ui: ellipsize fake-terminal pane lines wider than the terminal

Overflowing log lines in the pkh deb / pkh build rolling pane used to
wrap onto a second line, corrupting the pane layout. Truncate them to
the terminal width (minus the pane prefix) by display width and append
an ellipsis instead; lines are left whole when the terminal size is
unknown.

Cargo.toml

@@ -34,6 +34,7 @@ ssh2 = "0.9.5"
 gpgme = "0.11"
 serde_yaml = "0.9"
 lazy_static = "1.4.0"
+unicode-width = "0.2"
 
 [dev-dependencies]
 test-log = "0.2.19"

src/ui/deb.rs

@@ -19,6 +19,7 @@ use std::time::{Duration, Instant};
 use crossterm::{cursor, execute, style::Stylize, terminal::Clear, terminal::ClearType};
 use directories::ProjectDirs;
 use indicatif::{MultiProgress, ProgressBar, ProgressStyle};
+use unicode_width::{UnicodeWidthChar, UnicodeWidthStr};
 
 use crate::context::{LineSink, Stream};
 use crate::logfmt::{Action, Classifier, GenericClassifier};
@@ -411,19 +412,65 @@ fn push_line(shared: &Shared, st: &mut Pipeline, kind: Kind, text: String) {
     }
 }
 
-/// Render the pane content with per-kind colors
+/// Render the pane content with per-kind colors, ellipsizing lines that are
+/// wider than the terminal so they do not overflow onto a wrapped line
 fn render_pane(lines: &VecDeque<(Kind, String)>) -> String {
+    let max_width = terminal_width().map(|w| w.saturating_sub(PANE_PREFIX_WIDTH));
+    render_pane_with_width(lines, max_width)
+}
+
+/// [`render_pane`] with the available pane width injected (in display
+/// columns); `None` means the terminal size is unknown and lines are kept whole
+fn render_pane_with_width(lines: &VecDeque<(Kind, String)>, max_width: Option<usize>) -> String {
     lines
         .iter()
-        .map(|(kind, text)| match kind {
+        .map(|(kind, text)| {
+            let text = match max_width {
+                Some(width) => ellipsize(text, width),
+                None => text.clone(),
+            };
+            match kind {
                 Kind::Normal => format!("  │ {text}"),
                 Kind::Warning => format!("  │ {}", text.as_str().yellow()),
                 Kind::Error => format!("  │ {}", text.as_str().red()),
+            }
         })
         .collect::<Vec<_>>()
         .join("\n")
 }
 
+/// Display width of the `  │ ` prefix rendered before each pane line
+const PANE_PREFIX_WIDTH: usize = 4;
+
+/// Width of the terminal in columns, or `None` when it cannot be determined
+fn terminal_width() -> Option<usize> {
+    crossterm::terminal::size()
+        .ok()
+        .map(|(cols, _)| cols as usize)
+}
+
+/// Ellipsize `text` to at most `max_width` display columns, keeping its head
+/// and appending `…` when it does not fit
+fn ellipsize(text: &str, max_width: usize) -> String {
+    if UnicodeWidthStr::width(text) <= max_width {
+        return text.to_string();
+    }
+    // Reserve one column for the ellipsis itself
+    let budget = max_width.saturating_sub(1);
+    let mut out = String::new();
+    let mut width = 0;
+    for ch in text.chars() {
+        let w = UnicodeWidthChar::width(ch).unwrap_or(0);
+        if width + w > budget {
+            break;
+        }
+        out.push(ch);
+        width += w;
+    }
+    out.push('…');
+    out
+}
+
 /// Status bar style while no determinate progress is known
 ///
 /// The target lives on the first line and the current phase/message on its own
@@ -516,3 +563,96 @@ extern "C" fn on_sigint(_sig: libc::c_int) {
         libc::_exit(130);
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn ellipsize_keeps_short_lines() {
+        assert_eq!(ellipsize("short", 10), "short");
+        assert_eq!(ellipsize("exactly10!", 10), "exactly10!");
+    }
+
+    #[test]
+    fn ellipsize_truncates_long_lines_to_the_width_budget() {
+        let out = ellipsize("a very long build line that overflows", 20);
+        assert_eq!(UnicodeWidthStr::width(out.as_str()), 20);
+        assert!(out.ends_with('…'));
+        assert!(out.starts_with("a very long build"));
+    }
+
+    #[test]
+    fn ellipsize_never_exceeds_the_budget_with_wide_characters() {
+        let out = ellipsize("wíth émojis 🎉 and 文字 mixing", 12);
+        assert!(UnicodeWidthStr::width(out.as_str()) <= 12);
+        assert!(out.ends_with('…'));
+    }
+
+    #[test]
+    fn ellipsize_degenerate_width_still_terminates() {
+        assert_eq!(ellipsize("overflowing", 0), "…");
+        assert_eq!(ellipsize("overflowing", 1), "…");
+    }
+
+    #[test]
+    fn pane_lines_are_ellipsized_but_keep_their_prefix_and_color() {
+        let mut lines = VecDeque::new();
+        lines.push_back((
+            Kind::Normal,
+            "gcc -DHAVE_CONFIG_H -I. -I.. -g -O2 -c hello.c".to_string(),
+        ));
+        lines.push_back((
+            Kind::Error,
+            "an error much too long for the pane".to_string(),
+        ));
+
+        let rendered = render_pane_with_width(&lines, Some(20));
+
+        let rendered = rendered.lines().collect::<Vec<_>>();
+        assert_eq!(rendered.len(), 2);
+        // The injected budget is the text width; every rendered line stays
+        // within the simulated terminal width (prefix + budget)
+        for line in &rendered {
+            let plain = strip_ansi(line);
+            assert!(
+                UnicodeWidthStr::width(plain.as_str()) <= 20 + PANE_PREFIX_WIDTH,
+                "{plain}"
+            );
+        }
+        assert!(strip_ansi(rendered[0]).starts_with("  │ gcc -DHAVE_CONFIG_H"));
+        // The error keeps its color wrapping around the ellipsized text
+        assert!(rendered[1].contains('\x1b'), "{rendered:?}");
+        assert!(strip_ansi(rendered[1]).starts_with("  │ an error much too l…"));
+    }
+
+    #[test]
+    fn pane_lines_are_kept_whole_without_a_known_terminal_size() {
+        let mut lines = VecDeque::new();
+        lines.push_back((
+            Kind::Normal,
+            "a line that would overflow a narrow pane".to_string(),
+        ));
+
+        let rendered = render_pane_with_width(&lines, None);
+        assert!(rendered.contains("a line that would overflow a narrow pane"));
+    }
+
+    /// Best-effort ANSI escape stripper, enough for the assertions above
+    fn strip_ansi(line: &str) -> String {
+        let mut out = String::new();
+        let mut chars = line.chars();
+        while let Some(ch) = chars.next() {
+            if ch == '\x1b' {
+                for esc in chars.by_ref() {
+                    if esc.is_ascii_alphabetic() {
+                        break;
+                    }
+                }
+            } else {
+                out.push(ch);
+            }
+        }
+        out
+    }
+}