window-resize-apply

window-resize-apply is a built-in function in `C source code'.

(window-resize-apply &optional FRAME HORIZONTAL)

Apply requested size values for window-tree of FRAME.
If FRAME is omitted or nil, it defaults to the selected frame.

Optional argument HORIZONTAL omitted or nil means apply requested
height values. HORIZONTAL non-nil means apply requested width values.

The requested size values are those set by `set-window-new-pixel' and
`set-window-new-normal'. This function checks whether the requested
values sum up to a valid window layout, recursively assigns the new
sizes of all child windows and calculates and assigns the new start
positions of these windows.

Return t if the requested values have been applied correctly, nil
otherwise.

Note: This function does not check any of `window-fixed-size-p',
`window-min-height' or `window-min-width'. All these checks have to
be applied on the Elisp level.