The postitioning enum values are used by the position CSS property.
Unfortunately, the prior naming clashes with the CSS Values-4 type
named position, which will be implemented in a later commit.
The existing implementation has some pre-existing issues where it is
incorrectly assumes that byte offsets are given through the IDL instead
of UTF-16 code units. While making these changes, leave some FIXMEs for
that.
The value is originally set using a `CSSPixels` value converted to
double, then when it is used it is always converted back to a
`CSSPixels` again. Let's just store it as that instead.
Some replaced elements can have intrinsic aspect ratios but no
intrinsic size. In these cases, the tentative sizes are undefined, and
can therefore sometimes be zero. However, when resolving the size
constraints, we are already guaranteed to have an intrinsic aspect
ratio, so let's use that instead to calculate the resolved sizes.
Previously, we would run through all the constraints in the spec one by
one, but if we check and resolve each constraint in the order they are
defined in the spec, only the first four will ever match.
This leads me to believe that these constraints are meant to be
mutually exclusive instead, meaning that we must check the most
specific constraints first and return upon the first resolution that
matches.
This allows us to retain perfect precision for aspect ratios derived
from either the intrinsic sizes of replaced elements, or the
`aspect-ratio` CSS property.
There's a particularly awkward case where the static position of an
abspos child of a flex container is dependent on its height. This can
happen when `align-items: center` is in effect, as we have to adjust
the abspos child's Y position by half of its height.
This patch solves the issue by reordering operations in the abspos
height resolution algorithm, to make sure that height is resolved
before the static position is calculated.
Since we always pass the px value as an argument to resolved(), we can
pass it directly as CSSPixels instead of wrapping it in Length. This
approach allows us to avoid converting to a double, resulting in fewer
precision issues.
This is intended to annotate conversions from unknown floating-point
values to CSSPixels, and make it more obvious the fp value will be
rounded to the nearest fixed-point value.
In general it is not safe to convert any arbitrary floating-point value
to CSSPixels. CSSPixels has a resolution of 0.015625, which for small
values (e.g. scale factors between 0 and 1), can produce bad results
if converted to CSSPixels then scaled back up. In the worst case values
can underflow to zero and produce incorrect results.
And treat them as "auto" for now, per CSS-SIZING-3, with a FIXME about
supporting more layout directions.
This fixes an issue on MDN where `height: max-content` was not
overriding height from non-CSS presentational hints.
When a box is sized under max-content constraint, any percentage value
set for max-width should be considered as if it were infinite. In other
words, it should have no effect on restricting the box's width.
There's no reason for this API to require a Layout::Box as input.
Any node that can have layout state is welcome, so this patch makes it
take NodeWithStyleAndBoxModelMetrics.
Changing `calculate_min_content_heigh()` and
`calculate_min_content_heigh()` to accept width as `CSSPixels`, instead
of `AvailableSize` that might be indefinite, makes it more explicit
that width is supposed to be known by the time height is measured.
This change has a bit of collateral damage which is rows height
calculation regression in `table/inline-table-width` that worked before
by accident.
Change associativity in computing of replaced element size to improve
precision of division.
Fixes vertically squashed image from Mozilla splash page MDN example.
Before this change, we always derived a box's baseline from its last
child, even if the last child didn't have any line boxes inside.
This caused baselines to slip further down vertically than expected.
There are more baseline alignment issues to fix, but this one was
responsible for a fair chunk of trouble. :^)
Once we've resolved the used flex item width & height, we should allow
percentage flex item sizes to resolve against them instead of forcing
flex items to always treat percentages as auto while doing intrinsic
sizing layout.
Regressed in 8dd489da61.
Make sure the insets and margins calculated according to the spec are
not later ignored and ad-hoc recomputed in
layout_absolutely_positioned_element.
Use the static position calculation in a couple of places where the
spec (and comment) was indicating it should be used.
Fixes#19362
While CSS 2.2 does tell us to use the "auto height for BFC roots"
calculation when resolving auto heights for abspos elements, that
doesn't make sense for other formatting context roots, e.g flex.
In lieu of implementing the entire new absolute positioning model from
CSS-POSITION-3, this patch borrows one small nugget from it: using
fit-content height as the auto height for non-BFC-root abspos elements.
Absolutely positioned elements should have their percentage sizes
resolved against the padding box of the containing block, not the
content box.
From CSS-POSITION-3 <https://www.w3.org/TR/css-position-3/#def-cb>
"..the containing block is formed by the padding edge of the ancestor.."
When resolving a percentage min-width or min-height size against a
containing block currently under a min-content constraint, we should act
as if the containing block has zero size in that axis.
This is technically "undefined behavior" per CSS 2.2, but it seems
sensible to mirror the behavior of max-height in the same situation.
It also appears to match how other engines behave.
Fixes#19242
The spec says the result of this algorithm is undefined in such cases,
and it appears that other engines yield a zero size.
More importantly, this prevents us from leaking a non-finite value into
the layout tree.
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.
Calculate a "preferred aspect ratio" based on the value of
`aspect-ratio` and the presence of a natural aspect ratio, and use that
in layout.
This is by no means complete or perfect, but we do now apply the given
aspect-ratio to things.
The spec is a bit vague, just saying to calculate sizes for
aspect-ratio'ed boxes the same as you would for replaced elements. My
naive solution here is to find everywhere we were checking for a
ReplacedBox, and then also accept a regular Box with a preferred aspect
ratio. This gets us pretty far. :^)
https://www.w3.org/TR/css-sizing-4/#aspect-ratio-minimum is not at all
implemented.
Having this here instead of in ReplacedBox means we can access it when
figuring out what the "preferred aspect ratio" is.
There's some inconsistency between specs about what this is called, but
they're moving towards referring to this as "natural width/height/
aspect-ratio", so let's copy that terminology.
This fixes an issue where images with padding and/or border did not have
their size adjusted for `border-box`, thereby becoming larger than
intended by the author.
These are only used during layout, and always within formatting context
code, so we might as well put them in FormattingContext and avoid having
to pass the LayoutState around all the time.
At one point in the past, we had some functions that were called across
different formatting context types, which necessitated making them
static and taking the LayoutState as a parameter.
In all cases, those functions were used to do incorrect hacks, all of
which we've replaced with more correct solutions. :^)
