Avoid unnecessary CPU churn when reading from stdin for @ send-text

kitty/rc/send_text.py

@@ -69,9 +69,13 @@ Do not send text to the active window, even if it is one of the matched windows.
                 ret['exclude_active'] = True
                 keep_going = True
                 from kitty.utils import TTYIO
-                with TTYIO() as tty:
+                with TTYIO(read_with_timeout=False) as tty:
                     while keep_going:
+                        if not tty.wait_till_read_available():
+                            break
                         data = os.read(tty.tty_fd, limit)
+                        if not data:
+                            break
                         decoded_data = data.decode('utf-8')
                         if '\x04' in decoded_data:
                             decoded_data = decoded_data[:decoded_data.index('\x04')]

kitty/utils.py

@@ -442,15 +442,23 @@ def write_all(fd: int, data: Union[str, bytes]) -> None:
 
 class TTYIO:
 
+    def __init__(self, read_with_timeout: bool = True):
+        self.read_with_timeout = read_with_timeout
+
     def __enter__(self) -> 'TTYIO':
         from .fast_data_types import open_tty
-        self.tty_fd, self.original_termios = open_tty(True)
+        self.tty_fd, self.original_termios = open_tty(self.read_with_timeout)
         return self
 
     def __exit__(self, *a: Any) -> None:
         from .fast_data_types import close_tty
         close_tty(self.tty_fd, self.original_termios)
 
+    def wait_till_read_available(self) -> bool:
+        import select
+        rd = select.select([self.tty_fd], [], [])[0]
+        return bool(rd)
+
     def send(self, data: Union[str, bytes, Iterable[Union[str, bytes]]]) -> None:
         if isinstance(data, (str, bytes)):
             write_all(self.tty_fd, data)