feat(ux): show loading screen (#1997)

* feat(ux): show loading prompt

* style(fmt): rustfmt

4 files changed, 83 insertions, 3 deletions

diff --git a/zellij-client/src/input_handler.rs b/zellij-client/src/input_handler.rs
index 801ff0951..bf3bcc006 100644
--- a/zellij-client/src/input_handler.rs
+++ b/zellij-client/src/input_handler.rs
@@ -147,6 +147,20 @@ impl InputHandler {
                         self.handle_stdin_ansi_instruction(ansi_instruction);
                     }
                 },
+                Ok((InputInstruction::StartedParsing, _error_context)) => {
+                    log::info!("sending done loading");
+                    self.send_client_instructions
+                        .send(ClientInstruction::StartedParsingStdinQuery)
+                        .unwrap();
+                    log::info!("done sent done loading");
+                },
+                Ok((InputInstruction::DoneParsing, _error_context)) => {
+                    log::info!("sending done loading");
+                    self.send_client_instructions
+                        .send(ClientInstruction::DoneParsingStdinQuery)
+                        .unwrap();
+                    log::info!("done sent done loading");
+                },
                 Err(err) => panic!("Encountered read error: {:?}", err),
             }
         }
diff --git a/zellij-client/src/lib.rs b/zellij-client/src/lib.rs
index 0fd549ab4..51d6c99d6 100644
--- a/zellij-client/src/lib.rs
+++ b/zellij-client/src/lib.rs
@@ -43,6 +43,8 @@ pub(crate) enum ClientInstruction {
     SwitchToMode(InputMode),
     Connected,
     ActiveClients(Vec<ClientId>),
+    StartedParsingStdinQuery,
+    DoneParsingStdinQuery,
 }
 
 impl From<ServerToClientMsg> for ClientInstruction {
@@ -70,6 +72,8 @@ impl From<&ClientInstruction> for ClientContext {
             ClientInstruction::SwitchToMode(_) => ClientContext::SwitchToMode,
             ClientInstruction::Connected => ClientContext::Connected,
             ClientInstruction::ActiveClients(_) => ClientContext::ActiveClients,
+            ClientInstruction::StartedParsingStdinQuery => ClientContext::StartedParsingStdinQuery,
+            ClientInstruction::DoneParsingStdinQuery => ClientContext::DoneParsingStdinQuery,
         }
     }
 }
@@ -121,6 +125,8 @@ pub(crate) enum InputInstruction {
     KeyEvent(InputEvent, Vec<u8>),
     SwitchToMode(InputMode),
     AnsiStdinInstructions(Vec<AnsiStdinInstruction>),
+    StartedParsing,
+    DoneParsing,
 }
 
 pub fn start_client(
@@ -337,13 +343,51 @@ pub fn start_client(
     };
 
     let exit_msg: String;
+    let mut loading = true;
+    let mut pending_instructions = vec![];
+
+    let mut stdout = os_input.get_stdout_writer();
+    stdout
+        .write_all("\u{1b}[1mLoading Zellij\u{1b}[m".as_bytes())
+        .expect("cannot write to stdout");
+    stdout.flush().expect("could not flush");
 
     loop {
-        let (client_instruction, mut err_ctx) = receive_client_instructions
-            .recv()
-            .expect("failed to receive app instruction on channel");
+        let (client_instruction, mut err_ctx) = if !loading && !pending_instructions.is_empty() {
+            // there are buffered instructions, we need to go through them before processing the
+            // new ones
+            pending_instructions.remove(0)
+        } else {
+            receive_client_instructions
+                .recv()
+                .expect("failed to receive app instruction on channel")
+        };
+
+        if loading {
+            // when the app is still loading, we buffer instructions and show a loading screen
+            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())
+                        .expect("cannot write to stdout");
+                    stdout.flush().expect("could not flush");
+                },
+                ClientInstruction::DoneParsingStdinQuery => {
+                    stdout
+                        .write_all("done".as_bytes())
+                        .expect("cannot write to stdout");
+                    stdout.flush().expect("could not flush");
+                    loading = false;
+                },
+                instruction => {
+                    pending_instructions.push((instruction, err_ctx));
+                },
+            }
+            continue;
+        }
 
         err_ctx.add_call(ContextType::Client((&client_instruction).into()));
+
         match client_instruction {
             ClientInstruction::Exit(reason) => {
                 os_input.send_to_server(ClientToServerMsg::ClientExited);
diff --git a/zellij-client/src/stdin_ansi_parser.rs b/zellij-client/src/stdin_ansi_parser.rs
index 09247bf9b..23e869b2b 100644
--- a/zellij-client/src/stdin_ansi_parser.rs
+++ b/zellij-client/src/stdin_ansi_parser.rs
@@ -73,6 +73,9 @@ impl StdinAnsiParser {
         }
         false
     }
+    pub fn startup_query_duration(&self) -> u64 {
+        STARTUP_PARSE_DEADLINE_MS
+    }
     pub fn parse(&mut self, mut raw_bytes: Vec<u8>) -> Vec<AnsiStdinInstruction> {
         for byte in raw_bytes.drain(..) {
             self.parse_byte(byte);
diff --git a/zellij-client/src/stdin_handler.rs b/zellij-client/src/stdin_handler.rs
index 8d6e51b0a..75634a05b 100644
--- a/zellij-client/src/stdin_handler.rs
+++ b/zellij-client/src/stdin_handler.rs
@@ -5,6 +5,20 @@ use std::sync::{Arc, Mutex};
 use zellij_utils::channels::SenderWithContext;
 use zellij_utils::termwiz::input::{InputEvent, InputParser, MouseButtons};
 
+fn send_done_parsing_after_query_timeout(
+    send_input_instructions: SenderWithContext<InputInstruction>,
+    query_duration: u64,
+) {
+    std::thread::spawn({
+        move || {
+            std::thread::sleep(std::time::Duration::from_millis(query_duration));
+            send_input_instructions
+                .send(InputInstruction::DoneParsing)
+                .unwrap();
+        }
+    });
+}
+
 pub(crate) fn stdin_loop(
     mut os_input: Box<dyn ClientOsApi>,
     send_input_instructions: SenderWithContext<InputInstruction>,
@@ -15,6 +29,9 @@ pub(crate) fn stdin_loop(
     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()
@@ -23,6 +40,8 @@ pub(crate) fn stdin_loop(
         .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);
     loop {
         let buf = os_input.read_from_stdin();
         {