Sketch out some GBA backend ideas

backends/gba/src/lib.rs

@@ -1 +1,47 @@
 //! A backend for Surreal specifically for the GameBoy Advance.
+
+#![no_std] // GBA runs on bare metal, no stdlib
+
+pub struct GameBoy {}
+
+pub trait Display {
+  fn clear(&mut self);
+  fn draw_pixel(&mut self, x: u32, y: u32, color: u32);
+  fn draw_line(&mut self, x0: u32, y0: u32, x1: u32, y1: u32, color: u32);
+  fn draw_rect(&mut self, x: u32, y: u32, width: u32, height: u32, color: u32);
+  fn draw_circle(&mut self, x: u32, y: u32, radius: u32, color: u32);
+  fn draw_text(&mut self, x: u32, y: u32, text: &str, color: u32);
+  fn draw_text_centered(&mut self, x: u32, y: u32, text: &str, color: u32);
+  fn draw_text_right_aligned(&mut self, x: u32, y: u32, text: &str, color: u32);
+  fn draw_text_wrapped(&mut self, x: u32, y: u32, text: &str, color: u32);
+  fn draw_text_wrapped_centered(&mut self, x: u32, y: u32, text: &str, color: u32);
+  fn draw_sprite(&mut self, x: u32, y: u32, sprite: &dyn Sprite);
+  fn draw_sprite_centered(&mut self, x: u32, y: u32, sprite: &dyn Sprite);
+}
+
+pub trait Sprite {
+  fn width(&self) -> u32;
+  fn height(&self) -> u32;
+  fn pixel(&self, x: u32, y: u32) -> u32;
+}
+
+pub trait Controller {
+  fn is_button_down(&self, button: Button) -> bool;
+  fn is_button_up(&self, button: Button) -> bool;
+  fn is_button_pressed(&self, button: Button) -> bool;
+  fn is_button_released(&self, button: Button) -> bool;
+  fn is_button_held(&self, button: Button) -> bool;
+  fn is_button_not_held(&self, button: Button) -> bool;
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub enum Button {
+  A,
+  B,
+  Start,
+  Select,
+  Up,
+  Down,
+  Left,
+  Right,
+}