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Define textwidth for overlong chars #58602

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Merged
merged 2 commits into from
Jun 18, 2025
Merged

Define textwidth for overlong chars #58602

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2cd92ff
Define textwidth for overlong chars
jakobnissen Jun 1, 2025
6b92135
Fixup: Import is_overlong_enc
jakobnissen Jun 1, 2025
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16 changes: 7 additions & 9 deletions base/strings/unicode.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ module Unicode
import Base: show, ==, hash, string, Symbol, isless, length, eltype,
convert, isvalid, ismalformed, isoverlong, iterate,
AnnotatedString, AnnotatedChar, annotated_chartransform,
@assume_effects, annotations
@assume_effects, annotations, is_overlong_enc

# whether codepoints are valid Unicode scalar values, i.e. 0-0xd7ff, 0xe000-0x10ffff

Expand Down Expand Up @@ -262,17 +262,15 @@ julia> textwidth('⛵')
2
```
"""
function textwidth(c::AbstractChar)
ismalformed(c) && return 1
i = codepoint(c)
i < 0x7f && return Int(i >= 0x20) # ASCII fast path
Int(ccall(:utf8proc_charwidth, Cint, (UInt32,), i))
end
textwidth(c::AbstractChar) = textwidth(Char(c)::Char)

function textwidth(c::Char)
b = bswap(reinterpret(UInt32, c)) # from isascii(c)
u = reinterpret(UInt32, c)
b = bswap(u) # from isascii(c)
b < 0x7f && return Int(b >= 0x20) # ASCII fast path
ismalformed(c) && return 1
# We can't know a priori how terminals will render invalid UTF8 chars,
# so we conservatively decide a width of 1.
(ismalformed(c) || is_overlong_enc(u)) && return 1
Int(ccall(:utf8proc_charwidth, Cint, (UInt32,), c))
end

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2 changes: 2 additions & 0 deletions test/strings/util.jl
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Expand Up @@ -8,6 +8,8 @@ SubStr(s) = SubString("abc$(s)de", firstindex(s) + 3, lastindex(s) + 3)
@test textwidth(c^3) == w*3
@test w == @invoke textwidth(c::AbstractChar)
end
@test textwidth('\xc0\xa0') == 1 # overlong
@test textwidth('\xf0\x80\x80') == 1 # malformed
for i in 0x00:0x7f # test all ASCII chars (which have fast path)
w = Int(ccall(:utf8proc_charwidth, Cint, (UInt32,), i))
c = Char(i)
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