fix: enable grapheme clusters in panes

refs #243

3 files changed, 126 insertions, 0 deletions

diff --git a/src/ghostty/mod.rs b/src/ghostty/mod.rs
index a64fece1..08d0e117 100644
--- a/src/ghostty/mod.rs
+++ b/src/ghostty/mod.rs
@@ -161,6 +161,7 @@ pub const MODE_MOUSE_ALTERNATE_SCROLL: u16 = 1007;
 pub const MODE_MOUSE_SGR_PIXELS: u16 = 1016;
 pub const MODE_BRACKETED_PASTE: u16 = 2004;
 pub const MODE_SYNCHRONIZED_OUTPUT: u16 = 2026;
+pub const MODE_GRAPHEME_CLUSTER: u16 = 2027;
 
 const KITTY_IMAGE_STORAGE_LIMIT_BYTES: u64 = 64 * 1024 * 1024;
 const APC_MAX_BYTES: usize = 16 * 1024 * 1024;
@@ -678,6 +679,10 @@ impl Terminal {
         unsafe { ffi::ghostty_terminal_mode_set(self.raw, mode, value).into_result() }
     }
 
+    pub fn enable_grapheme_cluster_mode(&mut self) -> Result<(), Error> {
+        self.mode_set(MODE_GRAPHEME_CLUSTER, true)
+    }
+
     pub fn kitty_keyboard_flags(&self) -> Result<u8, Error> {
         let mut out = 0u8;
         unsafe {
@@ -2962,6 +2967,43 @@ mod tests {
     }
 
     #[test]
+    fn grapheme_cluster_mode_keeps_issue_453_payload_safe() {
+        let mut terminal = Terminal::new(80, 3, 100).unwrap();
+        terminal.enable_grapheme_cluster_mode().unwrap();
+        terminal.write("README 👨‍👩‍👧‍👦 🧑‍💻 ✅ ⚡ 漢字 café é 🏳️‍🌈 🚀\r\n".as_bytes());
+
+        let mut render_state = RenderState::new().unwrap();
+        render_state.update(&terminal).unwrap();
+
+        let mut row_iterator = RowIterator::new().unwrap();
+        let mut rows = render_state
+            .populate_row_iterator(&mut row_iterator)
+            .unwrap();
+        let mut row_cells = RowCells::new().unwrap();
+        let mut codepoints = Vec::new();
+        let mut text = String::new();
+
+        while rows.next() {
+            let mut cells = rows.populate_cells(&mut row_cells).unwrap();
+            while cells.next() {
+                cells
+                    .grapheme_text_into(&mut codepoints, &mut text)
+                    .unwrap();
+            }
+        }
+    }
+
+    #[test]
+    fn grapheme_cluster_mode_is_default_and_survives_full_reset() {
+        let mut terminal = Terminal::new(80, 3, 100).unwrap();
+        assert!(terminal.mode_get(MODE_GRAPHEME_CLUSTER).unwrap());
+
+        terminal.write(b"\x1bc");
+
+        assert!(terminal.mode_get(MODE_GRAPHEME_CLUSTER).unwrap());
+    }
+
+    #[test]
     fn render_state_row_dirty_can_be_cleared_independently() {
         let mut terminal = Terminal::new(8, 3, 100).unwrap();
         let mut render_state = RenderState::new().unwrap();
diff --git a/src/pane.rs b/src/pane.rs
index 19556ffe..214eeef2 100644
--- a/src/pane.rs
+++ b/src/pane.rs
@@ -1284,6 +1284,9 @@ impl PaneRuntime {
         let (response_tx, _response_rx) = mpsc::channel::<Bytes>(1);
         let mut terminal = crate::ghostty::Terminal::new(cols, rows, scrollback_limit_bytes)
             .map_err(|e| std::io::Error::other(e.to_string()))?;
+        terminal
+            .enable_grapheme_cluster_mode()
+            .map_err(|e| std::io::Error::other(e.to_string()))?;
         if crate::kitty_graphics::is_enabled() {
             terminal
                 .enable_kitty_graphics()
@@ -1395,6 +1398,9 @@ impl PaneRuntime {
         let (response_tx, _response_rx) = mpsc::channel::<Bytes>(1);
         let mut terminal = crate::ghostty::Terminal::new(cols, rows, scrollback_limit_bytes)
             .map_err(|e| std::io::Error::other(e.to_string()))?;
+        terminal
+            .enable_grapheme_cluster_mode()
+            .map_err(|e| std::io::Error::other(e.to_string()))?;
         if crate::kitty_graphics::is_enabled() {
             terminal
                 .enable_kitty_graphics()
diff --git a/src/pane/terminal.rs b/src/pane/terminal.rs
index f2fceaa8..cf8506ba 100644
--- a/src/pane/terminal.rs
+++ b/src/pane/terminal.rs
@@ -2432,6 +2432,8 @@ mod tests {
     #[test]
     fn ghostty_normalize_buffer_symbol_prefers_grapheme_width_when_metadata_disagrees() {
         const WIDE_GRAPHEME: &str = "🙂";
+        const FLAG_GRAPHEME: &str = "🇧🇷";
+        const FAMILY_GRAPHEME: &str = "👨‍👩‍👧";
         const VS16_GRAPHEME: &str = "⚠️";
         const EMOJI_GRAPHEME: &str = "💳";
 
@@ -2444,6 +2446,14 @@ mod tests {
             "  "
         );
         assert_eq!(
+            ghostty_normalize_buffer_symbol(FLAG_GRAPHEME, crate::ghostty::CellWide::Wide),
+            FLAG_GRAPHEME
+        );
+        assert_eq!(
+            ghostty_normalize_buffer_symbol(FAMILY_GRAPHEME, crate::ghostty::CellWide::Wide),
+            FAMILY_GRAPHEME
+        );
+        assert_eq!(
             ghostty_normalize_buffer_symbol("⌨️", crate::ghostty::CellWide::Narrow),
             "⌨️"
         );
@@ -2465,6 +2475,74 @@ mod tests {
         );
     }
 
+    fn render_cells_to_symbols(
+        terminal: &mut crate::ghostty::Terminal,
+    ) -> Vec<(crate::ghostty::CellWide, String)> {
+        let mut render_state = crate::ghostty::RenderState::new().unwrap();
+        render_state.update(terminal).unwrap();
+
+        let mut row_iterator = crate::ghostty::RowIterator::new().unwrap();
+        let mut rows = render_state
+            .populate_row_iterator(&mut row_iterator)
+            .unwrap();
+        let mut row_cells = crate::ghostty::RowCells::new().unwrap();
+        let mut grapheme_codepoints = Vec::new();
+        let mut symbol_scratch = String::new();
+        let mut out = Vec::new();
+
+        if rows.next() {
+            let mut cells = rows.populate_cells(&mut row_cells).unwrap();
+            while cells.next() {
+                let wide = cells.wide().unwrap_or(crate::ghostty::CellWide::Narrow);
+                let symbol = ghostty_buffer_symbol_into(
+                    &cells,
+                    wide,
+                    false,
+                    &mut grapheme_codepoints,
+                    &mut symbol_scratch,
+                )
+                .unwrap()
+                .to_string();
+                out.push((wide, symbol));
+            }
+        }
+
+        out
+    }
+
+    #[test]
+    fn grapheme_cluster_mode_renders_flag_emoji_in_single_wide_cell() {
+        let mut terminal = crate::ghostty::Terminal::new(40, 1, 0).unwrap();
+        terminal.enable_grapheme_cluster_mode().unwrap();
+        terminal.write("🇧🇷".as_bytes());
+
+        let cells = render_cells_to_symbols(&mut terminal);
+
+        assert!(
+            cells
+                .iter()
+                .any(|(wide, symbol)| *wide == crate::ghostty::CellWide::Wide && symbol == "🇧🇷"),
+            "expected a wide cell containing the full flag grapheme, got {cells:?}"
+        );
+    }
+
+    #[test]
+    fn grapheme_cluster_mode_renders_zwj_family_in_single_wide_cell() {
+        let mut terminal = crate::ghostty::Terminal::new(40, 1, 0).unwrap();
+        terminal.enable_grapheme_cluster_mode().unwrap();
+        terminal.write("👨\u{200d}👩\u{200d}👧".as_bytes());
+
+        let cells = render_cells_to_symbols(&mut terminal);
+
+        assert!(
+            cells
+                .iter()
+                .any(|(wide, symbol)| *wide == crate::ghostty::CellWide::Wide
+                    && symbol == "👨\u{200d}👩\u{200d}👧"),
+            "expected a wide cell containing the full ZWJ grapheme, got {cells:?}"
+        );
+    }
+
     #[test]
     fn pane_scrollback_controls_reach_top_without_ui_interference() {
         let (tx, _rx) = mpsc::channel(4);