We got some errors while loading https://twinings.co.uk/ about this
interface missing, and it looked fairly simple so I sketched it out.
Note that I did leave some FIXMEs where it's not clear exactly which
metrics we should be returning.
This object is available as `window.internals` (or just `internals`) and
is only accessible while running in "test mode".
This first version only has one API: gc(), which triggers a garbage
collection immediately.
In the future, we can add more APIs here to help us test parts of the
engine that are hard or impossible to reach via public web APIs.
Although DistinctNumeric, which is supposed to abstract the underlying
type, was used to represent CSSPixels, we have a whole bunch of places
in the layout code that assume CSSPixels::value() returns a
floating-point type. This assumption makes it difficult to replace the
underlying type in CSSPixels with a non-floating type.
To make it easier to transition CSSPixels to fixed-point math, one step
we can take is to prevent access to the underlying type using value()
and instead use explicit conversions with the to_float(), to_double(),
and to_int() methods.
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.
For example, consider the attribute:
interface Element {
[PutForwards=value] readonly attribute DOMTokenList classList;
}
When `classList` is set, we should instead set the attribute `value` on
the `classList` attribute of the Element interface.
This is where it belongs according to the spec, and where these methods'
IDL will be placed.
This forces us to implement a few steps closer to the spec as well.
LibGUI and WebDriver (read: JSON) API boundaries use DeprecatedString,
so that is as far as these changes can reach.
The one change which isn't just a DeprecatedString to String replacement
is handling the "null" prompt response. We previously checked for the
null DeprecatedString, whereas we now represent this as an empty
Optional<String>.
