[egui-wgpu] Device configuration is now dependent on adapter (#2951)

* [egui-wgpu] Device configuration is now dependent on adapter
Additionally, renamed `backends` into `supported_backends` and improved & unified wgpu config defaults.

* improve wgpu backend default

* clippy fix

* formatting

---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

crates/eframe/src/epi/mod.rs

@@ -497,21 +497,7 @@ impl Default for WebOptions {
             webgl_context_option: WebGlContextOption::BestFirst,
 
             #[cfg(feature = "wgpu")]
-            wgpu_options: egui_wgpu::WgpuConfiguration {
+            wgpu_options: egui_wgpu::WgpuConfiguration::default(),
-                // Use WebGPU or WebGL. Note that WebGL needs to be opted in via a wgpu feature.
-                backends: wgpu::Backends::BROWSER_WEBGPU | wgpu::Backends::GL,
-                device_descriptor: wgpu::DeviceDescriptor {
-                    label: Some("egui wgpu device"),
-                    features: wgpu::Features::default(),
-                    limits: wgpu::Limits {
-                        // When using a depth buffer, we have to be able to create a texture
-                        // large enough for the entire surface, and we want to support 4k+ displays.
-                        max_texture_dimension_2d: 8192,
-                        ..wgpu::Limits::downlevel_webgl2_defaults()
-                    },
-                },
-                ..Default::default()
-            },
         }
     }
 }

crates/eframe/src/web/web_painter_wgpu.rs

@@ -33,7 +33,6 @@ pub(crate) struct WebPainterWgpu {
     canvas_id: String,
     surface: wgpu::Surface,
     surface_configuration: wgpu::SurfaceConfiguration,
-    limits: wgpu::Limits,
     render_state: Option<RenderState>,
     on_surface_error: Arc<dyn Fn(wgpu::SurfaceError) -> SurfaceErrorAction>,
     depth_format: Option<wgpu::TextureFormat>,
@@ -78,7 +77,7 @@ impl WebPainterWgpu {
         log::debug!("Creating wgpu painter");
 
         let instance = wgpu::Instance::new(wgpu::InstanceDescriptor {
-            backends: options.wgpu_options.backends,
+            backends: options.wgpu_options.supported_backends,
             dx12_shader_compiler: Default::default(),
         });
 
@@ -111,7 +110,7 @@ impl WebPainterWgpu {
 
         let (device, queue) = adapter
             .request_device(
-                &options.wgpu_options.device_descriptor,
+                &(*options.wgpu_options.device_descriptor)(&adapter),
                 None, // Capture doesn't work in the browser environment.
             )
             .await
@@ -149,7 +148,6 @@ impl WebPainterWgpu {
             surface_configuration,
             depth_format,
             depth_texture_view: None,
-            limits: options.wgpu_options.device_descriptor.limits.clone(),
             on_surface_error: options.wgpu_options.on_surface_error.clone(),
         })
     }
@@ -161,7 +159,9 @@ impl WebPainter for WebPainterWgpu {
     }
 
     fn max_texture_side(&self) -> usize {
-        self.limits.max_texture_dimension_2d as _
+        self.render_state.as_ref().map_or(0, |state| {
+            state.device.limits().max_texture_dimension_2d as _
+        })
     }
 
     fn paint_and_update_textures(

crates/egui-wgpu/src/lib.rs

@@ -42,11 +42,11 @@ pub enum SurfaceErrorAction {
 /// Configuration for using wgpu with eframe or the egui-wgpu winit feature.
 #[derive(Clone)]
 pub struct WgpuConfiguration {
-    /// Configuration passed on device request.
-    pub device_descriptor: wgpu::DeviceDescriptor<'static>,
-
     /// Backends that should be supported (wgpu will pick one of these)
-    pub backends: wgpu::Backends,
+    pub supported_backends: wgpu::Backends,
+
+    /// Configuration passed on device request, given an adapter
+    pub device_descriptor: Arc<dyn Fn(&wgpu::Adapter) -> wgpu::DeviceDescriptor<'static>>,
 
     /// Present mode used for the primary surface.
     pub present_mode: wgpu::PresentMode,
@@ -63,16 +63,31 @@ pub struct WgpuConfiguration {
 impl Default for WgpuConfiguration {
     fn default() -> Self {
         Self {
-            device_descriptor: wgpu::DeviceDescriptor {
-                label: Some("egui wgpu device"),
-                features: wgpu::Features::default(),
-                limits: wgpu::Limits::default(),
-            },
             // Add GL backend, primarily because WebGPU is not stable enough yet.
             // (note however, that the GL backend needs to be opted-in via a wgpu feature flag)
-            backends: wgpu::Backends::PRIMARY | wgpu::Backends::GL,
+            supported_backends: wgpu::util::backend_bits_from_env()
+                .unwrap_or(wgpu::Backends::PRIMARY | wgpu::Backends::GL),
+            device_descriptor: Arc::new(|adapter| {
+                let base_limits = if adapter.get_info().backend == wgpu::Backend::Gl {
+                    wgpu::Limits::downlevel_webgl2_defaults()
+                } else {
+                    wgpu::Limits::default()
+                };
+
+                wgpu::DeviceDescriptor {
+                    label: Some("egui wgpu device"),
+                    features: wgpu::Features::default(),
+                    limits: wgpu::Limits {
+                        // When using a depth buffer, we have to be able to create a texture
+                        // large enough for the entire surface, and we want to support 4k+ displays.
+                        max_texture_dimension_2d: 8192,
+                        ..base_limits
+                    },
+                }
+            }),
             present_mode: wgpu::PresentMode::AutoVsync,
-            power_preference: wgpu::PowerPreference::HighPerformance,
+            power_preference: wgpu::util::power_preference_from_env()
+                .unwrap_or(wgpu::PowerPreference::HighPerformance),
             depth_format: None,
 
             on_surface_error: Arc::new(|err| {

crates/egui-wgpu/src/winit.rs

@@ -108,8 +108,8 @@ impl Painter {
         support_transparent_backbuffer: bool,
     ) -> Self {
         let instance = wgpu::Instance::new(wgpu::InstanceDescriptor {
-            backends: configuration.backends,
+            backends: configuration.supported_backends,
-            dx12_shader_compiler: Default::default(), //
+            dx12_shader_compiler: Default::default(),
         });
 
         Self {
@@ -141,7 +141,7 @@ impl Painter {
         target_format: wgpu::TextureFormat,
     ) -> Result<RenderState, wgpu::RequestDeviceError> {
         adapter
-            .request_device(&self.configuration.device_descriptor, None)
+            .request_device(&(*self.configuration.device_descriptor)(adapter), None)
             .await
             .map(|(device, queue)| {
                 let renderer =