[FEATURE] Fix #6482, options for showing upside-down labels

- Adv Labeling option to 'Show upside-down labels': never, when rotation defined, or always
- 'Never' (default) option is same as before, labels with 90 <= angle < 270 are turned so their text is always upright
- 'When rotation defined' option shows upside-down labels if their rotation is layer- or data-defined (dynamic labels are turned upright)
- 'Always' option shows upside-down labels at layer- or data-defined rotations and for dynamic labels

Author: dakcarto

python/core/qgspallabeling.sip

@@ -27,6 +27,13 @@ class QgsPalLayerSettings
       MapOrientation = 8
     };
 
+    enum UpsideDownLabels
+    {
+      Upright, // upside-down labels (90 <= angle < 270) are shown upright
+      ShowDefined, // show upside down when rotation is layer- or data-defined
+      ShowAll // show upside down for all labels, including dynamic ones
+    };
+
     // increment iterator in _writeDataDefinedPropertyMap() when adding more
     enum DataDefinedProperties
     {
@@ -105,6 +112,7 @@ class QgsPalLayerSettings
     // Adds '<' or '>' to the label string pointing to the direction of the line / polygon ring
     // Works only if Placement == Line
     bool addDirectionSymbol;
+    unsigned int upsidedownLabels; // whether, or how, to show upsidedown labels
     bool fontSizeInMapUnits; //true if font size is in map units (otherwise in points)
     bool bufferSizeInMapUnits; //true if buffer is in map units (otherwise in mm)
     bool labelOffsetInMapUnits; //true if label offset is in map units (otherwise in mm)

src/app/qgslabelinggui.cpp

@@ -173,6 +173,24 @@ QgsLabelingGui::QgsLabelingGui( QgsPalLabeling* lbl, QgsVectorLayer* layer, QgsM
   chkMergeLines->setChecked( lyr.mergeLines );
   mMinSizeSpinBox->setValue( lyr.minFeatureSize );
   chkAddDirectionSymbol->setChecked( lyr.addDirectionSymbol );
+
+  // upside-down labels
+  switch ( lyr.upsidedownLabels )
+  {
+    case QgsPalLayerSettings::Upright:
+      mUpsidedownRadioOff->setChecked( true );
+      break;
+    case QgsPalLayerSettings::ShowDefined:
+      mUpsidedownRadioDefined->setChecked( true );
+      break;
+    case QgsPalLayerSettings::ShowAll:
+      mUpsidedownRadioAll->setChecked( true );
+      break;
+    default:
+      mUpsidedownRadioOff->setChecked( true );
+      break;
+  }
+
   wrapCharacterEdit->setText( lyr.wrapChar );
   chkPreserveRotation->setChecked( lyr.preserveRotation );
 
@@ -428,6 +446,18 @@ QgsPalLayerSettings QgsLabelingGui::layerSettings()
   {
     lyr.addDirectionSymbol = false;
   }
+  if ( mUpsidedownRadioOff->isChecked() )
+  {
+    lyr.upsidedownLabels = QgsPalLayerSettings::Upright;
+  }
+  else if ( mUpsidedownRadioDefined->isChecked() )
+  {
+    lyr.upsidedownLabels = QgsPalLayerSettings::ShowDefined;
+  }
+  else if ( mUpsidedownRadioAll->isChecked() )
+  {
+    lyr.upsidedownLabels = QgsPalLayerSettings::ShowAll;
+  }
   lyr.minFeatureSize = mMinSizeSpinBox->value();
   lyr.fontSizeInMapUnits = ( mFontSizeUnitComboBox->currentIndex() == 1 );
   lyr.wrapChar = wrapCharacterEdit->text();

src/core/pal/feature.h

@@ -276,6 +276,10 @@ namespace pal
       double getLabelDistance() const { return f->distlabel; }
       void setLabelInfo( LabelInfo* info ) { f->labelInfo = info; }
 
+      bool getFixedRotation() { return f->fixedRotation; }
+      double getLabelAngle() { return f->fixedAngle; }
+      bool getFixedPosition() { return f->fixedPos; }
+
       int getNumSelfObstacles() const { return nbHoles; }
       PointSet* getSelfObstacle( int i ) { return holes[i]; }
 

src/core/pal/labelposition.cpp

@@ -93,30 +93,55 @@ namespace pal
     if ( feature->getLayer()->getArrangement() != P_CURVED &&
          this->alpha > M_PI / 2 && this->alpha <= 3*M_PI / 2 )
     {
-      tx = x[0];
-      ty = y[0];
+      bool uprightLabel = false;
 
-      x[0] = x[2];
-      y[0] = y[2];
+      switch ( feature->getLayer()->getUpsidedownLabels() )
+      {
+        case Layer::Upright:
+          uprightLabel = true;
+          break;
+        case Layer::ShowDefined:
+          // upright only dynamic labels
+          if ( !feature->getFixedRotation() || ( !feature->getFixedPosition() && feature->getLabelAngle() == 0.0 ) )
+          {
+            uprightLabel = true;
+          }
+          break;
+        case Layer::ShowAll:
+          break;
+        default:
+          uprightLabel = true;
+      }
+
+      if ( uprightLabel )
+      {
+        tx = x[0];
+        ty = y[0];
+
+        x[0] = x[2];
+        y[0] = y[2];
 
-      x[2] = tx;
-      y[2] = ty;
+        x[2] = tx;
+        y[2] = ty;
 
-      tx = x[1];
-      ty = y[1];
+        tx = x[1];
+        ty = y[1];
 
-      x[1] = x[3];
-      y[1] = y[3];
+        x[1] = x[3];
+        y[1] = y[3];
 
-      x[3] = tx;
-      y[3] = ty;
+        x[3] = tx;
+        y[3] = ty;
 
-      upsideDown = true;
+        if ( this->alpha < M_PI )
+          this->alpha += M_PI;
+        else
+          this->alpha -= M_PI;
 
-      if ( this->alpha < M_PI )
-        this->alpha += M_PI;
-      else
-        this->alpha -= M_PI;
+        // labels with text shown upside down are not classified as upsideDown,
+        // only those whose boundary points have been inverted
+        upsideDown = true;
+      }
     }
   }
 

src/core/pal/layer.h

@@ -75,6 +75,13 @@ namespace pal
 
     public:
       enum LabelMode { LabelPerFeature, LabelPerFeaturePart };
+      enum UpsideDownLabels
+      {
+        Upright, // upside-down labels (90 <= angle < 270) are shown upright
+        ShowDefined, // show upside down when rotation is layer- or data-defined
+        ShowAll // show upside down for all labels, including dynamic ones
+      };
+
       bool getDisplayAll() const { return displayAll; }
 
     protected:
@@ -106,6 +113,8 @@ namespace pal
       LabelMode mode;
       bool mergeLines;
 
+      UpsideDownLabels upsidedownLabels;
+
       // indexes (spatial and id)
       RTree<FeaturePart*, double, 2, double, 8, 4> *rtree;
       HashTable<Feature*> *hashtable;
@@ -279,6 +288,9 @@ namespace pal
       void setMergeConnectedLines( bool m ) { mergeLines = m; }
       bool getMergeConnectedLines() const { return mergeLines; }
 
+      void setUpsidedownLabels( UpsideDownLabels ud ) { upsidedownLabels = ud; }
+      UpsideDownLabels getUpsidedownLabels() const { return upsidedownLabels; }
+
       /**
        * \brief register a feature in the layer
        *

src/core/qgspallabeling.cpp

@@ -174,6 +174,7 @@ QgsPalLayerSettings::QgsPalLayerSettings()
   vectorScaleFactor = 1.0;
   rasterCompressFactor = 1.0;
   addDirectionSymbol = false;
+  upsidedownLabels = Upright;
   fontSizeInMapUnits = false;
   bufferSizeInMapUnits = false;
   labelOffsetInMapUnits = true;
@@ -221,6 +222,7 @@ QgsPalLayerSettings::QgsPalLayerSettings( const QgsPalLayerSettings& s )
   vectorScaleFactor = s.vectorScaleFactor;
   rasterCompressFactor = s.rasterCompressFactor;
   addDirectionSymbol = s.addDirectionSymbol;
+  upsidedownLabels = s.upsidedownLabels;
   fontSizeInMapUnits = s.fontSizeInMapUnits;
   bufferSizeInMapUnits = s.bufferSizeInMapUnits;
   distInMapUnits = s.distInMapUnits;
@@ -400,6 +402,7 @@ void QgsPalLayerSettings::readFromLayer( QgsVectorLayer* layer )
   displayAll = layer->customProperty( "labeling/displayAll", QVariant( false ) ).toBool();
   mergeLines = layer->customProperty( "labeling/mergeLines" ).toBool();
   addDirectionSymbol = layer->customProperty( "labeling/addDirectionSymbol" ).toBool();
+  upsidedownLabels = ( UpsideDownLabels ) layer->customProperty( "labeling/upsidedownLabels", QVariant( Upright ) ).toUInt();
   minFeatureSize = layer->customProperty( "labeling/minFeatureSize" ).toDouble();
   fontSizeInMapUnits = layer->customProperty( "labeling/fontSizeInMapUnits" ).toBool();
   bufferSizeInMapUnits = layer->customProperty( "labeling/bufferSizeInMapUnits" ).toBool();
@@ -458,6 +461,7 @@ void QgsPalLayerSettings::writeToLayer( QgsVectorLayer* layer )
   layer->setCustomProperty( "labeling/displayAll", displayAll );
   layer->setCustomProperty( "labeling/mergeLines", mergeLines );
   layer->setCustomProperty( "labeling/addDirectionSymbol", addDirectionSymbol );
+  layer->setCustomProperty( "labeling/upsidedownLabels", ( unsigned int )upsidedownLabels );
   layer->setCustomProperty( "labeling/minFeatureSize", minFeatureSize );
   layer->setCustomProperty( "labeling/fontSizeInMapUnits", fontSizeInMapUnits );
   layer->setCustomProperty( "labeling/bufferSizeInMapUnits", bufferSizeInMapUnits );
@@ -1064,6 +1068,17 @@ int QgsPalLabeling::prepareLayer( QgsVectorLayer* layer, QSet<int>& attrIndices,
   // set whether adjacent lines should be merged
   l->setMergeConnectedLines( lyr.mergeLines );
 
+  // set how to show upside-down labels
+  Layer::UpsideDownLabels upsdnlabels;
+  switch ( lyr.upsidedownLabels )
+  {
+    case QgsPalLayerSettings::Upright:     upsdnlabels = Layer::Upright; break;
+    case QgsPalLayerSettings::ShowDefined: upsdnlabels = Layer::ShowDefined; break;
+    case QgsPalLayerSettings::ShowAll:     upsdnlabels = Layer::ShowAll; break;
+    default: Q_ASSERT( "unsupported upside-down label setting" && 0 ); return 0;
+  }
+  l->setUpsidedownLabels( upsdnlabels );
+
   // fix for font size in map units causing font to show pointsize at small map scales
   int pixelFontSize = lyr.sizeToPixel( lyr.textFont.pointSizeF(), ctx );
 

src/core/qgspallabeling.h

@@ -81,6 +81,13 @@ class CORE_EXPORT QgsPalLayerSettings
       MapOrientation = 8
     };
 
+    enum UpsideDownLabels
+    {
+      Upright, // upside-down labels (90 <= angle < 270) are shown upright
+      ShowDefined, // show upside down when rotation is layer- or data-defined
+      ShowAll // show upside down for all labels, including dynamic ones
+    };
+
     // increment iterator in _writeDataDefinedPropertyMap() when adding more
     enum DataDefinedProperties
     {
@@ -159,6 +166,7 @@ class CORE_EXPORT QgsPalLayerSettings
     // Adds '<' or '>' to the label string pointing to the direction of the line / polygon ring
     // Works only if Placement == Line
     bool addDirectionSymbol;
+    unsigned int upsidedownLabels; // whether, or how, to show upsidedown labels
     bool fontSizeInMapUnits; //true if font size is in map units (otherwise in points)
     bool bufferSizeInMapUnits; //true if buffer is in map units (otherwise in mm)
     bool labelOffsetInMapUnits; //true if label offset is in map units (otherwise in mm)