[layouts] Add more unit choices to scalebars

Explicitly add options for kilometers, miles, etc as the current
UX for setting these is too confusing!

Fixes #16921

src/app/layout/qgslayoutscalebarwidget.cpp

@@ -78,10 +78,13 @@ QgsLayoutScaleBarWidget::QgsLayoutScaleBarWidget( QgsLayoutItemScaleBar *scaleBa
   mAlignmentComboBox->insertItem( 2, tr( "Right" ) );
 
   //units combo box
-  mUnitsComboBox->insertItem( 0, tr( "Map units" ), QgsUnitTypes::DistanceUnknownUnit );
-  mUnitsComboBox->insertItem( 1, tr( "Meters" ), QgsUnitTypes::DistanceMeters );
-  mUnitsComboBox->insertItem( 2, tr( "Feet" ), QgsUnitTypes::DistanceFeet );
-  mUnitsComboBox->insertItem( 3, tr( "Nautical Miles" ), QgsUnitTypes::DistanceNauticalMiles );
+  mUnitsComboBox->addItem( tr( "Map units" ), QgsUnitTypes::DistanceUnknownUnit );
+  mUnitsComboBox->addItem( tr( "Meters" ), QgsUnitTypes::DistanceMeters );
+  mUnitsComboBox->addItem( tr( "Kilometers" ), QgsUnitTypes::DistanceKilometers );
+  mUnitsComboBox->addItem( tr( "Feet" ), QgsUnitTypes::DistanceFeet );
+  mUnitsComboBox->addItem( tr( "Yards" ), QgsUnitTypes::DistanceYards );
+  mUnitsComboBox->addItem( tr( "Miles" ), QgsUnitTypes::DistanceMiles );
+  mUnitsComboBox->addItem( tr( "Nautical Miles" ), QgsUnitTypes::DistanceNauticalMiles );
 
   mFillColorButton->setColorDialogTitle( tr( "Select Fill Color" ) );
   mFillColorButton->setAllowOpacity( true );
@@ -193,7 +196,7 @@ void QgsLayoutScaleBarWidget::setGuiElements()
   mAlignmentComboBox->setCurrentIndex( ( int )( mScalebar->alignment() ) );
 
   //units
-  mUnitsComboBox->setCurrentIndex( mUnitsComboBox->findData( ( int )mScalebar->units() ) );
+  mUnitsComboBox->setCurrentIndex( mUnitsComboBox->findData( static_cast< int >( mScalebar->units() ) ) );
 
   if ( mScalebar->segmentSizeMode() == QgsScaleBarSettings::SegmentSizeFixed )
   {
@@ -546,36 +549,8 @@ void QgsLayoutScaleBarWidget::mUnitsComboBox_currentIndexChanged( int index )
   }
 
   disconnectUpdateSignal();
-  mScalebar->setUnits( ( QgsUnitTypes::DistanceUnit )unitData.toInt() );
-  switch ( mUnitsComboBox->currentIndex() )
-  {
-    case 0:
-    {
-      mScalebar->beginCommand( tr( "Set Scalebar Units" ) );
-      mScalebar->applyDefaultSize( QgsUnitTypes::DistanceUnknownUnit );
-      break;
-    }
-    case 2:
-    {
-      mScalebar->beginCommand( tr( "Set Scalebar Units" ) );
-      mScalebar->applyDefaultSize( QgsUnitTypes::DistanceFeet );
-      break;
-    }
-    case 3:
-    {
-      mScalebar->beginCommand( tr( "Set Scalebar Units" ) );
-      mScalebar->applyDefaultSize( QgsUnitTypes::DistanceNauticalMiles );
-      break;
-    }
-    case 1:
-    default:
-    {
-      mScalebar->beginCommand( tr( "Set Scalebar Units" ) );
-      mScalebar->applyDefaultSize( QgsUnitTypes::DistanceMeters );
-      break;
-    }
-  }
-
+  mScalebar->beginCommand( tr( "Set Scalebar Units" ) );
+  mScalebar->applyDefaultSize( static_cast<  QgsUnitTypes::DistanceUnit >( unitData.toInt() ) );
   mScalebar->update();
 
   mUnitLabelLineEdit->setText( mScalebar->unitLabel() );

src/core/layout/qgslayoutitemscalebar.cpp

@@ -423,13 +423,13 @@ void QgsLayoutItemScaleBar::applyDefaultSettings()
 
 void QgsLayoutItemScaleBar::applyDefaultSize( QgsUnitTypes::DistanceUnit units )
 {
+  mSettings.setUnits( units );
   if ( mMap )
   {
-    setUnits( units );
     double upperMagnitudeMultiplier = 1.0;
     double widthInSelectedUnits = mapWidth();
     double initialUnitsPerSegment = widthInSelectedUnits / 10.0; //default scalebar width equals half the map width
-    setUnitsPerSegment( initialUnitsPerSegment );
+    mSettings.setUnitsPerSegment( initialUnitsPerSegment );
 
     switch ( units )
     {
@@ -483,11 +483,11 @@ void QgsLayoutItemScaleBar::applyDefaultSize( QgsUnitTypes::DistanceUnit units )
     {
       unitsPerSegment = unitsPerSegment * multiplier;
     }
-    setUnitsPerSegment( unitsPerSegment );
-    setMapUnitsPerScaleBarUnit( upperMagnitudeMultiplier );
+    mSettings.setUnitsPerSegment( unitsPerSegment );
+    mSettings.setMapUnitsPerScaleBarUnit( upperMagnitudeMultiplier );
 
-    setNumberOfSegments( 4 );
-    setNumberOfSegmentsLeft( 2 );
+    mSettings.setNumberOfSegments( 4 );
+    mSettings.setNumberOfSegmentsLeft( 2 );
   }
 
   refreshSegmentMillimeters();
@@ -611,7 +611,7 @@ bool QgsLayoutItemScaleBar::writePropertiesToElement( QDomElement &composerScale
   //map id
   if ( mMap )
   {
-    composerScaleBarElem.setAttribute( QStringLiteral( "mapId" ), mMap->id() );
+    composerScaleBarElem.setAttribute( QStringLiteral( "mapUuid" ), mMap->uuid() );
   }
 
   //colors