Add Sdl2 backend

Cargo.toml

@@ -10,6 +10,7 @@ members = [
     "backends/conrod_rendy",
     "backends/conrod_vulkano",
     "backends/conrod_wgpu",
+    "backends/conrod_sdl2",
 ]
 
 # wgpu requires this feature resolver version.

backends/conrod_sdl2/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "conrod_sdl2"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+arrayvec = "0.7.2"
+conrod_core = { path = "../../conrod_core", version = "0.76" }
+thiserror = "1.0.30"
+sdl2 = { version = "0.35.1", features = ["gfx", "image"] }
+
+[dev-dependencies]
+conrod_example_shared = { path = "../conrod_example_shared", version = "0.76" }
+find_folder = "0.3.0"

backends/conrod_sdl2/examples/all_sdl2.rs

@@ -0,0 +1,94 @@
+use std::{thread::sleep, time::Duration};
+
+use conrod_core::UiBuilder;
+use conrod_example_shared::{DemoApp, WIN_H, WIN_W};
+use conrod_sdl2::{convert_event, DrawPrimitiveError};
+use sdl2::{
+    image::LoadTexture, render::TextureValueError, video::WindowBuildError, IntegerOrSdlError,
+};
+use thiserror::Error;
+
+fn main() -> Result<(), SdlError> {
+    let sdl = sdl2::init().map_err(SdlError::String)?;
+
+    let video_subsystem = sdl.video().map_err(SdlError::String)?;
+    let window = video_subsystem
+        .window("Conrod with SDL2!", WIN_W, WIN_H)
+        .resizable()
+        .allow_highdpi()
+        .build()?;
+    let mut canvas = window.into_canvas().present_vsync().build()?;
+    let texture_creator = canvas.texture_creator();
+
+    let mut event_pump = sdl.event_pump().map_err(SdlError::String)?;
+
+    // The assets directory, where the Rust logo and the font file belong.
+    let assets = find_folder::Search::KidsThenParents(3, 5)
+        .for_folder("assets")
+        .expect("Assets directory not found");
+
+    // Load Rust logo as a texture.
+    let rust_logo_path = assets.join("images/rust.png");
+    let mut image_map = conrod_core::image::Map::new();
+    let rust_logo = texture_creator
+        .load_texture(rust_logo_path)
+        .map_err(SdlError::String)?;
+    let rust_logo = image_map.insert(rust_logo);
+
+    // Create Ui and Ids of widgets to instantiate
+    let mut ui = UiBuilder::new([WIN_W as f64, WIN_H as f64])
+        .theme(conrod_example_shared::theme())
+        .build();
+    let ids = conrod_example_shared::Ids::new(ui.widget_id_generator());
+    // Demonstration app state that we'll control with our conrod GUI.
+    let mut app = DemoApp::new(rust_logo);
+
+    // Load font file
+    let font_path = assets.join("fonts/NotoSans/NotoSans-Regular.ttf");
+    ui.fonts.insert_from_file(font_path).unwrap();
+
+    // Renderer
+    let mut renderer = conrod_sdl2::Renderer::new(&texture_creator)?;
+
+    'main: loop {
+        for event in event_pump.poll_iter() {
+            match event {
+                sdl2::event::Event::Quit { .. }
+                | sdl2::event::Event::KeyDown {
+                    keycode: Some(sdl2::keyboard::Keycode::Escape),
+                    ..
+                } => break 'main,
+                _ => {}
+            }
+            for event in convert_event(event, canvas.window().size()) {
+                ui.handle_event(event);
+            }
+        }
+
+        conrod_example_shared::gui(&mut ui.set_widgets(), &ids, &mut app);
+        if let Some(primitives) = ui.draw_if_changed() {
+            renderer.draw(&mut canvas, &mut image_map, primitives)?;
+            canvas.present();
+        } else {
+            // We should sleep for a reasonable duration before polloing for new events
+            // in order to avoid polloing new events very frequently.
+            sleep(Duration::from_secs_f64(1. / 60.));
+        }
+    }
+
+    Ok(())
+}
+
+#[derive(Debug, Error)]
+pub enum SdlError {
+    #[error("SDL returned an error: {0}")]
+    String(String),
+    #[error("SDL failed to build a window: {0}")]
+    WindowBuildError(#[from] WindowBuildError),
+    #[error("Integer overflowed or SDL returned an error: {0}")]
+    IntegerOrSdlError(#[from] IntegerOrSdlError),
+    #[error("Failed to create a texture: {0}")]
+    TextureValueError(#[from] TextureValueError),
+    #[error("Failed to draw a primitive: {0}")]
+    DrawPrimitiveError(#[from] DrawPrimitiveError),
+}