From 6f9585f65f4b4e88c79bbefcf242c03ef67a414d Mon Sep 17 00:00:00 2001
From: cartermp <pcarter@fastmail.com>
Date: Wed, 25 Mar 2026 12:32:00 -0700
Subject: [PATCH] gutter

---
 src/main.rs     | 35 ++++++++++++++++++++++++++++++++---
 src/renderer.rs | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+), 3 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 825dc25..c71ae02 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -388,9 +388,9 @@ impl App {
                     "c" => {
                         // Copy selection if active; otherwise do nothing.
                         if self.selection.is_some() {
-                            let text = self.selection_text();
-                            if !text.is_empty() {
-                                copy_to_clipboard(&text);
+                            let raw = self.selection_text();
+                            if !raw.is_empty() {
+                                copy_to_clipboard(&strip_tcat_gutter(&raw));
                             }
                             self.selection = None;
                             if let Some(w) = &self.window {
@@ -887,6 +887,35 @@ fn copy_to_clipboard(text: &str) {
     }
 }
 
+/// Strip tcat's line-number gutter from copied text.
+/// tcat renders each line as "  {N} │ {content}".  We find the U+2502
+/// separator flanked by spaces, verify the prefix is digits+spaces, and
+/// return only the content.
+fn strip_tcat_gutter(text: &str) -> String {
+    const SEP: char = '\u{2502}'; // │
+    text.lines()
+        .map(|line| {
+            // Find │ with a space on each side
+            let chars: Vec<char> = line.chars().collect();
+            for i in 1..chars.len().saturating_sub(1) {
+                if chars[i] != SEP || chars[i - 1] != ' ' || chars[i + 1] != ' ' {
+                    continue;
+                }
+                // Prefix (0..i-1) must be spaces/digits with at least one digit
+                let prefix = &chars[..i - 1];
+                if prefix.iter().all(|&c| c == ' ' || c == '\0' || c.is_ascii_digit())
+                    && prefix.iter().any(|c| c.is_ascii_digit())
+                {
+                    // Content starts at i+2 (after │ and trailing space)
+                    return chars[i + 2..].iter().collect::<String>();
+                }
+            }
+            line.to_string()
+        })
+        .collect::<Vec<String>>()
+        .join("\n")
+}
+
 fn paste_from_clipboard() -> String {
     use std::process::Command;
     Command::new("pbpaste")
diff --git a/src/renderer.rs b/src/renderer.rs
index 116834b..2ae9f83 100644
--- a/src/renderer.rs
+++ b/src/renderer.rs
@@ -22,6 +22,35 @@ pub struct Renderer {
     font_size: f32,
 }
 
+/// Find the first content column of a tcat gutter line, or 0 if this row is
+/// not tcat output.  tcat renders: `  {digits} │ content` — we detect the
+/// BOX-DRAWINGS LIGHT VERTICAL (U+2502) with a space on each side, preceded
+/// only by spaces and digits.
+fn tcat_gutter_end(state: &TerminalState, row: usize, vis_cols: usize) -> usize {
+    // │ can't appear at col 0 (needs a space before it) or at the last col
+    for c in 1..vis_cols.saturating_sub(1) {
+        if state.visual_cell(row, c).c != '\u{2502}' {
+            continue;
+        }
+        if state.visual_cell(row, c - 1).c != ' ' {
+            continue;
+        }
+        if state.visual_cell(row, c + 1).c != ' ' {
+            continue;
+        }
+        // Everything in 0..c-1 must be spaces/null/digits, with at least one digit
+        let mut prefix = 0..c - 1;
+        let has_digit = prefix.clone().any(|i| state.visual_cell(row, i).c.is_ascii_digit());
+        let all_ok = prefix.all(|i| {
+            matches!(state.visual_cell(row, i).c, ' ' | '\0' | '0'..='9')
+        });
+        if has_digit && all_ok {
+            return c + 2; // column after "│ "
+        }
+    }
+    0
+}
+
 impl Renderer {
     pub fn new(scale_factor: f64) -> Self {
         let font_size = (FONT_SIZE_PT * scale_factor as f32).round();
@@ -390,6 +419,13 @@ impl Renderer {
         let sel_bg = Color::new(0x26, 0x4a, 0x7a).to_u32(); // muted blue selection
 
         for row in 0..vis_rows {
+            // Per-row: detect tcat gutter so it's excluded from selection highlight.
+            let gutter = if selection.is_some() {
+                tcat_gutter_end(state, row, vis_cols)
+            } else {
+                0
+            };
+
             for col in 0..vis_cols {
                 let cell = state.visual_cell(row, col);
                 let mut fg = cell.attrs.fg;
@@ -403,6 +439,7 @@ impl Renderer {
                         && row <= r1
                         && !(row == r0 && col < c0)
                         && !(row == r1 && col > c1)
+                        && col >= gutter
                 } else {
                     false
                 };
-- 
2.51.2