Compute the requested size in pixels or points, depending on the target format
Compute the requested size in pixels or points, depending on the target format

PNG requires pixels.

PDF/PS/EPS require points.

SVG surfaces can use any units; we'll deal with this later.

Part-of: <https://gitlab.gnome.org/GNOME/librsvg/-/merge_requests/547>

GNOME/librsvg,GNOME/librsvg,GNOME/librsvg,GNOME/librsvg