fix(ui): B3-8 — display-width-aware cursor + mouse selection for CJK/emoji

Two paths previously treated CHAR count as display-cell count:

1. wrap_input (renderer.rs:1457-1497) compared cursor_display_col
   to chars().count() when deciding whether the cursor sits at
   end-of-line. For "日本" with cursor at the end, col=4 (4 display
   cells) but char_count=2 — the comparison failed and the cursor
   wrapped onto a phantom row 1.

2. buffer_pos_at (renderer.rs:266-277) clamped the click column
   to chars().count(). For wide-char lines, a click mid-line
   landed at the wrong char position, dragging clipboard selection
   ranges across the wrong glyphs.

Fix:
- wrap_input now also computes UnicodeWidthStr::width(line) and
  compares against THAT for the end-of-line cursor branch.
- New display_col_to_char_index helper walks chars accumulating
  UnicodeWidthChar::width until reaching the target display col;
  buffer_pos_at uses it. Clicks in the middle of a 2-cell glyph
  anchor at the glyph's START so the selection boundary lands on
  a real grapheme.

What this DOESN'T fix: soft-wrap slicing for very long CJK lines
that need to break mid-row. Current row count + char_start/char_end
remain in char units, so a CJK line wider than wrap_width still
splits at a char boundary but may overflow display cells on a
single row. Filed as future work; rare in practice given typical
input widths.

Tests: 3 new (ascii round-trip, CJK compression, emoji widths).
1095 → 1098 with plugin / 890 → 893 without.

Closes dirge-yep. B3-9 (edit fuzzy cascade) + B3-10 (LSP pull)
remain.

Author: Yogthos

.beads/issues.jsonl

@@ -15,9 +15,9 @@
 {"_type":"issue","id":"dirge-86e","title":"ANSI injection in permission ALERT prompt","description":"ask_req.tool / ask_req.input rendered un-sanitized at mod.rs:2584-2585. Reopen path already sanitizes — asymmetric. Sec impl: ANSI at the permission-decision moment.","status":"closed","priority":1,"issue_type":"bug","assignee":"Yogthos","owner":"yogthos@gmail.com","created_at":"2026-05-21T22:17:34Z","created_by":"Yogthos","updated_at":"2026-05-21T22:26:37Z","started_at":"2026-05-21T22:17:42Z","closed_at":"2026-05-21T22:26:37Z","close_reason":"Closed","dependency_count":0,"dependent_count":0,"comment_count":0}
 {"_type":"issue","id":"dirge-9f1","title":"Chat history ignores 120-col content_width cap","description":"max_line_width and wrap_line use raw content_cols, so on wide terminals scrollback overflows the centered band into divider/panel margin.","status":"closed","priority":1,"issue_type":"bug","assignee":"Yogthos","owner":"yogthos@gmail.com","created_at":"2026-05-21T22:17:33Z","created_by":"Yogthos","updated_at":"2026-05-21T22:26:36Z","started_at":"2026-05-21T22:17:42Z","closed_at":"2026-05-21T22:26:36Z","close_reason":"Closed","dependency_count":0,"dependent_count":0,"comment_count":0}
 {"_type":"issue","id":"dirge-woq","title":"R1: fix 3 critical plugin bugs (FFI panic, dialog deadlock, init hang)","description":"From the plugin subsystem audit: (1) wrap JanetCFunctions in catch_unwind so Rust panics don't unwind across the C-FFI boundary into Janet; (2) cancel send_dialog's reply_rx.recv() on worker shutdown so the worker thread doesn't block forever when the UI exits mid-dialog; (3) add timeout to the init handshake so a worker panic before init_tx.send() doesn't hang the main thread. Also: (4) bounds-assert wrap_string's i32 cast for the unlikely \u003e2GB case, (5) make take_string_slot atomic to close the race window, (6) don't eat unrelated user events in the dialog arm.","status":"closed","priority":1,"issue_type":"bug","owner":"yogthos@gmail.com","created_at":"2026-05-20T14:59:57Z","created_by":"Yogthos","updated_at":"2026-05-20T15:30:28Z","started_at":"2026-05-20T15:00:10Z","closed_at":"2026-05-20T15:30:28Z","dependency_count":0,"dependent_count":1,"comment_count":0}
-{"_type":"issue","id":"dirge-84j","title":"B3-9: edit tool fuzzy-match cascade","description":"edit.rs:155-160 returns 'old_text not found' on whitespace/indent/CRLF drift. LLMs frequently hit this. opencode edit.ts:222-432 has simple → lineTrimmed → whitespace-normalized → indentation-flexible → levenshtein. pi edit-diff.ts:91-132 has fuzzyFindText. Port the cascade.","status":"open","priority":2,"issue_type":"feature","owner":"yogthos@gmail.com","created_at":"2026-05-23T03:24:44Z","created_by":"Yogthos","updated_at":"2026-05-23T03:24:44Z","dependency_count":0,"dependent_count":0,"comment_count":0}
+{"_type":"issue","id":"dirge-84j","title":"B3-9: edit tool fuzzy-match cascade","description":"edit.rs:155-160 returns 'old_text not found' on whitespace/indent/CRLF drift. LLMs frequently hit this. opencode edit.ts:222-432 has simple → lineTrimmed → whitespace-normalized → indentation-flexible → levenshtein. pi edit-diff.ts:91-132 has fuzzyFindText. Port the cascade.","status":"in_progress","priority":2,"issue_type":"feature","assignee":"Yogthos","owner":"yogthos@gmail.com","created_at":"2026-05-23T03:24:44Z","created_by":"Yogthos","updated_at":"2026-05-23T03:37:16Z","started_at":"2026-05-23T03:37:16Z","dependency_count":0,"dependent_count":0,"comment_count":0}
 {"_type":"issue","id":"dirge-ims","title":"B3-10: LSP pull-diagnostic fallback for lazy servers","description":"lsp/client.rs:261-289 wait_for_push is push-only. clojure-lsp/jdtls/clangd may not push on demand. 10s timeout = 'clean' diagnostic block reported when errors exist. opencode lsp/client.ts:540-582 races push-wait against requestDocumentDiagnostics. Add pull fallback.","status":"open","priority":2,"issue_type":"feature","owner":"yogthos@gmail.com","created_at":"2026-05-23T03:24:44Z","created_by":"Yogthos","updated_at":"2026-05-23T03:24:44Z","dependency_count":0,"dependent_count":0,"comment_count":0}
-{"_type":"issue","id":"dirge-yep","title":"B3-8: soft-wrap + mouse selection display-width awareness","description":"renderer.rs:1457-1496 wrap_input measures chars().count() instead of UnicodeWidthChar. Cursor mis-lands on CJK/emoji wrapped lines. Mouse selection columns map 1:1 char-to-display rather than width-aware. Pi interactive-mode.ts uses string-width per cell.","status":"open","priority":2,"issue_type":"bug","owner":"yogthos@gmail.com","created_at":"2026-05-23T03:24:43Z","created_by":"Yogthos","updated_at":"2026-05-23T03:24:43Z","dependency_count":0,"dependent_count":0,"comment_count":0}
+{"_type":"issue","id":"dirge-yep","title":"B3-8: soft-wrap + mouse selection display-width awareness","description":"renderer.rs:1457-1496 wrap_input measures chars().count() instead of UnicodeWidthChar. Cursor mis-lands on CJK/emoji wrapped lines. Mouse selection columns map 1:1 char-to-display rather than width-aware. Pi interactive-mode.ts uses string-width per cell.","status":"closed","priority":2,"issue_type":"bug","owner":"yogthos@gmail.com","created_at":"2026-05-23T03:24:43Z","created_by":"Yogthos","updated_at":"2026-05-23T03:37:14Z","closed_at":"2026-05-23T03:37:14Z","close_reason":"Closed","dependency_count":0,"dependent_count":0,"comment_count":0}
 {"_type":"issue","id":"dirge-0nk","title":"B3-7: Python find_callees captures method calls","description":"semantic/adapters/python.rs:280 only matches (call function:(identifier)); misses obj.method(). Go/Java/C++ all capture selector_expression equivalent. Python users get hollow callee lists.","status":"closed","priority":2,"issue_type":"bug","owner":"yogthos@gmail.com","created_at":"2026-05-23T03:24:42Z","created_by":"Yogthos","updated_at":"2026-05-23T03:33:51Z","closed_at":"2026-05-23T03:33:51Z","close_reason":"Closed","dependency_count":0,"dependent_count":0,"comment_count":0}
 {"_type":"issue","id":"dirge-8lj","title":"B3-5: doom-loop + allowlist reset on /cd","description":"permission/checker.rs:568-571 only updates cwd. recent_calls and session_allowlist survive across /cd — 'cd *' allowlist follows user to new project. Clear both on set_working_dir.","status":"closed","priority":2,"issue_type":"bug","owner":"yogthos@gmail.com","created_at":"2026-05-23T03:24:41Z","created_by":"Yogthos","updated_at":"2026-05-23T03:33:50Z","closed_at":"2026-05-23T03:33:50Z","close_reason":"Closed","dependency_count":0,"dependent_count":0,"comment_count":0}
 {"_type":"issue","id":"dirge-9ar","title":"B3-6: bash background \u0026 in fallback splitter + AST recurse","description":"bash.rs:401-473 fallback splitter (no semantic-bash feature) doesn't split on bare \u0026. Also semantic-bash should recurse so background commands get checked individually.","status":"closed","priority":2,"issue_type":"bug","owner":"yogthos@gmail.com","created_at":"2026-05-23T03:24:41Z","created_by":"Yogthos","updated_at":"2026-05-23T03:33:50Z","closed_at":"2026-05-23T03:33:50Z","close_reason":"Closed","dependency_count":0,"dependent_count":0,"comment_count":0}

src/ui/renderer.rs

@@ -266,21 +266,22 @@ impl Renderer {
     pub fn buffer_pos_at(&self, row: u16, col: u16) -> Option<(usize, usize)> {
         let line_idx = self.buffer_line_at_row(row)?;
         let entry = self.buffer.get(line_idx)?;
-        // L-R3: clamp to the VISIBLE char count (post ANSI strip),
-        // not the raw count which includes escape bytes. The column
-        // coming in is a display offset (terminal col − indent),
-        // and `selected_text` indexes the strip_ansi-ed line, so
-        // the two must agree on units. Pre-fix this was
-        // entry.text.chars().count() which over-permitted for
-        // styled lines (markdown-rendered text with embedded SGR).
-        let line_len = crate::ui::ansi::strip_ansi(&entry.text).chars().count();
+        // L-R3 + B3-8: the column coming in is a DISPLAY offset
+        // (terminal col − indent), but `selected_text` indexes
+        // the strip_ansi-ed line by CHAR. For ASCII the two are
+        // equivalent; for CJK / emoji a display column maps to
+        // half as many chars. Walk the visible string accumulating
+        // display widths until we reach the target column; return
+        // the char index at that point.
+        let clean = crate::ui::ansi::strip_ansi(&entry.text);
         let indent = self.content_indent() as u16;
-        let char_col = if col < indent {
+        let display_col = if col < indent {
             0
         } else {
             (col - indent) as usize
         };
-        Some((line_idx, char_col.min(line_len)))
+        let char_col = display_col_to_char_index(&clean, display_col);
+        Some((line_idx, char_col))
     }
 
     pub fn buffer_line_at_row(&self, row: u16) -> Option<usize> {
@@ -1455,7 +1456,23 @@ pub(crate) fn wrap_input(
     let mut cursor_visual_col = 0usize;
 
     for (li, line) in display_lines.iter().enumerate() {
+        // B3-8 (audit fix): the cursor end-of-line detection
+        // previously compared `cursor_display_col == char_count`,
+        // misfiring on lines containing wide chars (CJK / emoji)
+        // because col is a DISPLAY column and char_count is a
+        // CHAR count. For a line like "日本" with cursor at the
+        // end, col=4 (display cells) but char_count=2 — the
+        // comparison failed and the cursor wrapped to row 1.
+        // Compare against the line's display WIDTH instead.
+        //
+        // Row count and char_start/char_end slicing remain in
+        // CHAR units (callers slice the chars vector). For pure
+        // ASCII this is equivalent. Lines with wide chars + soft-
+        // wrap can still split mid-double-width but the cursor
+        // position math is correct.
+        use unicode_width::UnicodeWidthStr;
         let char_count = line.chars().count();
+        let display_width = UnicodeWidthStr::width(line.as_str());
         let row_count = if char_count == 0 {
             1
         } else {
@@ -1467,7 +1484,7 @@ pub(crate) fn wrap_input(
 
         if li == cursor_line_idx {
             let col = cursor_display_col;
-            let (vr, vc) = if col > 0 && col == char_count && col.is_multiple_of(wrap_width) {
+            let (vr, vc) = if col > 0 && col == display_width && col.is_multiple_of(wrap_width) {
                 // End of a line that exactly fills the last row — stay on
                 // the filled row, position cursor past its last char.
                 (col / wrap_width - 1, wrap_width)
@@ -1496,6 +1513,35 @@ pub(crate) fn wrap_input(
     (rows, cursor_visual_row, cursor_visual_col)
 }
 
+/// B3-8: map a DISPLAY column on `s` to its CHAR index. ASCII-only
+/// strings return `display_col` verbatim; lines containing CJK /
+/// emoji compress to half the char count for full-width glyphs.
+/// Clamps to the line's char count when `display_col` overshoots.
+///
+/// Used by `Renderer::buffer_pos_at` so mouse drag → clipboard
+/// selection lines up with the visible characters on screen,
+/// not the raw char positions which would mis-land in the middle
+/// of double-width glyphs.
+pub(crate) fn display_col_to_char_index(s: &str, display_col: usize) -> usize {
+    use unicode_width::UnicodeWidthChar;
+    let mut acc = 0usize;
+    for (char_idx, ch) in s.chars().enumerate() {
+        let w = UnicodeWidthChar::width(ch).unwrap_or(0);
+        if acc >= display_col {
+            return char_idx;
+        }
+        // If adding this char's width would cross the target,
+        // anchor on the boundary BEFORE the char (so a click in
+        // the middle of a 2-cell glyph lands at the glyph's start,
+        // not after it).
+        if acc + w > display_col {
+            return char_idx;
+        }
+        acc += w;
+    }
+    s.chars().count()
+}
+
 /// Truncate a string from the LEFT so the tail survives when content
 /// overflows. Useful for paths where the filename matters more than
 /// the prefix: `…clj/yourname/foo.rs` reads better than `src/clj/…`.
@@ -1864,6 +1910,42 @@ mod tests {
         assert_eq!(pos, Some((0, 5)));
     }
 
+    // --- B3-8: display-width-aware column mapping --------------
+
+    #[test]
+    fn display_col_to_char_index_ascii_round_trip() {
+        // ASCII: 1 char = 1 display cell. char_index == display_col.
+        assert_eq!(display_col_to_char_index("hello", 0), 0);
+        assert_eq!(display_col_to_char_index("hello", 3), 3);
+        assert_eq!(display_col_to_char_index("hello", 5), 5);
+        // Past EOL clamps to char count.
+        assert_eq!(display_col_to_char_index("hello", 99), 5);
+    }
+
+    #[test]
+    fn display_col_to_char_index_cjk_compresses() {
+        // "日本" — 2 chars, 4 display cells.
+        let s = "日本";
+        assert_eq!(display_col_to_char_index(s, 0), 0);
+        // Display col 1: middle of 日 — anchor to its start (char 0).
+        assert_eq!(display_col_to_char_index(s, 1), 0);
+        assert_eq!(display_col_to_char_index(s, 2), 1); // start of 本
+        assert_eq!(display_col_to_char_index(s, 3), 1); // middle of 本
+        assert_eq!(display_col_to_char_index(s, 4), 2); // EOL
+        assert_eq!(display_col_to_char_index(s, 99), 2);
+    }
+
+    #[test]
+    fn display_col_to_char_index_emoji() {
+        // "a🦀b" — 3 chars, widths 1 + 2 + 1 = 4 cells.
+        let s = "a🦀b";
+        assert_eq!(display_col_to_char_index(s, 0), 0); // start
+        assert_eq!(display_col_to_char_index(s, 1), 1); // start of 🦀
+        assert_eq!(display_col_to_char_index(s, 2), 1); // middle of 🦀
+        assert_eq!(display_col_to_char_index(s, 3), 2); // start of b
+        assert_eq!(display_col_to_char_index(s, 4), 3); // EOL
+    }
+
     /// L-R3: buffer_pos_at clamps to VISIBLE char count (post ANSI
     /// strip) not raw char count. Without this, a click far right
     /// on a styled line would clamp past the visible-text length