This fixes a plethora of rounding problems on many websites.
In the future, we may want to replace this with fixed-point arithmetic
(bug #18566) for performance (and consistency with other engines),
but in the meantime this makes the web look a bit better. :^)
There's a lot more things that could be converted to doubles, which
would reduce the amount of casting necessary in this patch.
We can do that incrementally, however.
This avoids a ton of work when painting large documents. Even though it
would eventually get clipped by the painter anyway, by bailing out
earlier, we avoid a lot more work (UTF-8 iteration, OpenType lookups,
etc).
It would be even nicer if we could skip entire line boxes, but we don't
have a fast way to get the bounding rect of a line box at the moment.
Store the ratio between device and CSS pixels on the PaintContext, so
that it can convert between the two.
Co-authored-by: MacDue <macdue@dueutil.tech>
We'll have to do something more proper to support this scenario
eventually, but for now let's at least not crash just because somebody
put an SVG <path> inside an HTML element.
