The CSS box-shadow property takes 2-4 properties that are `<length>`s,
those being:
- offset-x
- offset-y
- blur-radius
- spread-radius
Previously these were resolved directly to concrete Lengths at parse
time, but now they will be parsed as LengthStyleValues and/or
CalculatedStyleValues and be stored that way until styles are later
resolved.
As it turns out, making everyone piggyback on HTML::ImageRequest had
some major flaws, as HTMLImageElement may decide to abort an ongoing
fetch or wipe out image data, even when someone else is using the same
image request.
To avoid this issue, this patch introduces SharedImageRequest, and then
implements ImageRequest on top of that.
Other clients of the ImageRequest API are moved to SharedImageRequest
as well, and ImageRequest is now only used by HTMLImageElement.
This fixes an issue with image data disappearing and leading to asserts
and/or visually absent images.
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 is all ad-hoc since no spec currently exists for this behavior.
Basically, ImageStyleValue now uses ImageRequest for fetching and
decoding of images.
This already leads to visible improvements on many websites.
This fixes the issue that currently we use "auto" as initial value for
grid-template-column and grid-template-rows although spec says it
should be "none". This makes a lot of difference for these properties
because currently we represent "auto" as a list with one auto-sized
track which means initial value for grid-template-column defines one
"explicit" track while it should define none of them.
This change makes grid-auto-columns/rows be applied to the correct
tracks when initial values is used for grid-template-column/rows.
We have double precision in the parser, and currently use doubles for
most of layout, so we might as well keep that extra precision inside
NumberStyleValue too.
Having one StyleValue for `<number>` and `<integer>` is making user code
more complicated than it needs to be. We know based on the property
being parsed, whether it wants a `<number>` or an `<integer>`, so we
can use separate StyleValue types for these.
Specifically, stop letting NumericStyleValues holding `0` from
pretending to hold a Length. The parser is now smart enough that we
don't have to do this. :^)
Only NumericStyleValue holds integers.
I'm not sure our current distinction between NumericStyleValue holding
an integer or non-integer is useful given it always returns a float.
:thonk:
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.
