fix: calculate display width with unicode-width to handle emoji

Cargo.toml

@@ -15,7 +15,6 @@ pretty_assertions = "1.4.1"
 temp-dir = "0.1.16"
 criterion = "0.8.1"
 insta = "1.46.0"
-unicode-width = "0.2.0"
 temp-env = "0.3.6"
 stdext = "0.3.3"
 url = "2.5.7"
@@ -71,6 +70,7 @@ tree-sitter-elixir = "=0.3.4"
 regex = "1.12.2"
 strip-ansi-escapes = "0.2.1"
 unicode-segmentation = "1.12.0"
+unicode-width = "0.2.0"
 cached = "0.56.0"
 strum = { version = "0.26.3", features = ["strum_macros"] }
 tinyvec = "1.10.0"

src/screen/mod.rs

@@ -4,6 +4,7 @@ use crate::ui::{UiTree, layout_span};
 use crate::{item_data::ItemData, ui};
 use ratatui::{layout::Size, style::Style, text::Line};
 use unicode_segmentation::UnicodeSegmentation;
+use unicode_width::UnicodeWidthStr;
 
 use crate::{Res, config::Config, items::hash};
 
@@ -473,23 +474,30 @@ pub(crate) fn layout_screen<'a>(
                 line.display.spans.into_iter().for_each(|span| {
                     let style = bg.patch(line.display.style).patch(span.style);
 
-                    let span_width = span.content.graphemes(true).count();
+                    let span_width = UnicodeWidthStr::width(span.content.as_ref());
 
                     if line_end + span_width >= size.width as usize {
-                        // Truncate the span and insert an ellipsis to indicate overflow
-                        let overflow = line_end + span_width - size.width as usize;
+                        // Truncate the span and insert an ellipsis to indicate overflow.
+                        // Keep as many graphemes as fit in the remaining columns, leaving
+                        // one column for the ellipsis. Accumulate display width (not
+                        // grapheme count) so wide characters like emoji are handled.
+                        let budget = (size.width as usize).saturating_sub(line_end + 1);
+                        let mut used = 0;
+                        let truncated: String = span
+                            .content
+                            .graphemes(true)
+                            .take_while(|g| {
+                                let next = used + UnicodeWidthStr::width(*g);
+                                if next <= budget {
+                                    used = next;
+                                    true
+                                } else {
+                                    false
+                                }
+                            })
+                            .collect();
                         line_end = size.width as usize;
-                        ui::layout_span(
-                            layout,
-                            (
-                                span.content
-                                    .graphemes(true)
-                                    .take(span_width.saturating_sub(overflow + 1))
-                                    .collect::<String>()
-                                    .into(),
-                                style,
-                            ),
-                        );
+                        ui::layout_span(layout, (truncated.into(), style));
                         layout_span(layout, ("…".into(), bg));
                     } else {
                         // Insert the span as normal

src/ui.rs

@@ -10,6 +10,7 @@ use ratatui::Frame;
 use ratatui::prelude::*;
 use tui_prompts::State as _;
 use unicode_segmentation::UnicodeSegmentation;
+use unicode_width::UnicodeWidthStr;
 
 pub(crate) mod layout;
 mod menu;
@@ -127,7 +128,7 @@ pub(crate) fn layout_line<'a>(layout: &mut UiTree<'a>, line: Line<'a>) {
 }
 
 pub(crate) fn layout_span<'a>(layout: &mut UiTree<'a>, span: (Cow<'a, str>, Style)) {
-    let width = span.0.graphemes(true).count() as u16;
+    let width = UnicodeWidthStr::width(span.0.as_ref()) as u16;
     layout.leaf_with_size(span, [width, 1]);
 }
 

src/ui/layout/mod.rs

@@ -4,7 +4,7 @@ mod vec2;
 
 use std::iter;
 
-use unicode_segmentation::UnicodeSegmentation;
+use unicode_width::UnicodeWidthStr;
 
 use direction::Direction;
 use node::*;
@@ -121,7 +121,7 @@ impl LayoutTree<&'static str> {
     /// Add a text leaf, calculating size based on string length
     #[allow(dead_code)]
     pub fn text(&mut self, text: &'static str) -> &mut Self {
-        let width = text.graphemes(true).count();
+        let width = UnicodeWidthStr::width(text);
         self.leaf_with_size(text, [width as u16, 1]);
         self
     }
@@ -542,7 +542,22 @@ mod tests {
 
         layout.compute([10, 1]);
         let items: Vec<_> = layout.iter().collect();
-        assert_eq!(items[0].size, [4, 1]); // café has 4 graphemes
+        assert_eq!(items[0].size, [4, 1]); // café renders in 4 columns
+    }
+
+    #[test]
+    fn emoji_display_width() {
+        let mut layout = LayoutTree::new();
+
+        layout.horizontal(None, OPTS, |layout| {
+            // A single emoji is one grapheme but occupies two terminal columns.
+            layout.text("🚀").text("x");
+        });
+
+        layout.compute([10, 1]);
+        let items: Vec<_> = layout.iter().collect();
+        assert_eq!(items[0].size, [2, 1]); // emoji is 2 columns wide, not 1
+        assert_eq!(items[1].pos, [2, 0]); // following span starts after it
     }
 
     #[test]