fix(ux): cache stdin queries on startup (remove startup delay) (#2173)

* fix(ux): cache stdin queries on startup

* style(fmt): rustfmt

7 files changed, 88 insertions, 140 deletions

diff --git a/Cargo.lock b/Cargo.lock
index e782d4776..bc0565f1e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4017,6 +4017,7 @@ dependencies = [
  "log",
  "mio",
  "serde",
+ "serde_json",
  "serde_yaml",
  "url",
  "zellij-utils",
diff --git a/zellij-client/Cargo.toml b/zellij-client/Cargo.toml
index 114257b8e..f8d6045a1 100644
--- a/zellij-client/Cargo.toml
+++ b/zellij-client/Cargo.toml
@@ -13,6 +13,7 @@ mio = { version = "0.7.11", features = ['os-ext'] }
 serde = { version = "1.0", features = ["derive"] }
 url = { version = "2.2.2", features = ["serde"] }
 serde_yaml = "0.8"
+serde_json = "1.0"
 zellij-utils = { path = "../zellij-utils/", version = "0.34.5" }
 log = "0.4.17"
 
diff --git a/zellij-client/src/lib.rs b/zellij-client/src/lib.rs
index 51d6c99d6..67a7fb902 100644
--- a/zellij-client/src/lib.rs
+++ b/zellij-client/src/lib.rs
@@ -265,16 +265,6 @@ pub fn start_client(
                             os_api.send_to_server(ClientToServerMsg::TerminalResize(
                                 os_api.get_terminal_size_using_fd(0),
                             ));
-                            // send a query to the terminal emulator in case the font size changed
-                            // as well - we'll parse the response through STDIN
-                            let terminal_emulator_query_string = stdin_ansi_parser
-                                .lock()
-                                .unwrap()
-                                .window_size_change_query_string();
-                            let _ = os_api
-                                .get_stdout_writer()
-                                .write(terminal_emulator_query_string.as_bytes())
-                                .unwrap();
                         }
                     }),
                     Box::new({
@@ -348,7 +338,7 @@ pub fn start_client(
 
     let mut stdout = os_input.get_stdout_writer();
     stdout
-        .write_all("\u{1b}[1mLoading Zellij\u{1b}[m".as_bytes())
+        .write_all("\u{1b}[1mLoading Zellij\u{1b}[m\n\r".as_bytes())
         .expect("cannot write to stdout");
     stdout.flush().expect("could not flush");
 
@@ -368,7 +358,7 @@ pub fn start_client(
             match client_instruction {
                 ClientInstruction::StartedParsingStdinQuery => {
                     stdout
-                        .write_all("\n\rQuerying terminal emulator for \u{1b}[32;1mdefault colors\u{1b}[m and \u{1b}[32;1mpixel/cell\u{1b}[m ratio...".as_bytes())
+                        .write_all("Querying terminal emulator for \u{1b}[32;1mdefault colors\u{1b}[m and \u{1b}[32;1mpixel/cell\u{1b}[m ratio...".as_bytes())
                         .expect("cannot write to stdout");
                     stdout.flush().expect("could not flush");
                 },
diff --git a/zellij-client/src/stdin_ansi_parser.rs b/zellij-client/src/stdin_ansi_parser.rs
index 23e869b2b..4891c4f73 100644
--- a/zellij-client/src/stdin_ansi_parser.rs
+++ b/zellij-client/src/stdin_ansi_parser.rs
@@ -1,11 +1,17 @@
 use std::time::{Duration, Instant};
+use zellij_utils::consts::{VERSION, ZELLIJ_CACHE_DIR};
 
 const STARTUP_PARSE_DEADLINE_MS: u64 = 500;
-const SIGWINCH_PARSE_DEADLINE_MS: u64 = 200;
 use zellij_utils::{
     ipc::PixelDimensions, lazy_static::lazy_static, pane_size::SizeInPixels, regex::Regex,
 };
 
+use serde::{Deserialize, Serialize};
+use std::fs::{File, OpenOptions};
+use std::io::{Read, Write};
+use std::path::PathBuf;
+use zellij_utils::anyhow::Result;
+
 #[derive(Debug)]
 pub struct StdinAnsiParser {
     raw_buffer: Vec<u8>,
@@ -43,18 +49,6 @@ impl StdinAnsiParser {
             Some(Instant::now() + Duration::from_millis(STARTUP_PARSE_DEADLINE_MS));
         query_string
     }
-    pub fn window_size_change_query_string(&mut self) -> String {
-        // note that this assumes the String will be sent to the terminal emulator and so starts a
-        // deadline timeout (self.parse_deadline)
-
-        // <ESC>[14t => get text area size in pixels,
-        // <ESC>[16t => get character cell size in pixels
-        let query_string = String::from("\u{1b}[14t\u{1b}[16t");
-
-        self.parse_deadline =
-            Some(Instant::now() + Duration::from_millis(SIGWINCH_PARSE_DEADLINE_MS));
-        query_string
-    }
     fn drain_pending_events(&mut self) -> Vec<AnsiStdinInstruction> {
         let mut events = vec![];
         events.append(&mut self.pending_events);
@@ -82,6 +76,34 @@ impl StdinAnsiParser {
         }
         self.drain_pending_events()
     }
+    pub fn read_cache(&self) -> Option<Vec<AnsiStdinInstruction>> {
+        let path = self.cache_dir_path();
+        match OpenOptions::new().read(true).open(path.as_path()) {
+            Ok(mut file) => {
+                let mut json_cache = String::new();
+                file.read_to_string(&mut json_cache).ok()?;
+                let instructions =
+                    serde_json::from_str::<Vec<AnsiStdinInstruction>>(&json_cache).ok()?;
+                if instructions.is_empty() {
+                    None
+                } else {
+                    Some(instructions)
+                }
+            },
+            Err(e) => {
+                log::error!("Failed to open STDIN cache file: {:?}", e);
+                None
+            },
+        }
+    }
+    pub fn write_cache(&self, events: Vec<AnsiStdinInstruction>) {
+        let path = self.cache_dir_path();
+        if let Ok(serialized_events) = serde_json::to_string(&events) {
+            if let Ok(mut file) = File::create(path.as_path()) {
+                let _ = file.write_all(serialized_events.as_bytes());
+            }
+        };
+    }
     fn parse_byte(&mut self, byte: u8) {
         if byte == b't' {
             self.raw_buffer.push(byte);
@@ -112,9 +134,12 @@ impl StdinAnsiParser {
             self.raw_buffer.push(byte);
         }
     }
+    fn cache_dir_path(&self) -> PathBuf {
+        ZELLIJ_CACHE_DIR.join(&format!("zellij-stdin-cache-v{}", VERSION))
+    }
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Serialize, Deserialize)]
 pub enum AnsiStdinInstruction {
     PixelDimensions(PixelDimensions),
     BackgroundColor(String),
diff --git a/zellij-client/src/stdin_handler.rs b/zellij-client/src/stdin_handler.rs
index 75634a05b..01f1ab232 100644
--- a/zellij-client/src/stdin_handler.rs
+++ b/zellij-client/src/stdin_handler.rs
@@ -27,21 +27,37 @@ pub(crate) fn stdin_loop(
     let mut holding_mouse = false;
     let mut input_parser = InputParser::new();
     let mut current_buffer = vec![];
-    // on startup we send a query to the terminal emulator for stuff like the pixel size and colors
-    // we get a response through STDIN, so it makes sense to do this here
-    send_input_instructions
-        .send(InputInstruction::StartedParsing)
-        .unwrap();
-    let terminal_emulator_query_string = stdin_ansi_parser
-        .lock()
-        .unwrap()
-        .terminal_emulator_query_string();
-    let _ = os_input
-        .get_stdout_writer()
-        .write(terminal_emulator_query_string.as_bytes())
-        .unwrap();
-    let query_duration = stdin_ansi_parser.lock().unwrap().startup_query_duration();
-    send_done_parsing_after_query_timeout(send_input_instructions.clone(), query_duration);
+    {
+        // on startup we send a query to the terminal emulator for stuff like the pixel size and colors
+        // we get a response through STDIN, so it makes sense to do this here
+        let mut stdin_ansi_parser = stdin_ansi_parser.lock().unwrap();
+        match stdin_ansi_parser.read_cache() {
+            Some(events) => {
+                let _ =
+                    send_input_instructions.send(InputInstruction::AnsiStdinInstructions(events));
+                let _ = send_input_instructions
+                    .send(InputInstruction::DoneParsing)
+                    .unwrap();
+            },
+            None => {
+                send_input_instructions
+                    .send(InputInstruction::StartedParsing)
+                    .unwrap();
+                let terminal_emulator_query_string =
+                    stdin_ansi_parser.terminal_emulator_query_string();
+                let _ = os_input
+                    .get_stdout_writer()
+                    .write(terminal_emulator_query_string.as_bytes())
+                    .unwrap();
+                let query_duration = stdin_ansi_parser.startup_query_duration();
+                send_done_parsing_after_query_timeout(
+                    send_input_instructions.clone(),
+                    query_duration,
+                );
+            },
+        }
+    }
+    let mut ansi_stdin_events = vec![];
     loop {
         let buf = os_input.read_from_stdin();
         {
@@ -54,12 +70,19 @@ pub(crate) fn stdin_loop(
             if stdin_ansi_parser.should_parse() {
                 let events = stdin_ansi_parser.parse(buf);
                 if !events.is_empty() {
+                    ansi_stdin_events.append(&mut events.clone());
                     let _ = send_input_instructions
                         .send(InputInstruction::AnsiStdinInstructions(events));
                 }
                 continue;
             }
         }
+        if !ansi_stdin_events.is_empty() {
+            stdin_ansi_parser
+                .lock()
+                .unwrap()
+                .write_cache(ansi_stdin_events.drain(..).collect());
+        }
         current_buffer.append(&mut buf.to_vec());
         let maybe_more = false; // read_from_stdin should (hopefully) always empty the STDIN buffer completely
         let mut events = vec![];
diff --git a/zellij-client/src/unit/stdin_tests.rs b/zellij-client/src/unit/stdin_tests.rs
index c55283964..6bdd489bc 100644
--- a/zellij-client/src/unit/stdin_tests.rs
+++ b/zellij-client/src/unit/stdin_tests.rs
@@ -317,98 +317,3 @@ pub fn move_focus_left_in_normal_mode() {
         "All actions sent to server properly"
     );
 }
-
-#[test]
-pub fn terminal_info_queried_from_terminal_emulator() {
-    let events_sent_to_server = Arc::new(Mutex::new(vec![]));
-    let command_is_executing = CommandIsExecuting::new();
-    let client_os_api = FakeClientOsApi::new(events_sent_to_server, command_is_executing);
-
-    let client_os_api_clone = client_os_api.clone();
-    let (send_input_instructions, _receive_input_instructions): ChannelWithContext<
-        InputInstruction,
-    > = channels::bounded(50);
-    let send_input_instructions = SenderWithContext::new(send_input_instructions);
-    let stdin_ansi_parser = Arc::new(Mutex::new(StdinAnsiParser::new()));
-
-    let stdin_thread = thread::Builder::new()
-        .name("stdin_handler".to_string())
-        .spawn({
-            move || {
-                stdin_loop(
-                    Box::new(client_os_api),
-                    send_input_instructions,
-                    stdin_ansi_parser,
-                )
-            }
-        });
-    std::thread::sleep(std::time::Duration::from_millis(500)); // wait for initial query to be sent
-
-    let extracted_stdout_buffer = client_os_api_clone.stdout_buffer();
-    let mut expected_query =
-        String::from("\u{1b}[14t\u{1b}[16t\u{1b}]11;?\u{1b}\u{5c}\u{1b}]10;?\u{1b}\u{5c}");
-    for i in 0..256 {
-        expected_query.push_str(&format!("\u{1b}]4;{};?\u{1b}\u{5c}", i));
-    }
-    assert_eq!(
-        String::from_utf8(extracted_stdout_buffer),
-        Ok(expected_query),
-    );
-    drop(stdin_thread);
-}
-
-#[test]
-pub fn pixel_info_sent_to_server() {
-    let fake_stdin_buffer = read_fixture("terminal_emulator_startup_response");
-    let events_sent_to_server = Arc::new(Mutex::new(vec![]));
-    let command_is_executing = CommandIsExecuting::new();
-    let client_os_api =
-        FakeClientOsApi::new(events_sent_to_server.clone(), command_is_executing.clone())
-            .with_stdin_buffer(fake_stdin_buffer);
-    let config = Config::from_default_assets().unwrap();
-    let options = Options::default();
-
-    let (send_client_instructions, _receive_client_instructions): ChannelWithContext<
-        ClientInstruction,
-    > = channels::bounded(50);
-    let send_client_instructions = SenderWithContext::new(send_client_instructions);
-
-    let (send_input_instructions, receive_input_instructions): ChannelWithContext<
-        InputInstruction,
-    > = channels::bounded(50);
-    let send_input_instructions = SenderWithContext::new(send_input_instructions);
-    let stdin_ansi_parser = Arc::new(Mutex::new(StdinAnsiParser::new()));
-    let stdin_thread = thread::Builder::new()
-        .name("stdin_handler".to_string())
-        .spawn({
-            let client_os_api = client_os_api.clone();
-            move || {
-                stdin_loop(
-                    Box::new(client_os_api),
-                    send_input_instructions,
-                    stdin_ansi_parser,
-                )
-            }
-        });
-
-    let default_mode = InputMode::Normal;
-    let input_thread = thread::Builder::new()
-        .name("input_handler".to_string())
-        .spawn({
-            move || {
-                input_loop(
-                    Box::new(client_os_api),
-                    config,
-                    options,
-                    command_is_executing,
-                    send_client_instructions,
-                    default_mode,
-                    receive_input_instructions,
-                )
-            }
-        });
-    std::thread::sleep(std::time::Duration::from_millis(1000)); // wait for initial query to be sent
-    assert_snapshot!(*format!("{:?}", events_sent_to_server.lock().unwrap()));
-    drop(stdin_thread);
-    drop(input_thread);
-}
diff --git a/zellij-server/src/route.rs b/zellij-server/src/route.rs
index 3de62c092..36799b5ad 100644
--- a/zellij-server/src/route.rs
+++ b/zellij-server/src/route.rs
@@ -1,3 +1,4 @@
+use std::collections::VecDeque;
 use std::sync::{Arc, RwLock};
 
 use crate::{
@@ -670,7 +671,7 @@ macro_rules! send_to_screen_or_retry_queue {
             None => {
                 log::warn!("Server not ready, trying to place instruction in retry queue...");
                 if let Some(retry_queue) = $retry_queue.as_mut() {
-                    retry_queue.push($instruction);
+                    retry_queue.push_back($instruction);
                 }
                 Ok(())
             },
@@ -686,7 +687,7 @@ pub(crate) fn route_thread_main(
     mut receiver: IpcReceiverWithContext<ClientToServerMsg>,
     client_id: ClientId,
 ) -> Result<()> {
-    let mut retry_queue = vec![];
+    let mut retry_queue = VecDeque::new();
     let err_context = || format!("failed to handle instruction for client {client_id}");
     'route_loop: loop {
         match receiver.recv() {
@@ -694,7 +695,9 @@ pub(crate) fn route_thread_main(
                 err_ctx.update_thread_ctx();
                 let rlocked_sessions = session_data.read().to_anyhow().with_context(err_context)?;
                 let handle_instruction = |instruction: ClientToServerMsg,
-                                          mut retry_queue: Option<&mut Vec<ClientToServerMsg>>|
+                                          mut retry_queue: Option<
+                    &mut VecDeque<ClientToServerMsg>,
+                >|
                  -> Result<bool> {
                     let mut should_break = false;
                     match instruction {
@@ -837,7 +840,7 @@ pub(crate) fn route_thread_main(
                     }
                     Ok(should_break)
                 };
-                for instruction_to_retry in retry_queue.drain(..) {
+                while let Some(instruction_to_retry) = retry_queue.pop_front() {
                     log::warn!("Server ready, retrying sending instruction.");
                     let should_break = handle_instruction(instruction_to_retry, None)?;
                     if should_break {