Merge pull request #91 from mattn/add-is-combining-width

Add IsCombiningWidth function

Author: mattn

.github/workflows/test.yaml

@@ -12,13 +12,13 @@ jobs:
       matrix:
         os: [windows-latest, macos-latest, ubuntu-latest]
         go:
+          - "1.26"
           - "1.25"
           - "1.24"
-          - "1.23"
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v3
-      - uses: actions/setup-go@v4
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
         with:
           go-version: ${{ matrix.go }}
 
@@ -27,4 +27,4 @@ jobs:
       - run: go test ./... -v -cover -coverprofile coverage.out
       - run: go test -bench . -benchmem
 
-      - uses: codecov/codecov-action@v3
+      - uses: codecov/codecov-action@v5

runewidth.go

@@ -316,6 +316,11 @@ func IsAmbiguousWidth(r rune) bool {
 	return inTables(r, private, ambiguous)
 }
 
+// IsCombiningWidth returns whether is combining width or not.
+func IsCombiningWidth(r rune) bool {
+	return inTable(r, combining)
+}
+
 // IsNeutralWidth returns whether is neutral width or not.
 func IsNeutralWidth(r rune) bool {
 	return inTable(r, neutral)

runewidth_test.go

@@ -427,6 +427,27 @@ func TestIsNeutralWidth(t *testing.T) {
 	}
 }
 
+var iscombiningwidthtests = []struct {
+	in  rune
+	out bool
+}{
+	{'\u0300', true},  // COMBINING GRAVE ACCENT
+	{'\uFE0F', true},  // VARIATION SELECTOR-16
+	{'\uFE0E', true},  // VARIATION SELECTOR-15
+	{'\u180B', true},  // MONGOLIAN FREE VARIATION SELECTOR ONE
+	{'\U000E0100', true}, // VARIATION SELECTOR-17
+	{'A', false},
+	{'☆', false},
+}
+
+func TestIsCombiningWidth(t *testing.T) {
+	for _, tt := range iscombiningwidthtests {
+		if out := IsCombiningWidth(tt.in); out != tt.out {
+			t.Errorf("IsCombiningWidth(%q) = %v, want %v", tt.in, out, tt.out)
+		}
+	}
+}
+
 func TestFillLeft(t *testing.T) {
 	s := "あxいうえお"
 	expected := "    あxいうえお"