Add Harness::new_eframe and TestRenderer trait (#5539)

Co-authored-by: Andreas Reich <r_andreas2@web.de>

crates/egui-wgpu/src/lib.rs

@@ -24,7 +24,7 @@ pub use wgpu;
 mod renderer;
 
 pub use renderer::*;
-use wgpu::{Adapter, Device, Instance, Queue};
+use wgpu::{Adapter, Device, Instance, Queue, TextureFormat};
 
 /// Helpers for capturing screenshots of the UI.
 pub mod capture;
@@ -91,7 +91,7 @@ impl RenderState {
     pub async fn create(
         config: &WgpuConfiguration,
         instance: &wgpu::Instance,
-        surface: &wgpu::Surface<'static>,
+        compatible_surface: Option<&wgpu::Surface<'static>>,
         depth_format: Option<wgpu::TextureFormat>,
         msaa_samples: u32,
         dithering: bool,
@@ -113,7 +113,7 @@ impl RenderState {
                     instance
                         .request_adapter(&wgpu::RequestAdapterOptions {
                             power_preference,
-                            compatible_surface: Some(surface),
+                            compatible_surface,
                             force_fallback_adapter: false,
                         })
                         .await
@@ -186,11 +186,14 @@ impl RenderState {
             } => (adapter, device, queue),
         };
 
-        let capabilities = {
+        let surface_formats = {
             profiling::scope!("get_capabilities");
-            surface.get_capabilities(&adapter).formats
+            compatible_surface.map_or_else(
+                || vec![TextureFormat::Rgba8Unorm],
+                |s| s.get_capabilities(&adapter).formats,
+            )
         };
-        let target_format = crate::preferred_framebuffer_format(&capabilities)?;
+        let target_format = crate::preferred_framebuffer_format(&surface_formats)?;
 
         let renderer = Renderer::new(
             &device,

crates/egui-wgpu/src/winit.rs

@@ -212,7 +212,7 @@ impl Painter {
             let render_state = RenderState::create(
                 &self.configuration,
                 &self.instance,
-                &surface,
+                Some(&surface),
                 self.depth_format,
                 self.msaa_samples,
                 self.dithering,