Can't seem to emit a few dozens of key events at once on the virtual keyboard

[fr33-sh]

If I have a vector of around 30 InputEvents and try to emit them on a virtual keyboard, only a few of them and sometimes none of them will actually be emitted. Here's a minimal PoC for this issue, where I expect the 50 'A' to be typed, but in reality only a few are typed. And if I change 50 to 30, it seems like it only type out 'A's every 2 iterations. Is it an issue with this crate, or linux?

use evdev::KeyEvent;
use evdev::{Device, uinput::VirtualDevice, AttributeSet, EventType, InputEvent, KeyCode};
use std::collections::HashSet;
use std::thread::sleep;
use std::time;
use std::time::Duration;
use std::fs::File;
use std::io::{Read};


fn main() -> std::io::Result<()> {
 // Have to insert all allowed keys manually (?)
 // Is it because the evdev crate is minimal?
 let mut all_keys = vec![
 KeyCode::KEY_ESC,
 KeyCode::KEY_1,
 KeyCode::KEY_2,
 KeyCode::KEY_3,
 KeyCode::KEY_4,
 KeyCode::KEY_5,
 KeyCode::KEY_6,
 KeyCode::KEY_7,
 KeyCode::KEY_8,
 KeyCode::KEY_9,
 KeyCode::KEY_0,
 KeyCode::KEY_MINUS,
 KeyCode::KEY_EQUAL,
 KeyCode::KEY_BACKSPACE,
 KeyCode::KEY_TAB,
 KeyCode::KEY_Q,
 KeyCode::KEY_W,
 KeyCode::KEY_E,
 KeyCode::KEY_R,
 KeyCode::KEY_T,
 KeyCode::KEY_Y,
 KeyCode::KEY_U,
 KeyCode::KEY_I,
 KeyCode::KEY_O,
 KeyCode::KEY_P,
 KeyCode::KEY_LEFTBRACE,
 KeyCode::KEY_RIGHTBRACE,
 KeyCode::KEY_ENTER,
 KeyCode::KEY_LEFTCTRL,
 KeyCode::KEY_LEFTMETA,
 KeyCode::KEY_A,
 KeyCode::KEY_S,
 KeyCode::KEY_D,
 KeyCode::KEY_F,
 KeyCode::KEY_G,
 KeyCode::KEY_H,
 KeyCode::KEY_J,
 KeyCode::KEY_K,
 KeyCode::KEY_L,
 KeyCode::KEY_SEMICOLON,
 KeyCode::KEY_APOSTROPHE,
 KeyCode::KEY_GRAVE,
 KeyCode::KEY_LEFTSHIFT,
 KeyCode::KEY_BACKSLASH,
 KeyCode::KEY_Z,
 KeyCode::KEY_X,
 KeyCode::KEY_C,
 KeyCode::KEY_V,
 KeyCode::KEY_B,
 KeyCode::KEY_N,
 KeyCode::KEY_M,
 KeyCode::KEY_COMMA,
 KeyCode::KEY_DOT,
 KeyCode::KEY_SLASH,
 KeyCode::KEY_RIGHTSHIFT,
 KeyCode::KEY_LEFTALT,
 KeyCode::KEY_SPACE,
 KeyCode::KEY_CAPSLOCK,
 KeyCode::KEY_RIGHTCTRL,
 KeyCode::KEY_RIGHTALT,
 ];
 let mut v_keys = AttributeSet::<KeyCode>::new();
 for key in all_keys {
 v_keys.insert(key);
 }

 // Create a virtual keyboard.
 let mut v_keyboard = VirtualDevice::builder()?
 .name("Virtual Keyboard")
 .with_keys(&v_keys)?
 .build()
 .unwrap();
 for path in v_keyboard.enumerate_dev_nodes_blocking()? {
 let path = path?;
 println!("Available as {}", path.display());
 }

 let new_input_event_down = InputEvent::new(EventType::KEY.0, KeyCode::KEY_A.code(), 1);
 let new_input_event_up = InputEvent::new(EventType::KEY.0, KeyCode::KEY_A.code(), 0);
 let mut new_input_events: Vec<InputEvent> = Vec::new();
 for i in (1..50) {
 new_input_events.push(new_input_event_down);
 new_input_events.push(new_input_event_up);
 }
 loop {
 v_keyboard.emit(&new_input_events).unwrap();
 sleep(Duration::from_secs(2));
 }
 Ok(())
}

[waynr]

The problem seems to be that all the events you are creating have an identical timestamp set by the InputEvent::new function. I rewrote your example slightly to insert very short sleeps between calls to InputEvent::new and it works perfectly for me:

use evdev::{AttributeSet, EventType, InputEvent, KeyCode, uinput::VirtualDevice};
use std::thread::sleep;
use std::time::Duration;

fn main() -> std::io::Result<()> {
 let mut all_keys = vec![
 KeyCode::KEY_1,
 KeyCode::KEY_2,
 KeyCode::KEY_3,
 KeyCode::KEY_4,
 KeyCode::KEY_5,
 KeyCode::KEY_6,
 KeyCode::KEY_7,
 KeyCode::KEY_8,
 KeyCode::KEY_9,
 KeyCode::KEY_0,
 KeyCode::KEY_MINUS,
 KeyCode::KEY_EQUAL,
 KeyCode::KEY_Q,
 KeyCode::KEY_W,
 KeyCode::KEY_E,
 KeyCode::KEY_R,
 KeyCode::KEY_T,
 KeyCode::KEY_Y,
 KeyCode::KEY_U,
 KeyCode::KEY_I,
 KeyCode::KEY_O,
 KeyCode::KEY_P,
 KeyCode::KEY_LEFTBRACE,
 KeyCode::KEY_RIGHTBRACE,
 KeyCode::KEY_A,
 KeyCode::KEY_S,
 KeyCode::KEY_D,
 KeyCode::KEY_F,
 KeyCode::KEY_G,
 KeyCode::KEY_H,
 KeyCode::KEY_J,
 KeyCode::KEY_K,
 KeyCode::KEY_L,
 KeyCode::KEY_SEMICOLON,
 KeyCode::KEY_APOSTROPHE,
 KeyCode::KEY_GRAVE,
 KeyCode::KEY_BACKSLASH,
 KeyCode::KEY_Z,
 KeyCode::KEY_X,
 KeyCode::KEY_C,
 KeyCode::KEY_V,
 KeyCode::KEY_B,
 KeyCode::KEY_N,
 KeyCode::KEY_M,
 KeyCode::KEY_COMMA,
 KeyCode::KEY_DOT,
 KeyCode::KEY_SLASH,
 KeyCode::KEY_SPACE,
 ];
 let mut v_keys = AttributeSet::<KeyCode>::new();
 for key in &all_keys {
 v_keys.insert(*key);
 }

 // Create a virtual keyboard.
 let mut v_keyboard = VirtualDevice::builder()?
 .name("Virtual Keyboard")
 .with_keys(&v_keys)?
 .build()
 .unwrap();
 for path in v_keyboard.enumerate_dev_nodes_blocking()? {
 let path = path?;
 println!("Available as {}", path.display());
 }

 loop {
 for key in &all_keys {
 let down = InputEvent::new(EventType::KEY.0, key.code(), 1);
 v_keyboard.emit(&[down]).unwrap();

 sleep(Duration::from_nanos(10));Available as /dev/input/event30

 let up = InputEvent::new(EventType::KEY.0, key.code(), 0);
 v_keyboard.emit(&[up]).unwrap();
 }
 sleep(Duration::from_millis(50));
 }

 Ok(())
}

Note that I also iterate over all_keys here rather than simply printing the same character repeatedly to more clearly show that no key press is being missed in my output. Here's what I see when I run the program:

 Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.03s
 Running `/home/wayne/.cache/dfiles/cargo/agent-shared-target/debug/evdev-issue-166`
Available as /dev/input/event30
1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 123456asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 1234567890-=qwertyuiop[]asdfghjkl;'`\zxcvbnm,./ 

Also note that all output showing up after the Available as /dev/input/event30 line was sent to my terminal emulator by the virtual keyboard itself.

[waynr]

One thing that bothers me somewhat about the need to insert sleeps between the calls to InputEvent::new is that this makes it somewhat harder to send events in batches. I suspect it's probably probably necessary due to the need to communicate an actual SystemTime to the underlying operating system when emitting the event at the syscall boundary.