Added Kitty Multicursor Support

jonbitgood · jonbitgood · commit 4a9bf6230179 · 2025-11-08T12:08:10.000-06:00
Add support for kitty's multiple cursors protocol to show real terminal
cursors at all selection positions when using bar/underline cursors.
diff --git a/helix-term/src/application.rs b/helix-term/src/application.rs
@@ -124,6 +124,12 @@ impl Application {
         let backend = TestBackend::new(120, 150);
 
         let theme_mode = backend.get_theme_mode();
+
+        #[cfg(all(not(windows), not(feature = "integration")))]
+        let kitty_multi_cursor_support = backend.supports_kitty_multi_cursor();
+        #[cfg(any(windows, feature = "integration"))]
+        let kitty_multi_cursor_support = false;
+
         let terminal = Terminal::new(backend)?;
         let area = terminal.size();
         let mut compositor = Compositor::new(area);
@@ -138,6 +144,8 @@ impl Application {
             })),
             handlers,
         );
+        editor.kitty_multi_cursor_support = kitty_multi_cursor_support;
+
         Self::load_configured_theme(
             &mut editor,
             &config.load(),
@@ -298,7 +306,43 @@ impl Application {
         self.editor.cursor_cache.reset();
 
         let pos = pos.map(|pos| (pos.col as u16, pos.row as u16));
+
+        use helix_view::graphics::CursorKind;
+        let secondary_cursors = if !matches!(kind, CursorKind::Block | CursorKind::Hidden) {
+            self.get_secondary_cursor_positions()
+        } else {
+            Vec::new()
+        };
+
         self.terminal.draw(pos, kind).unwrap();
+        // Always update kitty cursors (clears if empty, sets if not)
+        self.terminal
+            .set_multiple_cursors(&secondary_cursors)
+            .unwrap();
+    }
+
+    fn get_secondary_cursor_positions(&self) -> Vec<(u16, u16)> {
+        use helix_view::current_ref;
+
+        let (view, doc) = current_ref!(&self.editor);
+        let text = doc.text().slice(..);
+        let selection = doc.selection(view.id);
+        let primary_idx = selection.primary_index();
+        let inner = view.inner_area(doc);
+
+        selection
+            .iter()
+            .enumerate()
+            .filter(|(idx, _)| *idx != primary_idx)
+            .filter_map(|(_, range)| {
+                let cursor = range.cursor(text);
+                view.screen_coords_at_pos(doc, text, cursor).map(|pos| {
+                    let x = (pos.col + inner.x as usize) as u16;
+                    let y = (pos.row + inner.y as usize) as u16;
+                    (x, y)
+                })
+            })
+            .collect()
     }
 
     pub async fn event_loop<S>(&mut self, input_stream: &mut S)
diff --git a/helix-term/src/ui/editor.rs b/helix-term/src/ui/editor.rs
@@ -25,7 +25,7 @@ use helix_core::{
 use helix_view::{
     annotations::diagnostics::DiagnosticFilter,
     document::{Mode, SCRATCH_BUFFER_NAME},
-    editor::{CompleteAction, CursorShapeConfig},
+    editor::CompleteAction,
     graphics::{Color, CursorKind, Modifier, Rect, Style},
     input::{KeyEvent, MouseButton, MouseEvent, MouseEventKind},
     keyboard::{KeyCode, KeyModifiers},
@@ -146,11 +146,10 @@ impl EditorView {
                 overlays.push(tabstops);
             }
             overlays.push(Self::doc_selection_highlights(
-                editor.mode(),
+                editor,
                 doc,
                 view,
                 theme,
-                &config.cursor_shape,
                 self.terminal_focused,
             ));
             if let Some(overlay) = Self::highlight_focused_view_elements(view, doc, theme) {
@@ -461,20 +460,24 @@ impl EditorView {
 
     /// Get highlight spans for selections in a document view.
     pub fn doc_selection_highlights(
-        mode: Mode,
+        editor: &Editor,
         doc: &Document,
         view: &View,
         theme: &Theme,
-        cursor_shape_config: &CursorShapeConfig,
         is_terminal_focused: bool,
     ) -> OverlayHighlights {
         let text = doc.text().slice(..);
         let selection = doc.selection(view.id);
         let primary_idx = selection.primary_index();
 
+        let mode = editor.mode();
+        let cursor_shape_config = &editor.config().cursor_shape;
         let cursorkind = cursor_shape_config.from_mode(mode);
         let cursor_is_block = cursorkind == CursorKind::Block;
 
+        // Skip rendering secondary cursors when kitty protocol handles them
+        let skip_secondary_cursors = editor.kitty_multi_cursor_support && !cursor_is_block;
+
         let selection_scope = theme
             .find_highlight_exact("ui.selection")
             .expect("could not find `ui.selection` scope in the theme!");
@@ -514,13 +517,10 @@ impl EditorView {
 
             // Special-case: cursor at end of the rope.
             if range.head == range.anchor && range.head == text.len_chars() {
-                if !selection_is_primary || (cursor_is_block && is_terminal_focused) {
-                    // Bar and underline cursors are drawn by the terminal
-                    // BUG: If the editor area loses focus while having a bar or
-                    // underline cursor (eg. when a regex prompt has focus) then
-                    // the primary cursor will be invisible. This doesn't happen
-                    // with block cursors since we manually draw *all* cursors.
-                    spans.push((cursor_scope, range.head..range.head + 1));
+                if selection_is_primary || !skip_secondary_cursors {
+                    if !selection_is_primary || (cursor_is_block && is_terminal_focused) {
+                        spans.push((cursor_scope, range.head..range.head + 1));
+                    }
                 }
                 continue;
             }
@@ -537,17 +537,17 @@ impl EditorView {
                         cursor_start
                     };
                 spans.push((selection_scope, range.anchor..selection_end));
-                // add block cursors
-                // skip primary cursor if terminal is unfocused - terminal cursor is used in that case
-                if !selection_is_primary || (cursor_is_block && is_terminal_focused) {
+                if (selection_is_primary || !skip_secondary_cursors)
+                    && (!selection_is_primary || (cursor_is_block && is_terminal_focused))
+                {
                     spans.push((cursor_scope, cursor_start..range.head));
                 }
             } else {
                 // Reverse case.
                 let cursor_end = next_grapheme_boundary(text, range.head);
-                // add block cursors
-                // skip primary cursor if terminal is unfocused - terminal cursor is used in that case
-                if !selection_is_primary || (cursor_is_block && is_terminal_focused) {
+                if (selection_is_primary || !skip_secondary_cursors)
+                    && (!selection_is_primary || (cursor_is_block && is_terminal_focused))
+                {
                     spans.push((cursor_scope, range.head..cursor_end));
                 }
                 // non block cursors look like they exclude the cursor
diff --git a/helix-tui/src/backend/mod.rs b/helix-tui/src/backend/mod.rs
@@ -37,6 +37,10 @@ pub trait Backend {
     fn show_cursor(&mut self, kind: CursorKind) -> Result<(), io::Error>;
     /// Sets the cursor to the given position
     fn set_cursor(&mut self, x: u16, y: u16) -> Result<(), io::Error>;
+    /// Sets multiple cursors using terminal-specific protocols (e.g., kitty)
+    fn set_multiple_cursors(&mut self, _cursors: &[(u16, u16)]) -> Result<(), io::Error> {
+        Ok(())
+    }
     /// Clears the terminal
     fn clear(&mut self) -> Result<(), io::Error>;
     /// Gets the size of the terminal in cells
diff --git a/helix-tui/src/backend/termina.rs b/helix-tui/src/backend/termina.rs
@@ -49,6 +49,7 @@ fn vte_version() -> Option<usize> {
 #[derive(Debug, Default, Clone, Copy)]
 struct Capabilities {
     kitty_keyboard: KittyKeyboardSupport,
+    kitty_multi_cursor: bool,
     synchronized_output: bool,
     true_color: bool,
     extended_underlines: bool,
@@ -125,7 +126,6 @@ impl TerminaBackend {
     ) -> io::Result<(Capabilities, String)> {
         use std::time::{Duration, Instant};
 
-        // Colibri "midnight"
         const TEST_COLOR: RgbColor = RgbColor::new(59, 34, 76);
 
         terminal.enter_raw_mode()?;
@@ -238,6 +238,15 @@ impl TerminaBackend {
             log::debug!("terminfo could not be read, using default cursor reset escape sequence: {reset_cursor_command:?}");
         }
 
+        // Detect kitty multi-cursor support (available in kitty >= 0.43.0)
+        if matches!(
+            term_program().as_deref(),
+            Some("kitty") | Some("xterm-kitty")
+        ) {
+            capabilities.kitty_multi_cursor = true;
+            log::debug!("Detected kitty terminal - enabling multi-cursor protocol support");
+        }
+
         terminal.enter_cooked_mode()?;
 
         Ok((capabilities, reset_cursor_command))
@@ -544,6 +553,25 @@ impl Backend for TerminaBackend {
         self.flush()
     }
 
+    fn set_multiple_cursors(&mut self, cursors: &[(u16, u16)]) -> io::Result<()> {
+        if !self.capabilities.kitty_multi_cursor {
+            return Ok(());
+        }
+
+        // Always clear existing cursors first
+        write!(self.terminal, "\x1b[>0;4 q")?;
+
+        if !cursors.is_empty() {
+            write!(self.terminal, "\x1b[>29")?; // Shape 29 = follow main cursor
+            for (x, y) in cursors {
+                write!(self.terminal, ";2:{}:{}", y + 1, x + 1)?; // 1-indexed coords
+            }
+            write!(self.terminal, " q")?;
+        }
+
+        self.flush()
+    }
+
     fn clear(&mut self) -> io::Result<()> {
         self.start_synchronized_render()?;
         write!(
@@ -572,6 +600,12 @@ impl Backend for TerminaBackend {
     }
 }
 
+impl TerminaBackend {
+    pub fn supports_kitty_multi_cursor(&self) -> bool {
+        self.capabilities.kitty_multi_cursor
+    }
+}
+
 impl Drop for TerminaBackend {
     fn drop(&mut self) {
         // Avoid resetting the terminal while panicking because we set a panic hook above in
diff --git a/helix-tui/src/terminal.rs b/helix-tui/src/terminal.rs
@@ -234,6 +234,10 @@ where
         self.backend.set_cursor(x, y)
     }
 
+    pub fn set_multiple_cursors(&mut self, cursors: &[(u16, u16)]) -> io::Result<()> {
+        self.backend.set_multiple_cursors(cursors)
+    }
+
     /// Clear the terminal and force a full redraw on the next draw call.
     pub fn clear(&mut self) -> io::Result<()> {
         self.backend.clear()?;
diff --git a/helix-view/src/editor.rs b/helix-view/src/editor.rs
@@ -1219,6 +1219,7 @@ pub struct Editor {
 
     pub mouse_down_range: Option<Range>,
     pub cursor_cache: CursorCache,
+    pub kitty_multi_cursor_support: bool,
 }
 
 pub type Motion = Box<dyn Fn(&mut Editor)>;
@@ -1340,6 +1341,7 @@ impl Editor {
             handlers,
             mouse_down_range: None,
             cursor_cache: CursorCache::default(),
+            kitty_multi_cursor_support: false,
         }
     }
 

Original file line number	Diff line number	Diff line change
`@@ -1219,6 +1219,7 @@ pub struct Editor {`
`1219`	`1219`
`1220`	`1220`	`pub mouse_down_range: Option<Range>,`
`1221`	`1221`	`pub cursor_cache: CursorCache,`
	`1222`	`+ pub kitty_multi_cursor_support: bool,`
`1222`	`1223`	`}`
`1223`	`1224`
`1224`	`1225`	`pub type Motion = Box<dyn Fn(&mut Editor)>;`
`@@ -1340,6 +1341,7 @@ impl Editor {`
`1340`	`1341`	`handlers,`
`1341`	`1342`	`mouse_down_range: None,`
`1342`	`1343`	`cursor_cache: CursorCache::default(),`
	`1344`	`+ kitty_multi_cursor_support: false,`
`1343`	`1345`	`}`
`1344`	`1346`	`}`
`1345`	`1347`