window::open_blocking(window_open_options, ParentWindowHandler::new);
+}