Port IdleDetector to QBasicTimer

QBasicTimer is lighter and it properly handles timeout values bigger
than INT32_MAX.

CCBUG: 482077

src/idledetector.cpp

@@ -14,13 +14,10 @@ namespace KWin
 
 IdleDetector::IdleDetector(std::chrono::milliseconds timeout, QObject *parent)
     : QObject(parent)
-    , m_timer(new QTimer(this))
+    , m_timeout(timeout)
 {
     Q_ASSERT(timeout >= 0ms);
-    m_timer->setSingleShot(true);
-    m_timer->setInterval(timeout);
-    connect(m_timer, &QTimer::timeout, this, &IdleDetector::markAsIdle);
-    m_timer->start();
+    m_timer.start(timeout, this);
 
     input()->addIdleDetector(this);
 }
@@ -32,6 +29,14 @@ IdleDetector::~IdleDetector()
     }
 }
 
+void IdleDetector::timerEvent(QTimerEvent *event)
+{
+    if (event->timerId() == m_timer.timerId()) {
+        m_timer.stop();
+        markAsIdle();
+    }
+}
+
 bool IdleDetector::isInhibited() const
 {
     return m_isInhibited;
@@ -44,16 +49,16 @@ void IdleDetector::setInhibited(bool inhibited)
     }
     m_isInhibited = inhibited;
     if (inhibited) {
-        m_timer->stop();
+        m_timer.stop();
     } else {
-        m_timer->start();
+        m_timer.start(m_timeout, this);
     }
 }
 
 void IdleDetector::activity()
 {
     if (!m_isInhibited) {
-        m_timer->start();
+        m_timer.start(m_timeout, this);
         markAsResumed();
     }
 }

src/idledetector.h

@@ -8,7 +8,8 @@
 
 #include <kwin_export.h>
 
-#include <QTimer>
+#include <QBasicTimer>
+#include <QObject>
 
 namespace KWin
 {
@@ -30,11 +31,15 @@ Q_SIGNALS:
     void idle();
     void resumed();
 
+protected:
+    void timerEvent(QTimerEvent *event) override;
+
 private:
     void markAsIdle();
     void markAsResumed();
 
-    QTimer *m_timer;
+    QBasicTimer m_timer;
+    std::chrono::milliseconds m_timeout;
     bool m_isIdle = false;
     bool m_isInhibited = false;
 };