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Test width = sum(grapheme cluster widths) #46

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May 10, 2024
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Test width = sum(grapheme cluster widths) #46

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3 changes: 2 additions & 1 deletion scripts/unicode.py
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Original file line number Diff line number Diff line change
Expand Up @@ -754,8 +754,9 @@ def main(module_path: str):
{EffectiveWidth.NARROW, EffectiveWidth.AMBIGUOUS},
)

# Download normalization test file for use by tests
# Download files for use by tests
fetch_open("NormalizationTest.txt", "../tests/")
fetch_open("auxiliary/GraphemeBreakTest.txt", "../tests/")

print("------------------------")
total_size = 0
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37 changes: 26 additions & 11 deletions src/lib.rs
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Expand Up @@ -30,19 +30,19 @@
//! # Rules for determining width
//!
//! This crate currently uses the following rules to determine the width of a
//! character or string, in order of decreasing precedence. These may be tweaked in the future.
//! character or string, in order of decreasing precedence. These may be tweaked in the future;
//! however see [guarantees](#guarantees) below.
//!
//! 1. [Emoji presentation sequences] have width 2.
//! (The width of a string may therefore differ from the sum of the widths of its characters.)
//! 2. Outside of an East Asian context, [text presentation sequences] fulfilling all the following requirements
//! have width 1:
//! 2. Outside of an East Asian context, [text presentation sequences] have width 1
//! if their base character:
//! - Has the [`Emoji_Presentation`] property, and
//! - Not in the [Enclosed Ideographic Supplement] block.
//! - Is not in the [Enclosed Ideographic Supplement] block.
//! 3. The sequence `"\r\n"` has width 1.
//! 4. [`'\u{115F}'` HANGUL CHOSEONG FILLER](https://util.unicode.org/UnicodeJsps/character.jsp?a=115F) has width 2.
//! 5. The following have width 0:
//! - [Characters](https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5Cp%7BDefault_Ignorable_Code_Point%7D)
//! with the [`Default_Ignorable_Code_Point`](https://www.unicode.org/versions/Unicode15.0.0/ch05.pdf#G40095) property.
//! with the [`Default_Ignorable_Code_Point`] property.
//! - [Characters](https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5Cp%7BGrapheme_Extend%7D)
//! with the [`Grapheme_Extend`] property.
//! - The following 8 characters, all of which have NFD decompositions consisting of two [`Grapheme_Extend`] characters:
Expand All @@ -62,6 +62,7 @@
//! with an [`East_Asian_Width`] of [`Ambiguous`] have width 2 in an East Asian context, and width 1 otherwise.
//! 8. All other characters have width 1.
//!
//! [`Default_Ignorable_Code_Point`]: https://www.unicode.org/versions/Unicode15.0.0/ch05.pdf#G40095
//! [`East_Asian_Width`]: https://www.unicode.org/reports/tr11/#ED1
//! [`Emoji_Presentation`]: https://unicode.org/reports/tr51/#def_emoji_presentation
//! [`Grapheme_Extend`]: https://www.unicode.org/versions/Unicode15.0.0/ch03.pdf#G52443
Expand All @@ -71,15 +72,21 @@
//! [`Wide`]: https://www.unicode.org/reports/tr11/#ED4
//! [`Ambiguous`]: https://www.unicode.org/reports/tr11/#ED6
//!
//! [Emoji presentation sequences]: (https://unicode.org/reports/tr51/#def_emoji_presentation_sequence)
//! [text presentation sequences]: (https://unicode.org/reports/tr51/#def_text_presentation_sequence)
//! [Emoji presentation sequences]: https://unicode.org/reports/tr51/#def_emoji_presentation_sequence
//! [text presentation sequences]: https://unicode.org/reports/tr51/#def_text_presentation_sequence
//!
//! [Enclosed Ideographic Supplement]: https://unicode.org/charts/PDF/U1F200.pdf
//!
//! ## Canonical equivalence
//! ## Guarantees
//!
//! The non-CJK width methods guarantee that canonically equivalent strings are assigned the same width.
//! However, this guarantee does not currently hold for the CJK width variants.
//! - Any two canonically equivalent strings have the same non-CJK width.
//! This will not change in any future semver-compatible version.
//! (This guarantee does not currently hold for the CJK width variants.)
//! - The width of any string equals the sum of the widths of its [extended grapheme clusters].
//! This is unlikely to change in any future semver-compatible version.
//! (This guarantee holds for both CJK and non-CJK width.)
//!
//! [extended grapheme clusters]: https://www.unicode.org/reports/tr29/#Grapheme_Cluster_Boundaries

#![forbid(unsafe_code)]
#![deny(missing_docs)]
Expand All @@ -95,6 +102,14 @@ pub use tables::UNICODE_VERSION;
mod tables;

/// Methods for determining displayed width of Unicode characters.
///
/// **NB:** the width of a string may differ from the sum of the widths of its characters;
/// see the [crate-level documentation](crate#rules-for-determining-width) for more.
/// Instead of working with individual characters, consider using [extended grapheme clusters],
/// perhaps with the [`unicode-segmentation`] crate.
///
/// [extended grapheme clusters]: https://www.unicode.org/reports/tr29/#Grapheme_Cluster_Boundaries
/// [`unicode-segmentation`]: https://docs.rs/unicode-segmentation/latest/unicode_segmentation/trait.UnicodeSegmentation.html#tymethod.graphemes
pub trait UnicodeWidthChar {
/// Returns the character's displayed width in columns, or `None` if the
/// character is a control character.
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