fix(startup): prevent Windows WebView2 focus crash (#37)

- Create the main Windows WebView without requesting focus until the native window exists.\n- Keep hidden Properties WebViews unfocused until their reveal path.\n- Make packaged smoke checks observe startup stability and clean up lingering Unix helpers.\n- Refs #37

scripts/smoke-packaged-app.js

@@ -17,6 +17,12 @@ if (!executableArg) {
 const executable = path.resolve(executableArg);
 const assertNoVisibleChildWindows = process.argv.includes('--assert-no-visible-child-windows');
 const assertPortableData = process.argv.includes('--assert-portable-data');
+const MAX_STABILITY_MS = 60_000;
+const MAX_CONSECUTIVE_STABILITY_FAILURES = 3;
+const stabilityMsValue = Number.parseInt(argValue('--stability-ms') || '5000', 10);
+const stabilityMs = Number.isFinite(stabilityMsValue) && stabilityMsValue >= 0
+  ? Math.min(stabilityMsValue, MAX_STABILITY_MS)
+  : 5000;
 const READY_PORT_TIMEOUT_MS = 500;
 const child = spawn(executable, [], {
   cwd: process.env.RUNNER_TEMP || process.env.TMPDIR || process.cwd(),
@@ -83,6 +89,55 @@ async function findReadyPort() {
   }
 }
 
+async function checkReadyPort() {
+  if (readyPort === null) return false;
+
+  try {
+    const response = await fetch(`http://127.0.0.1:${readyPort}/ping`, {
+      signal: AbortSignal.timeout(READY_PORT_TIMEOUT_MS),
+    });
+    const matchesChild = response.headers.get('x-firelink-server') === '1'
+      && response.headers.get('x-firelink-smoke-process-id') === String(child.pid);
+    await response.body?.cancel();
+    return matchesChild;
+  } catch {
+    return false;
+  }
+}
+
+async function assertStableReady() {
+  const deadline = Date.now() + stabilityMs;
+  let consecutiveFailures = 0;
+  while (Date.now() < deadline) {
+    if (spawnError) {
+      throw new Error(`Packaged Firelink failed during stability check: ${spawnError.message}`);
+    }
+    if (childExit) {
+      throw new Error(
+        `Packaged Firelink exited during stability check with code ${childExit.code} signal ${childExit.signal}.`,
+      );
+    }
+    if (await checkReadyPort()) {
+      consecutiveFailures = 0;
+    } else {
+      consecutiveFailures += 1;
+      if (consecutiveFailures >= MAX_CONSECUTIVE_STABILITY_FAILURES) {
+        throw new Error('Packaged Firelink stopped exposing its extension ping endpoint during stability check.');
+      }
+    }
+    await sleep(Math.min(250, Math.max(1, deadline - Date.now())));
+  }
+
+  if (childExit) {
+    throw new Error(
+      `Packaged Firelink exited during stability check with code ${childExit.code} signal ${childExit.signal}.`,
+    );
+  }
+  if (!await checkReadyPort() && !await checkReadyPort()) {
+    throw new Error('Packaged Firelink was not healthy at the end of its stability check.');
+  }
+}
+
 function assertNoVisibleWindows(rootPid) {
   if (process.platform !== 'win32') {
     return;
@@ -277,18 +332,16 @@ async function terminateChild() {
       }
     }
   }
-  if (await waitForChildExit(5000) && await waitForProcessGroupExit(child.pid, 5000)) {
+  const childExited = await waitForChildExit(5000);
+  const processGroupExited = await waitForProcessGroupExit(child.pid, 5000);
+  if (childExited && processGroupExited) {
     return true;
   }
 
-  if (!childWasRunning || childExit) {
-    return false;
-  }
-
   try {
     process.kill(-child.pid, 'SIGKILL');
   } catch {
-    if (!childExit) {
+    if (!childExited) {
       child.kill('SIGKILL');
     }
   }
@@ -338,11 +391,9 @@ try {
     await assertPortableStorage();
   }
 
-  if (childExit) {
-    throw new Error(`Packaged Firelink exited after exposing extension ping endpoint with code ${childExit.code} signal ${childExit.signal}.`);
-  }
+  await assertStableReady();
 
-  console.log(`Packaged Firelink smoke passed on 127.0.0.1:${readyPort}`);
+  console.log(`Packaged Firelink smoke passed on 127.0.0.1:${readyPort} with ${stabilityMs}ms stability`);
 } catch (error) {
   console.error(error instanceof Error ? error.message : String(error));
   process.exitCode = 1;

src-tauri/src/lib.rs

@@ -18512,9 +18512,28 @@ pub fn run() {
             main_window_builder = main_window_builder
                 .inner_size(startup_size.width as f64, startup_size.height as f64)
                 .prevent_overflow();
-            main_window_builder
+            #[cfg(target_os = "windows")]
+            {
+                // WebView2 can return E_INVALIDARG from MoveFocus while the
+                // newly-created host window is not focusable yet. Wry
+                // propagates that error from WebviewWindowBuilder::build,
+                // which destroys the native window and makes a release build
+                // look like it started headlessly before exiting. Focus the
+                // window only after WebView2 has been created successfully.
+                main_window_builder = main_window_builder.focused(false);
+            }
+            let main_window = main_window_builder
                 .build()
                 .map_err(|error| format!("failed to create main window: {error}"))?;
+            #[cfg(target_os = "windows")]
+            if let Err(error) = main_window.set_focus() {
+                // The window is already usable if the OS declines this
+                // best-effort activation request. A later user interaction
+                // can focus it without risking startup failure.
+                log::warn!("could not focus the main window after startup: {error}");
+            }
+            #[cfg(not(target_os = "windows"))]
+            let _ = main_window;
             restore_pending_main_window(app.handle());
 
             #[cfg(any(target_os = "windows", target_os = "linux"))]

src-tauri/src/properties_window.rs

@@ -437,6 +437,9 @@ pub fn open_download_properties_window(
         // native window becomes visible. Showing an opaque native surface
         // here exposes the webview's unpainted white background.
         .visible(false)
+        // A hidden WebView2 must not request focus during construction. The
+        // native reveal path focuses it after the window is visible.
+        .focused(false)
         .transparent(true);
     #[cfg(any(target_os = "windows", target_os = "macos", target_os = "linux"))]
     let builder = builder.decorations(false);