fix: notice input on the lock screen despite idle inhibitors

src/agent/inputwatcher.h

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+// Somebody touching the machine: a key, a click, the mouse, the touchpad.
+//
+// From ext_idle_notifier_v1, like KIdleTime, but with the input notification
+// of version 2. KIdleTime's own honours idle inhibitors: with a video playing
+// or an app keeping the screen on, no key reached it and the lock screen never
+// scanned.
+
+#pragma once
+
+#include <QObject>
+
+#include <memory>
+
+class IdleNotifier;
+class IdleNotification;
+
+class InputWatcher : public QObject
+{
+    Q_OBJECT
+public:
+    explicit InputWatcher(QObject *parent = nullptr);
+    ~InputWatcher() override;
+
+    // Emit input() once, for the first input after nothing was touched for
+    // calmMs. 0: the next input. Replaces what was watched before.
+    void watch(int calmMs);
+    void stop();
+
+Q_SIGNALS:
+    void input();
+
+private:
+    std::unique_ptr<IdleNotifier> m_notifier;
+    std::unique_ptr<IdleNotification> m_notification;
+};