Variable: cursor-in-non-selected-windows

cursor-in-non-selected-windows is a customizable and buffer-local variable defined in buffer.c.

Documentation

Non-nil means show a cursor in non-selected windows.

If nil, only shows a cursor in the selected window. If t, displays a cursor related to the usual cursor type
(a solid box becomes hollow, a bar becomes a narrower bar).
You can also specify the cursor type as in the cursor-type variable. Use Custom to set this variable and update the display.

View in manual

Probably introduced at or before Emacs version 21.1.

Source Code

// Defined in /usr/src/emacs/src/buffer.c
  DEFVAR_PER_BUFFER ("cursor-in-non-selected-windows",
		     &BVAR (current_buffer, cursor_in_non_selected_windows), Qnil,
		     doc: /* Non-nil means show a cursor in non-selected windows.
If nil, only shows a cursor in the selected window.
If t, displays a cursor related to the usual cursor type
\(a solid box becomes hollow, a bar becomes a narrower bar).