20.1.9 Slow Terminal Incremental Search
Incremental search on a slow terminal uses a modified style of display
that is designed to take less time. Instead of redisplaying the buffer at
each place the search gets to, it creates a new single-line window and uses
that to display the line that the search has found. The single-line window
comes into play as soon as point moves outside of the text that is already
on the screen.
When you terminate the search, the single-line window is removed.
Emacs then redisplays the window in which the search was done, to show
its new position of point.
The slow terminal style of display is used when the terminal baud rate is
less than or equal to the value of the variable
initially 1200. See also the discussion of the variable
(see Customization of Display).
The number of lines to use in slow terminal search display is controlled
by the variable
search-slow-window-lines. Its normal value is 1.