[composer] Add nautical miles support to scalebar, more rational default scale

python/core/composer/qgscomposerscalebar.sip

@@ -23,7 +23,8 @@ class QgsComposerScaleBar: QgsComposerItem
     {
       MapUnits = 0,
       Meters,
-      Feet
+      Feet,
+      NauticalMiles
     };
 
     QgsComposerScaleBar( QgsComposition* composition /TransferThis/ );
@@ -95,7 +96,7 @@ class QgsComposerScaleBar: QgsComposerItem
     void applyDefaultSettings();
     /**Apply default size (scale bar 1/5 of map item width)
       @note this method was added in version 1.7*/
-    void applyDefaultSize();
+    void applyDefaultSize( ScaleBarUnits u = Meters );
 
     /**Sets style by name
      @param styleName (untranslated) style name. Possibilities are: 'Single Box', 'Double Box', 'Line Ticks Middle', 'Line Ticks Down', 'Line Ticks Up', 'Numeric'*/

src/app/composer/qgscomposerscalebarwidget.cpp

@@ -51,7 +51,7 @@ QgsComposerScaleBarWidget::QgsComposerScaleBarWidget( QgsComposerScaleBar* scale
   mUnitsComboBox->insertItem( 0, tr( "Map units" ), 0 );
   mUnitsComboBox->insertItem( 1, tr( "Meters" ), 1 );
   mUnitsComboBox->insertItem( 2, tr( "Feet" ), 2 );
-
+  mUnitsComboBox->insertItem( 3, tr( "Nautical Miles" ), 3 );
   blockMemberSignals( false );
   setGuiElements(); //set the GUI elements to the state of scaleBar
 }
@@ -532,9 +532,37 @@ void QgsComposerScaleBarWidget::on_mUnitsComboBox_currentIndexChanged( int index
     return;
   }
 
-  mComposerScaleBar->beginCommand( tr( "Scalebar unit changed" ) );
   disconnectUpdateSignal();
   mComposerScaleBar->setUnits(( QgsComposerScaleBar::ScaleBarUnits )unitData.toInt() );
+  switch ( mUnitsComboBox->currentIndex() )
+  {
+    case 0:
+    {
+      mComposerScaleBar->beginCommand( tr( "Scalebar changed to map units" ) );
+      mComposerScaleBar->applyDefaultSize( QgsComposerScaleBar::MapUnits );
+      break;
+    }
+    case 2:
+    {
+      mComposerScaleBar->beginCommand( tr( "Scalebar changed to feet" ) );
+      mComposerScaleBar->applyDefaultSize( QgsComposerScaleBar::Feet );
+      break;
+    }
+    case 3:
+    {
+      mComposerScaleBar->beginCommand( tr( "Scalebar changed to nautical miles" ) );
+      mComposerScaleBar->applyDefaultSize( QgsComposerScaleBar::NauticalMiles );
+      break;
+    }
+    case 1:
+    default:
+    {
+      mComposerScaleBar->beginCommand( tr( "Scalebar changed to meters" ) );
+      mComposerScaleBar->applyDefaultSize( QgsComposerScaleBar::Meters );
+      break;
+    }
+  }
+
   mComposerScaleBar->update();
   connectUpdateSignal();
   mComposerScaleBar->endCommand();

src/core/composer/qgscomposerscalebar.cpp

@@ -194,10 +194,14 @@ double QgsComposerScaleBar::mapWidth() const
     da.setEllipsoid( QgsProject::instance()->readEntry( "Measure", "/Ellipsoid", "WGS84" ) );
 
     double measure = da.measureLine( QgsPoint( composerMapRect.xMinimum(), composerMapRect.yMinimum() ), QgsPoint( composerMapRect.xMaximum(), composerMapRect.yMinimum() ) );
-    if ( mUnits == Feet )
+    if ( mUnits == QgsComposerScaleBar::Feet )
     {
       measure /= 0.3048;
     }
+    else if ( mUnits == QgsComposerScaleBar::NauticalMiles )
+    {
+      measure /= 1852.0;
+    }
     return measure;
   }
 }
@@ -250,25 +254,71 @@ void QgsComposerScaleBar::applyDefaultSettings()
   emit itemChanged();
 }
 
-void QgsComposerScaleBar::applyDefaultSize()
+void QgsComposerScaleBar::applyDefaultSize( QgsComposerScaleBar::ScaleBarUnits u )
 {
   if ( mComposerMap )
   {
-    setUnits( Meters );
+    setUnits( u );
-    double widthMeter = mapWidth();
+    double upperMagnitudeMultiplier;
-    int nUnitsPerSegment =  widthMeter / 10.0; //default scalebar width equals half the map width
+    double widthInSelectedUnits = mapWidth();
-    setNumUnitsPerSegment( nUnitsPerSegment );
+    double initialUnitsPerSegment =  widthInSelectedUnits / 10.0; //default scalebar width equals half the map width
+    setNumUnitsPerSegment( initialUnitsPerSegment );
 
-    if ( nUnitsPerSegment > 1000 )
+    switch ( mUnits )
     {
-      setNumUnitsPerSegment(( int )( numUnitsPerSegment() / 1000.0 + 0.5 ) * 1000 );
+      case MapUnits:
-      setUnitLabeling( tr( "km" ) );
+      {
-      setNumMapUnitsPerScaleBarUnit( 1000 );
+        upperMagnitudeMultiplier = 1.0;
+        setUnitLabeling( tr( "units" ) );
+        break;
+      }
+      case Meters:
+      {
+        if ( initialUnitsPerSegment > 1000.0 )
+        {
+          upperMagnitudeMultiplier = 1000.0;
+          setUnitLabeling( tr( "km" ) );
+        }
+        else
+        {
+          upperMagnitudeMultiplier = 1.0;
+          setUnitLabeling( tr( "m" ) );
+        }
+        break;
+      }
+      case Feet:
+      {
+        if ( initialUnitsPerSegment > 5419.95 )
+        {
+          upperMagnitudeMultiplier = 5419.95;
+          setUnitLabeling( tr( "miles" ) );
+        }
+        else
+        {
+          upperMagnitudeMultiplier = 1.0;
+          setUnitLabeling( tr( "ft" ) );
+        }
+        break;
+      }
+      case NauticalMiles:
+      {
+        upperMagnitudeMultiplier = 1;
+        setUnitLabeling( tr( "Nm" ) );
+        break;
+      }
     }
-    else
+
+    double segmentWidth = initialUnitsPerSegment / upperMagnitudeMultiplier;
+    int segmentMagnitude = floor( log10( segmentWidth ) );
+    double unitsPerSegment = upperMagnitudeMultiplier * ( pow( 10, segmentMagnitude ) );
+    double multiplier = floor(( widthInSelectedUnits / ( unitsPerSegment * 10 ) ) / 2.5 ) * 2.5;
+
+    if ( multiplier > 0 )
     {
-      setUnitLabeling( tr( "m" ) );
+      unitsPerSegment = unitsPerSegment * multiplier;
     }
+    setNumUnitsPerSegment( unitsPerSegment );
+    setNumMapUnitsPerScaleBarUnit( upperMagnitudeMultiplier );
 
     setNumSegments( 4 );
     setNumSegmentsLeft( 2 );

src/core/composer/qgscomposerscalebar.h

@@ -46,7 +46,8 @@ class CORE_EXPORT QgsComposerScaleBar: public QgsComposerItem
     {
       MapUnits = 0,
       Meters,
-      Feet
+      Feet,
+      NauticalMiles
     };
 
     QgsComposerScaleBar( QgsComposition* composition );
@@ -118,7 +119,7 @@ class CORE_EXPORT QgsComposerScaleBar: public QgsComposerItem
     void applyDefaultSettings();
     /**Apply default size (scale bar 1/5 of map item width)
       @note this method was added in version 1.7*/
-    void applyDefaultSize();
+    void applyDefaultSize( ScaleBarUnits u = Meters );
 
     /**Sets style by name
      @param styleName (untranslated) style name. Possibilities are: 'Single Box', 'Double Box', 'Line Ticks Middle', 'Line Ticks Down', 'Line Ticks Up', 'Numeric'*/
@@ -203,8 +204,9 @@ class CORE_EXPORT QgsComposerScaleBar: public QgsComposerItem
     /**Calculates with of a segment in mm and stores it in mSegmentMillimeters*/
     void refreshSegmentMillimeters();
 
-    /**Returns diagonal of composer map in selected units (map units / meters / feet)*/
+    /**Returns diagonal of composer map in selected units (map units / meters / feet / nautical miles)*/
     double mapWidth() const;
+
 };
 
 #endif //QGSCOMPOSERSCALEBAR_H