Fix panic when creating a surface while no backend is available (#5166)

* Fix panic when creating a surface while no backend is available

* changelog entry

CHANGELOG.md

@@ -103,6 +103,7 @@ Bottom level categories:
 - Fix `serde` feature not compiling for `wgpu-types`. By @KirmesBude in [#5149](https://github.com/gfx-rs/wgpu/pull/5149)
 - Fix the validation of vertex and index ranges. By @nical in [#5144](https://github.com/gfx-rs/wgpu/pull/5144) and [#5156](https://github.com/gfx-rs/wgpu/pull/5156)
 - Device lost callbacks are invoked when replaced and when global is dropped. By @bradwerth in [#5168](https://github.com/gfx-rs/wgpu/pull/5168)
+- Fix panic when creating a surface while no backend is available. By @wumpf [#5166](https://github.com/gfx-rs/wgpu/pull/5166)
 
 #### WGL
 

wgpu-core/src/instance.rs

@@ -471,6 +471,15 @@ pub enum RequestAdapterError {
     InvalidSurface(SurfaceId),
 }
 
+#[derive(Clone, Debug, Error)]
+#[non_exhaustive]
+pub enum CreateSurfaceError {
+    #[error("No backend is available")]
+    NoSupportedBackend,
+    #[error(transparent)]
+    InstanceError(#[from] hal::InstanceError),
+}
+
 impl Global {
     /// # Safety
     ///
@@ -483,7 +492,7 @@ impl Global {
         display_handle: raw_window_handle::RawDisplayHandle,
         window_handle: raw_window_handle::RawWindowHandle,
         id_in: Option<SurfaceId>,
-    ) -> Result<SurfaceId, hal::InstanceError> {
+    ) -> Result<SurfaceId, CreateSurfaceError> {
         profiling::scope!("Instance::create_surface");
 
         fn init<A: HalApi>(
@@ -521,8 +530,7 @@ impl Global {
             hal_surface = init::<hal::api::Gles>(&self.instance.gl, display_handle, window_handle);
         }
 
-        //  This is only None if there's no instance at all.
-        let hal_surface = hal_surface.unwrap()?;
+        let hal_surface = hal_surface.ok_or(CreateSurfaceError::NoSupportedBackend)??;
 
         let surface = Surface {
             presentation: Mutex::new(None),

wgpu/src/lib.rs

@@ -2812,7 +2812,7 @@ pub struct CreateSurfaceError {
 enum CreateSurfaceErrorKind {
     /// Error from [`wgpu_hal`].
     #[cfg(wgpu_core)]
-    Hal(hal::InstanceError),
+    Hal(wgc::instance::CreateSurfaceError),
 
     /// Error from WebGPU surface creation.
     #[allow(dead_code)] // may be unused depending on target and features
@@ -2847,8 +2847,8 @@ impl error::Error for CreateSurfaceError {
 }
 
 #[cfg(wgpu_core)]
-impl From<hal::InstanceError> for CreateSurfaceError {
-    fn from(e: hal::InstanceError) -> Self {
+impl From<wgc::instance::CreateSurfaceError> for CreateSurfaceError {
+    fn from(e: wgc::instance::CreateSurfaceError) -> Self {
         Self {
             inner: CreateSurfaceErrorKind::Hal(e),
         }