Unify the two truncate helpers and measure display width

src/app/model/dagruns/popup/trigger/table.rs

@@ -8,8 +8,9 @@ use ratatui::{
 use crate::ui::theme::theme;
 
 use super::params::{ParamEntry, ParamKind};
-use super::text::{truncate_cols, value_window, wrap_text};
+use super::text::{value_window, wrap_text};
 use super::TriggerDagRunPopUp;
+use crate::ui::common::truncate_cols;
 
 /// Total inter-column padding the table reserves (1 col between each of 3 columns).
 const COLUMN_GAPS: usize = 2;

src/app/model/dagruns/popup/trigger/text.rs

@@ -63,21 +63,9 @@ pub(super) fn value_window(value: &str, cursor_pos: usize, width: usize) -> (Str
     (before, cursor_char, after)
 }
 
-/// Truncate a string to at most `max_cols` columns, appending `…` if clipped.
-pub(super) fn truncate_cols(s: &str, max_cols: usize) -> String {
-    if s.chars().count() <= max_cols {
-        return s.to_string();
-    }
-    if max_cols == 0 {
-        return String::new();
-    }
-    let kept: String = s.chars().take(max_cols - 1).collect();
-    format!("{kept}…")
-}
-
 #[cfg(test)]
 mod tests {
-    use super::{truncate_cols, value_window, wrap_text};
+    use super::{value_window, wrap_text};
 
     #[test]
     fn wrap_text_breaks_on_word_boundaries() {
@@ -88,13 +76,6 @@ mod tests {
         assert_eq!(wrap_text("abcdefgh", 3), vec!["abc", "def", "gh"]);
     }
 
-    #[test]
-    fn truncate_appends_ellipsis_when_clipped() {
-        assert_eq!(truncate_cols("hello", 10), "hello");
-        assert_eq!(truncate_cols("hello world", 5), "hell…");
-        assert_eq!(truncate_cols("hello", 0), "");
-    }
-
     #[test]
     fn window_shows_whole_value_when_it_fits() {
         let (before, cursor, after) = value_window("abc", 1, 20);

src/app/state/breadcrumb.rs

@@ -3,6 +3,7 @@ use std::sync::LazyLock;
 use time::format_description::BorrowedFormatItem;
 
 use super::{App, Panel};
+use crate::ui::common::truncate_cols;
 
 /// Cached date format for breadcrumb display (YYYY-MM-DD)
 static BREADCRUMB_DATE_FORMAT: LazyLock<Vec<BorrowedFormatItem<'static>>> = LazyLock::new(|| {
@@ -20,7 +21,7 @@ impl App {
 
         if self.active_panel != Panel::Config && self.active_panel != Panel::Dag {
             if let Some(dag_id) = self.nav_context.dag_id() {
-                let truncated = Self::truncate_breadcrumb_part(dag_id, 25);
+                let truncated = truncate_cols(dag_id, 25);
                 parts.push(truncated);
             }
         }
@@ -33,18 +34,18 @@ impl App {
                         .unwrap_or_else(|_| "unknown".to_string());
                     parts.push(formatted);
                 } else if let Some(dag_run_id) = self.nav_context.dag_run_id() {
-                    let truncated = Self::truncate_breadcrumb_part(dag_run_id, 20);
+                    let truncated = truncate_cols(dag_run_id, 20);
                     parts.push(truncated);
                 }
             } else if let Some(dag_run_id) = self.nav_context.dag_run_id() {
-                let truncated = Self::truncate_breadcrumb_part(dag_run_id, 20);
+                let truncated = truncate_cols(dag_run_id, 20);
                 parts.push(truncated);
             }
         }
 
         if self.active_panel == Panel::Logs {
             if let Some(task_id) = self.nav_context.task_id() {
-                let truncated = Self::truncate_breadcrumb_part(task_id, 20);
+                let truncated = truncate_cols(task_id, 20);
                 parts.push(truncated);
             }
         }
@@ -57,18 +58,4 @@ impl App {
             None
         }
     }
-
-    fn truncate_breadcrumb_part(s: &str, max_chars: usize) -> String {
-        let char_count = s.chars().count();
-        if char_count <= max_chars {
-            s.to_string()
-        } else {
-            let truncate_at = max_chars.saturating_sub(3);
-            let byte_index = s
-                .char_indices()
-                .nth(truncate_at)
-                .map_or(s.len(), |(idx, _)| idx);
-            format!("{}...", &s[..byte_index])
-        }
-    }
 }

src/ui/common.rs

@@ -3,10 +3,38 @@ use ratatui::{
     text::{Line, Span},
     widgets::{Block, BorderType, Borders},
 };
+use unicode_width::{UnicodeWidthChar, UnicodeWidthStr};
 
 use super::constants::AirflowStateColor;
 use super::theme::theme;
 
+/// Truncate `s` to at most `max_cols` terminal columns, appending `…` if clipped.
+///
+/// Measures display width rather than counting `char`s, so wide characters
+/// (CJK, emoji) cannot overflow the cell they are rendered into.
+pub fn truncate_cols(s: &str, max_cols: usize) -> String {
+    if s.width() <= max_cols {
+        return s.to_string();
+    }
+    if max_cols == 0 {
+        return String::new();
+    }
+    // Reserve one column for the ellipsis.
+    let budget = max_cols - 1;
+    let mut out = String::new();
+    let mut used = 0;
+    for ch in s.chars() {
+        let w = ch.width().unwrap_or(0);
+        if used + w > budget {
+            break;
+        }
+        out.push(ch);
+        used += w;
+    }
+    out.push('…');
+    out
+}
+
 /// Builds a modal popup `Block` with the shared popup chrome: rounded, fully
 /// bordered, themed border and background, and a title padded with a single
 /// space on each side (`" title "`) styled bold in `accent`.
@@ -36,3 +64,25 @@ pub fn create_headers<'a>(
 pub fn state_to_colored_square<'a>(color: AirflowStateColor) -> Span<'a> {
     Span::styled("■", Style::default().fg(color.into()))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::truncate_cols;
+
+    #[test]
+    fn truncate_appends_ellipsis_when_clipped() {
+        assert_eq!(truncate_cols("hello", 10), "hello");
+        assert_eq!(truncate_cols("hello world", 5), "hell…");
+        assert_eq!(truncate_cols("hello", 0), "");
+    }
+
+    #[test]
+    fn truncate_measures_display_width_not_char_count() {
+        // Each CJK glyph occupies two columns, so only two fit alongside the
+        // ellipsis in a six-column cell. Counting chars would have kept five
+        // and overflowed to ten columns.
+        assert_eq!(truncate_cols("日本語テスト", 6), "日本…");
+        // A string of wide chars that exactly fills the cell is left alone.
+        assert_eq!(truncate_cols("日本語", 6), "日本語");
+    }
+}