Optimize rendering. Don't output escape codes for hiding/showing the cursor if not needed. (#1968)

This fixes a regression that was introduced in
#1925

Author: jonathanslenders

src/prompt_toolkit/output/vt100.py

@@ -436,6 +436,11 @@ def __init__(
         # default, we don't change them.)
         self._cursor_shape_changed = False
 
+        # Don't hide/show the cursor when this was already done.
+        # (`None` means that we don't know whether the cursor is visible or
+        # not.)
+        self._cursor_visible: bool | None = None
+
     @classmethod
     def from_pty(
         cls,
@@ -651,10 +656,14 @@ def cursor_backward(self, amount: int) -> None:
             self.write_raw("\x1b[%iD" % amount)
 
     def hide_cursor(self) -> None:
-        self.write_raw("\x1b[?25l")
+        if self._cursor_visible in (True, None):
+            self._cursor_visible = False
+            self.write_raw("\x1b[?25l")
 
     def show_cursor(self) -> None:
-        self.write_raw("\x1b[?12l\x1b[?25h")  # Stop blinking cursor and show.
+        if self._cursor_visible in (False, None):
+            self._cursor_visible = True
+            self.write_raw("\x1b[?12l\x1b[?25h")  # Stop blinking cursor and show.
 
     def set_cursor_shape(self, cursor_shape: CursorShape) -> None:
         if cursor_shape == CursorShape._NEVER_CHANGE:

src/prompt_toolkit/renderer.py

@@ -353,6 +353,11 @@ def __init__(
         self.mouse_support = to_filter(mouse_support)
         self.cpr_not_supported_callback = cpr_not_supported_callback
 
+        # TODO: Move following state flags into `Vt100_Output`, similar to
+        #       `_cursor_shape_changed` and `_cursor_visible`. But then also
+        #       adjust the `Win32Output` to not call win32 APIs if nothing has
+        #       to be changed.
+
         self._in_alternate_screen = False
         self._mouse_support_enabled = False
         self._bracketed_paste_enabled = False