feat(ui): hide cursor when terminal is unfocused (#4012)

packages/cli/src/ui/hooks/useFocus.ts

@@ -0,0 +1,48 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { useStdin, useStdout } from 'ink';
+import { useEffect, useState } from 'react';
+
+// ANSI escape codes to enable/disable terminal focus reporting
+const ENABLE_FOCUS_REPORTING = '\x1b[?1004h';
+const DISABLE_FOCUS_REPORTING = '\x1b[?1004l';
+
+// ANSI escape codes for focus events
+const FOCUS_IN = '\x1b[I';
+const FOCUS_OUT = '\x1b[O';
+
+export const useFocus = () => {
+  const { stdin } = useStdin();
+  const { stdout } = useStdout();
+  const [isFocused, setIsFocused] = useState(true);
+
+  useEffect(() => {
+    const handleData = (data: Buffer) => {
+      const sequence = data.toString();
+      const lastFocusIn = sequence.lastIndexOf(FOCUS_IN);
+      const lastFocusOut = sequence.lastIndexOf(FOCUS_OUT);
+
+      if (lastFocusIn > lastFocusOut) {
+        setIsFocused(true);
+      } else if (lastFocusOut > lastFocusIn) {
+        setIsFocused(false);
+      }
+    };
+
+    // Enable focus reporting
+    stdout?.write(ENABLE_FOCUS_REPORTING);
+    stdin?.on('data', handleData);
+
+    return () => {
+      // Disable focus reporting on cleanup
+      stdout?.write(DISABLE_FOCUS_REPORTING);
+      stdin?.removeListener('data', handleData);
+    };
+  }, [stdin, stdout]);
+
+  return isFocused;
+};