frame-inhibit-implied-resize

frame-inhibit-implied-resize is a variable defined in `C source code'.
Its value is

nil

Documentation:
Whether frames should be resized implicitly.
If this option is nil, setting font, menu bar, tool bar, internal
borders, fringes or scroll bars of a specific frame may resize the frame
in order to preserve the number of columns or lines it displays. If
this option is `t', no such resizing is done. Note that the size of
fullscreen and maximized frames, the height of fullheight frames and the
width of fullwidth frames never change implicitly.

The value of this option can be also be a list of frame parameters. In
this case, resizing is inhibited when changing a parameter that appears
in that list. The parameters currently handled by this option include
`font', `font-backend', `internal-border-width', `menu-bar-lines' and
`tool-bar-lines'.

Changing any of the parameters `scroll-bar-width', `scroll-bar-height',
`vertical-scroll-bars', `horizontal-scroll-bars', `left-fringe' and
`right-fringe' is handled as if the frame contained just one live
window. This means, for example, that removing vertical scroll bars on
a frame containing several side by side windows will shrink the frame
width by the width of one scroll bar provided this option is nil and
keep it unchanged if this option is either `t' or a list containing
`vertical-scroll-bars'.

The default value is '(tool-bar-lines) on Lucid, Motif and Windows
(which means that adding/removing a tool bar does not change the frame
height), nil on all other window systems including GTK+ (which means
that changing any of the parameters listed above may change the size of
the frame), and `t' otherwise (which means the frame size never changes
implicitly when there's no window system support).

Note that when a frame is not large enough to accommodate a change of
any of the parameters listed above, Emacs may try to enlarge the frame
even if this option is non-nil.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 25.1 of Emacs.