[FEATURE REQUEST] Underline terminal links on mouse hover

src/term/frame.rs

@@ -84,7 +84,12 @@ impl Frame {
 }
 
 /// The screen as it shows now, scrolled back or not; `lit` matches wear their washes.
-pub fn frame<T: EventListener>(term: &Term<T>, ink: &Ink, lit: &[(Match, Hsla)]) -> Frame {
+pub fn frame<T: EventListener>(
+    term: &Term<T>,
+    ink: &Ink,
+    lit: &[(Match, Hsla)],
+    link: Option<&Match>,
+) -> Frame {
     let content = term.renderable_content();
     let offset = content.display_offset as i32;
     let mut rows = vec![Row::default(); term.screen_lines()];
@@ -117,6 +122,13 @@ pub fn frame<T: EventListener>(term: &Term<T>, ink: &Ink, lit: &[(Match, Hsla)])
             .intersects(Flags::WIDE_CHAR_SPACER | Flags::LEADING_WIDE_CHAR_SPACER);
         // A placeholder's image draws over its cell; its glyph never.
         let hidden = cell.flags.contains(Flags::HIDDEN) || cell.c == super::graphics::PLACEHOLDER;
+        if !hidden
+            && look.underline == Underline::None
+            && link.is_some_and(|link| covers(&|at| link.contains(&at)))
+        {
+            look.underline = Underline::Single;
+            look.underline_color = look.fg;
+        }
         let marks = cell.zerowidth().filter(|marks| !marks.is_empty());
         let alone = (!hidden && (marks.is_some() || boxes::drawn(cell.c))).then(|| {
             std::iter::once(cell.c)
@@ -204,6 +216,9 @@ fn style(cell: &Cell, ink: &Ink, set: &Colors) -> Style {
     }
 }
 
+#[cfg(test)]
+mod hover_tests;
+
 #[cfg(test)]
 mod tests {
     use alacritty_terminal::{
@@ -220,7 +235,7 @@ mod tests {
         let mut parser: Processor = Processor::new();
         parser.advance(&mut term, bytes);
         let ink = Ink::new(themes::find("dracula").expect("dracula"), term.colors());
-        (frame(&term, &ink, &[]), ink)
+        (frame(&term, &ink, &[], None), ink)
     }
 
     #[test]
@@ -338,7 +353,7 @@ mod tests {
         selection.update(Point::new(Line(0), Column(3)), Side::Left);
         term.selection = Some(selection);
         let ink = Ink::new(themes::find("dracula").expect("dracula"), term.colors());
-        let frame = frame(&term, &ink, &[]);
+        let frame = frame(&term, &ink, &[], None);
         let grounds: Vec<_> = frame.rows[0]
             .runs
             .iter()
@@ -369,7 +384,7 @@ mod tests {
                 .map(|(bytes, style)| (*bytes, style.bg))
                 .collect()
         };
-        let shown = frame(&term, &ink, &lit);
+        let shown = frame(&term, &ink, &lit, None);
         assert_eq!(
             &grounds(&shown)[..5],
             [
@@ -386,7 +401,7 @@ mod tests {
             .as_mut()
             .expect("a selection")
             .update(at(6), Side::Right);
-        let shown = frame(&term, &ink, &lit);
+        let shown = frame(&term, &ink, &lit, None);
         assert_eq!(
             grounds(&shown)[3],
             (1, Some(ink.selection)),

src/term/frame/hover_tests.rs

@@ -0,0 +1,86 @@
+use super::*;
+use crate::{term::links::hit_at, themes};
+use alacritty_terminal::{
+    event::VoidListener,
+    grid::Scroll,
+    index::{Column, Line},
+    term::{Config, test::TermSize},
+    vte::ansi::Processor,
+};
+
+fn term(text: &str) -> Term<VoidListener> {
+    let mut term = Term::new(Config::default(), &TermSize::new(12, 3), VoidListener);
+    <Processor>::new().advance(&mut term, text.as_bytes());
+    term
+}
+
+fn styles(frame: &Frame) -> Vec<Style> {
+    frame
+        .rows
+        .iter()
+        .flat_map(|row| {
+            row.runs
+                .iter()
+                .flat_map(|(bytes, style)| std::iter::repeat_n(*style, *bytes))
+        })
+        .collect()
+}
+
+fn shown(term: &Term<VoidListener>, hover: Option<Point>) -> Frame {
+    let ink = Ink::new(themes::find("dracula").expect("a theme"), term.colors());
+    let link = hover.and_then(|point| hit_at(term, point));
+    frame(term, &ink, &[], link.as_ref())
+}
+
+#[test]
+fn hover_underlines_the_whole_link_and_leaving_restores_its_style() {
+    let term = term("(https://a.b/c) ");
+    let hover = Point::new(Line(0), Column(4));
+    let painted = styles(&shown(&term, Some(hover)));
+    assert_eq!(painted[0].underline, Underline::None);
+    assert!(
+        painted[1..14]
+            .iter()
+            .all(|style| style.underline == Underline::Single)
+    );
+    assert_eq!(painted[14].underline, Underline::None);
+    assert!(
+        styles(&shown(&term, None))
+            .iter()
+            .all(|style| style.underline == Underline::None)
+    );
+    assert!(!term.grid()[hover].flags.contains(Flags::UNDERLINE));
+}
+
+#[test]
+fn hover_preserves_explicit_underlines_and_hidden_text() {
+    let term = term("\x1b[4:3m\x1b]8;;https://a.b\x07label\x1b]8;;\x07");
+    let hover = Point::new(Line(0), Column(2));
+    assert_eq!(shown(&term, Some(hover)).rows, shown(&term, None).rows);
+    let term = self::term("\x1b[8mhttps://a.b\x1b[0m");
+    assert!(
+        styles(&shown(&term, Some(hover)))
+            .iter()
+            .all(|style| style.underline == Underline::None)
+    );
+}
+
+#[test]
+fn hover_follows_history_and_output_changes_without_a_mouse_move() {
+    let mut term = term("https://a.b\r\nnext\r\nlast\r\nbottom");
+    term.scroll_display(Scroll::Top);
+    let hover = Point::new(Line(-1), Column(2));
+    assert!(
+        styles(&shown(&term, Some(hover)))[..11]
+            .iter()
+            .all(|style| style.underline == Underline::Single)
+    );
+    let mut term = self::term("https://a.b");
+    let hover = Point::new(Line(0), Column(2));
+    <Processor>::new().advance(&mut term, b"\r\x1b[2Kplain");
+    assert!(
+        styles(&shown(&term, Some(hover)))
+            .iter()
+            .all(|style| style.underline == Underline::None)
+    );
+}