Use the new Gfx::Font::AllowInexactSizeMatch parameter when doing CSS
font lookups. This fixes a long-standing issue where text with e.g text
with "font-size:12px" would be larger than "font-size:13px" since there
was an exact match for 12, but none for 13 (so we'd fall back to 10).
This works a little differently from the other caches - ALL rules
containing a pseudo-element are in this bucket. This lets us only look
at this bucket when finding styles for a pseudo-element, and ignore it
if we're not.
Since each selector can only have zero or one pseudo-element, we match
against it as a separate step, before matching the rest of the
selector. This should be faster, but mostly I did this because I could
not figure out how else to stop selectors without a pseudo-element from
matching the pseudo-element, eg so `.foo` styles don't affect
`.foo::before`.
"5em" means 5*font-size, but by forcing "em" to mean the presentation
size of the bitmap font actually used, we broke a bunch of layouts that
depended on a correct interpretation of "em".
This means that "em" units will no longer be relative to the exact
size of the bitmap font in use, but I think that's a compromise we'll
have to make, since accurate layouts are more important.
This yields a visual progression on both ACID2 and ACID3. :^)
The ICB (initial containing block) gets its style from StyleComputer's
create_document_style(). It's basically a generic style for the root of
the layout tree.
With this patch, we now assign the width and height of the viewport rect
as two CSS "px" lengths to the "width" and "height" properties of the
ICB style. (Previously they were just defaulting to "auto" and we
assigned override dimensions during layout.)
This fixes an issue where position:absolute elements with relative width
and/or height were not dimensioned correctly, since the values were
relative to the width and/or height of the ICB style.
After style computation, every StyleProperties has a value for every
PropertyID. Given this, it's simpler, faster and less memory-heavy to
use an Array instead of a HashMap. :^)
This patch introduces the StyleComputer::RuleCache, which divides all of
our (author) CSS rules into buckets.
Currently, there are two buckets:
- Rules where a specific class must be present.
- All other rules.
This allows us to check a significantly smaller set of rules for each
element, since we can skip over any rule that requires a class attribute
not present on the element.
This takes the typical numer of rules tested per element on Discord from
~16000 to ~550. :^)
We can definitely improve the cache invalidation. It currently happens
too often due to media queries. And we also need to make sure we
invalidate when mutating style through CSSOM APIs.
Previously we would re-run the entire CSS selector machinery for each
property resolved. Instead of doing that, we now resolve a final set of
custom property key/value pairs at the start of the cascade.
- Replace "auto" with "auto const" where appropriate.
- Remove an unused struct.
- Make sort_matching_rules() a file-local static function.
- Remove some unnecessary includes.
Modified the test-page because FontDatabase looks for exact font-weight
matches, so requesting weight 800 in a font that only has 700, causes
it to return the default font instead. So, we ask for 700 here.
The actual fix is to improve our font-matching but I am trying not to
get distracted today. :^)
CSS has rules about automatic blockification or inlinification of boxes
in certain circumstances.
This patch implements automatic blockification of absolutely positioned
and floating elements. This makes the smile appear on ACID2. :^)
We now detect situations like this, where variables infinitely recur,
without crashing:
```css
div {
--a: var(--b);
--b: var(--a);
background: var(--a);
}
p {
--foo: var(--foo);
background: var(--foo);
}
```
We now stop processing variables once a length of 16384 tokens is
reached. This is an arbitrary number, but should be far beyond what
anyone will reasonably use, and small enough to not crash.
If a property is custom or contains a `var()` reference, it cannot be
parsed into a proper StyleValue immediately, so we store it as an
UnresolvedStyleValue until the property is compute. Then, at compute
time, we resolve them by expanding out any `var()` references, and
parsing the result.
The implementation here is very naive, and involves copying the
UnresolvedStyleValue's tree of StyleComponentValueRules while copying
the contents of any `var()`s it finds along the way. This is quite an
expensive operation to do every time that the style is computed.
While right now this doesn't save much complexity, it will do once we
care about multiple background layers per node. Then, having a single
repeat value per layer will simplify things.
It also means we can remove the pseudo-property concept entirely! :^)
This is step 1 in removing the two `background-repeat-x/y`
pseudo-properties. Since adding the concept of compound StyleValues, we
don't need `background-repeat` to be split in two any more.
This is done a bit differently from other properties: using a
TokenStream instead of just a Vector of ComponentValues. The reason for
this is, we can then use call the same function when parsing the
`background` shorthand. Otherwise, we would have to know in advance how
many values to pass down, which basically would involve duplicating the
`background-position` parsing code inside `background`.
The StyleValue is PositionStyleValue, since it represents a
`<position>`: https://www.w3.org/TR/css-values-4/#typedef-position
Unfortunately, background-position's parsing is a bit different from
`<position>`'s, (background-position allows 3-value syntax and
`<position>` doesn't) so we'll need to come back and write a different
parsing function for that later.
Previously: CSSImportRule::loaded_style_sheet() (and others) depend on
the definition of class CSSStyleSheet. Meanwhile,
CSSStyleSheet::template for_each_effective_style_rule (and others)
depend on the definition of class CSSImportRule.
This hasn't caused any problems so far because CSSStyleSheet.h happened
to be always included after CSSImportRule.h (in part due to alphabetical
ordering).
However, a compilation unit that (for example) only contains
#include <Userland/Libraries/LibWeb/CSSImportRule.h>
would fail to compile.
This patch resolves this issue by pushing the inline definition of
Web::CSS::CSSStyleSheet::for_each_effective_style_rule and
for_first_not_loaded_import_rule into a different file, and adding the
missing headers.
This doesn't work correctly in the new world where fonts are resolved
during the CSS cascade. Let's patch it out with a FIXME and get back to
it once everything has fallen into place.
Resolved style is a spec concept that refers to the weird mix of
computed style and used style reflected by getComputedStyle().
The purpose of this class is to produce the *computed* style for a given
element, so let's call it StyleComputer.
