Visible elements in a WPF canvas

I have a WPF Canvas and a lot of Shapes (StreamGeometry / Path) added to it. I have ScaleTransform defined to zoom into specific region.

I have zoomed into a arbitrary space开发者_开发知识库 in the canvas and the Shapes are scaled. Now, is it possible to get the Shapes that are in the visible region of the Canvas.

Thanks for any pointers.

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You can use HitTest to perform a hit test against the Canvas's bounding rectangle. For details, see Hit Testing in the Visual Layer and refer to the sample for hit testing with DrawingVisuals.

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Should this help?

Iterate thru all children shapes of canvas and check the following for each myShape ....

     hitArea
       = new EllipseGeometry(
           new Point(Canvas.GetLeft(myShape), Canvas.GetTop(myShape)),
           1.0, 
           1.0); 

     VisualTreeHelper.HitTest(
          myShape, null,
          new HitTestResultCallback(HitTestCallback),
          new GeometryHitTestParameters(hitArea)); 

     public HitTestResultBehavior HitTestCallback(HitTestResult result)
     {
         if (result.VisualHit == myShape)
         {
              //// This shape is on the visible area.
         }
     }