fix(completion): say when a candidate's description was cut

The completion menu stops at 480px and clipped whatever ran past it, mid
word and without a mark: git's menu offered "Move or rename a file, a
directory, or a symli" and "Create an empty Git repository or reinitiali".

The menu is monospaced, so what fits is arithmetic: the row spends its
width on the padding, the kind icon, and the name, and the description gets
the cells that are left. Anything longer is elided with the ellipsis inside
that budget, so the cut lands on the menu's edge and says it happened.

`min_w_0` + `truncate` was the obvious reach and the wrong one — it takes
the row's contribution to the container's width down to nothing, and the
whole menu collapses to its 120px floor.

src/terminal/view.rs

@@ -4660,6 +4660,7 @@ impl TerminalView {
 
         let theme = cx.theme();
         let lh = self.line_height;
+        let cell = self.cell_width.as_f32();
         let row = |i: usize| {
             let cand = items[i];
             let selected = s.index == Some(i);
@@ -4674,6 +4675,7 @@ impl TerminalView {
             } else {
                 cand.text.clone()
             };
+            let budget = description_budget(cell, label.chars().count());
             div()
                 .h(lh)
                 .flex()
@@ -4687,7 +4689,12 @@ impl TerminalView {
                 .child(icon)
                 .child(div().flex_shrink_0().child(label))
                 .when_some(cand.description.clone(), |d, desc| {
-                    d.child(div().ml_2().text_color(theme.muted_foreground).child(desc))
+                    d.child(
+                        div()
+                            .ml_2()
+                            .text_color(theme.muted_foreground)
+                            .child(elide(&desc, budget)),
+                    )
                 })
                 .into_any_element()
         };
@@ -4726,7 +4733,7 @@ impl TerminalView {
                 .flex_col()
                 .py_1()
                 .min_w(px(120.))
-                .max_w(px(480.))
+                .max_w(px(COMPLETION_MENU_MAX_W))
                 .overflow_hidden()
                 .bg(theme.popover)
                 .border_1()
@@ -5498,6 +5505,40 @@ fn fig_query_param<'a>(raw: &'a str, key: &str) -> Option<&'a str> {
     })
 }
 
+/// Where the completion menu stops growing.
+const COMPLETION_MENU_MAX_W: f32 = 480.;
+
+/// How many characters of a candidate's description fit beside its name.
+///
+/// The menu is monospaced and clips whatever runs past its edge, so a long
+/// description used to end mid-word — "…or a symli" — with nothing to say it
+/// had been cut. The row spends its width on `px_2` either side, the kind
+/// icon, the gap after it and the margin before the description; whatever is
+/// left, in cells, is the description's.
+fn description_budget(cell_width: f32, label_cells: usize) -> usize {
+    const ROW_CHROME: f32 = 8. + 8. + 16. + 6. + 8.;
+    if cell_width <= 0. {
+        return 0;
+    }
+    let free = COMPLETION_MENU_MAX_W - ROW_CHROME - label_cells as f32 * cell_width;
+    (free / cell_width).floor().max(0.) as usize
+}
+
+/// `text` cut to `budget` characters, with the last one spent on an ellipsis.
+/// A budget too small to say anything with returns nothing rather than a bare
+/// "…", which reads as a description that is there but unreadable.
+fn elide(text: &str, budget: usize) -> String {
+    if text.chars().count() <= budget {
+        return text.to_string();
+    }
+    if budget < 2 {
+        return String::new();
+    }
+    let mut out: String = text.chars().take(budget - 1).collect();
+    out.push('…');
+    out
+}
+
 fn menu_layout(
     total_rows: usize,
     srow: usize,
@@ -5655,11 +5696,11 @@ mod tests {
     };
     use super::{SCROLL_ANIM_FRAME, scroll_anim_step};
     use super::{
-        drag_scroll_step, encode_mouse, escape_candidate, expand_file_command_template,
-        fallback_chain, fig_icon_emoji, fig_icon_glyph, focus_report_bytes, input_overflow_shift,
-        input_overlay_rows, menu_layout, paste_bytes, select_end_copy, shell_escape_path,
-        should_show_context_menu, smooth_scroll_step, submit_bytes, trim_trailing_spaces,
-        wheel_route, wrapped_click_index,
+        description_budget, drag_scroll_step, elide, encode_mouse, escape_candidate,
+        expand_file_command_template, fallback_chain, fig_icon_emoji, fig_icon_glyph,
+        focus_report_bytes, input_overflow_shift, input_overlay_rows, menu_layout, paste_bytes,
+        select_end_copy, shell_escape_path, should_show_context_menu, smooth_scroll_step,
+        submit_bytes, trim_trailing_spaces, wheel_route, wrapped_click_index,
     };
     use super::{
         remote_paste_spec, staged_path_for_pane, stages_clipboard_image, staging_cache,
@@ -6767,6 +6808,40 @@ mod tests {
         assert_eq!(input_overflow_shift(21, 0, 30, 22), 21);
     }
 
+    #[test]
+    fn a_description_that_fits_is_left_alone() {
+        assert_eq!(elide("Show commit logs", 40), "Show commit logs");
+        // Exactly the budget is still a fit; nothing is spent on an ellipsis.
+        assert_eq!(elide("abcd", 4), "abcd");
+    }
+
+    #[test]
+    fn an_overlong_description_ends_in_an_ellipsis_inside_its_budget() {
+        let out = elide("Move or rename a file, a directory, or a symlink", 12);
+        assert_eq!(out.chars().count(), 12, "the ellipsis is inside the budget");
+        assert!(out.ends_with('…'));
+        assert!(out.starts_with("Move or ren"));
+    }
+
+    #[test]
+    fn a_budget_with_no_room_to_say_anything_says_nothing() {
+        // A lone "…" reads as a description that is there but unreadable.
+        assert_eq!(elide("Show commit logs", 1), "");
+        assert_eq!(elide("Show commit logs", 0), "");
+    }
+
+    #[test]
+    fn the_description_budget_is_what_the_name_leaves_of_the_menu() {
+        // A 9px cell: 46px of row chrome, so a bare row leaves (480-46)/9 cells.
+        assert_eq!(description_budget(9., 0), 48);
+        // Every cell the name takes is one the description does not get.
+        assert_eq!(description_budget(9., 10), 38);
+        // A name that fills the menu on its own leaves nothing, and never
+        // underflows into a huge budget.
+        assert_eq!(description_budget(9., 200), 0);
+        assert_eq!(description_budget(0., 10), 0);
+    }
+
     #[test]
     fn menu_layout_prefers_below_and_flips_above_when_cramped() {
         assert_eq!(menu_layout(24, 3, 5, 0, 10), (false, 5, 0));