QGeoCoordinate: fix toString() conversion

Applying qRound() to check if the minutes/seconds should overflow was
not the right solution in some cases. It could lead to incorrect
overflows, and so - to wrong conversion results.

The actual logic of overflow is related to the behavior of QString::number.
This patch fixes the logic and also introduces some minor optimizations.
After overflow, the minutes or seconds value is always 0.0, because
the actual minutes/seconds value is always in range [0; 60). This allows
us to get rid of some checks.

Fixes: QTBUG-95221
Change-Id: Ie3dcb6cef226b04c43dd973c09c4ae297c583f3b
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
(cherry picked from commit 15f06eca6a5085ce14d2eb0b743c5a06365068ea)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

2 files changed, 41 insertions, 26 deletions

diff --git a/src/positioning/qgeocoordinate.cpp b/src/positioning/qgeocoordinate.cpp
index fdc7ae4f..e0b1a0b3 100644
--- a/src/positioning/qgeocoordinate.cpp
+++ b/src/positioning/qgeocoordinate.cpp
@@ -594,19 +594,18 @@ QString QGeoCoordinate::toString(CoordinateFormat format) const
             double latMin = (absLat - int(absLat)) * 60;
             double lngMin = (absLng - int(absLng)) * 60;
 
-            if (qRound(latMin) >= 60) {
+            // We use QString::number(val, 'f', 3) to represent minutes.
+            // It rounds up to the next integer in case the fraction > 0.9995.
+            // Such behavior should be handled specifically when the rounded
+            // value is 60, so that we overflow to degrees correctly.
+            // If we overflow, the minutes should unconditionally be 0.0.
+            if (latMin > 59.9995) {
                 absLat++;
-                latMin = qAbs(latMin - 60.0f);
-                //avoid invalid latitude due to latMin rounding below
-                if (qRound(absLat) >= 90)
-                    latMin = 0.0f;
+                latMin = 0.0f;
             }
-            if (qRound(lngMin) >= 60) {
+            if (lngMin > 59.9995) {
                 absLng++;
-                lngMin = qAbs(lngMin - 60.0f);
-                // avoid invalid longitude due to lngMin rounding below
-                if (qRound(absLng) >= 180)
-                    lngMin = 0.0f;
+                lngMin = 0.0f;
             }
 
             latStr = QString::fromLatin1("%1%2 %3'")
@@ -626,28 +625,28 @@ QString QGeoCoordinate::toString(CoordinateFormat format) const
             double latSec = (latMin - int(latMin)) * 60;
             double lngSec = (lngMin - int(lngMin)) * 60;
 
-            // overflow to full minutes
-            if (qRound(latSec) >= 60) {
+            // We use QString::number(val, 'f', 1) to represent seconds.
+            // It rounds up to the next integer in case the fraction >= 0.95.
+            // Such behavior should be handled specifically when the rounded
+            // value is 60, so that we overflow to minutes correctly.
+            // If we overflow, the seconds should unconditionally be 0.0.
+            if (latSec >= 59.95) {
                 latMin++;
-                latSec = qAbs(latSec - 60.0f);
-                // overflow to full degrees
+                latSec = 0.0f;
+                // We cast to int to represent minutes, so we can use qRound()
+                // to determine if we need to overflow to full degrees.
+                // If we overflow, the minutes will unconditionally be 0.0.
                 if (qRound(latMin) >= 60) {
                     absLat++;
-                    latMin = qAbs(latMin - 60.0f);
-                    // avoid invalid latitude due to latSec rounding below
-                    if (qRound(absLat) >= 90)
-                        latSec = 0.0f;
+                    latMin = 0.0f;
                 }
             }
-            if (qRound(lngSec) >= 60) {
+            if (lngSec >= 59.95) {
                 lngMin++;
-                lngSec = qAbs(lngSec - 60.0f);
+                lngSec = 0.0f;
                 if (qRound(lngMin) >= 60) {
                     absLng++;
-                    lngMin = qAbs(lngMin - 60.0f);
-                    // avoid invalid longitude due to lngSec rounding below
-                    if (qRound(absLng) >= 180)
-                        lngSec = 0.0f;
+                    lngMin = 0.0f;
                 }
             }
 
diff --git a/tests/auto/qgeocoordinate/tst_qgeocoordinate.cpp b/tests/auto/qgeocoordinate/tst_qgeocoordinate.cpp
index 1b30f647..28f10aca 100644
--- a/tests/auto/qgeocoordinate/tst_qgeocoordinate.cpp
+++ b/tests/auto/qgeocoordinate/tst_qgeocoordinate.cpp
@@ -843,13 +843,29 @@ private slots:
                 << QString( "2%1 0.000', 2%1 0.000'").arg(DEGREES_SYMB);
 
         QTest::newRow("Wrap seconds to minutes to Degrees DM -> above valid long/lat values")
-                << QGeoCoordinate(89.9999, 179.9999) << QGeoCoordinate::DegreesMinutesSeconds
+                << QGeoCoordinate(89.999999, 179.999999) << QGeoCoordinate::DegreesMinutesSeconds
                 << QString( "90%1 0' 0.0\", 180%1 0' 0.0\"").arg(DEGREES_SYMB);
 
+        QTest::newRow("Seconds and minutes near valid long/lat values border")
+                << QGeoCoordinate(89.9999, 179.9999) << QGeoCoordinate::DegreesMinutesSeconds
+                << QString("89%1 59' 59.6\", 179%1 59' 59.6\"").arg(DEGREES_SYMB);
+
         QTest::newRow("Wrap minutes to Degrees DM ->above valid long/lat values")
-                << QGeoCoordinate(89.9999, 179.9999) << QGeoCoordinate::DegreesMinutes
+                << QGeoCoordinate(89.999999, 179.999999) << QGeoCoordinate::DegreesMinutes
                 << QString( "90%1 0.000', 180%1 0.000'").arg(DEGREES_SYMB);
 
+        QTest::newRow("Minutes near valid long/lat values border")
+                << QGeoCoordinate(89.9999, 179.9999) << QGeoCoordinate::DegreesMinutes
+                << QString("89%1 59.994', 179%1 59.994'").arg(DEGREES_SYMB);
+
+        QTest::newRow("Fix incorrect wrap minutes to degrees")
+                << QGeoCoordinate(0.995833, 0.995833) << QGeoCoordinate::DegreesMinutes
+                << QString("0%1 59.750', 0%1 59.750'").arg(DEGREES_SYMB);
+
+        QTest::newRow("Fix incorrect wrap seconds to minutes")
+                << QGeoCoordinate(0.9832222, 0.9832222) << QGeoCoordinate::DegreesMinutesSeconds
+                << QString("0%1 58' 59.6\", 0%1 58' 59.6\"").arg(DEGREES_SYMB);
+
     }
 
     void datastream()