Managing some transparency and some view box positioning

Fix something.
I think solution is different and i have some idea that i tried but i'm not able to finish.

I Started to implement viewbox in different way.
if viewbox is present, a svg_matrix is created that represents a scale and traslate transformation.
This matrix is then applied as topmost transformation for every element of svg ( NEED HELP FOR THIS ).
This should be more correct than the minX and minY ( that works, but doesn't look like correct )