There are a few canvas2d-related dependencies that haven't updated, but they
only use euclid internally so that's not blocking landing the rest of the
changes.
Given the size of this patch, I think it's useful to get this landed as-is.
Before this change, if we needed to create a Font which we've already
created, but at a new size, then we'd fetch the FontTemplateInfo again.
If the bytes of the font are held in memory, then this could be
expensive as we need to pass those bytes over IPC.
Prior to this change, if none of the fonts specified in CSS contained a
glyph for a codepoint, we tried only one fallback font. If that font
didn't contain the glyph, we'd give up.
With this change, we try multiple fonts in turn. The font names we try
differ across each platform, and based on the codepoint we're trying to
match. The current implementation is heavily inspired by the analogous
code in Gecko, but I've used to ucd lib to make it more readable,
whereas Gecko matches raw unicode ranges.
This fixes some of the issues reported in #17267, although colour emoji
support is not implemented.
== Notes on changes to WPT metadata ==
=== css/css-text/i18n/css3-text-line-break-opclns-* ===
A bunch of these have started failing on macos when they previously
passed.
These tests check that the browser automatically inserts line breaks
near certain characters that are classified as "opening and closing
punctuation". The idea is that if we have e.g. an opening parenthesis,
it does not make sense for it to appear at the end of a line box; it
should "stick" to the next character and go into the next line box.
Before this change, a lot of these codepoints rendered as a missing
glyph on Mac and Linux. In some cases, that meant that the test was
passing.
After this change, a bunch of these codepoints are now rendering glyphs
on Mac (but not Linux). In some cases, the test should continue to pass
where it previously did when rendering with the missing glyph.
However, it seems this has also exposed a layout bug. The "ref" div in
these tests contains a <br> element, and it seems that this, combined
with these punctuation characters, makes the spacing between glyphs ever
so slightly different to the "test" div. (Speculation: might be
something to do with shaping?)
Therefore I've had to mark a bunch of these tests failing on mac.
=== css/css-text/i18n/css3-text-line-break-baspglwj-* ===
Some of these previously passed on Mac due to a missing glyph. Now that
we're rendering the correct glyph, they are failing.
=== css/css-text/word-break/word-break-normal-bo-000.html ===
The characters now render correctly on Mac, and the test is passing. But
we do not find a suitable fallback font on Linux, so it is still failing
on that platform.
=== css/css-text/word-break/word-break-break-all-007.html ===
This was previously passing on Mac, but only because missing character
glyphs were rendered. Now that a fallback font is able to be found, it
(correctly) fails.
=== mozilla/tests/css/font_fallback_* ===
These are new tests added in this commit. 01 and 02 are marked failing
on Linux because the builders don't have the appropriate fonts installed
(that will be a follow-up).
Fix build errors from rebase
FontTemplateDescriptor can no longer just derive(Hash). We need to
implement it on each component part, because the components now
generally wrap floats, which do not impl Hash because of NaN. However in
this case we know that we won't have a NaN, so it is safe to manually
impl Hash.
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.
WR now has a concept of font templates and font instances. This
makes the WR font interfaces closer to Cairo and Gecko, and also
makes some future performance optimizations possible.
A font template is the font family, and data backing the font.
A font instance is a reference to a font template and per-instance
options, such as font size, anti-aliasing settings etc.
To update Servo in a minimally invasive way, I added a new font
cache call, that creates a font instance. This means that when
a font is created, and doesn't exist in the cache there are now
two calls to the font cache thread. We could refactor the font
cache to make this work in one call, which we should do in the
future. However, refactoring the font cache is a large chunk of
work by itself. The extra call is only when a font doesn't already
exist in the font context cache, so it should have minimal
performance impact.
Fix panic when font face name is not available
I got a panic in Servo when I ran it with `RUST_LOG=debug`, which was due to `FT_Get_Postscript_Name` returning a null pointer.
I'm not sure how to add a test for this, so there is none right now.
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This removes paint threads, rust-layers dependency, and changes
optional webrender types to be required.
The use_webrender option has been removed, however I've left
the "-w" command line option in place so that wpt
runner can continue to pass that. Once it's removed from there
we can also remove the -w option.
Once this stage is complete, it should be fine to change the
display list building code to generate webrender display
lists directly and avoid the conversion step.
Replace character indices with UTF-8 byte offsets throughout the code dealing
with text shaping and breaking. This eliminates a lot of complexity when
converting from one to the other, and interoperates better with the rest of
the Rust ecosystem.
WebRender is an experimental GPU accelerated rendering backend for Servo.
The WebRender backend can be specified by running Servo with the -w option (otherwise the default rendering backend will be used).
WebRender has many bugs, and missing features - but it is usable to browse most websites - please report any WebRender specific rendering bugs you encounter!
