Introduce `internal_backend` to `iced_wgpu::Settings`

2 files changed, 42 insertions, 40 deletions

diff --git a/wgpu/src/settings.rs b/wgpu/src/settings.rs
index 26763e22..abc404dc 100644
--- a/wgpu/src/settings.rs
+++ b/wgpu/src/settings.rs
@@ -16,6 +16,9 @@ pub struct Settings {
     /// [`Backend`]: crate::Backend
     pub present_mode: wgpu::PresentMode,
 
+    /// The internal graphics backend to use.
+    pub internal_backend: wgpu::BackendBit,
+
     /// The bytes of the font that will be used by default.
     ///
     /// If `None` is provided, a default system font will be chosen.
@@ -30,14 +33,52 @@ pub struct Settings {
     pub antialiasing: Option<Antialiasing>,
 }
 
+impl Settings {
+    /// Creates new [`Settings`] using environment configuration.
+    ///
+    /// Specifically:
+    ///
+    /// - The `internal_backend` can be configured using the `WGPU_BACKEND`
+    /// environment variable. If the variable is not set, the primary backend
+    /// will be used. The following values are allowed:
+    ///     - `vulkan`
+    ///     - `metal`
+    ///     - `dx12`
+    ///     - `dx11`
+    ///     - `gl`
+    ///     - `webgpu`
+    pub fn from_env() -> Self {
+        Settings {
+            internal_backend: backend_from_env()
+                .unwrap_or(wgpu::BackendBit::PRIMARY),
+            ..Self::default()
+        }
+    }
+}
+
 impl Default for Settings {
     fn default() -> Settings {
         Settings {
             format: wgpu::TextureFormat::Bgra8UnormSrgb,
             present_mode: wgpu::PresentMode::Mailbox,
+            internal_backend: wgpu::BackendBit::PRIMARY,
             default_font: None,
             default_text_size: 20,
             antialiasing: None,
         }
     }
 }
+
+fn backend_from_env() -> Option<wgpu::BackendBit> {
+    std::env::var("WGPU_BACKEND").ok().map(|backend| {
+        match backend.to_lowercase().as_str() {
+            "vulkan" => wgpu::BackendBit::VULKAN,
+            "metal" => wgpu::BackendBit::METAL,
+            "dx12" => wgpu::BackendBit::DX12,
+            "dx11" => wgpu::BackendBit::DX11,
+            "gl" => wgpu::BackendBit::GL,
+            "webgpu" => wgpu::BackendBit::BROWSER_WEBGPU,
+            other => panic!("Unknown backend: {}", other),
+        }
+    })
+}
diff --git a/wgpu/src/window/compositor.rs b/wgpu/src/window/compositor.rs
index 3d785f71..fdd648e8 100644
--- a/wgpu/src/window/compositor.rs
+++ b/wgpu/src/window/compositor.rs
@@ -15,35 +15,6 @@ pub struct Compositor {
     local_pool: futures::executor::LocalPool,
 }
 
-#[derive(Clone)]
-pub enum WgpuBackend {
-    Auto,
-    Vulkan,
-    Metal,
-    Dx12,
-    Dx11,
-    Gl,
-    BrowserWgpu,
-}
-
-impl WgpuBackend {
-    fn from_env() -> Self {
-        if let Ok(backend) = std::env::var("WGPU_BACKEND") {
-            match backend.to_lowercase().as_str() {
-                "vulkan" => WgpuBackend::Vulkan,
-                "metal" => WgpuBackend::Metal,
-                "dx12" => WgpuBackend::Dx12,
-                "dx11" => WgpuBackend::Dx11,
-                "gl" => WgpuBackend::Gl,
-                "webgpu" => WgpuBackend::BrowserWgpu,
-                other => panic!("Unknown backend: {}", other),
-            }
-        } else {
-            WgpuBackend::Auto
-        }
-    }
-}
-
 impl Compositor {
     const CHUNK_SIZE: u64 = 10 * 1024;
 
@@ -51,17 +22,7 @@ impl Compositor {
     ///
     /// Returns `None` if no compatible graphics adapter could be found.
     pub async fn request(settings: Settings) -> Option<Self> {
-        let backend = match WgpuBackend::from_env() {
-            WgpuBackend::Auto => wgpu::BackendBit::PRIMARY,
-            WgpuBackend::Vulkan => wgpu::BackendBit::VULKAN,
-            WgpuBackend::Metal => wgpu::BackendBit::METAL,
-            WgpuBackend::Dx12 => wgpu::BackendBit::DX12,
-            WgpuBackend::Dx11 => wgpu::BackendBit::DX11,
-            WgpuBackend::Gl => wgpu::BackendBit::GL,
-            WgpuBackend::BrowserWgpu => wgpu::BackendBit::BROWSER_WEBGPU,
-        };
-
-        let instance = wgpu::Instance::new(backend);
+        let instance = wgpu::Instance::new(settings.internal_backend);
 
         let adapter = instance
             .request_adapter(&wgpu::RequestAdapterOptions {