api/window: add .closed

gluon.d.ts

@@ -339,7 +339,10 @@ type Window = {
   controls: ControlsApi,
 
   /** Close the Gluon window. */
-  close(): void
+  close(): void,
+
+  /** If the window has been closed or not. */
+  closed: Boolean
 };
 
 

src/launcher/inject.js

@@ -134,12 +134,17 @@ export default async (CDP, proc, injectionType = 'browser', { dataPath, browserN
     },
 
     close: () => {
+      if (Window.closed) return false;
+
       for (const handler of closeHandlers) handler(); // extra api handlers which need to be closed
 
       CDP.sendMessage('Browser.close');
       CDP.close();
       proc.kill();
+
+      return Window.closed = true;
     },
+    closed: false,
 
     versions
   };