Fix incorrect cursor placement with CJK characters.

Fixes #270

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ## [Unreleased] <!-- ReleaseDate -->
 
+- Fix incorrect cursor placement when inputting CJK characters. Thanks @phostann (#270) for reporting it!
 - Removed unused dependency (newline-converter). Thanks @jonassmedegaard (#267) for catching it!
 
 ## [0.7.5] - 2024-04-23

inquire/src/input/test.rs

@@ -114,6 +114,17 @@ fn new_with_content_is_correctly_initialized() {
     let input = Input::new_with(content);
     assert_eq!(11, input.length());
     assert_eq!(11, input.cursor());
+    assert_eq!("great idea!", input.pre_cursor());
+    assert_eq!(content, input.content());
+}
+
+#[test]
+fn new_with_chinese_content_is_correctly_initialized() {
+    let content = "请输";
+    let input = Input::new_with(content);
+    assert_eq!(2, input.length());
+    assert_eq!(2, input.cursor());
+    assert_eq!("请输", input.pre_cursor());
     assert_eq!(content, input.content());
 }
 
@@ -138,6 +149,15 @@ fn with_cursor_is_correctly_initialized() {
     assert_eq!("great i", input.pre_cursor());
 }
 
+#[test]
+fn chinese_with_cursor_is_correctly_initialized() {
+    let input = Input::new_with("请输入").with_cursor(1);
+    assert_eq!(3, input.length());
+    assert_eq!(1, input.cursor());
+    assert_eq!("请输入", input.content());
+    assert_eq!("请", input.pre_cursor());
+}
+
 #[test]
 fn with_placeholder_is_correctly_initialized() {
     let input = Input::new_with("great idea!").with_placeholder("placeholder");

inquire/src/ui/backend.rs

@@ -1,5 +1,7 @@
 use std::{collections::BTreeSet, fmt::Display, io::Result};
 
+use unicode_width::UnicodeWidthStr;
+
 use crate::{
     error::InquireResult,
     input::Input,
@@ -185,9 +187,12 @@ where
     fn print_input(&mut self, input: &Input) -> Result<()> {
         self.frame_renderer.write(" ")?;
 
-        let cursor_offset = input.pre_cursor().chars().count();
+        // The cursor is at the beginning of the input line.
+        // From here it's easier to mark the wanted cursor position
+        // (based on the underlying input struct), as it's a simple
+        // cur_pos + offset calculation.
         self.frame_renderer
-            .mark_cursor_position(cursor_offset as isize);
+            .mark_cursor_position(input.pre_cursor().width() as isize);
 
         if input.is_empty() {
             match input.placeholder() {