Fix capacity overflow panic wrapping a wide char at narrow terminal width

CHANGELOG.md

@@ -37,6 +37,7 @@
 - `--strip-ansi`: also strip 8-bit C1 introducers (U+0090, U+0098, U+009B, U+009D, U+009E, U+009F) and DCS/SOS/PM/APC sequence bodies, which previously passed through. See #3729 (@curious-rabbit)
 - Fix `--ignored-suffix` not falling back to first-line/shebang detection when the ignored suffix is also a registered extension (e.g. `--ignored-suffix .txt` on a shebang script), see #2745 and #3816 (@adnrivera)
 - Fix `capacity overflow` panic when printing a snip separator at `--terminal-width=1` with multiple line ranges. Closes #3803, see #3804 (@leeewee)
+- Fix `capacity overflow` panic when character-wrapping a line containing a character wider than `--terminal-width` with a painted background (e.g. `--highlight-line`). Closes #3844, see #3886 (@vjymisal0)
 - Pass `--no-paging` to `bat` invocations inside the bash / zsh / fish / PowerShell shell completion scripts so that shell-level pager wiring (e.g. `LESSOPEN='|-bat -f -pp %s'`) cannot inject ANSI escape sequences into the completion candidates. Closes #3760 (@mvanhorn)
 - Quote filenames before substituting them into `$LESSOPEN` / `$LESSCLOSE` templates, preventing shell injection when a filename contains shell metacharacters, see #3726 (@curious-rabbit)
 - Fix `--list-themes` unconditionally probing the terminal via OSC 10/11 even when `--theme` was set to an explicit value, see #3700 (regression introduced in bc42149a). (@optimistiCli)

src/printer.rs

@@ -826,7 +826,7 @@ impl Printer for InteractivePrinter<'_> {
                             let text = self
                                 .preprocess(text.trim_end_matches(['\r', '\n']), &mut cursor_total);
 
-                            let mut max_width = cursor_max - cursor;
+                            let mut max_width = cursor_max.saturating_sub(cursor);
 
                             // line buffer (avoid calling write! for every character)
                             let mut line_buf = String::with_capacity(max_width * 4);
@@ -965,7 +965,7 @@ impl Printer for InteractivePrinter<'_> {
                 write!(
                     handle,
                     "{}",
-                    ansi_style.paint(" ".repeat(cursor_max - cursor))
+                    ansi_style.paint(" ".repeat(cursor_max.saturating_sub(cursor)))
                 )?;
             }
             writeln!(handle)?;

tests/integration_tests.rs

@@ -445,6 +445,24 @@ fn snip_at_terminal_width_one_does_not_panic() {
         .success();
 }
 
+#[test]
+fn wide_char_wrap_at_terminal_width_one_with_highlight_does_not_panic() {
+    // Regression test: a character wider than the terminal (e.g. a
+    // double-width emoji) combined with character wrapping and a painted
+    // background (via --highlight-line) used to make the cursor advance
+    // past `cursor_max`, causing `cursor_max - cursor` to underflow and
+    // `str::repeat` to abort with "capacity overflow".
+    bat()
+        .arg("--highlight-line=1")
+        .arg("--terminal-width=1")
+        .arg("--wrap=character")
+        .arg("--color=always")
+        .arg("--paging=never")
+        .write_stdin("\u{1F4E6}\u{1F4E6}\n")
+        .assert()
+        .success();
+}
+
 #[test]
 fn line_range_multiple_with_context() {
     bat()