feat(client): terminal synchronized output (#2798)

3 files changed, 83 insertions, 3 deletions

diff --git a/zellij-client/src/input_handler.rs b/zellij-client/src/input_handler.rs
index cf5b3d326..158659a42 100644
--- a/zellij-client/src/input_handler.rs
+++ b/zellij-client/src/input_handler.rs
@@ -197,6 +197,11 @@ impl InputHandler {
                 self.os_input
                     .send_to_server(ClientToServerMsg::ColorRegisters(color_registers));
             },
+            AnsiStdinInstruction::SynchronizedOutput(enabled) => {
+                self.send_client_instructions
+                    .send(ClientInstruction::SetSynchronizedOutput(enabled))
+                    .unwrap();
+            },
         }
     }
     fn handle_mouse_event(&mut self, mouse_event: &MouseEvent) {
diff --git a/zellij-client/src/lib.rs b/zellij-client/src/lib.rs
index 716592640..6cb855118 100644
--- a/zellij-client/src/lib.rs
+++ b/zellij-client/src/lib.rs
@@ -16,7 +16,7 @@ use std::sync::{Arc, Mutex};
 use std::thread;
 use zellij_utils::errors::FatalError;
 
-use crate::stdin_ansi_parser::{AnsiStdinInstruction, StdinAnsiParser};
+use crate::stdin_ansi_parser::{AnsiStdinInstruction, StdinAnsiParser, SyncOutput};
 use crate::{
     command_is_executing::CommandIsExecuting, input_handler::input_loop,
     os_input_output::ClientOsApi, stdin_handler::stdin_loop,
@@ -47,6 +47,7 @@ pub(crate) enum ClientInstruction {
     DoneParsingStdinQuery,
     Log(Vec<String>),
     SwitchSession(ConnectToSession),
+    SetSynchronizedOutput(Option<SyncOutput>),
 }
 
 impl From<ServerToClientMsg> for ClientInstruction {
@@ -82,6 +83,7 @@ impl From<&ClientInstruction> for ClientContext {
             ClientInstruction::StartedParsingStdinQuery => ClientContext::StartedParsingStdinQuery,
             ClientInstruction::DoneParsingStdinQuery => ClientContext::DoneParsingStdinQuery,
             ClientInstruction::SwitchSession(..) => ClientContext::SwitchSession,
+            ClientInstruction::SetSynchronizedOutput(..) => ClientContext::SetSynchronisedOutput,
         }
     }
 }
@@ -381,6 +383,10 @@ pub fn start_client(
     let mut exit_msg = String::new();
     let mut loading = true;
     let mut pending_instructions = vec![];
+    let mut synchronised_output = match os_input.env_variable("TERM").as_deref() {
+        Some("alacritty") => Some(SyncOutput::DCS),
+        _ => None,
+    };
 
     let mut stdout = os_input.get_stdout_writer();
     stdout
@@ -439,9 +445,19 @@ pub fn start_client(
             },
             ClientInstruction::Render(output) => {
                 let mut stdout = os_input.get_stdout_writer();
+                if let Some(sync) = synchronised_output {
+                    stdout
+                        .write_all(sync.start_seq())
+                        .expect("cannot write to stdout");
+                }
                 stdout
                     .write_all(output.as_bytes())
                     .expect("cannot write to stdout");
+                if let Some(sync) = synchronised_output {
+                    stdout
+                        .write_all(sync.end_seq())
+                        .expect("cannot write to stdout");
+                }
                 stdout.flush().expect("could not flush");
             },
             ClientInstruction::UnblockInputThread => {
@@ -462,6 +478,9 @@ pub fn start_client(
                 os_input.send_to_server(ClientToServerMsg::ClientExited);
                 break;
             },
+            ClientInstruction::SetSynchronizedOutput(enabled) => {
+                synchronised_output = enabled;
+            },
             _ => {},
         }
     }
diff --git a/zellij-client/src/stdin_ansi_parser.rs b/zellij-client/src/stdin_ansi_parser.rs
index a34eac5be..6816803bb 100644
--- a/zellij-client/src/stdin_ansi_parser.rs
+++ b/zellij-client/src/stdin_ansi_parser.rs
@@ -11,6 +11,33 @@ use std::fs::{File, OpenOptions};
 use std::io::{Read, Write};
 use zellij_utils::anyhow::Result;
 
+/// Describe the terminal implementation of synchronised output
+#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
+pub enum SyncOutput {
+    DCS,
+    CSI,
+}
+
+impl SyncOutput {
+    pub fn start_seq(&self) -> &'static [u8] {
+        static CSI_BSU_SEQ: &'static [u8] = "\u{1b}[?2026h".as_bytes();
+        static DCS_BSU_SEQ: &'static [u8] = "\u{1b}P=1s\u{1b}".as_bytes();
+        match self {
+            SyncOutput::DCS => DCS_BSU_SEQ,
+            SyncOutput::CSI => CSI_BSU_SEQ,
+        }
+    }
+
+    pub fn end_seq(&self) -> &'static [u8] {
+        static CSI_ESU_SEQ: &'static [u8] = "\u{1b}[?2026l".as_bytes();
+        static DCS_ESU_SEQ: &'static [u8] = "\u{1b}P=2s\u{1b}".as_bytes();
+        match self {
+            SyncOutput::DCS => DCS_ESU_SEQ,
+            SyncOutput::CSI => CSI_ESU_SEQ,
+        }
+    }
+}
+
 #[derive(Debug)]
 pub struct StdinAnsiParser {
     raw_buffer: Vec<u8>,
@@ -36,8 +63,10 @@ impl StdinAnsiParser {
         // <ESC>[16t => get character cell size in pixels
         // <ESC>]11;?<ESC>\ => get background color
         // <ESC>]10;?<ESC>\ => get foreground color
-        let mut query_string =
-            String::from("\u{1b}[14t\u{1b}[16t\u{1b}]11;?\u{1b}\u{5c}\u{1b}]10;?\u{1b}\u{5c}");
+        // <ESC>[?2026$p => get synchronised output mode
+        let mut query_string = String::from(
+            "\u{1b}[14t\u{1b}[16t\u{1b}]11;?\u{1b}\u{5c}\u{1b}]10;?\u{1b}\u{5c}\u{1b}[?2026$p",
+        );
 
         // query colors
         // eg. <ESC>]4;5;?<ESC>\ => query color register number 5
@@ -130,6 +159,14 @@ impl StdinAnsiParser {
             } else {
                 self.raw_buffer.clear();
             }
+        } else if byte == b'y' {
+            self.raw_buffer.push(byte);
+            if let Some(ansi_sequence) =
+                AnsiStdinInstruction::synchronized_output_from_bytes(&self.raw_buffer)
+            {
+                self.pending_events.push(ansi_sequence);
+                self.raw_buffer.clear();
+            }
         } else {
             self.raw_buffer.push(byte);
         }
@@ -142,6 +179,7 @@ pub enum AnsiStdinInstruction {
     BackgroundColor(String),
     ForegroundColor(String),
     ColorRegisters(Vec<(usize, String)>),
+    SynchronizedOutput(Option<SyncOutput>),
 }
 
 impl AnsiStdinInstruction {
@@ -225,6 +263,24 @@ impl AnsiStdinInstruction {
         }
         Some(AnsiStdinInstruction::ColorRegisters(registers))
     }
+
+    pub fn synchronized_output_from_bytes(bytes: &[u8]) -> Option<Self> {
+        lazy_static! {
+            static ref RE: Regex = Regex::new(r"^\u{1b}\[\?2026;([0|1|2|3|4])\$y$").unwrap();
+        }
+        let key_string = String::from_utf8_lossy(bytes);
+        if let Some(captures) = RE.captures_iter(&key_string).next() {
+            match captures[1].parse::<usize>().ok()? {
+                1 | 2 => Some(AnsiStdinInstruction::SynchronizedOutput(Some(
+                    SyncOutput::CSI,
+                ))),
+                0 | 4 => Some(AnsiStdinInstruction::SynchronizedOutput(None)),
+                _ => None,
+            }
+        } else {
+            None
+        }
+    }
 }
 
 fn color_sequence_from_bytes(bytes: &[u8]) -> Result<(usize, String), &'static str> {