Support lots of ligatures (#53)

Author: Jules-Bertholet

.github/workflows/rust.yml

@@ -27,7 +27,13 @@ jobs:
     - name: Check formatting
       run: cargo fmt --check
     - name: Check clippy
-      run: cargo clippy --lib --tests
+      run: cargo clippy --verbose --lib --tests
+    - name: Build (no default features)
+      run: cargo build --verbose --no-default-features
+    - name: Run tests (no default features)
+      run: cargo test --verbose --no-default-features
+    - name: Check clippy (no default features)
+      run: cargo clippy --verbose --lib --tests --no-default-features
 
   regen:
     runs-on: ubuntu-latest
@@ -37,6 +43,6 @@ jobs:
       with:
         python-version: '3.12'
     - name: Regen
-      run: rm tests/NormalizationTest.txt && cd scripts && python3 unicode.py
+      run: rm tests/emoji-test.txt && cd scripts && python3 unicode.py
     - name: Diff
       run: git update-index --refresh && git diff-index --quiet HEAD --

Cargo.toml

@@ -32,7 +32,8 @@ core = { version = "1.0", package = "rustc-std-workspace-core", optional = true
 compiler_builtins = { version = "0.1", optional = true }
 
 [features]
-default = []
+cjk = []
+default = ["cjk"]
 rustc-dep-of-std = ['std', 'core', 'compiler_builtins']
 
 # Legacy, now a no-op

README.md

@@ -25,25 +25,26 @@ 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. 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:
+width. For example, many Brahmic scripts like Devanagari have complex rendering rules
+which this crate does not currently handle (and will never fully handle, because
+the exact rendering depends on the font):
 
 ```rust
 extern crate unicode_width;
 use unicode_width::UnicodeWidthStr;
 
 fn main() {
-    assert_eq!("👩".width(), 2); // Woman
-    assert_eq!("🔬".width(), 2); // Microscope
-    assert_eq!("👩‍🔬".width(), 4); // Woman scientist
+    assert_eq!("क".width(), 1); // Devanagari letter Ka
+    assert_eq!("ष".width(), 1); // Devanagari letter Ssa
+    assert_eq!("क्ष".width(), 2); // Ka + Virama + Ssa
 }
 ```
 
 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.)
+exhaustive list.) For a list of what this crate *does* handle, see
+[docs.rs](https://docs.rs/unicode-width/latest/unicode_width/#rules-for-determining-width).
 
 ## crates.io