Move `winit` logic from `iced` to `iced_winit`

- Added new `renderer::Windowed` trait. This shoud allow users to easily
  try different renderers by simply changing one line.
- Renamed `UserInterface` traits to `Application`, as the `run` method
  takes total control of the current thread.
- Moved `MouseCursor` back to `iced_native`. The new
  `renderer::Windowed` trait returns one on `draw`.
- Split `iced_native` renderer in multiple modules, for consistency.

1 files changed, 126 insertions, 0 deletions

diff --git a/winit/src/lib.rs b/winit/src/lib.rs
index 54a0bd9a..93e922d5 100644
--- a/winit/src/lib.rs
+++ b/winit/src/lib.rs
@@ -1,2 +1,128 @@
 pub use iced_native::*;
 pub use winit;
+
+pub use iced_native::renderer::Windowed;
+
+pub trait Application {
+    type Renderer: iced_native::renderer::Windowed
+        + iced_native::column::Renderer;
+
+    type Message;
+
+    fn update(&mut self, message: Self::Message);
+
+    fn view(&mut self) -> Element<Self::Message, Self::Renderer>;
+
+    fn run(mut self)
+    where
+        Self: 'static + Sized,
+    {
+        use winit::{
+            event::{Event, WindowEvent},
+            event_loop::{ControlFlow, EventLoop},
+            window::WindowBuilder,
+        };
+
+        let event_loop = EventLoop::new();
+
+        // TODO: Ask for window settings and configure this properly
+        let window = WindowBuilder::new()
+            .build(&event_loop)
+            .expect("Open window");
+
+        let size = window.inner_size().to_physical(window.hidpi_factor());;
+        let (width, height) = (size.width as u16, size.height as u16);
+
+        let mut renderer = Self::Renderer::new(&window);
+        let mut target = renderer.target(width, height);
+
+        let user_interface = UserInterface::build(
+            document(&mut self, width, height),
+            Cache::default(),
+            &mut renderer,
+        );
+
+        let mut primitive = user_interface.draw(&mut renderer);
+        let mut cache = Some(user_interface.into_cache());
+        let mut events = Vec::new();
+
+        window.request_redraw();
+
+        event_loop.run(move |event, _, control_flow| match event {
+            Event::EventsCleared => {
+                // TODO: We should be able to keep a user interface alive
+                // between events once we remove state references.
+                //
+                // This will allow us to rebuild it only when a message is
+                // handled.
+                let mut user_interface = UserInterface::build(
+                    document(&mut self, width, height),
+                    cache.take().unwrap(),
+                    &mut renderer,
+                );
+
+                let messages = user_interface.update(events.drain(..));
+
+                if messages.is_empty() {
+                    primitive = user_interface.draw(&mut renderer);
+
+                    cache = Some(user_interface.into_cache());
+                } else {
+                    // When there are messages, we are forced to rebuild twice
+                    // for now :^)
+                    let temp_cache = user_interface.into_cache();
+
+                    for message in messages {
+                        self.update(message);
+                    }
+
+                    let user_interface = UserInterface::build(
+                        document(&mut self, width, height),
+                        temp_cache,
+                        &mut renderer,
+                    );
+
+                    primitive = user_interface.draw(&mut renderer);
+
+                    cache = Some(user_interface.into_cache());
+                }
+
+                window.request_redraw();
+            }
+            Event::WindowEvent {
+                event: WindowEvent::RedrawRequested,
+                ..
+            } => {
+                renderer.draw(&mut target, &primitive);
+
+                // TODO: Handle animations!
+                // Maybe we can use `ControlFlow::WaitUntil` for this.
+            }
+            Event::WindowEvent {
+                event: WindowEvent::CloseRequested,
+                ..
+            } => {
+                *control_flow = ControlFlow::Exit;
+            }
+            _ => {
+                *control_flow = ControlFlow::Wait;
+            }
+        })
+    }
+}
+
+fn document<Application>(
+    application: &mut Application,
+    width: u16,
+    height: u16,
+) -> Element<Application::Message, Application::Renderer>
+where
+    Application: self::Application,
+    Application::Message: 'static,
+{
+    Column::new()
+        .width(Length::Units(width))
+        .height(Length::Units(height))
+        .push(application.view())
+        .into()
+}