svg scaling drawing or viewport ?

[Pro Turm <proturm6 gmail com>]

Hello,

how is a svg scaled depending on the set viewport? Is the whole drawing scaled first, and then only the viewport rendered  or   only the viewport is being rendered ? Is trimming the viewport the optimal strategy of scaling only a portion of the svg?

Are any known considerations regarding the scaling factor regarding memory size, performance and the order of the scaling factor itself ?

What does negative values in a viewport  would mean?

Any documentation suggestions about where to find your answers?

BR,