Added utility function toLayerCoords

git-svn-id: http://svn.osgeo.org/qgis/trunk@5192 c8812cc2-4d05-0410-92ff-de0c093fc19c

Author: wonder

src/gui/qgsmaptool.cpp

@@ -15,8 +15,10 @@
 /* $Id$ */
 
 #include "qgsmaptool.h"
+#include "qgsmaplayer.h"
 #include "qgsmapcanvas.h"
 #include "qgsmaptopixel.h"
+#include "qgsproject.h"
 #include <QAction>
 
 QgsMapTool::QgsMapTool(QgsMapCanvas* canvas)
@@ -36,6 +38,30 @@ QgsPoint QgsMapTool::toMapCoords(const QPoint& point)
 }
 
 
+QgsPoint QgsMapTool::toLayerCoords(QgsMapLayer* layer, const QPoint& point)
+{
+  // FIXME: this information should be accessible elsewhere without accessing QgsProject!
+  bool projectionsEnabled = (QgsProject::instance()->readNumEntry("SpatialRefSys","/ProjectionsEnabled",0)!=0);
+  
+  if (projectionsEnabled)
+  {
+  
+    if (!layer || !layer->coordinateTransform())
+      return QgsPoint(0,0);
+    
+    // first transform from canvas coords to map coordinates
+    QgsPoint pnt = toMapCoords(point);
+    
+    // then convert from 
+    return layer->coordinateTransform()->transform(pnt, QgsCoordinateTransform::INVERSE);
+  }
+  else
+  {
+    return toMapCoords(point);
+  }
+}
+
+
 QPoint QgsMapTool::toCanvasCoords(const QgsPoint& point)
 {
   double x = point.x(), y = point.y();

src/gui/qgsmaptool.h

@@ -20,6 +20,7 @@
 #include <QCursor>
 #include <QString>
 
+class QgsMapLayer;
 class QgsMapCanvas;
 class QMouseEvent;
 class QgsPoint;
@@ -74,6 +75,9 @@ class QgsMapTool
     //! transformation from screen coordinates to map coordinates
     QgsPoint toMapCoords(const QPoint& point);
 
+    //! transformation from screen coordinates to layer's coordinates
+    QgsPoint toLayerCoords(QgsMapLayer* layer, const QPoint& point);
+    
     //! transformation from map coordinates to screen coordinates
     QPoint toCanvasCoords(const QgsPoint& point);