Merge pull request #8 from jorgensigvardsson/PCL

Proper calculation of label control position and angle.

Examples/ShowcaseApp.WPF/Templates/TestTemplates.xaml

@@ -96,11 +96,11 @@
                 </ControlTemplate>
             </Setter.Value>
         </Setter>
+        <Setter Property="RenderTransformOrigin" Value="0.5,0.5"></Setter>
         <Setter Property="RenderTransform">
             <Setter.Value>
-                <RotateTransform CenterX="0.5" CenterY="0.5" Angle="{Binding RelativeSource={RelativeSource AncestorType=gxl:EdgeLabelControl} , Path=Angle}"/>
+                <RotateTransform CenterX="0" CenterY="0" Angle="{Binding RelativeSource={RelativeSource AncestorType=gxl:EdgeLabelControl} , Path=Angle}"/>
             </Setter.Value>
         </Setter>
-
     </Style>
 </ResourceDictionary>

GraphX.Controls/Controls/EdgeLabels/EdgeLabelControl.cs

@@ -105,7 +105,6 @@ namespace GraphX
             else Arrange(LastKnownRectSize);
         }
 
-        
 
         private static double GetLabelDistance(double edgeLength)
         {
@@ -190,32 +189,34 @@ namespace GraphX
                     p2 = newp2;
                 }
             }
-            // align the point so that it  passes through the center of the label content
-            var p = p1;
-            var desiredSize = DesiredSize;
-            p.Offset(-desiredSize.Width / 2, -desiredSize.Height / 2);
 
-            // move it "edgLength" on the segment
-            double tmpAngle;
-            var angleBetweenPoints = tmpAngle = MathHelper.GetAngleBetweenPoints(p1, p2);
-            //set angle in degrees
+            // The label control should be laid out on a rectangle, in the middle of the edge
+            var angleBetweenPoints = MathHelper.GetAngleBetweenPoints(p1, p2);
+            var desiredSize = DesiredSize;
+            bool flipAxis = p1.X > p2.X; // Flip axis if source is "after" target
+
+            // Calculate the center point of the edge
+            var centerPoint = new Point(p1.X + edgeLength * Math.Cos(angleBetweenPoints), p1.Y - edgeLength * Math.Sin(angleBetweenPoints));
             if (EdgeControl.AlignLabelsToEdges)
             {
-                if (p1.X > p2.X)
-                    tmpAngle = MathHelper.GetAngleBetweenPoints(p2, p1);
-                Angle = -tmpAngle * 180 / Math.PI;
+                // If we're aligning labels to the edges make sure add the label vertical offset
+                var yEdgeOffset = EdgeControl.LabelVerticalOffset;
+                if (flipAxis) // If we've flipped axis, move the offset to the other side of the edge
+                    yEdgeOffset = -yEdgeOffset;
+
+                // Adjust offset for rotation. Remember, the offset is perpendicular from the edge tangent.
+                // Slap on 90 degrees to the angle between the points, to get the direction of the offset.
+                centerPoint.Y -= yEdgeOffset * Math.Sin(angleBetweenPoints + Math.PI / 2);
+                centerPoint.X += yEdgeOffset * Math.Cos(angleBetweenPoints + Math.PI / 2);
+
+                // Angle is in degrees
+                Angle = -angleBetweenPoints * 180 / Math.PI;
+                if (flipAxis)
+                    Angle += 180; // Reorient the label so that it's always "pointing north"
             }
-  
-            p.Offset(edgeLength * Math.Cos(angleBetweenPoints), -edgeLength * Math.Sin(angleBetweenPoints));
-            if (EdgeControl.AlignLabelsToEdges)
-                p = MathHelper.RotatePoint(new Point(p.X, p.Y - EdgeControl.LabelVerticalOffset), p, Angle);
-            //optimized offset here
-            /*float x = 12.5f, y = 12.5f;
-            double sin = Math.Sin(angleBetweenPoints);
-            double cos = Math.Cos(angleBetweenPoints);
-            double sign = sin * cos / Math.Abs(sin * cos);
-            p.Offset(x * sin * sign + edgeLength * cos, y * cos * sign - edgeLength * sin);*/
-            LastKnownRectSize = new Rect(p.X,p.Y, desiredSize.Width, desiredSize.Height);
+
+            LastKnownRectSize = new Rect(centerPoint.X - desiredSize.Width / 2, centerPoint.Y - desiredSize.Height / 2, desiredSize.Width, desiredSize.Height);
+            
             Arrange(LastKnownRectSize);
         }