`pane:is_alt_screen_active()`

Since: nightly builds only

Returns whether the alternate screen is active for the pane.

The alternate screen is a secondary screen that is activated by certain escape codes. The alternate screen has no scrollback, which makes it ideal for a "full-screen" terminal program like vim or less to do whatever they want on the screen without fear of destroying the user's scrollback. Those programs emit escape codes to return to the normal screen when they exit.