Variable: resize-mini-windows
resize-mini-windows is a customizable variable defined in xdisp.c.
Value
grow-only
Documentation
How to resize mini-windows (the minibuffer and the echo area).
A value of nil means don't automatically resize mini-windows.
A value of t means resize them to fit the text displayed in them.
A value of grow-only, the default, means let mini-windows grow only;
they return to their normal size when the minibuffer is closed, or the
echo area becomes empty.
This variable does not affect resizing of the minibuffer window of
minibuffer-only frames. These are handled by resize-mini-frames
only.
This variable was added, or its default value changed, in Emacs 25.1.
Probably introduced at or before Emacs version 21.1.
Source Code
// Defined in /usr/src/emacs/src/xdisp.c
DEFVAR_LISP ("resize-mini-windows", Vresize_mini_windows,
doc: /* How to resize mini-windows (the minibuffer and the echo area).
A value of nil means don't automatically resize mini-windows.
A value of t means resize them to fit the text displayed in them.
A value of `grow-only', the default, means let mini-windows grow only;
they return to their normal size when the minibuffer is closed, or the
echo area becomes empty.
This variable does not affect resizing of the minibuffer window of
minibuffer-only frames. These are handled by `resize-mini-frames'
only. */);