asterisms: fix reading long integers

src/core/StelUtils.cpp

@@ -30,7 +30,9 @@
 #include <QRegularExpression>
 #include <QProcess>
 #include <QSysInfo>
+#include <QJsonValue>
 #include <cmath> // std::fmod
+#include <limits>
 #include <zlib.h>
 
 #ifdef CYGWIN
@@ -2788,6 +2790,16 @@ QByteArray uncompress(QIODevice& device, qint64 maxBytes)
 	return out;
 }
 
+qint64 getLongLong(const QJsonValue& v)
+{
+	if(v.isString()) return v.toString().toLongLong();
+	const auto value = v.toDouble();
+	constexpr qint64 max = (1LL<<std::numeric_limits<double>::digits) - 1;
+	if(std::abs(value) > max) return 0;
+	const auto integer = static_cast<qint64>(value);
+	if(value != integer) return 0; // fractional part must be zero
+	return integer;
+}
 
 } // end of the StelUtils namespace
 

src/core/StelUtils.hpp

@@ -117,6 +117,18 @@ namespace StelUtils
 	//! Return the user agent name, i.e. "Stellarium/0.15.0 (Linux)"
 	QString getUserAgentString();
 
+	/*! \brief Get a long integer from a JSON value
+	 *
+	 *  QJsonValue stores JSON numbers as double-precision floating-point values. This means
+	 *  that numbers greater than 2^53-1 will be rounded, which is unacceptable for e.g. ids
+	 *  like those of the Gaia catalog.
+	 *  This function supports, in addition to normal JSON numbers, also representations of
+	 *  numbers by JSON strings. If the value passed is a JSON string, it will be parsed to a
+	 *  number. If it's a JSON number less than 2^53, it will be returned as is. Otherwise it
+	 *  will return 0, as QJsonValue's getters would in case of a type mismatch.
+	 */
+	qint64 getLongLong(const class QJsonValue& v);
+
 	inline const QString getEndLineChar() {
 		#ifdef Q_OS_WIN
 		const QString stelEndl="\r\n";

src/core/modules/Asterism.cpp

@@ -109,11 +109,7 @@ bool Asterism::read(const QJsonObject& data, StarMgr *starMgr)
 					                     << lineIndex << ": isn't a number";
 					return false;
 				}
-#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
-				const StarId HIP = point.toInteger();
-#else
-				const StarId HIP = point.toInt(); // Won't support Gaia id unless it fits into 32 bits
-#endif
+				const StarId HIP = StelUtils::getLongLong(point);
 				if (HIP <= NR_OF_HIP)
 					asterism.push_back(starMgr->searchHP(HIP));
 				else