Prefer /dev/tty over stdin in terminal functions

This is part of crossterm-rs#500.

src/terminal/sys/unix.rs

@@ -1,11 +1,11 @@
 //! UNIX related logic for terminal manipulation.
 use std::{io, mem, process, sync::Mutex};
 
-use crate::event::sys::unix::file_descriptor::FileDesc;
+use crate::event::sys::unix::file_descriptor::{tty_fd, FileDesc};
 use lazy_static::lazy_static;
 use libc::{
-    cfmakeraw, ioctl, tcgetattr, tcsetattr, termios as Termios, winsize, STDIN_FILENO,
-    STDOUT_FILENO, TCSANOW, TIOCGWINSZ,
+    cfmakeraw, ioctl, tcgetattr, tcsetattr, termios as Termios, winsize, STDOUT_FILENO, TCSANOW,
+    TIOCGWINSZ,
 };
 
 use crate::error::{ErrorKind, Result};
@@ -54,11 +54,13 @@ pub(crate) fn enable_raw_mode() -> Result<()> {
         return Ok(());
     }
 
-    let mut ios = get_terminal_attr()?;
+    let tty = tty_fd()?;
+    let fd = tty.raw_fd();
+    let mut ios = get_terminal_attr(fd)?;
     let original_mode_ios = ios;
 
     raw_terminal_attr(&mut ios);
-    set_terminal_attr(&ios)?;
+    set_terminal_attr(fd, &ios)?;
 
     // Keep it last - set the original mode only if we were able to switch to the raw mode
     *original_mode = Some(original_mode_ios);
@@ -70,7 +72,8 @@ pub(crate) fn disable_raw_mode() -> Result<()> {
     let mut original_mode = TERMINAL_MODE_PRIOR_RAW_MODE.lock().unwrap();
 
     if let Some(original_mode_ios) = original_mode.as_ref() {
-        set_terminal_attr(original_mode_ios)?;
+        let tty = tty_fd()?;
+        set_terminal_attr(tty.raw_fd(), original_mode_ios)?;
         // Keep it last - remove the original mode only if we were able to switch back
         *original_mode = None;
     }
@@ -116,16 +119,16 @@ fn raw_terminal_attr(termios: &mut Termios) {
     unsafe { cfmakeraw(termios) }
 }
 
-fn get_terminal_attr() -> Result<Termios> {
+fn get_terminal_attr(fd: i32) -> Result<Termios> {
     unsafe {
         let mut termios = mem::zeroed();
-        wrap_with_result(tcgetattr(STDIN_FILENO, &mut termios))?;
+        wrap_with_result(tcgetattr(fd, &mut termios))?;
         Ok(termios)
     }
 }
 
-fn set_terminal_attr(termios: &Termios) -> Result<bool> {
-    wrap_with_result(unsafe { tcsetattr(STDIN_FILENO, TCSANOW, termios) })
+fn set_terminal_attr(fd: i32, termios: &Termios) -> Result<bool> {
+    wrap_with_result(unsafe { tcsetattr(fd, TCSANOW, termios) })
 }
 
 pub fn wrap_with_result(result: i32) -> Result<bool> {