Zoom Viewing Rectangle w/ checkEnclosure

When the svg image is zoomed/panned, determine the size of the viewing rectangle. This example shows elements if they are fully contained in the viewing rectangle. Uses getCTM.
Computing the Viewing Rectangle:
upper left: X0 = - translationX / scale
upper left: Y0 = - translationY / scale
width: W = X0 + svgWidth / scale
height: H = Y0 + svgHeight / scale

OK in:IE11/CH31/FF23