Fix #167: default Windows startup to DirectX 12

README.md

@@ -119,6 +119,20 @@ CRAFT_FONTS_DIR="$PWD/../craft-fonts" cargo run --release -p designcraft   # abs
 Without it, Japanese falls back to the system's fonts (none on the web). Release builds always
 include it.
 
+On Windows, the desktop app initializes only DirectX 12 by default. This avoids an AMD
+OpenGL driver startup crash in `atio6axx.dll`; no custom launcher or shortcut is needed.
+For graphics troubleshooting, `WGPU_BACKEND` overrides this default (for example, `dx12`
+or `vulkan`). In PowerShell, run this from the directory containing the executable:
+
+```powershell
+$env:WGPU_BACKEND = "vulkan"
+& .\designcraft.exe
+Remove-Item Env:WGPU_BACKEND                     # restore the default for later launches
+```
+
+An explicit `opengl` override can reintroduce the driver crash on affected systems.
+The macOS, Linux and web backend defaults are unchanged.
+
 To drive a running app, send JSON lines to `127.0.0.1:7979`. The protocol is described in
 [`docs/control-protocol.md`](docs/control-protocol.md).
 

apps/designcraft/src/graphics.rs

@@ -0,0 +1,41 @@
+//! Windows instance configuration, applied before wgpu can initialize any driver.
+
+use eframe::{NativeOptions, egui_wgpu::WgpuSetup, wgpu::Backends};
+
+pub fn configure(options: &mut NativeOptions, backend_override: Option<Backends>) {
+    if let WgpuSetup::CreateNew(create) = &mut options.wgpu_options.wgpu_setup {
+        // eframe's default includes GL. Creating that backend can crash inside
+        // AMD's atio6axx.dll before adapter selection or Rust error handling.
+        // Match the verified WGPU_BACKEND=dx12 workaround without mutating
+        // process environment variables or initializing GL as a fallback.
+        create.instance_descriptor.backends = backend_override.unwrap_or(Backends::DX12);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn configured_backends(backend_override: Option<Backends>) -> Backends {
+        let mut options = NativeOptions::default();
+        configure(&mut options, backend_override);
+        let WgpuSetup::CreateNew(create) = options.wgpu_options.wgpu_setup else {
+            panic!("default native options must create a wgpu instance");
+        };
+        create.instance_descriptor.backends
+    }
+
+    #[test]
+    fn windows_default_initializes_only_dx12() {
+        // Adapter preference is too late: enabling GL can crash inside atio6axx.dll
+        // while creating the instance, even when a different adapter is selected.
+        assert_eq!(configured_backends(None), Backends::DX12);
+    }
+
+    #[test]
+    fn explicit_backend_override_is_preserved() {
+        for backends in [Backends::VULKAN, Backends::GL, Backends::DX12, Backends::VULKAN | Backends::DX12, Backends::empty()] {
+            assert_eq!(configured_backends(Some(backends)), backends);
+        }
+    }
+}

apps/designcraft/src/main.rs

@@ -9,6 +9,8 @@
 #![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
 
 mod control_server;
+#[cfg(any(target_os = "windows", test))]
+mod graphics;
 #[cfg(target_os = "macos")]
 mod native_menu;
 
@@ -209,6 +211,8 @@ fn main() -> eframe::Result {
             .with_title_shown(false),
         ..Default::default()
     };
+    #[cfg(target_os = "windows")]
+    graphics::configure(&mut options, eframe::wgpu::Backends::from_env());
     options.viewport = options.viewport.with_app_id(APP_ID);
     if let Some(icon) = app_icon() {
         options.viewport = options.viewport.with_icon(icon);