Support automated UX testing

Author: yizhepku

Cargo.lock

@@ -36,6 +36,7 @@ unicode-segmentation = "1.9.0"
 unicode-width = "0.1.9"
 
 [dev-dependencies]
+alacritty-test = { git = "https://github.com/YizhePKU/alacritty-test.git", rev = "2f63ebe" }
 gethostname = "0.4.0"
 pretty_assertions = "1.4.0"
 rstest = { version = "0.18.0", default-features = false }

Cargo.toml

@@ -0,0 +1,71 @@
+//! Measure the typing latency of Reedline with default configurations.
+
+use alacritty_test::{pty_spawn, EventedReadWrite, Terminal};
+use reedline::{DefaultPrompt, Reedline, Signal};
+use std::{
+    io::Write,
+    time::{Duration, Instant},
+};
+
+fn child() -> ! {
+    let mut line_editor = Reedline::create();
+    let prompt = DefaultPrompt::default();
+
+    loop {
+        let sig = line_editor.read_line(&prompt).unwrap();
+        match sig {
+            Signal::Success(buffer) => {
+                println!("We processed: {buffer}");
+            }
+            _ => std::process::exit(-1),
+        }
+    }
+}
+
+fn main() -> std::io::Result<()> {
+    if let Some(arg) = std::env::args().nth(1) {
+        if arg == "--child" {
+            child();
+        }
+    }
+
+    let mut pty = pty_spawn(
+        "target/debug/examples/typing_latency",
+        vec!["--child"],
+        None,
+    )?;
+    let mut terminal = Terminal::new();
+    terminal.read_from_pty(&mut pty, Some(Duration::from_millis(50)))?;
+
+    // Test latency of a single keystroke.
+    let mut total_latency = Duration::from_millis(0);
+    for loop_cnt in 1.. {
+        let old_cursor = terminal.inner().grid().cursor.point;
+
+        // input a single keystroke
+        pty.writer().write_all(b"A").unwrap();
+
+        let start_time = Instant::now();
+        loop {
+            // measure with 10us accuracy
+            terminal.read_from_pty(&mut pty, Some(Duration::from_micros(10)))?;
+
+            let new_cursor = terminal.inner().grid().cursor.point;
+            if new_cursor.column > old_cursor.column {
+                break;
+            }
+        }
+        total_latency += start_time.elapsed();
+
+        println!(
+            "single keystroke latency = {:.2}ms, averaging over {loop_cnt} iterations",
+            (total_latency.as_millis() as f64) / (loop_cnt as f64),
+        );
+
+        // delete the keystroke
+        pty.writer().write_all(b"\x7f\x7f\x7f\x7f").unwrap();
+        terminal.read_from_pty(&mut pty, Some(Duration::from_millis(50)))?;
+    }
+
+    Ok(())
+}