mostly ok, but why magic number?
Revert "mostly ok, but why magic number?"

This reverts commit 04ac2a302631657d5ce5c35be327ddfea44a93f4.
Revert "rendering is now robust w.r.t. resizing/rescaling of container element"

This reverts commit d8c1710a2d7cd7d8cfaef8d80028cb837554a6c1.
clipping issues solved by replacing getBBox() with getBoundingClientRect()