Don't duplicate calculation of next trigger time of alarms

Calculating the next trigger time can sometimes be processor
intensive.

src/kalarmapp.cpp

@@ -844,10 +844,10 @@ void KAlarmApp::checkNextDueAlarm()
     if (!mAlarmsEnabled)
         return;
     // Find the first alarm due
-    const KAEvent nextEvent = ResourcesCalendar::earliestAlarm();
+    KADateTime nextDt;
+    const KAEvent nextEvent = ResourcesCalendar::earliestAlarm(nextDt);
     if (!nextEvent.isValid())
         return;   // there are no alarms pending
-    const KADateTime nextDt = nextEvent.nextTrigger(KAEvent::ALL_TRIGGER).effectiveKDateTime();
     const KADateTime now = KADateTime::currentDateTime(Preferences::timeSpec());
     qint64 interval = now.msecsTo(nextDt);
     qCDebug(KALARM_LOG) << "KAlarmApp::checkNextDueAlarm: now:" << qPrintable(now.toString(QStringLiteral("%Y-%m-%d %H:%M %:Z"))) << ", next:" << qPrintable(nextDt.toString(QStringLiteral("%Y-%m-%d %H:%M %:Z"))) << ", due:" << interval;

src/resourcescalendar.cpp

@@ -647,7 +647,7 @@ void ResourcesCalendar::findEarliestAlarm(const Resource& resource)
 * Return the active alarm with the earliest trigger time.
 * Reply = invalid if none.
 */
-KAEvent ResourcesCalendar::earliestAlarm()
+KAEvent ResourcesCalendar::earliestAlarm(KADateTime& nextTriggerTime)
 {
     KAEvent earliest;
     KADateTime earliestTime;
@@ -663,7 +663,7 @@ KAEvent ResourcesCalendar::earliestAlarm()
             // Something went wrong: mEarliestAlarm wasn't updated when it should have been!!
             qCCritical(KALARM_LOG) << "ResourcesCalendar::earliestAlarm: resource" << eit.key() << "does not contain" << id;
             mInstance->findEarliestAlarm(res);
-            return earliestAlarm();
+            return earliestAlarm(nextTriggerTime);
         }
         const KADateTime dt = event.nextTrigger(KAEvent::ALL_TRIGGER).effectiveKDateTime();
         if (dt.isValid()  &&  (!earliest.isValid() || dt < earliestTime))
@@ -672,6 +672,7 @@ KAEvent ResourcesCalendar::earliestAlarm()
             earliest = event;
         }
     }
+    nextTriggerTime = earliestTime;
     return earliest;
 }
 

src/resourcescalendar.h

@@ -36,7 +36,13 @@ public:
     ~ResourcesCalendar() override;
     static void             initialise(const QByteArray& appName, const QByteArray& appVersion);
     static void             terminate();
-    static KAEvent          earliestAlarm();
+
+    /** Return the active alarm with the earliest trigger time.
+     *  @param nextTriggerTime  The next trigger time of the earliest alarm.
+     *  @return  The earliest alarm.
+     */
+    static KAEvent          earliestAlarm(KADateTime& nextTriggerTime);
+
     static void             setAlarmPending(const KAEvent&, bool pending = true);
     static bool             haveDisabledAlarms()       { return mHaveDisabledAlarms; }
     static void             disabledChanged(const KAEvent&);

src/traywindow.cpp

@@ -261,11 +261,11 @@ void TrayWindow::updateStatus()
         active = theApp()->alarmsEnabled();
         if (active)
         {
-            const KAEvent& event = ResourcesCalendar::earliestAlarm();
+            KADateTime dt;
+            const KAEvent& event = ResourcesCalendar::earliestAlarm(dt);
             active = event.isValid();
             if (active  &&  period > 0)
             {
-                const KADateTime dt = event.nextTrigger(KAEvent::ALL_TRIGGER).effectiveKDateTime();
                 qint64 delay = KADateTime::currentLocalDateTime().secsTo(dt);
                 delay -= static_cast<qint64>(period) * 60;   // delay until icon to be shown
                 active = (delay <= 0);