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mirror of https://github.com/wez/wezterm.git synced 2024-12-27 07:18:13 +03:00
wezterm/bidi/examples
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 85a6b178cf

and probably others.

However, as of this commit, if you `experimental_bidi=true` then

```
echo This is RTL -> عربي فارسی bidi
```

(that text was sourced from:
https://github.com/microsoft/terminal/issues/538#issuecomment-677017322)

then wezterm will display the text in the same order as the text
renders in Chrome for that github comment.

```
; ./target/debug/wezterm --config experimental_bidi=false ls-fonts --text "عربي فارسی ->"
LeftToRight
 0 ع    \u{639}      x_adv=8  glyph=300  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
 2 ر    \u{631}      x_adv=3.78125 glyph=273  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
 4 ب    \u{628}      x_adv=4  glyph=244  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
 6 ي    \u{64a}      x_adv=4  glyph=363  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
 8      \u{20}       x_adv=8  glyph=2    wezterm.font("Operator Mono SSm Lig", {weight="DemiLight", stretch="Normal", italic=false})
                                      /Users/wez/.fonts/OperatorMonoSSmLig-Medium.otf, FontDirs
 9 ف    \u{641}      x_adv=11 glyph=328  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
11 ا    \u{627}      x_adv=4  glyph=240  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
13 ر    \u{631}      x_adv=3.78125 glyph=273  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
15 س    \u{633}      x_adv=10 glyph=278  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
17 ی    \u{6cc}      x_adv=4  glyph=664  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
19      \u{20}       x_adv=8  glyph=2    wezterm.font("Operator Mono SSm Lig", {weight="DemiLight", stretch="Normal", italic=false})
                                      /Users/wez/.fonts/OperatorMonoSSmLig-Medium.otf, FontDirs
20 -    \u{2d}       x_adv=8  glyph=276  wezterm.font("Operator Mono SSm Lig", {weight="DemiLight", stretch="Normal", italic=false})
                                      /Users/wez/.fonts/OperatorMonoSSmLig-Medium.otf, FontDirs
21 >    \u{3e}       x_adv=8  glyph=338  wezterm.font("Operator Mono SSm Lig", {weight="DemiLight", stretch="Normal", italic=false})
                                      /Users/wez/.fonts/OperatorMonoSSmLig-Medium.otf, FontDirs
```

```
; ./target/debug/wezterm --config experimental_bidi=true ls-fonts --text "عربي فارسی ->"
RightToLeft
17 ی    \u{6cc}      x_adv=9  glyph=906  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
15 س    \u{633}      x_adv=10 glyph=277  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
13 ر    \u{631}      x_adv=4.78125 glyph=272  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
11 ا    \u{627}      x_adv=4  glyph=241  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
 9 ف    \u{641}      x_adv=5  glyph=329  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
 8      \u{20}       x_adv=8  glyph=2    wezterm.font("Operator Mono SSm Lig", {weight="DemiLight", stretch="Normal", italic=false})
                                      /Users/wez/.fonts/OperatorMonoSSmLig-Medium.otf, FontDirs
 6 ي    \u{64a}      x_adv=9  glyph=904  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
 4 ب    \u{628}      x_adv=4  glyph=243  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
 2 ر    \u{631}      x_adv=5  glyph=273  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
 0 ع    \u{639}      x_adv=6  glyph=301  wezterm.font(".Geeza Pro Interface", {weight="Regular", stretch="Normal", italic=false})
                                      /System/Library/Fonts/GeezaPro.ttc index=2 variation=0, CoreText
LeftToRight
 0      \u{20}       x_adv=8  glyph=2    wezterm.font("Operator Mono SSm Lig", {weight="DemiLight", stretch="Normal", italic=false})
                                      /Users/wez/.fonts/OperatorMonoSSmLig-Medium.otf, FontDirs
 1 -    \u{2d}       x_adv=8  glyph=480  wezterm.font("Operator Mono SSm Lig", {weight="DemiLight", stretch="Normal", italic=false})
                                      /Users/wez/.fonts/OperatorMonoSSmLig-Medium.otf, FontDirs
 2 >    \u{3e}       x_adv=8  glyph=470  wezterm.font("Operator Mono SSm Lig", {weight="DemiLight", stretch="Normal", italic=false})
                                      /Users/wez/.fonts/OperatorMonoSSmLig-Medium.otf, FontDirs
;
```

refs: https://github.com/wez/wezterm/issues/784
2022-01-25 09:00:53 -07:00
..
shaping.rs wezterm: add experimental_bidi config option and very basic bidi 2022-01-25 09:00:53 -07:00