File indexing completed on 2024-11-10 04:57:04

 /*
     KWin - the KDE window manager
     This file is part of the KDE project.
 
     SPDX-FileCopyrightText: 2017 Roman Gilg <subdiff@gmail.com>
 
     SPDX-License-Identifier: GPL-2.0-or-later
 */
 #include "suncalc.h"
 #include "constants.h"
 
 #include <QDateTime>
 #include <QTimeZone>
 #include <QtMath>
 
 namespace KWin
 {
 
 #define TWILIGHT_NAUT -12.0
 #define TWILIGHT_CIVIL -6.0
 #define SUN_RISE_SET -0.833
 #define SUN_HIGH 2.0
 
 static QTime convertToLocalTime(const QDateTime &when, const QTime &utcTime)
 {
     const QTimeZone timeZone = QTimeZone::systemTimeZone();
     const int utcOffset = timeZone.offsetFromUtc(when);
     return utcTime.addSecs(utcOffset);
 }
 
 QPair<QDateTime, QDateTime> calculateSunTimings(const QDateTime &dateTime, double latitude, double longitude, bool morning)
 {
     // calculations based on https://aa.quae.nl/en/reken/zonpositie.html
     // accuracy: +/- 5min
 
     // positioning
     const double rad = M_PI / 180.;
     const double earthObliquity = 23.4397; // epsilon
 
     const double lat = latitude; // phi
     const double lng = -longitude; // lw
 
     // times
     const QDateTime utcDateTime = dateTime.toUTC();
     const double juPrompt = utcDateTime.date().toJulianDay(); // J
     const double ju2000 = 2451545.; // J2000
 
     // geometry
     auto mod360 = [](double number) -> double {
         return std::fmod(number, 360.);
     };
 
     auto sin = [&rad](double angle) -> double {
         return std::sin(angle * rad);
     };
     auto cos = [&rad](double angle) -> double {
         return std::cos(angle * rad);
     };
     auto asin = [&rad](double val) -> double {
         return std::asin(val) / rad;
     };
     auto acos = [&rad](double val) -> double {
         return std::acos(val) / rad;
     };
 
     auto anomaly = [&](const double date) -> double { // M
         return mod360(357.5291 + 0.98560028 * (date - ju2000));
     };
 
     auto center = [&sin](double anomaly) -> double { // C
         return 1.9148 * sin(anomaly) + 0.02 * sin(2 * anomaly) + 0.0003 * sin(3 * anomaly);
     };
 
     auto ecliptLngMean = [](double anom) -> double { // Mean ecliptical longitude L_sun = Mean Anomaly + Perihelion + 180°
         return anom + 282.9372; // anom + 102.9372 + 180°
     };
 
     auto ecliptLng = [&](double anom) -> double { // lambda = L_sun + C
         return ecliptLngMean(anom) + center(anom);
     };
 
     auto declination = [&](const double date) -> double { // delta
         const double anom = anomaly(date);
         const double eclLng = ecliptLng(anom);
 
         return mod360(asin(sin(earthObliquity) * sin(eclLng)));
     };
 
     // sun hour angle at specific angle
     auto hourAngle = [&](const double date, double angle) -> double { // H_t
         const double decl = declination(date);
         const double ret0 = (sin(angle) - sin(lat) * sin(decl)) / (cos(lat) * cos(decl));
 
         double ret = mod360(acos(ret0));
         if (180. < ret) {
             ret = ret - 360.;
         }
         return ret;
     };
 
     /*
      * Sun positions
      */
 
     // transit is at noon
     auto getTransit = [&](const double date) -> double { // Jtransit
         const double juMeanSolTime = juPrompt - ju2000 - 0.0009 - lng / 360.; // n_x = J - J_2000 - J_0 - l_w / 360°
         const double juTrEstimate = date + qRound64(juMeanSolTime) - juMeanSolTime; // J_x = J + n - n_x
         const double anom = anomaly(juTrEstimate); // M
         const double eclLngM = ecliptLngMean(anom); // L_sun
 
         return juTrEstimate + 0.0053 * sin(anom) - 0.0068 * sin(2 * eclLngM);
     };
 
     auto getSunMorning = [&hourAngle](const double angle, const double transit) -> double {
         return transit - hourAngle(transit, angle) / 360.;
     };
 
     auto getSunEvening = [&hourAngle](const double angle, const double transit) -> double {
         return transit + hourAngle(transit, angle) / 360.;
     };
 
     /*
      * Begin calculations
      */
 
     // noon - sun at the highest point
     const double juNoon = getTransit(juPrompt);
 
     double begin, end;
     if (morning) {
         begin = getSunMorning(TWILIGHT_CIVIL, juNoon);
         end = getSunMorning(SUN_HIGH, juNoon);
     } else {
         begin = getSunEvening(SUN_HIGH, juNoon);
         end = getSunEvening(TWILIGHT_CIVIL, juNoon);
     }
     // transform to QDateTime
     begin += 0.5;
     end += 0.5;
 
     QDateTime dateTimeBegin;
     QDateTime dateTimeEnd;
 
     if (!std::isnan(begin)) {
         const double dayFraction = begin - int(begin);
         const QTime utcTime = QTime::fromMSecsSinceStartOfDay(dayFraction * MSC_DAY);
         const QTime localTime = convertToLocalTime(dateTime, utcTime);
         dateTimeBegin = QDateTime(dateTime.date(), localTime);
     }
 
     if (!std::isnan(end)) {
         const double dayFraction = end - int(end);
         const QTime utcTime = QTime::fromMSecsSinceStartOfDay(dayFraction * MSC_DAY);
         const QTime localTime = convertToLocalTime(dateTime, utcTime);
         dateTimeEnd = QDateTime(dateTime.date(), localTime);
     }
 
     return {dateTimeBegin, dateTimeEnd};
 }
 
 }