fix: render ansi undercurl styles

refs #895

2 files changed, 79 insertions, 6 deletions

diff --git a/src/pane/terminal.rs b/src/pane/terminal.rs
index b36ae0ee..708a7d28 100644
--- a/src/pane/terminal.rs
+++ b/src/pane/terminal.rs
@@ -2010,6 +2010,7 @@ fn ghostty_cell_style(
     if basic.style.strikethrough {
         modifiers |= Modifier::CROSSED_OUT;
     }
+    modifiers = crate::protocol::modifier_with_underline_style(modifiers, basic.style.underline);
     style.add_modifier(modifiers)
 }
 
@@ -3783,8 +3784,7 @@ mod tests {
         let pane = GhosttyPaneTerminal::new(terminal, tx.clone()).unwrap();
         let pane_id = PaneId::from_raw(1);
 
-        let result =
-            pane.process_pty_bytes(pane_id, 0, b"\x1bP+q6E6F7065;536D756C78;4D7\x1b\\", &tx);
+        let result = pane.process_pty_bytes(pane_id, 0, b"\x1bP+q6E6F7065;4D7\x1b\\", &tx);
 
         assert!(result.terminal_responses.is_empty());
         assert!(rx.try_recv().is_err());
@@ -3797,12 +3797,18 @@ mod tests {
         let pane = GhosttyPaneTerminal::new(terminal, tx.clone()).unwrap();
         let pane_id = PaneId::from_raw(1);
 
-        let result = pane.process_pty_bytes(pane_id, 0, b"\x1bP+q5375;536574756C63\x1b\\", &tx);
+        let result = pane.process_pty_bytes(
+            pane_id,
+            0,
+            b"\x1bP+q5375;536D756C78;536574756C63\x1b\\",
+            &tx,
+        );
 
         assert_eq!(
             result.terminal_responses,
             vec![
                 expected_xtgettcap_response("5375", None),
+                expected_xtgettcap_response("536D756C78", Some(b"\\E[4:%p1%dm")),
                 expected_xtgettcap_response(
                     "536574756C63",
                     Some(b"\\E[58:2::%p1%{65536}%/%d:%p1%{256}%/%{255}%&%d:%p1%{255}%&%d%;m")
@@ -3834,6 +3840,59 @@ mod tests {
     }
 
     #[test]
+    fn dirty_patch_preserves_curly_underline_style() {
+        let (tx, _rx) = mpsc::channel(4);
+        let terminal = crate::ghostty::Terminal::new(20, 5, 0).unwrap();
+        let pane = GhosttyPaneTerminal::new(terminal, tx).unwrap();
+        let backend = ratatui::backend::TestBackend::new(20, 5);
+        let mut terminal = ratatui::Terminal::new(backend).unwrap();
+        terminal
+            .draw(|frame| pane.render(frame, Rect::new(0, 0, 20, 5), false))
+            .unwrap();
+        {
+            let mut core = pane.core.lock().unwrap();
+            core.terminal.write(b"\x1b[4:3mU");
+        }
+
+        let patch = match pane.collect_dirty_patch(20, 5) {
+            TerminalDirtyPatchOutcome::Patch(patch) => patch,
+            other => panic!("expected dirty patch, got {other:?}"),
+        };
+
+        let cell = &patch.rows[0].1[0];
+        assert_eq!(cell.symbol, "U");
+        assert_eq!(
+            crate::protocol::underline_style_from_modifier(cell.modifier),
+            3
+        );
+    }
+
+    #[test]
+    fn full_frame_preserves_curly_underline_style() {
+        let (tx, _rx) = mpsc::channel(4);
+        let terminal = crate::ghostty::Terminal::new(20, 5, 0).unwrap();
+        let pane = GhosttyPaneTerminal::new(terminal, tx).unwrap();
+        {
+            let mut core = pane.core.lock().unwrap();
+            core.terminal.write(b"\x1b[4:3mU");
+        }
+
+        let backend = ratatui::backend::TestBackend::new(20, 5);
+        let mut terminal = ratatui::Terminal::new(backend).unwrap();
+        terminal
+            .draw(|frame| pane.render(frame, Rect::new(0, 0, 20, 5), false))
+            .unwrap();
+
+        let frame =
+            crate::protocol::FrameData::from_ratatui_buffer(terminal.backend().buffer(), None);
+        assert_eq!(frame.cells[0].symbol, "U");
+        assert_eq!(
+            crate::protocol::underline_style_from_modifier(frame.cells[0].modifier),
+            3
+        );
+    }
+
+    #[test]
     fn process_pty_bytes_orders_default_color_reply_before_following_device_attribute_reply() {
         let (tx, mut rx) = mpsc::channel(4);
         let terminal = crate::ghostty::Terminal::new(20, 5, 0).unwrap();
diff --git a/src/pane/xtgettcap.rs b/src/pane/xtgettcap.rs
index f0a91df5..7d2dfc5d 100644
--- a/src/pane/xtgettcap.rs
+++ b/src/pane/xtgettcap.rs
@@ -174,8 +174,7 @@ fn xtgettcap_response(cap_hex: &[u8]) -> Option<Bytes> {
 }
 
 fn xtgettcap_value(cap_hex: &[u8]) -> Option<Option<&'static [u8]>> {
-    // Mirror only the Ghostty terminfo capabilities that this pane path can
-    // stand behind. Smulx is intentionally absent until underline shapes render.
+    // Mirror only the Ghostty terminfo capabilities that this pane path can stand behind.
     match cap_hex {
         b"5463" => Some(None),
         b"524742" => Some(Some(b"8")),
@@ -183,6 +182,7 @@ fn xtgettcap_value(cap_hex: &[u8]) -> Option<Option<&'static [u8]>> {
         b"73657472676262" => Some(Some(b"\\E[48:2:%p1%d:%p2%d:%p3%dm")),
         b"4D73" => Some(Some(b"\\E]52;%p1%s;%p2%s\\007")),
         b"5375" => Some(None),
+        b"536D756C78" => Some(Some(b"\\E[4:%p1%dm")),
         b"536574756C63" => Some(Some(
             b"\\E[58:2::%p1%{65536}%/%d:%p1%{256}%/%{255}%&%d:%p1%{255}%&%d%;m",
         )),
@@ -255,12 +255,26 @@ mod tests {
     fn tracker_ignores_unsupported_capabilities() {
         let mut tracker = XtgettcapQueryTracker::default();
 
-        tracker.observe(b"\x1bP+q536D756C78;6E6F7065\x1b\\");
+        tracker.observe(b"\x1bP+q6E6F7065\x1b\\");
 
         assert!(response_bytes(tracker.drain_pending()).is_empty());
     }
 
     #[test]
+    fn tracker_returns_underline_style_capability() {
+        let mut tracker = XtgettcapQueryTracker::default();
+
+        tracker.observe(b"\x1bP+q536D756C78\x1b\\");
+
+        assert_eq!(
+            response_bytes(tracker.drain_pending()),
+            vec![Bytes::from_static(
+                b"\x1bP1+r536D756C78=5C455B343A25703125646D\x1b\\"
+            )]
+        );
+    }
+
+    #[test]
     fn tracker_keeps_split_query_until_string_terminator() {
         let mut tracker = XtgettcapQueryTracker::default();