unicode-rs · Manishearth · Feb 13, 2024 · Feb 10, 2024 · Feb 10, 2024 · Feb 11, 2024
diff --git a/README.md b/README.md
@@ -26,7 +26,8 @@ fn main() {
 
 **NOTE:** The computed width values may not match the actual rendered column
 width. For example, the woman scientist emoji comprises of a woman emoji, a
-zero-width joiner and a microscope emoji.
+zero-width joiner and a microscope emoji. Such [emoji ZWJ sequences](https://www.unicode.org/reports/tr51/#Emoji_ZWJ_Sequences)
+are considered to have the sum of the widths of their constituent parts:
 
 ```rust
 extern crate unicode_width;
@@ -39,8 +40,10 @@ fn main() {
 }
 ```
 
-See [Unicode Standard Annex #11][UAX11] for precise details on what is and isn't
-covered by this crate.
+Additionally, [defective combining character sequences](https://unicode.org/glossary/#defective_combining_character_sequence)
+and nonstandard [Korean jamo](https://unicode.org/glossary/#jamo) sequences may
+be rendered with a different width than what this crate says. (This is not an
+exhaustive list.)
 
 ## features
 

diff --git a/scripts/unicode.py b/scripts/unicode.py
@@ -64,7 +64,8 @@ class OffsetType(enum.IntEnum):
 
 def fetch_open(filename: str):
     """Opens `filename` and return its corresponding file object. If `filename` isn't on disk,
-    fetches it from `http://www.unicode.org/Public/UNIDATA/`. Exits with code 1 on failure."""
+    fetches it from `http://www.unicode.org/Public/UNIDATA/`. Exits with code 1 on failure.
+    """
     if not os.path.exists(os.path.basename(filename)):
         os.system(f"curl -O http://www.unicode.org/Public/UNIDATA/{filename}")
     try:
@@ -83,7 +84,8 @@ def load_unicode_version() -> "tuple[int, int, int]":
 
 class EffectiveWidth(enum.IntEnum):
     """Represents the width of a Unicode character. All East Asian Width classes resolve into
-    either `EffectiveWidth.NARROW`, `EffectiveWidth.WIDE`, or `EffectiveWidth.AMBIGUOUS`."""
+    either `EffectiveWidth.NARROW`, `EffectiveWidth.WIDE`, or `EffectiveWidth.AMBIGUOUS`.
+    """
 
     ZERO = 0
     """ Zero columns wide. """
@@ -146,10 +148,17 @@ def load_east_asian_widths() -> "list[EffectiveWidth]":
 
 def load_zero_widths() -> "list[bool]":
     """Returns a list `l` where `l[c]` is true if codepoint `c` is considered a zero-width
-    character. `c` is considered a zero-width character if `c` is in general categories
-    `Cc`, `Cf`, `Mn`, or `Me` (determined by fetching and processing `UnicodeData.txt`)."""
+    character. `c` is considered a zero-width character if
+
+    - it is in general categories `Cc`, `Mn`, or `Me` (determined from `UnicodeData.txt`),
+    - or if it has the `Default_Ignorable_Code_Point` property (determined from `DerivedCoreProperties.txt`),
+    - or if it has a `Hangul_Syllable_Type` of `Vowel_Jamo` or `Trailing_Jamo` (determined from `HangulSyllableType.txt`).
+    """
+
+    zw_map = []
+
+    # Characters with general category  `Cc`, `Mn`, or `Me` have 0 width...
     with fetch_open("UnicodeData.txt") as categories:
-        zw_map = []
         current = 0
         for line in categories.readlines():
             if len(raw_data := line.split(";")) != 15:
@@ -159,7 +168,7 @@ def load_zero_widths() -> "list[bool]":
                 raw_data[1],
                 raw_data[2],
             ]
-            zero_width = cat_code in ["Cc", "Cf", "Mn", "Me"]
+            zero_width = cat_code in ["Cc", "Mn", "Me"]
 
             assert current <= codepoint
             while current <= codepoint:
@@ -176,12 +185,68 @@ def load_zero_widths() -> "list[bool]":
             # Catch any leftover codepoints. They must be unassigned (so nonzero width)
             zw_map.append(False)
 
-        return zw_map
+    # `Default_Ignorable_Code_Point`s also have 0 width:
+    # https://www.unicode.org/faq/unsup_char.html#3
+    # https://www.unicode.org/versions/Unicode15.1.0/ch05.pdf#G40095
+    with fetch_open("DerivedCoreProperties.txt") as properties:
+        single = re.compile(r"^([0-9A-F]+)\s+;\s+Default_Ignorable_Code_Point\s+")
+        multiple = re.compile(
+            r"^([0-9A-F]+)\.\.([0-9A-F]+)\s+;\s+Default_Ignorable_Code_Point\s+"
+        )
+
+        for line in properties.readlines():
+            raw_data = None  # (low, high)
+            if match := single.match(line):
+                raw_data = (match.group(1), match.group(1))
+            elif match := multiple.match(line):
+                raw_data = (match.group(1), match.group(2))
+            else:
+                continue
+            low = int(raw_data[0], 16)
+            high = int(raw_data[1], 16)
+            for cp in range(low, high + 1):
+                zw_map[cp] = True
+
+    # Treat `Hangul_Syllable_Type`s of `Vowel_Jamo` and `Trailing_Jamo`
+    # as zero-width. This matches the behavior of glibc `wcwidth`.
+    #
+    # Decomposed Hangul characters consist of 3 parts: a `Leading_Jamo`,
+    # a `Vowel_Jamo`, and an optional `Trailing_Jamo`. Together these combine
+    # into a single wide grapheme. So we treat vowel and trailing jamo as
+    # 0-width, such that only the width of the leading jamo is counted
+    # and the resulting grapheme has width 2.
+    #
+    # (See the Unicode Standard sections 3.12 and 18.6 for more on Hangul)
+    with fetch_open("HangulSyllableType.txt") as categories:
+        single = re.compile(r"^([0-9A-F]+)\s+;\s+(V|T)\s+")
+        multiple = re.compile(r"^([0-9A-F]+)\.\.([0-9A-F]+)\s+;\s+(V|T)\s+")
+
+        for line in categories.readlines():
+            raw_data = None  # (low, high)
+            if match := single.match(line):
+                raw_data = (match.group(1), match.group(1))
+            elif match := multiple.match(line):
+                raw_data = (match.group(1), match.group(2))
+            else:
+                continue
+            low = int(raw_data[0], 16)
+            high = int(raw_data[1], 16)
+            for cp in range(low, high + 1):
+                zw_map[cp] = True
+
+    # Special case: U+115F HANGUL CHOSEONG FILLER.
+    # U+115F is a `Default_Ignorable_Code_Point`, and therefore would normally have
+    # zero width. However, the expected usage is to combine it with vowel or trailing jamo
+    # (which are considered 0-width on their own) to form a composed Hangul syllable with
+    # width 2. Therefore, we treat it as having width 2.
+    zw_map[0x115F] = False
+    return zw_map
 
 
 class Bucket:
     """A bucket contains a group of codepoints and an ordered width list. If one bucket's width
-    list overlaps with another's width list, those buckets can be merged via `try_extend`."""
+    list overlaps with another's width list, those buckets can be merged via `try_extend`.
+    """
 
     def __init__(self):
         """Creates an empty bucket."""
@@ -230,9 +295,9 @@ def make_buckets(entries, low_bit: BitPos, cap_bit: BitPos) -> "list[Bucket]":
     same bucket. Returns a list of the buckets in increasing order of those bits."""
     num_bits = cap_bit - low_bit
     assert num_bits > 0
-    buckets = [Bucket() for _ in range(0, 2 ** num_bits)]
+    buckets = [Bucket() for _ in range(0, 2**num_bits)]
     mask = (1 << num_bits) - 1
-    for (codepoint, width) in entries:
+    for codepoint, width in entries:
         buckets[(codepoint >> low_bit) & mask].append(codepoint, width)
     return buckets
 
@@ -269,7 +334,7 @@ def __init__(
             buckets.extend(make_buckets(entries, self.low_bit, self.cap_bit))
 
         for bucket in buckets:
-            for (i, existing) in enumerate(self.indexed):
+            for i, existing in enumerate(self.indexed):
                 if existing.try_extend(bucket):
                     self.entries.append(i)
                     break
@@ -283,7 +348,8 @@ def __init__(
 
     def indices_to_widths(self):
         """Destructively converts the indices in this table to the `EffectiveWidth` values of
-        their buckets. Assumes that no bucket contains codepoints with different widths."""
+        their buckets. Assumes that no bucket contains codepoints with different widths.
+        """
         self.entries = list(map(lambda i: int(self.indexed[i].width()), self.entries))
         del self.indexed
 
@@ -315,7 +381,7 @@ def make_tables(
     to include in the top-level table."""
     tables = []
     entry_groups = [entries]
-    for (low_bit, cap_bit, offset_type) in table_cfgs:
+    for low_bit, cap_bit, offset_type in table_cfgs:
         table = Table(entry_groups, low_bit, cap_bit, offset_type)
         entry_groups = map(lambda bucket: bucket.entries(), table.buckets())
         tables.append(table)
@@ -326,7 +392,8 @@ def emit_module(
     out_name: str, unicode_version: "tuple[int, int, int]", tables: "list[Table]"
 ):
     """Outputs a Rust module to `out_name` using table data from `tables`.
-    If `TABLE_CFGS` is edited, you may need to edit the included code for `lookup_width`."""
+    If `TABLE_CFGS` is edited, you may need to edit the included code for `lookup_width`.
+    """
     if os.path.exists(out_name):
         os.remove(out_name)
     with open(out_name, "w", newline="\n", encoding="utf-8") as module:
@@ -432,7 +499,7 @@ def emit_module(
         )
 
         subtable_count = 1
-        for (i, table) in enumerate(tables):
+        for i, table in enumerate(tables):
             new_subtable_count = len(table.buckets())
             if i == len(tables) - 1:
                 table.indices_to_widths()  # for the last table, indices == widths
@@ -442,7 +509,7 @@ def emit_module(
     /// Autogenerated. {subtable_count} sub-table(s). Consult [`lookup_width`] for layout info.
     static TABLES_{i}: [u8; {len(byte_array)}] = ["""
             )
-            for (j, byte) in enumerate(byte_array):
+            for j, byte in enumerate(byte_array):
                 # Add line breaks for every 15th entry (chosen to match what rustfmt does)
                 if j % 15 == 0:
                     module.write("\n       ")
@@ -458,16 +525,17 @@ def main(module_filename: str):
     `module_filename`.
 
     We obey the following rules in decreasing order of importance:
-    - The soft hyphen (`U+00AD`) is single-width.
-    - Hangul Jamo medial vowels & final consonants (`U+1160..=U+11FF`) are zero-width.
-    - All codepoints in general categories `Cc`, `Cf`, `Mn`, and `Me` are zero-width.
+    - The soft hyphen (`U+00AD`) is single-width. (https://archive.is/fCT3c)
+    - Hangul jamo medial vowels & final consonants are zero-width.
+    - All `Default_Ignorable_Code_Point`s are zero-width, except for U+115F HANGUL CHOSEONG FILLER.
+    - All codepoints in general categories `Cc`, `Mn`, or `Me` are zero-width.
     - All codepoints with an East Asian Width of `Ambigous` are ambiguous-width.
     - All codepoints with an East Asian Width of `Wide` or `Fullwidth` are double-width.
     - All other codepoints (including unassigned codepoints and codepoints with an East Asian Width
-    of `Neutral`, `Narrow`, or `Halfwidth`) are single-width.
+      of `Neutral`, `Narrow`, or `Halfwidth`) are single-width.
 
-    These rules are based off of Markus Kuhn's free `wcwidth()` implementation:
-    http://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c"""
+    These rules are based off of UAX11, other Unicode standards, and various `wcwidth()` implementations.
+    """
     version = load_unicode_version()
     print(f"Generating module for Unicode {version[0]}.{version[1]}.{version[2]}")
 
@@ -482,15 +550,11 @@ def main(module_filename: str):
     # Override for soft hyphen
     width_map[0x00AD] = EffectiveWidth.NARROW
 
-    # Override for Hangul Jamo medial vowels & final consonants
-    for i in range(0x1160, 0x11FF + 1):
-        width_map[i] = EffectiveWidth.ZERO
-
     tables = make_tables(TABLE_CFGS, enumerate(width_map))
 
     print("------------------------")
     total_size = 0
-    for (i, table) in enumerate(tables):
+    for i, table in enumerate(tables):
         size_bytes = len(table.to_bytes())
         print(f"Table {i} Size: {size_bytes} bytes")
         total_size += size_bytes

diff --git a/src/lib.rs b/src/lib.rs
@@ -43,9 +43,10 @@
 //! ```
 
 #![deny(missing_docs, unsafe_code)]
-#![doc(html_logo_url = "https://unicode-rs.github.io/unicode-rs_sm.png",
-       html_favicon_url = "https://unicode-rs.github.io/unicode-rs_sm.png")]
-
+#![doc(
+    html_logo_url = "https://unicode-rs.github.io/unicode-rs_sm.png",
+    html_favicon_url = "https://unicode-rs.github.io/unicode-rs_sm.png"
+)]
 #![cfg_attr(feature = "bench", feature(test))]
 #![no_std]
 
@@ -87,10 +88,14 @@ pub trait UnicodeWidthChar {
 
 impl UnicodeWidthChar for char {
     #[inline]
-    fn width(self) -> Option<usize> { cw::width(self, false) }
+    fn width(self) -> Option<usize> {
+        cw::width(self, false)
+    }
 
     #[inline]
-    fn width_cjk(self) -> Option<usize> { cw::width(self, true) }
+    fn width_cjk(self) -> Option<usize> {
+        cw::width(self, true)
+    }
 }
 
 /// Methods for determining displayed width of Unicode strings.
@@ -103,7 +108,7 @@ pub trait UnicodeWidthStr {
     /// to [Unicode Standard Annex #11](http://www.unicode.org/reports/tr11/)
     /// as 1 column wide. This is consistent with the recommendations for
     /// non-CJK contexts, or when the context cannot be reliably determined.
-    fn width<'a>(&'a self) -> usize;
+    fn width(&self) -> usize;
 
     /// Returns the string's displayed width in columns.
     ///
@@ -113,7 +118,7 @@ pub trait UnicodeWidthStr {
     /// to [Unicode Standard Annex #11](http://www.unicode.org/reports/tr11/)
     /// as 2 column wide. This is consistent with the recommendations for
     /// CJK contexts.
-    fn width_cjk<'a>(&'a self) -> usize;
+    fn width_cjk(&self) -> usize;
 }
 
 impl UnicodeWidthStr for str {