Previously if a font didn't have a space advance and it was needed to
make advances for tabs, Servo would try to read the advance from the
font. If the font didn't have a space glyph, Servo would panic. This
fixes that issue by making the space advance part of the `FontMetrics`
of a font (like Gecko) and falling back properly if that glyph doesn't
exist. The rendered glyph is still the "space" glyph, but we make
sure to select a font that supports that glyph explicitly.
This prevents a crash, but tabs still aren't handled properly. In
reality, tab stops should be calculated in layout and the size of
the space character of the current font shouldn't come into play.
The addition of the space advance metric will make this easier.
Fixes#32970.
Signed-off-by: Martin Robinson <mrobinson@igalia.com>
The old logic was assuming that all whitespace was a break opportunity,
and that no newlines would be preserved.
Note that text shaping considers the advance of a newline to be the same
as a space. This was problematic because if we have a segment with a
preserved space and newline, only the advance of the space should
contrinute to the size of the block container. Therefore, I'm changing
the breaker logic in other to have newline characters in their own
segment.
Then glyph_run_is_whitespace_ending_with_preserved_newline can just be
renamed to glyph_run_is_preserved_newline.
This patch is still not perfect because it doesn't check allow_wrap(),
so `nowrap` is treated like `normal`, and `pre-wrap` like `pre`.
Most tests were only being run for layout-2013, not for layout-2020.
This wasn't great since layout-2020 is now the default.
So this patch unifies the lists of included tests for both layouts.
For layout-2013 this implies adding css/css-content/, css/css-logical/
and css/css-masking/clip/.
For layout-2020 this implies adding several additional css tests, and
also tests like dom/, js/, html/, etc.
