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* style(comment): remove outdated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

2 files changed, 39 insertions, 16 deletions

diff --git a/zellij-server/src/ui/boundaries.rs b/zellij-server/src/ui/boundaries.rs
index c0827c24e..2ba3e67e5 100644
--- a/zellij-server/src/ui/boundaries.rs
+++ b/zellij-server/src/ui/boundaries.rs
@@ -27,10 +27,10 @@ pub mod boundary_type {
     pub const CROSS: &str = "┼";
 }
 
-pub(crate) type BoundaryType = &'static str; // easy way to refer to boundary_type above
+pub type BoundaryType = &'static str; // easy way to refer to boundary_type above
 
-#[derive(Clone, Copy, Debug)]
-pub(crate) struct BoundarySymbol {
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct BoundarySymbol {
     boundary_type: BoundaryType,
     invisible: bool,
     color: Option<PaletteColor>,
@@ -420,7 +420,7 @@ fn combine_symbols(
 }
 
 #[derive(PartialEq, Eq, Hash, Debug)]
-pub(crate) struct Coordinates {
+pub struct Coordinates {
     x: usize,
     y: usize,
 }
@@ -433,7 +433,7 @@ impl Coordinates {
 
 pub struct Boundaries {
     viewport: Viewport,
-    boundary_characters: HashMap<Coordinates, BoundarySymbol>,
+    pub boundary_characters: HashMap<Coordinates, BoundarySymbol>,
 }
 
 impl Boundaries {
@@ -540,9 +540,19 @@ impl Boundaries {
             }
         }
     }
-    pub fn render(&self) -> Result<Vec<CharacterChunk>> {
+    pub fn render(
+        &self,
+        existing_boundaries_on_screen: Option<&Boundaries>,
+    ) -> Result<Vec<CharacterChunk>> {
         let mut character_chunks = vec![];
         for (coordinates, boundary_character) in &self.boundary_characters {
+            let already_on_screen = existing_boundaries_on_screen
+                .and_then(|e| e.boundary_characters.get(coordinates))
+                .map(|e| e == boundary_character)
+                .unwrap_or(false);
+            if already_on_screen {
+                continue;
+            }
             character_chunks.push(CharacterChunk::new(
                 vec![boundary_character
                     .as_terminal_character()
diff --git a/zellij-server/src/ui/pane_contents_and_ui.rs b/zellij-server/src/ui/pane_contents_and_ui.rs
index 946d9f681..1cc715d83 100644
--- a/zellij-server/src/ui/pane_contents_and_ui.rs
+++ b/zellij-server/src/ui/pane_contents_and_ui.rs
@@ -65,15 +65,17 @@ impl<'a> PaneContentsAndUi<'a> {
                 self.z_index,
             );
             if let Some(raw_vte_output) = raw_vte_output {
-                self.output.add_post_vte_instruction_to_multiple_clients(
-                    clients.iter().copied(),
-                    &format!(
-                        "\u{1b}[{};{}H\u{1b}[m{}",
-                        self.pane.y() + 1,
-                        self.pane.x() + 1,
-                        raw_vte_output
-                    ),
-                );
+                if !raw_vte_output.is_empty() {
+                    self.output.add_post_vte_instruction_to_multiple_clients(
+                        clients.iter().copied(),
+                        &format!(
+                            "\u{1b}[{};{}H\u{1b}[m{}",
+                            self.pane.y() + 1,
+                            self.pane.x() + 1,
+                            raw_vte_output
+                        ),
+                    );
+                }
             }
         }
         Ok(())
@@ -140,11 +142,22 @@ impl<'a> PaneContentsAndUi<'a> {
         }
         Ok(())
     }
-    pub fn render_terminal_title_if_needed(&mut self, client_id: ClientId, client_mode: InputMode) {
+    pub fn render_terminal_title_if_needed(
+        &mut self,
+        client_id: ClientId,
+        client_mode: InputMode,
+        previous_title: &mut Option<String>,
+    ) {
         if !self.focused_clients.contains(&client_id) {
             return;
         }
         let vte_output = self.pane.render_terminal_title(client_mode);
+        if let Some(previous_title) = previous_title {
+            if *previous_title == vte_output {
+                return;
+            }
+        }
+        *previous_title = Some(vte_output.clone());
         self.output
             .add_post_vte_instruction_to_client(client_id, &vte_output);
     }