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2 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Wez Furlong
|
0324ff66f0 |
wezterm: add experimental_bidi config option and very basic bidi
This commit is larger than it appears to due fanout from threading
through bidi parameters. The main changes are:
* When clustering cells, add an additional phase to resolve embedding
levels and further sub-divide a cluster based on the resolved bidi
runs; this is where we get the direction for a run and this needs
to be passed through to the shaper.
* When doing bidi, the forced cluster boundary hack that we use to
de-ligature when cursoring through text needs to be disabled,
otherwise the cursor appears to push/rotate the text in that
cluster when moving through it! We'll need to find a different
way to handle shading the cursor that eliminates the original
cursor/ligature/black issue.
* In the shaper, the logic for coalescing unresolved runs for font
fallback assumed LTR and needed to be adjusted to cluster RTL.
That meant also computing a little index of codepoint lengths.
* Added `experimental_bidi` boolean option that defaults to false.
When enabled, it activates the bidi processing phase in clustering
with a strong hint that the paragraph is LTR.
This implementation is incomplete and/or wrong for a number of cases:
* The config option should probably allow specifying the paragraph
direction hint to use by default.
* https://terminal-wg.pages.freedesktop.org/bidi/recommendation/paragraphs.html
recommends that bidi be applied to logical lines, not physical
lines (or really: ranges within physical lines) that we're doing
at the moment
* The paragraph direction hint should be overridden by cell attributes
and other escapes; see
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Wez Furlong
|
601a85e12b |
Add wezterm-bidi crate
In order to support RTL/BIDI, wezterm needs a bidi implementation. I don't think a well-conforming rust implementation exists today; what I found were implementations that didn't pass 100% of the conformance tests. So I decided to port "bidiref", the reference implementation of the UBA described in http://unicode.org/reports/tr9/ to Rust. This implementation focuses on conformance: no special measures have been taken to optimize it so far, with my focus having been to ensure that all of the approx 780,000 test cases in the unicode data for unicode 14 pass. Having the tests passing 100% allows for making performance improvements with confidence in the future. The API isn't completely designed/fully baked. Until I get to hooking it up to wezterm's shaper, I'm not 100% sure exactly what I'll need. There's a good discussion on API in https://github.com/open-i18n/rust-unic/issues/273 that suggests omitting "legacy" operations such as reordering. I suspect that wezterm may actually need that function to support monospace text layout in some terminal scenarios, but regardless: reordering is part of the conformance test suite so it remains a part of the API. That said: the API does model the major operations as separate phases, so you should be able to pay for just what you use: * Resolving the embedding levels from a paragraph * Returning paragraph runs of those levels (and their directions) * Returning the whitespace-level-reset runs for a line-slice within the paragraph * Returning the reordered indices + levels for a line-slice within the paragraph. refs: https://github.com/wez/wezterm/issues/784 refs: https://github.com/kas-gui/kas-text/issues/20 |