This fixes#99 for me.
Without this fix I end up with paddings of `3.333333` because my DPI is
`125.0` on Linux. If I set it to `144.0` manually so that the `/ 72`
gives me a clean `2.0`, the blurry fonts are gone.
I do think the calculation here is correct (even though I'm not sure
whether we should use 72? Why not 96? Or another system value?), so
let's use `std.math.floor` to get us to a "clean" padding of `3.0`.
That also solves blurry fonts for me.
ead997b5ec