Force workers 1

Fixes #5346

.github/workflows/e2e-tests.yml

@@ -1,7 +1,7 @@
 name: E2E Tests
 on:
   push:
-    branches: [ main ]
+    branches: [ main, pierremtb/issue5346-Multi-second-blank-screen-on-second-instance-of-the-app-workers-1 ]
   pull_request:
 
 concurrency:

playwright.electron.config.ts

@@ -13,7 +13,7 @@ export default defineConfig({
   /* Do not retry */
   retries: 0,
   /* Different amount of parallelism on CI and local. */
-  workers: 8,
+  workers: 1,
   /* Reporter to use. See https://playwright.dev/docs/test-reporters */
   reporter: [
     ['dot'],

src/main.ts

@@ -53,6 +53,7 @@ process.env.VITE_KC_CONNECTION_TIMEOUT_MS ??=
 console.log('process.env', process.env)
 
 /// Register our application to handle all "zoo-studio:" protocols.
+const singleInstanceLock = app.requestSingleInstanceLock()
 if (process.defaultApp) {
   if (process.argv.length >= 2) {
     app.setAsDefaultProtocolClient(ZOO_STUDIO_PROTOCOL, process.execPath, [
@@ -65,7 +66,13 @@ if (process.defaultApp) {
 
 // Global app listeners
 // Must be done before ready event.
+// Checking against this lock is needed for Windows and Linux, see
+// https://www.electronjs.org/docs/latest/tutorial/launch-app-from-url-in-another-app#windows-and-linux-code
+if (!singleInstanceLock) {
+  app.quit()
+} else {
   registerStartupListeners()
+}
 
 const createWindow = (pathToOpen?: string, reuse?: boolean): BrowserWindow => {
   let newWindow