This patch makes a few changes to the way we calculate line-height:
- `line-height: normal` is now resolved using metrics from the used
font (specifically, round(A + D + lineGap)).
- `line-height: calc(...)` is now resolved at style compute time.
- `line-height` values are now absolutized at style compute time.
As a consequence of the above, we no longer need to walk the DOM
ancestor chain looking for line-heights during style computation.
Instead, values are inherited, resolved and absolutized locally.
This is not only much faster, but also makes our line-height metrics
match those of other engines like Gecko and Blink.
Fetching the viewport rect is currently somewhat expensive, since it
requires finding the navigable the document is active in.
We can avoid the cost of repeated calls by simply allowing StyleComputer
to cache the viewport rect at the start of style computation.
We have two known PlatformObjects that need to implement some of the
behavior of LegacyPlatformObjects to date: Window, and HTMLFormElement.
To make this not require double (or virtual) inheritance of
PlatformObject, move the behavior of LegacyPlatformObject into
PlatformObject. The selection of LegacyPlatformObject behavior is done
with a new bitfield of feature flags instead of a dozen virtual
functions that return bool. This change simplifies every class involved
in the diff with the notable exception of Window, which now needs some
ugly const casts to implement named property access.
When the caller of NumericCalculationNode::resolve() does not provide
a percentage_basis, it expects the method to return a raw percentage
value.
Fixes crashing on https://discord.com/login
The grammar which we implemented did not match the spec, resulting in us
rejecting background positions which contained 'center' position
keywords.
Fixes: #22401
On platinenmacher.tech there is a document without a window. During
size attribute parsing the window pointer is dereferenced which
causes a crash. This checks for the window to be actually there
before dereferencing.
As the spec points out:
> Note that a pair of keywords can be reordered while a combination of
> keyword and length or percentage cannot. So center left is valid while
> 50% left is not.
This was a bug in our implementation of alternative 2 of css-values-3,
resulting in the following CSS failing to be parsed:
`background-position: center right;`
This commit fixes the issue as part of an update of the parsing to
css-values-4. As far as I can tell, the grammar is equivalent - but
simpler to implement due to the lack of optional values.
The fix for this issue is also as part of alternative 2 parsing in the
new grammar.
Progress towards: #22401
Instead of serializing two calc() values to String and then comparing
those strings, we can now compare calc() values by actually traversing
their internal CalculationNode tree.
This makes style recomputation faster on pages with lots of calc()
values since it's now much cheaper to check whether a property with
some calc() value actually changed.
In 4bc38300ad this function was modified
to accept only Angle instead of being templated, with the purpose of
preventing Length from being passed.
This change reverts the function to being templated but adds a
constraint specifically forbidding Length. This adjustment will allow
for the future use of Frequency, Number, Time, etc., if we would want.
CSSPixels should not be wrapped into CSS::Length before being passed
to resolved() to end up resolving percentages without losing
precision.
Fixes thrashing layout when 33.3333% width is used together with
"box-sizing: border-box".
Before this change, parsed grid-template-columns/grid-template-rows
were represented as two lists: line names and track sizes. The problem
with this approach is that it erases the relationship between tracks
and their names, which results in unnecessarily complicated code that
restores this data (incorrectly if repeat() is involved) during layout.
This change solves that by representing line definitions as a list of
sizes and names in the order they were defined.
Visual progression https://genius.com/
This is quite niche, but lets us convert parsing methods to accepting
TokenStream, while still being able to call them when we just have a
lone token. Specifically we'll use this in the next commit, but it's
likely to also be useful as a stop-gap measure when converting more
parsing methods.
Frequently we want to parse "anything that's a `<length-percentage>`" or
similar, which could be a constant value or a calculation, but didn't
have a nice way of doing so. That meant repeating the same "try and
parse a dimension, see if it's the right type, then maybe try and parse
a calculation and see if that's the right type" boilerplate code. Or
more often, forgetting about calculations entirely.
These helpers should make that a lot more convenient to do. And they
also use TokenStream, so we can eventually drop the old `parse_length()`
method.
Before this change, we would only cache and reuse Gfx::ScaledFont
instances for downloaded CSS fonts.
By moving it into Gfx::VectorFont, we get caching for all vector fonts,
including local system TTFs etc.
This avoids a *lot* of style invalidations in LibWeb, since we now vend
the same Gfx::Font pointer for the same font when used repeatedly.
