2 files changed, 122 insertions, 0 deletions
diff --git a/graphics/src/window/compositor.rs b/graphics/src/window/compositor.rs
new file mode 100644
index 00000000..d5920c95
--- /dev/null
+++ b/graphics/src/window/compositor.rs
@@ -0,0 +1,55 @@
+use crate::Viewport;
+use iced_native::mouse;
+use raw_window_handle::HasRawWindowHandle;
+
+/// A graphics compositor that can draw to windows.
+pub trait Compositor: Sized {
+    /// The settings of the backend.
+    type Settings: Default;
+
+    /// The iced renderer of the backend.
+    type Renderer: iced_native::Renderer;
+
+    /// The surface of the backend.
+    type Surface;
+
+    /// The swap chain of the backend.
+    type SwapChain;
+
+    /// Creates a new [`Backend`].
+    ///
+    /// [`Backend`]: trait.Backend.html
+    fn new(settings: Self::Settings) -> (Self, Self::Renderer);
+
+    /// Crates a new [`Surface`] for the given window.
+    ///
+    /// [`Surface`]: #associatedtype.Surface
+    fn create_surface<W: HasRawWindowHandle>(
+        &mut self,
+        window: &W,
+    ) -> Self::Surface;
+
+    /// Crates a new [`SwapChain`] for the given [`Surface`].
+    ///
+    /// [`SwapChain`]: #associatedtype.SwapChain
+    /// [`Surface`]: #associatedtype.Surface
+    fn create_swap_chain(
+        &mut self,
+        surface: &Self::Surface,
+        width: u32,
+        height: u32,
+    ) -> Self::SwapChain;
+
+    /// Draws the output primitives to the next frame of the given [`SwapChain`].
+    ///
+    /// [`SwapChain`]: #associatedtype.SwapChain
+    /// [`Surface`]: #associatedtype.Surface
+    fn draw<T: AsRef<str>>(
+        &mut self,
+        renderer: &mut Self::Renderer,
+        swap_chain: &mut Self::SwapChain,
+        viewport: &Viewport,
+        output: &<Self::Renderer as iced_native::Renderer>::Output,
+        overlay: &[T],
+    ) -> mouse::Interaction;
+}
diff --git a/graphics/src/window/gl_compositor.rs b/graphics/src/window/gl_compositor.rs
new file mode 100644
index 00000000..542213b5
--- /dev/null
+++ b/graphics/src/window/gl_compositor.rs
@@ -0,0 +1,67 @@
+use crate::{Size, Viewport};
+use iced_native::mouse;
+
+use core::ffi::c_void;
+
+/// A basic OpenGL compositor.
+///
+/// A compositor is responsible for initializing a renderer and managing window
+/// surfaces.
+///
+/// For now, this compositor only deals with a single global surface
+/// for drawing. However, the trait will most likely change in the near future
+/// to handle multiple surfaces at once.
+///
+/// If you implement an OpenGL renderer, you can implement this trait to ease
+/// integration with existing windowing shells, like `iced_glutin`.
+pub trait GLCompositor: Sized {
+    /// The renderer of the [`Compositor`].
+    ///
+    /// This should point to your renderer type, which could be a type alias
+    /// of the [`Renderer`] provided in this crate with with a specific
+    /// [`Backend`].
+    ///
+    /// [`Compositor`]: trait.Compositor.html
+    /// [`Renderer`]: ../struct.Renderer.html
+    /// [`Backend`]: ../backend/trait.Backend.html
+    type Renderer: iced_native::Renderer;
+
+    /// The settings of the [`Compositor`].
+    ///
+    /// It's up to you to decide the configuration supported by your renderer!
+    type Settings: Default;
+
+    /// Creates a new [`Compositor`] and [`Renderer`] with the given
+    /// [`Settings`] and an OpenGL address loader function.
+    ///
+    /// [`Compositor`]: trait.Compositor.html
+    /// [`Renderer`]: #associatedtype.Renderer
+    /// [`Backend`]: ../backend/trait.Backend.html
+    #[allow(unsafe_code)]
+    unsafe fn new(
+        settings: Self::Settings,
+        loader_function: impl FnMut(&str) -> *const c_void,
+    ) -> (Self, Self::Renderer);
+
+    /// Returns the amount of samples that should be used when configuring
+    /// an OpenGL context for this [`Compositor`].
+    ///
+    /// [`Compositor`]: trait.Compositor.html
+    fn sample_count(settings: &Self::Settings) -> u32;
+
+    /// Resizes the viewport of the [`Compositor`].
+    ///
+    /// [`Compositor`]: trait.Compositor.html
+    fn resize_viewport(&mut self, physical_size: Size<u32>);
+
+    /// Draws the provided output with the given [`Renderer`].
+    ///
+    /// [`Compositor`]: trait.Compositor.html
+    fn draw<T: AsRef<str>>(
+        &mut self,
+        renderer: &mut Self::Renderer,
+        viewport: &Viewport,
+        output: &<Self::Renderer as iced_native::Renderer>::Output,
+        overlay: &[T],
+    ) -> mouse::Interaction;
+}