fix(tui): wrap CJK runs in diff and pager

Hard-wrap overlong CJK/no-whitespace runs in diff and pager text wrappers so they do not overflow the right edge.

Fixes #1571.

Co-authored-by: Aitensa <1900013029@pku.edu.cn>

crates/tui/src/tui/diff_render.rs

@@ -2,7 +2,7 @@
 
 use ratatui::style::{Modifier, Style};
 use ratatui::text::{Line, Span};
-use unicode_width::UnicodeWidthStr;
+use unicode_width::{UnicodeWidthChar, UnicodeWidthStr};
 
 use crate::palette;
 
@@ -357,6 +357,14 @@ fn wrap_text(text: &str, width: usize) -> Vec<String> {
 
     for word in text.split_whitespace() {
         let word_width = word.width();
+        if word_width > width {
+            if !current.is_empty() {
+                lines.push(std::mem::take(&mut current));
+                current_width = 0;
+            }
+            push_word_breaking_chars(word, width, &mut current, &mut current_width, &mut lines);
+            continue;
+        }
         let additional = if current.is_empty() {
             word_width
         } else {
@@ -385,6 +393,24 @@ fn wrap_text(text: &str, width: usize) -> Vec<String> {
     lines
 }
 
+fn push_word_breaking_chars(
+    word: &str,
+    width: usize,
+    current: &mut String,
+    current_width: &mut usize,
+    lines: &mut Vec<String>,
+) {
+    for ch in word.chars() {
+        let char_width = ch.width().unwrap_or(1);
+        if *current_width + char_width > width && *current_width > 0 {
+            lines.push(std::mem::take(current));
+            *current_width = 0;
+        }
+        current.push(ch);
+        *current_width += char_width;
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -450,4 +476,16 @@ diff --git a/src/a.rs b/src/a.rs
             "deleted line should carry - gutter: {text:?}"
         );
     }
+
+    #[test]
+    fn wrap_text_breaks_overlong_cjk_runs() {
+        let text = "这是一个非常长的中文字符串".repeat(10);
+        let lines = wrap_text(&text, 16);
+
+        for line in &lines {
+            assert!(line.width() <= 16, "line {line:?} exceeds width 16");
+        }
+
+        assert_eq!(lines.join(""), text);
+    }
 }

crates/tui/src/tui/pager.rs

@@ -23,7 +23,7 @@ use ratatui::{
     text::{Line, Span},
     widgets::{Block, Borders, Clear, Padding, Paragraph, Widget, Wrap},
 };
-use unicode_width::UnicodeWidthStr;
+use unicode_width::{UnicodeWidthChar, UnicodeWidthStr};
 
 use crate::palette;
 use crate::tui::views::{ModalKind, ModalView, ViewAction, ViewEvent};
@@ -482,6 +482,14 @@ fn wrap_text(text: &str, width: usize) -> Vec<String> {
 
     for word in text.split_whitespace() {
         let word_width = word.width();
+        if word_width > width {
+            if !current.is_empty() {
+                lines.push(std::mem::take(&mut current));
+                current_width = 0;
+            }
+            push_word_breaking_chars(word, width, &mut current, &mut current_width, &mut lines);
+            continue;
+        }
         let additional = if current.is_empty() {
             word_width
         } else {
@@ -510,6 +518,24 @@ fn wrap_text(text: &str, width: usize) -> Vec<String> {
     lines
 }
 
+fn push_word_breaking_chars(
+    word: &str,
+    width: usize,
+    current: &mut String,
+    current_width: &mut usize,
+    lines: &mut Vec<String>,
+) {
+    for ch in word.chars() {
+        let char_width = ch.width().unwrap_or(1);
+        if *current_width + char_width > width && *current_width > 0 {
+            lines.push(std::mem::take(current));
+            *current_width = 0;
+        }
+        current.push(ch);
+        *current_width += char_width;
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -886,4 +912,16 @@ mod tests {
             "expected a Yellow/DarkGray highlight cell on the matched-line text columns"
         );
     }
+
+    #[test]
+    fn wrap_text_breaks_overlong_cjk_runs() {
+        let text = "这是一个非常长的中文字符串".repeat(10);
+        let lines = wrap_text(&text, 16);
+
+        for line in &lines {
+            assert!(line.width() <= 16, "line {line:?} exceeds width 16");
+        }
+
+        assert_eq!(lines.join(""), text);
+    }
 }