performance(rendering): improve rendering performance (#1960)

* refactor(plugins): plugins now need to explicitly ask to be rendered

* performance(render): remove various needless renders

* performance(render): cache boundaries

* performance(render): adjust tests and cache cursor location/shape

* style(comment): remove outdated

* style(fmt): rustfmt

1 files changed, 41 insertions, 19 deletions

diff --git a/zellij-server/src/tab/mod.rs b/zellij-server/src/tab/mod.rs
index 374fe1ce3..e98b46143 100644
--- a/zellij-server/src/tab/mod.rs
+++ b/zellij-server/src/tab/mod.rs
@@ -112,6 +112,9 @@ pub(crate) struct Tab {
     terminal_emulator_colors: Rc<RefCell<Palette>>,
     terminal_emulator_color_codes: Rc<RefCell<HashMap<usize, String>>>,
     pids_waiting_resize: HashSet<u32>, // u32 is the terminal_id
+    cursor_positions_and_shape: HashMap<ClientId, (usize, usize, String)>, // (x_position,
+                                       // y_position,
+                                       // cursor_shape_csi)
 }
 
 #[derive(Clone, Debug, Default, Serialize, Deserialize)]
@@ -485,6 +488,7 @@ impl Tab {
             terminal_emulator_colors,
             terminal_emulator_color_codes,
             pids_waiting_resize: HashSet::new(),
+            cursor_positions_and_shape: HashMap::new(),
         }
     }
 
@@ -1427,7 +1431,6 @@ impl Tab {
             floating_panes_stack,
         );
 
-        self.hide_cursor_and_clear_display_as_needed(output);
         self.tiled_panes
             .render(output, self.floating_panes.panes_are_visible())
             .with_context(err_context)?;
@@ -1437,15 +1440,18 @@ impl Tab {
                 .with_context(err_context)?;
         }
 
-        // FIXME: Once clients can be distinguished
-        if let Some(overlay_vte) = &overlay {
-            output.add_post_vte_instruction_to_multiple_clients(
-                connected_clients.iter().copied(),
-                overlay_vte,
-            );
+        self.render_cursor(output);
+        if output.is_dirty() {
+            self.hide_cursor_and_clear_display_as_needed(output);
+            // FIXME: Once clients can be distinguished
+            if let Some(overlay_vte) = &overlay {
+                output.add_post_vte_instruction_to_multiple_clients(
+                    connected_clients.iter().copied(),
+                    overlay_vte,
+                );
+            }
         }
 
-        self.render_cursor(output);
         Ok(())
     }
 
@@ -1466,25 +1472,41 @@ impl Tab {
             self.should_clear_display_before_rendering = false;
         }
     }
-    fn render_cursor(&self, output: &mut Output) {
+    fn render_cursor(&mut self, output: &mut Output) {
         let connected_clients: Vec<ClientId> =
             { self.connected_clients.borrow().iter().copied().collect() };
         for client_id in connected_clients {
             match self.get_active_terminal_cursor_position(client_id) {
                 Some((cursor_position_x, cursor_position_y)) => {
-                    let show_cursor = "\u{1b}[?25h";
-                    let change_cursor_shape = self
+                    let desired_cursor_shape = self
                         .get_active_pane(client_id)
                         .map(|ap| ap.cursor_shape_csi())
                         .unwrap_or_default();
-                    let goto_cursor_position = &format!(
-                        "\u{1b}[{};{}H\u{1b}[m{}",
-                        cursor_position_y + 1,
-                        cursor_position_x + 1,
-                        change_cursor_shape
-                    ); // goto row/col
-                    output.add_post_vte_instruction_to_client(client_id, show_cursor);
-                    output.add_post_vte_instruction_to_client(client_id, goto_cursor_position);
+                    let cursor_changed_position_or_shape = self
+                        .cursor_positions_and_shape
+                        .get(&client_id)
+                        .map(|(previous_x, previous_y, previous_shape)| {
+                            previous_x != &cursor_position_x
+                                || previous_y != &cursor_position_y
+                                || previous_shape != &desired_cursor_shape
+                        })
+                        .unwrap_or(true);
+
+                    if output.is_dirty() || cursor_changed_position_or_shape {
+                        let show_cursor = "\u{1b}[?25h";
+                        let goto_cursor_position = &format!(
+                            "\u{1b}[{};{}H\u{1b}[m{}",
+                            cursor_position_y + 1,
+                            cursor_position_x + 1,
+                            desired_cursor_shape
+                        ); // goto row/col
+                        output.add_post_vte_instruction_to_client(client_id, show_cursor);
+                        output.add_post_vte_instruction_to_client(client_id, goto_cursor_position);
+                        self.cursor_positions_and_shape.insert(
+                            client_id,
+                            (cursor_position_x, cursor_position_y, desired_cursor_shape),
+                        );
+                    }
                 },
                 None => {
                     let hide_cursor = "\u{1b}[?25l";