Instead of keeping a per-FontGroup cache of the previously used fallback
font, cache this value in the caller of `FontGroup::find_by_codepoint`.
The problem with caching this value in the `FontGroup` is that it can
make one layout different from the next.
Still, it is important to cache the value somewhere so that, for
instance, Chinese character don't have to continuously walk through the
entire fallback list when laying out. The heuristic here is to try to
last used font first if the `Script`s match. At the very least this
should make one layout consistent with the next.
Fixes#35704.
Fixes#35697.
Fixes#35689.
Fixes#35679.
Signed-off-by: Martin Robinson <mrobinson@igalia.com>
This adds supports for right-to-left text assigning bidi levels to all
line items when necessary. This includes support for the `dir` attribute
as well as corresponding CSS properties like `unicode-bidi`. It only
implements right-to-left rendering for inline layout at the moment and
doesn't include support for `dir=auto`. Because of missing features,
this causes quite a few tests to start failing, as references become
incorrect due to right-to-left rendering being active in some cases,
but not others (before it didn't exist at all).
Analysis of most of the new failures:
```
- /css/css-flexbox/gap-001-rtl.html
/css/css-flexbox/gap-004-rtl.html
- Require implementing BiDi in Flexbox, because the start and
end inline margins are opposite the order of items.
- /css/CSS2/bidi-text/direction-applies-to-*.xht
/css/CSS2/bidi-text/direction-applies-to-002.xht
/css/CSS2/bidi-text/direction-applies-to-003.xht
/css/CSS2/bidi-text/direction-applies-to-004.xht
- Broken due to a bug in tables, not allocating the
right amount of width for a column.
- /css/css-lists/inline-list.html
- This fails because we wrongly insert a soft wrap opportunity between the
start of an inline box and its first content.
- /css/css-text/bidi/bidi-lines-001.html
/css/css-text/bidi/bidi-lines-002.html
/css/CSS2/text/bidi-flag-emoji.html
- We do not fully support unicode-bidi: plaintext
- /css/css-text/text-align/text-align-end-010.html
/css/css-text/text-align/text-align-justify-006.html
/css/css-text/text-align/text-align-start-010.html
/html/dom/elements/global-attributes/*
- We do not support dir=auto yet.
- /css/css-text/white-space/tab-bidi-001.html
- Servo doesn't support tab stops
- /css/CSS2/positioning/abspos-block-level-001.html
/css/css-text/word-break/word-break-normal-ar-000.html
- Do not yet support RTL layout in block
- /css/css-text/white-space/pre-wrap-018.html
- Even in RTL contexts, spaces at the end of the line must hang and
not be reordered
- /css/css-text/white-space/trailing-space-and-text-alignment-rtl-002.html
- We are letting spaces hang with white-space: pre, but they shouldn't
hang.
```
Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Rakhi Sharma <atbrakhi@igalia.com>
