Add a remainingTime() method to the public interface of the QTimer class

It is an extension coming from the use case when you, for instance, need to
implement a countdown timer in client codes, and manually maintain a dedicated
variable for counting down with the help of yet another Timer. There might be
other use cases as well. The returned value is meant to be in milliseconds, as
the method documentation says, since it is reasonable, and consistent with the
rest (ie. the interval accessor).

The elapsed time is already being tracked inside the event dispatcher, thus the
effort is only exposing that for all platforms supported according to the
desired timer identifier, and propagating up to the QTimer public API. It is
done by using the QTimerInfoList class in the glib and unix dispatchers, and the
WinTimeInfo struct for the windows dispatcher.

It might be a good idea to to establish a QWinTimerInfo
(qtimerinfo_win{_p.h,cpp}) in the future for resembling the interface for
windows with the glib/unix management so that it would be consistent. That would
mean abstracting out a base class (~interface) for the timer info classes.
Something like that QAbstractTimerInfo.

Test: Build test only on (Arch)Linux, Windows and Mac. I have also run the unit
tests and they passed as well.

Change-Id: Ie37b3aff909313ebc92e511e27d029abb070f110
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>

src/corelib/kernel/qabstracteventdispatcher.cpp

@@ -295,6 +295,16 @@ int QAbstractEventDispatcher::registerTimer(int interval, Qt::TimerType timerTyp
     \sa Qt::TimerType
 */
 
+/*!
+    \fn int QAbstractEventDispatcher::remainingTime(int timerId)
+
+    Returns the remaining time in milliseconds with the given \a timerId.
+    If the timer is inactive, the returned value will be -1. If the timer is
+    overdue, the returned value will be 0.
+
+    \sa Qt::TimerType
+*/
+
 /*! \fn void QAbstractEventDispatcher::wakeUp()
     \threadsafe
 

src/corelib/kernel/qabstracteventdispatcher.h

@@ -93,6 +93,8 @@ public:
     virtual bool unregisterTimers(QObject *object) = 0;
     virtual QList<TimerInfo> registeredTimers(QObject *object) const = 0;
 
+    virtual int remainingTime(int timerId) = 0;
+
     virtual void wakeUp() = 0;
     virtual void interrupt() = 0;
     virtual void flush() = 0;

src/corelib/kernel/qeventdispatcher_glib.cpp

@@ -567,6 +567,19 @@ QList<QEventDispatcherGlib::TimerInfo> QEventDispatcherGlib::registeredTimers(QO
     return d->timerSource->timerList.registeredTimers(object);
 }
 
+int QEventDispatcherGlib::remainingTime(int timerId)
+{
+#ifndef QT_NO_DEBUG
+    if (timerId < 1) {
+        qWarning("QEventDispatcherGlib::remainingTimeTime: invalid argument");
+        return -1;
+    }
+#endif
+
+    Q_D(QEventDispatcherGlib);
+    return d->timerSource->timerList.timerRemainingTime(timerId);
+}
+
 void QEventDispatcherGlib::interrupt()
 {
     wakeUp();

src/corelib/kernel/qeventdispatcher_glib_p.h

@@ -85,6 +85,8 @@ public:
     bool unregisterTimers(QObject *object);
     QList<TimerInfo> registeredTimers(QObject *object) const;
 
+    int remainingTime(int timerId);
+
     void wakeUp();
     void interrupt();
     void flush();

src/corelib/kernel/qeventdispatcher_unix.cpp

@@ -628,6 +628,19 @@ bool QEventDispatcherUNIX::hasPendingEvents()
     return qGlobalPostedEventsCount();
 }
 
+int QEventDispatcherUNIX::remainingTime(int timerId)
+{
+#ifndef QT_NO_DEBUG
+    if (timerId < 1) {
+        qWarning("QEventDispatcherUNIX::remainingTime: invalid argument");
+        return -1;
+    }
+#endif
+
+    Q_D(QEventDispatcherUNIX);
+    return d->timerList.timerRemainingTime(timerId);
+}
+
 void QEventDispatcherUNIX::wakeUp()
 {
     Q_D(QEventDispatcherUNIX);

src/corelib/kernel/qeventdispatcher_unix_p.h

@@ -116,6 +116,8 @@ public:
     bool unregisterTimers(QObject *object);
     QList<TimerInfo> registeredTimers(QObject *object) const;
 
+    int remainingTime(int timerId);
+
     void wakeUp();
     void interrupt();
     void flush();

src/corelib/kernel/qeventdispatcher_win.cpp

@@ -50,6 +50,7 @@
 #include "qvarlengtharray.h"
 #include "qwineventnotifier.h"
 
+#include "qelapsedtimer.h"
 #include "qcoreapplication_p.h"
 #include <private/qthread_p.h>
 #include <private/qmutexpool_p.h>
@@ -532,6 +533,8 @@ void QEventDispatcherWin32Private::registerTimer(WinTimerInfo *t)
         ok = SetTimer(internalHwnd, t->timerId, interval, 0);
     }
 
+    t->timeout = qt_msectime() + interval;
+
     if (ok == 0)
         qErrnoWarning("QEventDispatcherWin32::registerTimer: Failed to create a timer");
 }
@@ -998,6 +1001,42 @@ void QEventDispatcherWin32::activateEventNotifiers()
     }
 }
 
+int QEventDispatcherWin32::remainingTime(int timerId)
+{
+#ifndef QT_NO_DEBUG
+    if (timerId < 1) {
+        qWarning("QEventDispatcherWin32::remainingTime: invalid argument");
+        return -1;
+    }
+#endif
+
+    Q_D(QEventDispatcherWin32);
+
+    if (d->timerVec.isEmpty())
+        return -1;
+
+    quint64 currentTime = qt_msectime();
+
+    register WinTimerInfo *t;
+    for (int i=0; i<d->timerVec.size(); i++) {
+        t = d->timerVec.at(i);
+        if (t && t->timerId == timerId) {                // timer found
+            if (currentTime < t->timeout) {
+                // time to wait
+                return t->timeout - currentTime;
+            } else {
+                return 0;
+            }
+        }
+    }
+
+#ifndef QT_NO_DEBUG
+    qWarning("QEventDispatcherWin32::remainingTime: timer id %s not found", timerId);
+#endif
+
+    return -1;
+}
+
 void QEventDispatcherWin32::wakeUp()
 {
     Q_D(QEventDispatcherWin32);

src/corelib/kernel/qeventdispatcher_win_p.h

@@ -66,6 +66,7 @@ class QEventDispatcherWin32Private;
 
 // forward declaration
 LRESULT QT_WIN_CALLBACK qt_internal_proc(HWND hwnd, UINT message, WPARAM wp, LPARAM lp);
+int qt_msectime();
 
 class Q_CORE_EXPORT QEventDispatcherWin32 : public QAbstractEventDispatcher
 {
@@ -94,6 +95,8 @@ public:
     void unregisterEventNotifier(QWinEventNotifier *notifier);
     void activateEventNotifiers();
 
+    int remainingTime(int timerId);
+
     void wakeUp();
     void interrupt();
     void flush();
@@ -123,6 +126,7 @@ struct WinTimerInfo {                           // internal timer info
     int timerId;
     int interval;
     Qt::TimerType timerType;
+    quint64 timeout;                            // - when to actually fire
     QObject *obj;                               // - object to receive events
     bool inTimerEvent;
     int fastTimerId;

src/corelib/kernel/qtimer.cpp

@@ -386,6 +386,25 @@ void QTimer::setInterval(int msec)
     }
 }
 
+/*!
+    \property QTimer::remainingTime
+    \brief the remaining time in milliseconds
+
+    Returns the timer's remaining value in milliseconds left until the timeout.
+    If the timer is inactive, the returned value will be -1. If the timer is
+    overdue, the returned value will be 0.
+
+    \sa interval
+*/
+int QTimer::remainingTime() const
+{
+    if (id != INV_TIMER) {
+        return QAbstractEventDispatcher::instance()->remainingTime(id);
+    }
+
+    return -1;
+}
+
 /*!
     \property QTimer::timerType
     \brief controls the accuracy of the timer

src/corelib/kernel/qtimer.h

@@ -57,6 +57,7 @@ class Q_CORE_EXPORT QTimer : public QObject
     Q_OBJECT
     Q_PROPERTY(bool singleShot READ isSingleShot WRITE setSingleShot)
     Q_PROPERTY(int interval READ interval WRITE setInterval)
+    Q_PROPERTY(int remainingTime READ remainingTime)
     Q_PROPERTY(Qt::TimerType timerType READ timerType WRITE setTimerType)
     Q_PROPERTY(bool active READ isActive)
 public:
@@ -69,6 +70,8 @@ public:
     void setInterval(int msec);
     int interval() const { return inter; }
 
+    int remainingTime() const;
+
     void setTimerType(Qt::TimerType atype) { this->type = atype; }
     Qt::TimerType timerType() const { return Qt::TimerType(type); }
 

src/corelib/kernel/qtimerinfo_unix.cpp

@@ -412,6 +412,37 @@ bool QTimerInfoList::timerWait(timeval &tm)
     return true;
 }
 
+/*
+  Returns the timer's remaining time in milliseconds with the given timerId, or
+  null if there is nothing left. If the timer id is not found in the list, the
+  returned value will be -1. If the timer is overdue, the returned value will be 0.
+*/
+int QTimerInfoList::timerRemainingTime(int timerId)
+{
+    timeval currentTime = updateCurrentTime();
+    repairTimersIfNeeded();
+    timeval tm = {0, 0};
+
+    for (int i = 0; i < count(); ++i) {
+        register QTimerInfo *t = at(i);
+        if (t->id == timerId) {
+            if (currentTime < t->timeout) {
+                // time to wait
+                tm = roundToMillisecond(t->timeout - currentTime);
+                return tm.tv_sec*1000 + tm.tv_usec/1000;
+            } else {
+                return 0;
+            }
+        }
+    }
+
+#ifndef QT_NO_DEBUG
+    qWarning("QTimerInfoList::timerRemainingTime: timer id %i not found", timerId);
+#endif
+
+    return -1;
+}
+
 void QTimerInfoList::registerTimer(int timerId, int interval, Qt::TimerType timerType, QObject *object)
 {
     QTimerInfo *t = new QTimerInfo;

src/corelib/kernel/qtimerinfo_unix_p.h

@@ -104,6 +104,8 @@ public:
     bool timerWait(timeval &);
     void timerInsert(QTimerInfo *);
 
+    int timerRemainingTime(int timerId);
+
     void registerTimer(int timerId, int interval, Qt::TimerType timerType, QObject *object);
     bool unregisterTimer(int timerId);
     bool unregisterTimers(QObject *object);

src/corelib/tools/qelapsedtimer_win.cpp

@@ -120,6 +120,11 @@ static quint64 getTickCount()
     return val | (quint64(highdword) << 32);
 }
 
+int qt_msectime()
+{
+    return ticksToNanoseconds(getTickCount()) / 1000000;
+}
+
 QElapsedTimer::ClockType QElapsedTimer::clockType()
 {
     resolveLibs();

src/plugins/platforms/cocoa/qcocoaeventdispatcher.h

@@ -128,6 +128,8 @@ public:
     bool unregisterTimers(QObject *object);
     QList<TimerInfo> registeredTimers(QObject *object) const;
 
+    int remainingTime(int timerId);
+
     void wakeUp();
     void interrupt();
     void flush();

src/plugins/platforms/cocoa/qcocoaeventdispatcher.mm

@@ -680,6 +680,19 @@ bool QCocoaEventDispatcher::processEvents(QEventLoop::ProcessEventsFlags flags)
     return retVal;
 }
 
+int QCocoaEventDispatcher::remainingTime(int timerId)
+{
+#ifndef QT_NO_DEBUG
+    if (timerId < 1) {
+        qWarning("QCocoaEventDispatcher::remainingTime: invalid argument");
+        return -1;
+    }
+#endif
+
+    Q_D(QCocoaEventDispatcher);
+    return d->timerInfoList.timerRemainingTime(timerId);
+}
+
 void QCocoaEventDispatcher::wakeUp()
 {
     Q_D(QCocoaEventDispatcher);

tests/auto/corelib/kernel/qcoreapplication/tst_qcoreapplication.cpp

@@ -616,6 +616,7 @@ public:
     bool unregisterTimer(int ) { return false; }
     bool unregisterTimers(QObject *) { return false; }
     QList<TimerInfo> registeredTimers(QObject *) const { return QList<TimerInfo>(); }
+    int remainingTime(int) { return 0; }
     void wakeUp() {}
     void interrupt() {}
     void flush() {}

tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp

@@ -55,6 +55,7 @@ private slots:
     void zeroTimer();
     void singleShotTimeout();
     void timeout();
+    void remainingTime();
     void livelock_data();
     void livelock();
     void timerInfiniteRecursion_data();
@@ -143,6 +144,22 @@ void tst_QTimer::timeout()
     QVERIFY(helper.count > oldCount);
 }
 
+void tst_QTimer::remainingTime()
+{
+    TimerHelper helper;
+    QTimer timer;
+
+    connect(&timer, SIGNAL(timeout()), &helper, SLOT(timeout()));
+    timer.start(200);
+
+    QCOMPARE(helper.count, 0);
+
+    QTest::qWait(50);
+    QCOMPARE(helper.count, 0);
+
+    int remainingTime = timer.remainingTime();
+    QVERIFY2(qAbs(remainingTime - 150) < 50, qPrintable(QString::number(remainingTime)));
+}
 
 void tst_QTimer::livelock_data()
 {

tests/auto/corelib/thread/qthread/tst_qthread.cpp

@@ -1234,6 +1234,7 @@ public:
     bool unregisterTimer(int ) { return false; }
     bool unregisterTimers(QObject *) { return false; }
     QList<TimerInfo> registeredTimers(QObject *) const { return QList<TimerInfo>(); }
+    int remainingTime(int) { return 0; }
     void wakeUp() {}
     void interrupt() {}
     void flush() {}

tests/auto/testlib/selftests/benchlibeventcounter/tst_benchlibeventcounter.cpp

@@ -62,6 +62,7 @@ public:
     void unregisterSocketNotifier(QSocketNotifier*) {}
     bool unregisterTimer(int) { return false; }
     bool unregisterTimers(QObject*) { return false; }
+    int remainingTime(int) { return 0; }
     void wakeUp() {}
 };
 

tests/auto/testlib/selftests/benchliboptions/tst_benchliboptions.cpp

@@ -62,6 +62,7 @@ public:
     void unregisterSocketNotifier(QSocketNotifier*) {}
     bool unregisterTimer(int) { return false; }
     bool unregisterTimers(QObject*) { return false; }
+    int remainingTime(int) { return 0; }
     void wakeUp() {}
 };