Using fixed-point saturated arithmetics for CSSPixels allows to avoid
accumulating floating-point errors.
This implementation is not complete yet: currently saturated
arithmetics implemented only for addition. But it is enough to not
regress any of layout tests we have :)
See https://github.com/SerenityOS/serenity/issues/18566
Instead of just measuring the layout viewport, we now measure overflow
in every box that is a scroll container.
This has the side effect of no longer creating paintables for layout
boxes that didn't participate in layout. (For example, empty/anonymous
boxes that were ignored by flex itemization.)
Such boxes are now marked as "(not painted)" in the layout tree dumps,
as they have no paintable to dump geometry from.
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 change addresses the incorrect assumption that the available width
inside a grid item is equal to the width of the track it belongs to.
For instance, if a grid item has a width of 200px, the available width
inside that item is also 200px regardless of its column(s) base size.
To solve this issue, it was necessary to move the final resolution of
grid items to occur immediately after the final column track sizes are
determined. By doing so, it becomes possible to obtain correct
available width inside grid items while resolving the row track sizes.
This patch does three things:
- Factors out the code that determines whether a box will create a new
formatting context for its children (and which type of context)
- Uses that code to mark all formatting context roots in layout tree
dumps. This makes it much easier to follow along with layout since
you can now see exactly where control is transferred to a new
formatting context.
- Rebaselines all existing layout tests, since the output format has
changed slightly.
