Fixed handling of tolerance for projected layers (#1634).

Patch contributed by Richard Kostecky.


git-svn-id: http://svn.osgeo.org/qgis/trunk/qgis@10555 c8812cc2-4d05-0410-92ff-de0c093fc19c

python/core/qgstolerance.sip

@@ -16,27 +16,26 @@ public:
     };
 
     /**
-    * Static function to get vertex tolerance value from settings
-    * @param mapUnitsPerPixel number of map units per pixel
+    * Static function to get vertex tolerance value for a layer.
+    * The value is read from settings and transformed if necessary.
     * @return value of vertex tolerance in map units
     */
-    static double vertexSearchRadius( double mapUnitsPerPixel );
+    static double vertexSearchRadius( QgsMapLayer* layer, QgsMapRenderer* renderer );
 
     /**
-    * Static function to get default tolerance value from settings
-    * @param mapUnitsPerPixel number of map units per pixel
+    * Static function to get default tolerance value for a layer.
+    * The value is read from settings and transformed if necessary.
     * @return value of default tolerance in map units
     */
-    static double defaultTolerance( double mapUnitsPerPixel );
+    static double defaultTolerance( QgsMapLayer* layer, QgsMapRenderer* renderer );
 
-    /** 
+    /**
     * Static function to translate tolerance value into current map unit value
     * @param tolerace tolerance value to be translated
-    * @param mapUnitsPerPixel number of map units per pixel
     * @param units type of units to be translated
     * @return value of tolerance in map units
     */
-    static double toleranceInMapUnits(double tolerance, double mapUnitsPerPixel, UnitType units = MapUnits);
+    static double toleranceInMapUnits( double tolerance, QgsMapLayer* layer, QgsMapRenderer* renderer, UnitType units = MapUnits );
 
 };
 

src/app/qgsmaptoolmovefeature.cpp

@@ -72,7 +72,7 @@ void QgsMapToolMoveFeature::canvasPressEvent( QMouseEvent * e )
   //find first geometry under mouse cursor and store iterator to it
   QgsPoint layerCoords = toLayerCoordinates(( QgsMapLayer* )vlayer, e->pos() );
   QSettings settings;
-  double searchRadius = QgsTolerance::vertexSearchRadius( mCanvas->mapUnitsPerPixel() );
+  double searchRadius = QgsTolerance::vertexSearchRadius( mCanvas->currentLayer(), mCanvas->mapRenderer() );
   QgsRectangle selectRect( layerCoords.x() - searchRadius, layerCoords.y() - searchRadius,
                            layerCoords.x() + searchRadius, layerCoords.y() + searchRadius );
 

src/core/qgssnapper.cpp

@@ -57,7 +57,7 @@ int QgsSnapper::snapPoint( const QPoint& startPoint, QList<QgsSnappingResult>& s
     //transform point from map coordinates to layer coordinates
     layerCoordPoint = mMapRenderer->mapToLayerCoordinates( snapLayerIt->mLayer, mapCoordPoint );
 
-    double tolerance = QgsTolerance::toleranceInMapUnits( snapLayerIt->mTolerance, mMapRenderer->mapUnitsPerPixel(), snapLayerIt->mUnitType );
+    double tolerance = QgsTolerance::toleranceInMapUnits( snapLayerIt->mTolerance, snapLayerIt->mLayer, mMapRenderer, snapLayerIt->mUnitType );
     if ( snapLayerIt->mLayer->snapWithContext( layerCoordPoint, tolerance,
          currentResultList, snapLayerIt->mSnapTo ) != 0 )
     {

src/core/qgstolerance.cpp

@@ -15,29 +15,70 @@
 
 #include "qgstolerance.h"
 #include <QSettings>
+#include <QPoint>
+#include <math.h>
 
 
-double QgsTolerance::toleranceInMapUnits( double tolerance, double mapUnitsPerPixel, UnitType units )
+
+double QgsTolerance::toleranceInMapUnits( double tolerance, QgsMapLayer* layer, QgsMapRenderer* renderer, UnitType units )
 {
   if ( units == MapUnits )
   {
     return tolerance;
   }
+  double mapUnitsPerPixel = computeMapUnitPerPixel( layer, renderer );
   return tolerance * mapUnitsPerPixel;
 }
 
-double QgsTolerance::vertexSearchRadius( double mapUnitsPerPixel )
+
+double QgsTolerance::vertexSearchRadius( QgsMapLayer* layer, QgsMapRenderer* renderer )
 {
   QSettings settings;
   double tolerance = settings.value( "/qgis/digitizing/search_radius_vertex_edit", 10 ).toDouble();
   UnitType units = ( QgsTolerance::UnitType ) settings.value( "/qgis/digitizing/search_radius_vertex_edit_unit", 0 ).toInt();
-  return toleranceInMapUnits( tolerance, mapUnitsPerPixel, units );
+  return toleranceInMapUnits( tolerance, layer, renderer, units );
 }
 
-double QgsTolerance::defaultTolerance( double mapUnitsPerPixel )
+
+double QgsTolerance::defaultTolerance( QgsMapLayer* layer, QgsMapRenderer* renderer )
 {
   QSettings settings;
   double tolerance = settings.value( "/qgis/digitizing/default_snapping_tolerance", 0 ).toDouble();
   UnitType units = ( QgsTolerance::UnitType ) settings.value( "/qgis/digitizing/default_snapping_tolerance_unit", 0 ).toInt();
-  return toleranceInMapUnits( tolerance, mapUnitsPerPixel, units );
+  return toleranceInMapUnits( tolerance, layer, renderer, units );
+}
+
+
+double QgsTolerance::computeMapUnitPerPixel( QgsMapLayer* layer, QgsMapRenderer* renderer )
+{
+  if ( ! renderer->hasCrsTransformEnabled() )
+  {
+    // if the on-the-fly projections are not enabled, layer units pre pixel are the same as map units per pixel
+    return renderer->mapUnitsPerPixel();
+  }
+
+  // the layer is projected. Find out how many pixels are in one map unit - either horizontal and vertical direction
+  // this check might not work correctly in some cases
+  // (on a large area the pixels projected around "0,0" can have different properties from the actual point)
+  QgsPoint p1 = toLayerCoordinates(layer, renderer, QPoint(0,1));
+  QgsPoint p2 = toLayerCoordinates(layer, renderer, QPoint(0,2));
+  QgsPoint p3 = toLayerCoordinates(layer, renderer, QPoint(1,0));
+  QgsPoint p4 = toLayerCoordinates(layer, renderer, QPoint(2,0));
+  double x = p1.sqrDist(p2);
+  double y = p3.sqrDist(p4);
+  if (x > y) 
+  {
+    return sqrt(x);
+  }
+  else
+  {
+    return sqrt(y);
+  }
+}
+
+
+QgsPoint QgsTolerance::toLayerCoordinates( QgsMapLayer* layer, QgsMapRenderer* renderer, const QPoint& point )
+{
+  QgsPoint pt = renderer->coordinateTransform()->toMapCoordinates( point );
+  return renderer->mapToLayerCoordinates( layer, pt );
 }

src/core/qgstolerance.h

@@ -15,7 +15,10 @@
 
 #ifndef QGSTOLERANCE_H
 #define QGSTOLERANCE_H
-
+#include "qgsmaptopixel.h"
+#include "qgsmaprenderer.h"
+#include "qgsmaplayer.h"
+#include "qgspoint.h"
 
 /** \ingroup core
  * This is the class is providing tolerance value in map unit values.
@@ -36,27 +39,30 @@ class CORE_EXPORT QgsTolerance
     };
 
     /**
-    * Static function to get vertex tolerance value from settings
-    * @param mapUnitsPerPixel number of map units per pixel
+    * Static function to get vertex tolerance value for a layer.
+    * The value is read from settings and transformed if necessary.
     * @return value of vertex tolerance in map units
     */
-    static double vertexSearchRadius( double mapUnitsPerPixel );
+    static double vertexSearchRadius( QgsMapLayer* layer, QgsMapRenderer* renderer );
 
     /**
-    * Static function to get default tolerance value from settings
-    * @param mapUnitsPerPixel number of map units per pixel
+    * Static function to get default tolerance value for a layer.
+    * The value is read from settings and transformed if necessary.
     * @return value of default tolerance in map units
     */
-    static double defaultTolerance( double mapUnitsPerPixel );
+    static double defaultTolerance( QgsMapLayer* layer, QgsMapRenderer* renderer );
 
     /**
     * Static function to translate tolerance value into current map unit value
     * @param tolerace tolerance value to be translated
-    * @param mapUnitsPerPixel number of map units per pixel
     * @param units type of units to be translated
     * @return value of tolerance in map units
     */
-    static double toleranceInMapUnits( double tolerance, double mapUnitsPerPixel, UnitType units = MapUnits );
+    static double toleranceInMapUnits( double tolerance, QgsMapLayer* layer, QgsMapRenderer* renderer, UnitType units = MapUnits );
+
+  private:
+    static double computeMapUnitPerPixel( QgsMapLayer* layer, QgsMapRenderer* renderer );
+    static QgsPoint toLayerCoordinates( QgsMapLayer* layer, QgsMapRenderer* renderer, const QPoint& point );
 
 };
 

src/gui/qgsmapcanvassnapper.cpp

@@ -101,7 +101,7 @@ int QgsMapCanvasSnapper::snapToCurrentLayer( const QPoint& p, QList<QgsSnappingR
     if ( snappingTol < 0 )
     {
       //use search tolerance for vertex editing
-      snapLayer.mTolerance = QgsTolerance::vertexSearchRadius( mMapCanvas->mapUnitsPerPixel() );
+      snapLayer.mTolerance = QgsTolerance::vertexSearchRadius( vlayer, mMapCanvas->mapRenderer() );
     }
     else
     {
@@ -248,7 +248,7 @@ int QgsMapCanvasSnapper::snapToBackgroundLayers( const QPoint& p, QList<QgsSnapp
       }
 
       //default snapping tolerance (returned in map units)
-      snapLayer.mTolerance = QgsTolerance::defaultTolerance( mMapCanvas->mapUnitsPerPixel() );
+      snapLayer.mTolerance = QgsTolerance::defaultTolerance( currentVectorLayer, mMapCanvas->mapRenderer() );
       snapLayer.mUnitType = QgsTolerance::MapUnits;
 
       snapLayers.append( snapLayer );