fix(terminal): render halfwidth katakana voiced marks (#2257)

Co-authored-by: oyoguhito <oyoguhito@kamatanoMacBook-Pro.local>
Co-authored-by: Can Celik <ogulcancelik@gmail.com>

1 files changed, 93 insertions, 5 deletions

diff --git a/src/pane/terminal.rs b/src/pane/terminal.rs
index d4f167a9..4bd50669 100644
--- a/src/pane/terminal.rs
+++ b/src/pane/terminal.rs
@@ -2654,10 +2654,26 @@ pub(super) fn ghostty_normalize_buffer_symbol(
     if wide == crate::ghostty::CellWide::Narrow && actual_width == 2 {
         return symbol.to_string();
     }
+    if wide == crate::ghostty::CellWide::Wide && is_halfwidth_katakana_voiced_grapheme(symbol) {
+        return symbol.to_string();
+    }
 
     ghostty_blank_symbol_for_width(wide).to_string()
 }
 
+fn is_halfwidth_katakana_voiced_grapheme(symbol: &str) -> bool {
+    let mut chars = symbol.chars();
+    let Some(base) = chars.next() else {
+        return false;
+    };
+    let Some(mark) = chars.next() else {
+        return false;
+    };
+    chars.next().is_none()
+        && ('\u{ff66}'..='\u{ff9d}').contains(&base)
+        && matches!(mark, '\u{ff9e}' | '\u{ff9f}')
+}
+
 fn ghostty_buffer_symbol_into<'a>(
     cells: &crate::ghostty::RowCellIter<'_>,
     wide: crate::ghostty::CellWide,
@@ -2689,6 +2705,8 @@ fn ghostty_buffer_symbol_into<'a>(
     let actual_width = symbol_scratch.width();
     if actual_width != expected_width
         && !(wide == crate::ghostty::CellWide::Narrow && actual_width == 2)
+        && !(wide == crate::ghostty::CellWide::Wide
+            && is_halfwidth_katakana_voiced_grapheme(symbol_scratch))
     {
         symbol_scratch.clear();
         symbol_scratch.push_str(ghostty_blank_symbol_for_width(wide));
@@ -2721,11 +2739,7 @@ fn blank_cell_data(default_fg: Option<Color>, default_bg: Option<Color>) -> Cell
 
 fn cell_data_from_style(symbol: String, style: Style) -> CellData {
     CellData {
-        symbol: if symbol.is_empty() {
-            " ".to_string()
-        } else {
-            symbol
-        },
+        symbol,
         fg: crate::protocol::color_to_u32(style.fg.unwrap_or(Color::Reset)),
         bg: crate::protocol::color_to_u32(style.bg.unwrap_or(Color::Reset)),
         modifier: crate::protocol::modifier_to_u16(style.add_modifier),
@@ -4441,6 +4455,14 @@ mod tests {
             ghostty_normalize_buffer_symbol("xx", crate::ghostty::CellWide::SpacerHead),
             " "
         );
+        assert_eq!(
+            ghostty_normalize_buffer_symbol("ｶ\u{ff9e}", crate::ghostty::CellWide::Wide),
+            "ｶ\u{ff9e}"
+        );
+        assert_eq!(
+            ghostty_normalize_buffer_symbol("ﾊ\u{ff9f}", crate::ghostty::CellWide::Wide),
+            "ﾊ\u{ff9f}"
+        );
     }
 
     fn render_cells_to_symbols(
@@ -4510,6 +4532,72 @@ mod tests {
     }
 
     #[test]
+    fn halfwidth_katakana_voiced_marks_render() {
+        let mut terminal = crate::ghostty::Terminal::new(40, 1, 0).unwrap();
+        terminal.write("ｱｲｳｴｵ ｶﾞｷﾞｸﾞｹﾞｺﾞ ﾊﾟﾋﾟﾌﾟﾍﾟﾎﾟ".as_bytes());
+
+        let cells = render_cells_to_symbols(&mut terminal);
+        let rendered: String = cells.iter().map(|(_, symbol)| symbol.as_str()).collect();
+
+        assert!(
+            rendered.contains("ｱｲｳｴｵ ｶﾞｷﾞｸﾞｹﾞｺﾞ ﾊﾟﾋﾟﾌﾟﾍﾟﾎﾟ"),
+            "expected halfwidth katakana with voiced marks to survive, got {cells:?}"
+        );
+    }
+
+    #[test]
+    fn render_keeps_halfwidth_katakana_voiced_tail_empty() {
+        let (tx, _rx) = mpsc::channel(4);
+        let mut terminal = crate::ghostty::Terminal::new(20, 1, 0).unwrap();
+        terminal.write("ｶﾞZ".as_bytes());
+        let pane = GhosttyPaneTerminal::new(terminal, tx).unwrap();
+
+        let backend = ratatui::backend::TestBackend::new(20, 1);
+        let mut terminal = ratatui::Terminal::new(backend).unwrap();
+        terminal
+            .draw(|frame| pane.render(frame, Rect::new(0, 0, 20, 1), false))
+            .unwrap();
+        let buffer = terminal.backend().buffer();
+
+        assert_eq!(buffer[(0, 0)].symbol(), "ｶ\u{ff9e}");
+        assert_eq!(
+            buffer[(1, 0)].symbol(),
+            "",
+            "wide spacer tail must stay empty so the host terminal does not overwrite the voiced kana"
+        );
+        assert_eq!(buffer[(2, 0)].symbol(), "Z");
+    }
+
+    #[test]
+    fn dirty_patch_keeps_halfwidth_katakana_voiced_tail_empty() {
+        let (tx, _rx) = mpsc::channel(4);
+        let terminal = crate::ghostty::Terminal::new(20, 1, 0).unwrap();
+        let pane = GhosttyPaneTerminal::new(terminal, tx).unwrap();
+        let backend = ratatui::backend::TestBackend::new(20, 1);
+        let mut terminal = ratatui::Terminal::new(backend).unwrap();
+        terminal
+            .draw(|frame| pane.render(frame, Rect::new(0, 0, 20, 1), false))
+            .unwrap();
+        {
+            let mut core = pane.core.lock().unwrap();
+            core.terminal.write("ｶﾞZ".as_bytes());
+        }
+
+        let patch = match pane.collect_dirty_patch(20, 1) {
+            TerminalDirtyPatchOutcome::Patch(patch) => patch,
+            other => panic!("expected dirty patch, got {other:?}"),
+        };
+        let row = &patch.rows[0].1;
+
+        assert_eq!(row[0].symbol, "ｶ\u{ff9e}");
+        assert_eq!(
+            row[1].symbol, "",
+            "wide spacer tail must stay empty in retained terminal patches"
+        );
+        assert_eq!(row[2].symbol, "Z");
+    }
+
+    #[test]
     fn pane_scrollback_controls_round_trip_and_clamp_without_ui_interference() {
         let (tx, _rx) = mpsc::channel(4);
         let mut terminal = crate::ghostty::Terminal::new(80, 3, 100).unwrap();