- Better detect situations where emoji is necessary by looking ahead one
character while laying out. This allow processing Unicode presentation
selectors. When detecting emoji, put emoji fonts at the front of
fallback lists for all platforms.
This enables monochrome emoji on Windows. Full-color emoji on Windows
probably needs full support for processing the COLR table and drawing
separate glyph color layers.
- Improve the font fallback list on FreeType platforms. Ideally, Servo
would be able to look through the entire font list to find the best
font for a certain character, but until that time we can make sure the
font list contains the "Noto Sans" fonts which cover most situations.
Fixes#31664.
Fixes#12944.
This allows sharing font templates, fonts, and platform fonts across
layout threads. It's the first step toward storing web fonts in the
layout versus the shared `FontCacheThread`. Now fonts and font groups
have some locking (especially on FreeType), which will probably affect
performance. On the other hand, we measured memory usage and this saves
roughly 40 megabytes of memory when loading servo.org based on data from
the memory profiler.
Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Mukilan Thiyagarajan <mukilan@igalia.com>
Bumps Stylo to servo/stylo#37
`white-space` is split into `white-space-collapse` and `text-wrap-mode`:
| white-space | white-space-collapse | text-wrap-mode |
| ----------- | -------------------- | -------------- |
| normal | collapse | wrap |
| nowrap | collapse | nowrap |
| pre-wrap | preserve | wrap |
| pre | preserve | nowrap |
| pre-line | preserve-breaks | wrap |
| - | preserve-breaks | nowrap |
Note this introduces a combination that wasn't previously possible,
but I think the existing logic can handle it well enough.
The old `allow_wrap()` is replaced by checking whether `text-wrap-mode`
is set to `wrap`.
The old `preserve_newlines()` is replaced by checking whether
`white-space-collapse` is *not* set to `collapse`.
The old `preserve_spaces()` is replaced by checking whether
`white-space-collapse` is set to `preserve`.
Instead of using a simple `Atom` to identify a local font, use a data
structure. This allows us to carry more information necessary to
identify a local font (such as a path on MacOS). We need this for the
new version of WebRender, as fonts on MacOS now require a path.
This has a lot of benefits:
1. We can avoid loading fonts without paths on MacOS, which should
avoid a lot of problems with flakiness and ensure we always load the
same font for a given identifier.
2. This clarifies the difference between web fonts and local fonts,
though there is more work to do here.
3. This avoid a *lot* of font shenanigans, such as trying to work
backwards from the name of the font to the path of the font we
actually matched. In general, we can remove a lot of code trying to
accomplish these shenanigans.
4. Getting the font bytes always returns an `Arc` now avoiding an extra
full font copy in the case of Canvas.
Synthetic small caps is supported by the font subsystem, but this is
disabled in Layout 2020. We can turn this on to bring support to parity
with the old layout system.
In addition to turning on synthetic small-caps this change also improves
the way that they work. Before, synthetic small caps meant that every
character was a small version of capitalized character. After this
change, capital letters are larger than small caps versions of small
letters -- matching other browsers and the common expectation of how
small caps works.
It's not possible anymore, in the presence of min() / max(), to split a
<length-percentage> value into a <length> and a <percentage> component.
Tweak word_spacing to do what Gecko does (resolving it in advance).
We can encounter control characters here, for example when processing a
<pre> element which contains newlines. Control characters are inherently
non-printing, therefore if we try to call find_by_codepoint for these
characters we will end up triggering an unnecessary font fallback
search.
Unfortunately, this required quite a bit of changes to the non-test
code. That's because FontContext depends on a FontCacheThread, which in
turn depends on a CoreResourceThread and therefore lots of other data
structures.
It seemed like it would be very difficult to instantiate a FontContext
as it was, and even if we could it seems like overkill to have all these
data structures present for a relatively focused test.
Therefore, I created a FontSource trait which represents the interface
which FontContext uses to talk to FontCacheThread. FontCacheThread then
implements FontSource. Then, in the test, we can create a dummy
implementation of FontSource rather than using FontCacheThread.
This actually has the advantage that we can make our dummy
implementation behave in certain specific way which are useful for
testing, for example it can count the number of times
find_font_template() is called, which helps us verify that
caching/lazy-loading is working as intended.
This is a step towards fixing #17267. To fix that, we need to be able to
try various different fallback fonts in turn, which would become
unweildy with the prior eager-loading strategy.
Prior to this change, FontGroup loaded up all Font instances, including
the fallback font, before any of them were checked for the presence of
the glyphs we're trying to render.
So for the following CSS:
font-family: Helvetica, Arial;
The FontGroup would contain a Font instance for Helvetica, and a Font
instance for Arial, and a Font instance for the fallback font.
It may be that Helvetica contains glyphs for every character in the
document, and therefore Arial and the fallback font are not needed at
all.
This change makes the strategy lazy, so that we'll only create a Font
for Arial if we cannot find a glyph within Helvetica. I've also
substantially refactored the existing code in the process and added
some documentation along the way.
First, we define computed::CSSPixelLength which contains a CSSFloat, a
pixel value, and then we replace computed::Length with CSSPixelLength.
Therefore, the |ComputedValue| of NoCalcLength, AbsoluteLength,
FontRelativeLength, ViewportPercentageLength, CharacterWidth, and
PhysicalLength is CSSPixelLength.
Besides, we drop NonNegativeAu, and replace computed::NonNegativeLength
with NonNegative<computed::Length>. (i.e. NonNegative<CSSPixelLength>)
The alias is left there temporarilly and will be removed completely in a later commit where
also components/style/gecko/generated/structs_{debug|release}.rs are re-generated (they still
use the old alias).
