Fix composer scale bar when crs units are non-meters and OTF is off (fix #13610)

(cherry-picked from d56dcdb)

Author: nyalldawson

src/core/composer/qgscomposerscalebar.cpp

@@ -209,14 +209,24 @@ double QgsComposerScaleBar::mapWidth() const
     da.setSourceCrs( mComposition->mapSettings().destinationCrs().srsid() );
     da.setEllipsoid( QgsProject::instance()->readEntry( "Measure", "/Ellipsoid", "WGS84" ) );
 
-    double measure = da.measureLine( QgsPoint( composerMapRect.xMinimum(), composerMapRect.yMinimum() ), QgsPoint( composerMapRect.xMaximum(), composerMapRect.yMinimum() ) );
-    if ( mUnits == QgsComposerScaleBar::Feet )
-    {
-      measure /= QGis::fromUnitToUnitFactor( QGis::Feet, QGis::Meters );
-    }
-    else if ( mUnits == QgsComposerScaleBar::NauticalMiles )
+    QGis::UnitType units = QGis::Meters;
+    double measure = da.measureLine( QgsPoint( composerMapRect.xMinimum(), composerMapRect.yMinimum() ),
+                                     QgsPoint( composerMapRect.xMaximum(), composerMapRect.yMinimum() ),
+                                     units );
+    switch ( mUnits )
     {
-      measure /= QGis::fromUnitToUnitFactor( QGis::NauticalMiles, QGis::Meters );
+      case QgsComposerScaleBar::Feet:
+        measure /= QGis::fromUnitToUnitFactor( QGis::Feet, units );
+        break;
+      case QgsComposerScaleBar::NauticalMiles:
+        measure /= QGis::fromUnitToUnitFactor( QGis::NauticalMiles, units );
+        break;
+      case QgsComposerScaleBar::Meters:
+        measure /= QGis::fromUnitToUnitFactor( QGis::Meters, units );
+        break;
+      case QgsComposerScaleBar::MapUnits:
+        //avoid warning
+        break;
     }
     return measure;
   }

src/core/qgsdistancearea.cpp

@@ -460,8 +460,15 @@ double QgsDistanceArea::measureLine( const QList<QgsPoint> &points )
 }
 
 double QgsDistanceArea::measureLine( const QgsPoint &p1, const QgsPoint &p2 )
+{
+  QGis::UnitType units;
+  return measureLine( p1, p2, units );
+}
+
+double QgsDistanceArea::measureLine( const QgsPoint& p1, const QgsPoint& p2, QGis::UnitType& units ) const
 {
   double result;
+  units = mCoordTransform->sourceCrs().mapUnits();
 
   try
   {
@@ -470,6 +477,7 @@ double QgsDistanceArea::measureLine( const QgsPoint &p1, const QgsPoint &p2 )
     QgsDebugMsgLevel( QString( "Measuring from %1 to %2" ).arg( p1.toString( 4 ) ).arg( p2.toString( 4 ) ), 3 );
     if ( mEllipsoidalMode && ( mEllipsoid != GEO_NONE ) )
     {
+      units = QGis::Meters;
       QgsDebugMsgLevel( QString( "Ellipsoidal calculations is enabled, using ellipsoid %1" ).arg( mEllipsoid ), 4 );
       QgsDebugMsgLevel( QString( "From proj4 : %1" ).arg( mCoordTransform->sourceCrs().toProj4() ), 4 );
       QgsDebugMsgLevel( QString( "To   proj4 : %1" ).arg( mCoordTransform->destCRS().toProj4() ), 4 );

src/core/qgsdistancearea.h

@@ -95,8 +95,21 @@ class CORE_EXPORT QgsDistanceArea
     //! measures line
     double measureLine( const QList<QgsPoint>& points );
 
-    //! measures line with one segment
-    double measureLine( const QgsPoint& p1, const QgsPoint& p2 );
+    /** Measures length of line with one segment
+     * @param p1 start of line
+     * @param p2 end of line
+     * @returns distance in meters, or map units if cartesian calculation was performed
+     */
+    double measureLine( const QgsPoint& p1, const QgsPoint& p2 ) const;
+
+    /** Measures length of line with one segment and returns units of distance.
+     * @param p1 start of line
+     * @param p2 end of line
+     * @param units will be set to units of measure
+     * @returns calculated distance between points. Distance units are stored in units parameter.
+     * @note added in QGIS 2.12
+     */
+    double measureLine( const QgsPoint& p1, const QgsPoint& p2, QGis::UnitType& units ) const;
 
     //! measures polygon area
     double measurePolygon( const QList<QgsPoint>& points );

tests/src/core/testqgsdistancearea.cpp

@@ -163,7 +163,31 @@ void TestQgsDistanceArea::unit_conversions()
   QString myTxt = QgsDistanceArea::textUnit( inputValue, 7, inputUnit, true, false );
   QString expectedTxt = QLocale::system().toString( 2.4710538146717, 'g', 1 + 7 );
   QVERIFY( myTxt.startsWith( expectedTxt ) ); // Ignore units for now.
-};
+}
+
+void TestQgsDistanceArea::measureUnits()
+{
+  //test regression #13610
+  QgsDistanceArea calc;
+  calc.setEllipsoidalMode( false );
+  calc.setEllipsoid( "NONE" );
+  calc.setSourceCrs( 254L );
+  QGis::UnitType units;
+  QgsPoint p1( 1341683.9854275715, 408256.9562717728 );
+  QgsPoint p2( 1349321.7807031618, 408256.9562717728 );
+
+  double result = calc.measureLine( p1, p2, units );
+  //no OTF, result will be in CRS unit (feet)
+  QCOMPARE( units, QGis::Feet );
+  QVERIFY( qgsDoubleNear( result, 7637.7952755903825, 0.001 ) );
+
+  calc.setEllipsoidalMode( true );
+  calc.setEllipsoid( "WGS84" );
+  result = calc.measureLine( p1, p2, units );
+  //OTF, result will be in meters
+  QCOMPARE( units, QGis::Meters );
+  QVERIFY( qgsDoubleNear( result, 2328.0988253106957, 0.001 ) );
+}
 
 QTEST_MAIN( TestQgsDistanceArea )
 #include "testqgsdistancearea.moc"