Merge PR #1644: fix(gpu): no popup when renderer falls back from DX12 at pro

apps/lightcraft/src/window_gpu.rs

@@ -93,7 +93,6 @@ pub fn choose(files: &Files) -> Chosen {
     let compiled = wgpu::Instance::enabled_backend_features();
     let os = std::env::consts::OS;
     let order = backend::window_renderer_order(forced, remembered, failed, os, compiled, true);
-    let mut notice = failed.map(|f| format!("The window could not start with its {} renderer last time.", f.name()));
     let mut problems = Vec::new();
     let chosen = if cfg!(windows) {
         pick_probed(&order, &mut problems)
@@ -104,18 +103,7 @@ pub fn choose(files: &Files) -> Chosen {
         Some((WindowRenderer::Wgpu(backend::window_backends()), None))
     };
     let (which, existing) = chosen.unwrap_or((WindowRenderer::Glow, None));
-    if !problems.is_empty() {
-        notice = Some(format!("{} {}", notice.unwrap_or_default(), problems.join(" ")).trim().to_string());
-    }
-    let notice = notice.map(|n| {
-        format!(
-            "{n} {app} now draws its window with {}. To choose another, start {app} with {var}=dx12, vulkan, gl or glow \
-             (see docs/gpu-pipeline.md → Troubleshooting).",
-            which.name(),
-            app = "LightCraft",
-            var = "LIGHTCRAFT_GPU_BACKEND",
-        )
-    });
+    let notice = user_notice(failed, forced, &problems, which);
     log::info!("window: renderer {} (order {:?})", which.name(), order.iter().map(|r| r.name()).collect::<Vec<_>>());
     let mut wgpu_options = base_options();
     let renderer = match (which, existing) {
@@ -134,6 +122,25 @@ pub fn choose(files: &Files) -> Chosen {
     Chosen { renderer, wgpu_options, which, notice }
 }
 
+/// What to tell the user about the window's renderer. A renderer that failed its probe is skipped
+/// silently (it is logged, and the one that worked is remembered): the app works, so a pop-up with
+/// wgpu's error only alarms (#1624). Shown: the last start died, or the forced renderer failed.
+fn user_notice(failed: Option<WindowRenderer>, forced: Option<WindowRenderer>, problems: &[String], which: WindowRenderer) -> Option<String> {
+    let mut notice = failed.map(|f| format!("The window could not start with its {} renderer last time.", f.name()));
+    if forced.is_some() && !problems.is_empty() {
+        notice = Some(format!("{} {}", notice.unwrap_or_default(), problems.join(" ")).trim().to_string());
+    }
+    notice.map(|n| {
+        format!(
+            "{n} {app} now draws its window with {}. To choose another, start {app} with {var}=dx12, vulkan, gl or glow \
+             (see docs/gpu-pipeline.md → Troubleshooting).",
+            which.name(),
+            app = "LightCraft",
+            var = "LIGHTCRAFT_GPU_BACKEND",
+        )
+    })
+}
+
 /// eframe's defaults with the app's backends and DX12 shader compiler (issues #136, #471).
 pub fn base_options() -> WgpuConfiguration {
     let mut c = WgpuConfiguration::default();
@@ -269,6 +276,20 @@ mod tests {
         let _ = std::fs::remove_dir_all(&d);
     }
 
+    /// #1624: a renderer skipped by the probe (DX12 → Vulkan) is no pop-up; a died start or a
+    /// failed forced renderer still is.
+    #[test]
+    fn probe_fallback_is_silent() {
+        let (dx, vk) = (WindowRenderer::Wgpu(Backends::DX12), WindowRenderer::Wgpu(Backends::VULKAN));
+        let problems = vec!["The dx12 renderer failed (Validation Error).".to_string()];
+        assert_eq!(user_notice(None, None, &problems, vk), None);
+        assert_eq!(user_notice(None, None, &[], vk), None);
+        let forced = user_notice(None, Some(dx), &problems, vk).unwrap();
+        assert!(forced.starts_with("The dx12 renderer failed") && forced.contains("now draws its window with vulkan"), "{forced}");
+        let died = user_notice(Some(dx), None, &problems, vk).unwrap();
+        assert!(died.contains("last time") && !died.contains("Validation Error"), "{died}");
+    }
+
     /// The crash report: a pipeline that fails validation must come back as an error, never as
     /// wgpu's default panic. Needs an adapter; skipped where there is none (CI without a GPU).
     #[test]

docs/gpu-pipeline.md

@@ -105,7 +105,8 @@ or worked around with `LIGHTCRAFT_GPU_BACKEND`.
 **The window's renderer and its fallback (Windows).** Before the window opens, each renderer is probed in
 order: DX12, Vulkan, GL, then eframe's OpenGL renderer (glow). A probe creates a device and builds egui's
 pipeline inside wgpu error scopes, so a driver that cannot compile egui's shaders ("The parameter is
-incorrect. (0x80070057)" in `egui_pipeline`) is logged and skipped instead of killing the app. The renderer
+incorrect. (0x80070057)" in `egui_pipeline`) is logged and skipped instead of killing the app; no pop-up
+unless that renderer was forced (#1624). The renderer
 that worked is remembered in the settings folder (`window-renderer`); a start that dies before the window is up
 leaves `window-init.marker`, and the next start (relaunched automatically, at most 4 times) tries that
 renderer last. `LIGHTCRAFT_GPU_BACKEND=dx12 | vulkan | gl | glow` (or `WGPU_BACKEND`) forces one; DX12 stays