2 files changed, 35 insertions, 3 deletions
diff --git a/tui/widget/widget.ha b/tui/widget/widget.ha
index be6c255..3e6cf8d 100644
--- a/tui/widget/widget.ha
+++ b/tui/widget/widget.ha
@@ -198,7 +198,7 @@ export fn print(w: *widget) void = {
 	w.state.clear = false;
 };
 
-// Applies styling (style) to the given string. 
+// Applies styling (style) to the given string slice.
 fn applystyles(st: (*style | void), s: []str) []str = {
 	return match (st) {
 	case let st: *style =>
@@ -234,11 +234,11 @@ fn truncate_to_size(w: *widget) []str = {
 		const line = w.buf.lines[i];
 		let item = match (w.sz) {
 		case let sz: tty::ttysize =>
-			const s = if (len(line) > sz.columns) strings::sub(line, 0z, sz.columns) else line;
+			const s = if (tui::strwidth(line) > sz.columns) strings::sub(line, 0z, sz.columns) else line;
 			yield strings::rpad(s, ' ', sz.columns);
 		case void =>
 			const wsz = tty::winsize(w.state.out)!;
-			const s = if (len(line) > wsz.columns) strings::sub(line, 0z, wsz.columns) else line;
+			const s = if (tui::strwidth(line) > wsz.columns) strings::sub(line, 0z, wsz.columns) else line;
 			yield strings::dup(s);
 		};
 		append(lines, item)!;
diff --git a/tui/width.ha b/tui/width.ha
new file mode 100644
index 0000000..6f9631c
--- /dev/null
+++ b/tui/width.ha
@@ -0,0 +1,32 @@
+use strings;
+
+export fn runewidth(r: rune) uint = {
+	let ru = r: u32;
+	// emoticons: https://en.wikipedia.org/wiki/Emoticons_(Unicode_block)
+	if (ru >= '\U0001F600' && ru <= '\U0001F64F') {
+		return 2;
+	};
+	// hiragana: https://en.wikipedia.org/wiki/Hiragana_%28Unicode_block%29
+	if (ru >= '\U00003040' && ru <= '\U0000309F') {
+		return 2;
+	};
+	// katakana: https://en.wikipedia.org/wiki/Katakana_(Unicode_block)
+	if (ru >= '\U000030A0' && ru <= '\U000030FF') {
+		return 2;
+	};
+	// CJK: https://en.wikipedia.org/wiki/CJK_Unified_Ideographs_(Unicode_block)
+	if (ru >= '\U00004E00' && ru <= '\U00009FFF') {
+		return 2;
+	};
+	return 1;
+};
+
+export fn strwidth(s: str) uint = {
+	const runes = strings::torunes(s);
+	defer free(runes);
+	let sum = 0u;
+	for (let r .. runes) {
+		sum += runewidth(r);
+	};
+	return sum;
+};