Use EGL surfaceless platform when windowing system is not found

wgpu-hal/src/gles/egl.rs

@@ -15,6 +15,7 @@ const EGL_PLATFORM_X11_KHR: u32 = 0x31D5;
 const EGL_PLATFORM_ANGLE_ANGLE: u32 = 0x3202;
 const EGL_PLATFORM_ANGLE_NATIVE_PLATFORM_TYPE_ANGLE: u32 = 0x348F;
 const EGL_PLATFORM_ANGLE_DEBUG_LAYERS_ENABLED: u32 = 0x3451;
+const EGL_PLATFORM_SURFACELESS_MESA: u32 = 0x31DD;
 const EGL_GL_COLORSPACE_KHR: u32 = 0x309D;
 const EGL_GL_COLORSPACE_SRGB_KHR: u32 = 0x3089;
 
@@ -162,11 +163,19 @@ fn choose_config(
     let tiers = [
         (
             "off-screen",
-            &[egl::RENDERABLE_TYPE, egl::OPENGL_ES2_BIT][..],
+            &[
+                egl::SURFACE_TYPE,
+                egl::PBUFFER_BIT,
+                egl::RENDERABLE_TYPE,
+                egl::OPENGL_ES2_BIT,
+            ][..],
         ),
-        ("presentation", &[egl::SURFACE_TYPE, egl::WINDOW_BIT]),
+        ("presentation", &[egl::SURFACE_TYPE, egl::WINDOW_BIT][..]),
         #[cfg(not(target_os = "android"))]
-        ("native-render", &[egl::NATIVE_RENDERABLE, egl::TRUE as _]),
+        (
+            "native-render",
+            &[egl::NATIVE_RENDERABLE, egl::TRUE as _][..],
+        ),
     ];
 
     let mut attributes = Vec::with_capacity(9);
@@ -617,8 +626,21 @@ impl crate::Instance<super::Api> for Instance {
                 )
                 .unwrap();
             (display, Some(Arc::new(library)), WindowKind::AngleX11)
+        } else if client_ext_str.contains("EGL_MESA_platform_surfaceless") {
+            log::info!("No windowing system present. Using surfaceless platform");
+            let egl = egl
+                .upcast::<egl::EGL1_5>()
+                .expect("Failed to get EGL 1.5 for surfaceless");
+            let display = egl
+                .get_platform_display(
+                    EGL_PLATFORM_SURFACELESS_MESA,
+                    std::ptr::null_mut(),
+                    &[egl::ATTRIB_NONE],
+                )
+                .unwrap();
+            (display, None, WindowKind::Unknown)
         } else {
-            log::info!("Using default platform");
+            log::info!("EGL_MESA_platform_surfaceless not available. Using default platform");
             let display = egl.get_display(egl::DEFAULT_DISPLAY).unwrap();
             (display, None, WindowKind::Unknown)
         };

wgpu/examples/capture/main.rs

@@ -28,10 +28,12 @@ async fn create_red_image_with_dimensions(
     width: usize,
     height: usize,
 ) -> (Device, Buffer, BufferDimensions) {
-    let adapter = wgpu::Instance::new(wgpu::Backends::all())
-        .request_adapter(&wgpu::RequestAdapterOptions::default())
-        .await
-        .unwrap();
+    let adapter = wgpu::Instance::new(
+        wgpu::util::backend_bits_from_env().unwrap_or_else(wgpu::Backends::all),
+    )
+    .request_adapter(&wgpu::RequestAdapterOptions::default())
+    .await
+    .unwrap();
 
     let (device, queue) = adapter
         .request_device(

wgpu/examples/skybox/main.rs

@@ -499,7 +499,7 @@ fn skybox_etc2() {
         optional_features: wgpu::Features::TEXTURE_COMPRESSION_ETC2,
         base_test_parameters: framework::test_common::TestParameters::default(),
         tolerance: 5,
-        max_outliers: 100, // Bounded by llvmpipe
+        max_outliers: 105, // Bounded by llvmpipe
     });
 }