[composer] Make atlas fixed and predefined scales options work correctly with geographic coordinate systems (fix #9839)

Author: nyalldawson

src/core/composer/qgsatlascomposition.cpp

@@ -444,7 +444,7 @@ void QgsAtlasComposition::prepareMap( QgsComposerMap* map )
   double xa2 = mTransformedFeatureBounds.xMaximum();
   double ya1 = mTransformedFeatureBounds.yMinimum();
   double ya2 = mTransformedFeatureBounds.yMaximum();
-  QgsRectangle new_extent = mTransformedFeatureBounds;
+  QgsRectangle newExtent = mTransformedFeatureBounds;
   QgsRectangle mOrigExtent = map->extent();
 
   //sanity check - only allow fixed scale mode for point layers
@@ -462,85 +462,96 @@ void QgsAtlasComposition::prepareMap( QgsComposerMap* map )
       break;
   }
 
-  if ( map->atlasScalingMode() == QgsComposerMap::Fixed || isPointLayer )
+  if ( map->atlasScalingMode() == QgsComposerMap::Fixed || map->atlasScalingMode() == QgsComposerMap::Predefined || isPointLayer )
   {
-    // only translate, keep the original scale (i.e. width x height)
-
-    double geom_center_x = ( xa1 + xa2 ) / 2.0;
-    double geom_center_y = ( ya1 + ya2 ) / 2.0;
-    double xx = geom_center_x - mOrigExtent.width() / 2.0;
-    double yy = geom_center_y - mOrigExtent.height() / 2.0;
-    new_extent = QgsRectangle( xx,
-                               yy,
-                               xx + mOrigExtent.width(),
-                               yy + mOrigExtent.height() );
-  }
-  else if ( map->atlasScalingMode() == QgsComposerMap::Predefined )
-  {
-    // choose one of the predefined scales
     QgsScaleCalculator calc;
     calc.setMapUnits( composition()->mapSettings().mapUnits() );
     calc.setDpi( 25.4 );
-    double scale = calc.calculate( map->extent(), map->rect().width() );
-    QgsRectangle extent = map->extent();
+    double originalScale = calc.calculate( mOrigExtent, map->rect().width() );
+    double geomCenterX = ( xa1 + xa2 ) / 2.0;
+    double geomCenterY = ( ya1 + ya2 ) / 2.0;
 
-    double n_width = extent.width(), n_height = extent.height();
-    const QVector<double>& scales = mPredefinedScales;
-    for ( int i = 0; i < scales.size(); i++ )
+    if ( map->atlasScalingMode() == QgsComposerMap::Fixed || isPointLayer )
     {
-      double ratio = scales[i] / scale;
-      n_width = extent.width() * ratio;
-      n_height = extent.height() * ratio;
-      if (( n_width >= new_extent.width() ) && ( n_height >= new_extent.height() ) )
+      // only translate, keep the original scale (i.e. width x height)
+      double xMin = geomCenterX - mOrigExtent.width() / 2.0;
+      double yMin = geomCenterY - mOrigExtent.height() / 2.0;
+      newExtent = QgsRectangle( xMin,
+                                yMin,
+                                xMin + mOrigExtent.width(),
+                                yMin + mOrigExtent.height() );
+
+      //scale newExtent to match original scale of map
+      //this is required for geographic coordinate systems, where the scale varies by extent
+      double newScale = calc.calculate( newExtent, map->rect().width() );
+      newExtent.scale( originalScale / newScale );
+    }
+    else if ( map->atlasScalingMode() == QgsComposerMap::Predefined )
+    {
+      // choose one of the predefined scales
+      double newWidth = mOrigExtent.width();
+      double newHeight = mOrigExtent.height();
+      const QVector<double>& scales = mPredefinedScales;
+      for ( int i = 0; i < scales.size(); i++ )
       {
-        // this is the smallest extent that embeds the feature, stop here
-        break;
+        double ratio = scales[i] / originalScale;
+        newWidth = mOrigExtent.width() * ratio;
+        newHeight = mOrigExtent.height() * ratio;
+
+        // compute new extent, centered on feature
+        double xMin = geomCenterX - newWidth / 2.0;
+        double yMin = geomCenterY - newHeight / 2.0;
+        newExtent = QgsRectangle( xMin,
+                                  yMin,
+                                  xMin + newWidth,
+                                  yMin + newHeight );
+
+        //scale newExtent to match desired map scale
+        //this is required for geographic coordinate systems, where the scale varies by extent
+        double newScale = calc.calculate( newExtent, map->rect().width() );
+        newExtent.scale( scales[i] / newScale );
+
+        if (( newExtent.width() >= mTransformedFeatureBounds.width() ) && ( newExtent.height() >= mTransformedFeatureBounds.height() ) )
+        {
+          // this is the smallest extent that embeds the feature, stop here
+          break;
+        }
       }
     }
-
-    // compute new extent, centered on feature
-    double geom_center_x = ( xa1 + xa2 ) / 2.0;
-    double geom_center_y = ( ya1 + ya2 ) / 2.0;
-    double xx = geom_center_x - n_width / 2.0;
-    double yy = geom_center_y - n_height / 2.0;
-    new_extent = QgsRectangle( xx,
-                               yy,
-                               xx + n_width,
-                               yy + n_height );
   }
   else if ( map->atlasScalingMode() == QgsComposerMap::Auto )
   {
     // auto scale
 
-    double geom_ratio = mTransformedFeatureBounds.width() / mTransformedFeatureBounds.height();
-    double map_ratio = mOrigExtent.width() / mOrigExtent.height();
+    double geomRatio = mTransformedFeatureBounds.width() / mTransformedFeatureBounds.height();
+    double mapRatio = mOrigExtent.width() / mOrigExtent.height();
 
     // geometry height is too big
-    if ( geom_ratio < map_ratio )
+    if ( geomRatio < mapRatio )
     {
       // extent the bbox's width
-      double adj_width = ( map_ratio * mTransformedFeatureBounds.height() - mTransformedFeatureBounds.width() ) / 2.0;
-      xa1 -= adj_width;
-      xa2 += adj_width;
+      double adjWidth = ( mapRatio * mTransformedFeatureBounds.height() - mTransformedFeatureBounds.width() ) / 2.0;
+      xa1 -= adjWidth;
+      xa2 += adjWidth;
     }
     // geometry width is too big
-    else if ( geom_ratio > map_ratio )
+    else if ( geomRatio > mapRatio )
     {
       // extent the bbox's height
-      double adj_height = ( mTransformedFeatureBounds.width() / map_ratio - mTransformedFeatureBounds.height() ) / 2.0;
-      ya1 -= adj_height;
-      ya2 += adj_height;
+      double adjHeight = ( mTransformedFeatureBounds.width() / mapRatio - mTransformedFeatureBounds.height() ) / 2.0;
+      ya1 -= adjHeight;
+      ya2 += adjHeight;
     }
-    new_extent = QgsRectangle( xa1, ya1, xa2, ya2 );
+    newExtent = QgsRectangle( xa1, ya1, xa2, ya2 );
 
     if ( map->atlasMargin() > 0.0 )
     {
-      new_extent.scale( 1 + map->atlasMargin() );
+      newExtent.scale( 1 + map->atlasMargin() );
     }
   }
 
   // set the new extent (and render)
-  map->setNewAtlasFeatureExtent( new_extent );
+  map->setNewAtlasFeatureExtent( newExtent );
 }
 
 const QString& QgsAtlasComposition::currentFilename() const