[Wpf] Set TextRenderingHint when creating the drawing context

Xwt.WPF/Xwt.WPFBackend/ContextBackendHandler.cs

@@ -285,7 +285,6 @@ namespace Xwt.WPFBackend
 				stringFormat.Trimming = trimming;
 			}
 
-			c.Graphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
 			c.Graphics.DrawString (layout.Text, layout.Font.ToDrawingFont (), c.Brush,
 			                       new RectangleF ((float)x, (float)y, (float)measure.Width, h),
 			                       stringFormat);

Xwt.WPF/Xwt.WPFBackend/DrawingContext.cs

@@ -43,8 +43,10 @@ namespace Xwt.WPFBackend
 			graphics.CompositingQuality = CompositingQuality.HighSpeed;
 
 			// necessary for correct text rendering with System.Drawing
-			graphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.SingleBitPerPixelGridFit;
+			//graphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.SingleBitPerPixelGridFit;
-			
+			// necessary for none-pixelated text drawing in images, revert to above line if it introduces a performance problem
+			graphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
+
 			Graphics = graphics;
 		}