Improve error message when using an under-powered GPU (#6252)

### What
Using `scripts/fetch_crashes.py` to look at our analytics, I noticed
that missing wgpu capabilities would lead to a assert/panic, which is
not a nice way to report errors to users.

I added an egui issue to improve this further in the future:
* emilk/egui#4474

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested the web demo (if applicable):
* Using examples from latest `main` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/6252?manifest_url=https://app.rerun.io/version/main/examples_manifest.json)
* Using full set of examples from `nightly` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/6252?manifest_url=https://app.rerun.io/version/nightly/examples_manifest.json)
* [x] The PR title and labels are set such as to maximize their
usefulness for the next release's CHANGELOG
* [x] If applicable, add a new check to the [release
checklist](https://github.com/rerun-io/rerun/blob/main/tests/python/release_checklist)!

- [PR Build Summary](https://build.rerun.io/pr/6252)
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
- [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)

To run all checks from `main`, comment on the PR with `@rerun-bot
full-check`.

Author: emilk

crates/re_renderer/src/context.rs

@@ -120,7 +120,7 @@ impl RenderContext {
         device: Arc<wgpu::Device>,
         queue: Arc<wgpu::Queue>,
         config: RenderContextConfig,
-    ) -> Self {
+    ) -> Result<Self, String> {
         re_tracing::profile_function!();
 
         let frame_index_for_uncaptured_errors = Arc::new(AtomicU64::new(STARTUP_FRAME_IDX));
@@ -155,38 +155,46 @@ impl RenderContext {
         let global_bindings = GlobalBindings::new(&gpu_resources, &device);
 
         // Validate capabilities of the device.
-        assert!(
-            config.device_caps.limits().check_limits(&device.limits()),
-            "The given device doesn't support the required limits for the given hardware caps {:?}.
-            Required:
-            {:?}
-            Actual:
-            {:?}",
-            config.device_caps,
-            config.device_caps.limits(),
-            device.limits(),
-        );
-        assert!(
-            device.features().contains(config.device_caps.features()),
-            "The given device doesn't support the required features for the given hardware caps {:?}.
-            Required:
-            {:?}
-            Actual:
-            {:?}",
-            config.device_caps,
-            config.device_caps.features(),
-            device.features(),
-        );
-        assert!(adapter.get_downlevel_capabilities().flags.contains(config.device_caps.required_downlevel_capabilities().flags),
-            "The given device doesn't support the required downlevel capabilities for the given hardware caps {:?}.
-            Required:
-            {:?}
-            Actual:
-            {:?}",
-            config.device_caps,
-            config.device_caps.required_downlevel_capabilities(),
-            adapter.get_downlevel_capabilities(),
-        );
+        if !config.device_caps.limits().check_limits(&device.limits()) {
+            return Err(format!(
+                "The given device doesn't support the required limits for the given hardware caps {:?}.
+                Required:
+                {:?}
+                Actual:
+                {:?}",
+                config.device_caps,
+                config.device_caps.limits(),
+                device.limits(),
+            ));
+        }
+        if !device.features().contains(config.device_caps.features()) {
+            return Err(format!(
+                "The given device doesn't support the required features for the given hardware caps {:?}.
+                Required:
+                {:?}
+                Actual:
+                {:?}",
+                config.device_caps,
+                config.device_caps.features(),
+                device.features(),
+            ));
+        }
+        if !adapter
+            .get_downlevel_capabilities()
+            .flags
+            .contains(config.device_caps.required_downlevel_capabilities().flags)
+        {
+            return Err(format!(
+                "The given device doesn't support the required downlevel capabilities for the given hardware caps {:?}.
+                Required:
+                {:?}
+                Actual:
+                {:?}",
+                config.device_caps,
+                config.device_caps.required_downlevel_capabilities(),
+                adapter.get_downlevel_capabilities(),
+            ));
+        }
 
         let resolver = crate::new_recommended_file_resolver();
         let mesh_manager = RwLock::new(MeshManager::new());
@@ -222,7 +230,7 @@ impl RenderContext {
             Self::GPU_READBACK_BELT_DEFAULT_CHUNK_SIZE.unwrap(),
         ));
 
-        RenderContext {
+        Ok(RenderContext {
             device,
             queue,
             config,
@@ -240,7 +248,7 @@ impl RenderContext {
             active_frame,
             frame_index_for_uncaptured_errors,
             gpu_resources,
-        }
+        })
     }
 
     fn poll_device(&mut self) {

crates/re_renderer_examples/framework.rs

@@ -152,7 +152,8 @@ impl<E: Example + 'static> Application<E> {
                 output_format_color,
                 device_caps,
             },
-        );
+        )
+        .map_err(|err| anyhow::format_err!("{err}"))?;
 
         let example = E::new(&re_ctx);
 

crates/re_viewer/src/lib.rs

@@ -198,23 +198,38 @@ pub(crate) fn wgpu_options(force_wgpu_backend: Option<String>) -> egui_wgpu::Wgp
 
 /// Customize eframe and egui to suit the rerun viewer.
 #[must_use]
-pub fn customize_eframe(cc: &eframe::CreationContext<'_>) -> re_ui::ReUi {
+pub fn customize_eframe_and_setup_renderer(cc: &eframe::CreationContext<'_>) -> re_ui::ReUi {
     re_tracing::profile_function!();
 
     if let Some(render_state) = &cc.wgpu_render_state {
         use re_renderer::{config::RenderContextConfig, RenderContext};
 
         let paint_callback_resources = &mut render_state.renderer.write().callback_resources;
 
-        paint_callback_resources.insert(RenderContext::new(
+        let render_ctx = RenderContext::new(
             &render_state.adapter,
             render_state.device.clone(),
             render_state.queue.clone(),
             RenderContextConfig {
                 output_format_color: render_state.target_format,
                 device_caps: re_renderer::config::DeviceCaps::from_adapter(&render_state.adapter),
             },
-        ));
+        );
+
+        match render_ctx {
+            Ok(render_ctx) => {
+                paint_callback_resources.insert(render_ctx);
+            }
+            Err(err) => {
+                re_log::error!("Failed to create render context: {err}");
+
+                #[allow(clippy::exit)]
+                {
+                    // TODO(egui#4474): return errors to eframe -> `main`
+                    std::process::exit(1);
+                }
+            }
+        };
     }
 
     re_ui::ReUi::load_and_apply(&cc.egui_ctx)

crates/re_viewer/src/native.rs

@@ -18,7 +18,7 @@ pub fn run_native_app(
         window_title,
         native_options,
         Box::new(move |cc| {
-            let re_ui = crate::customize_eframe(cc);
+            let re_ui = crate::customize_eframe_and_setup_renderer(cc);
             app_creator(cc, re_ui)
         }),
     )

crates/re_viewer/src/web.rs

@@ -229,7 +229,7 @@ fn create_app(
         expect_data_soon: None,
         force_wgpu_backend: None,
     };
-    let re_ui = crate::customize_eframe(cc);
+    let re_ui = crate::customize_eframe_and_setup_renderer(cc);
 
     let mut app = crate::App::new(build_info, &app_env, startup_options, re_ui, cc.storage);
 

examples/rust/extend_viewer_ui/src/main.rs

@@ -42,7 +42,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         window_title,
         native_options,
         Box::new(move |cc| {
-            let re_ui = re_viewer::customize_eframe(cc);
+            let re_ui = re_viewer::customize_eframe_and_setup_renderer(cc);
 
             let mut rerun_app = re_viewer::App::new(
                 re_viewer::build_info(),