x-server-max-request-size

x-server-max-request-size is a built-in function in `C source code'.

(x-server-max-request-size &optional TERMINAL)

Return the maximum request size of the X server of display TERMINAL.
The optional argument TERMINAL specifies which display to ask about.
TERMINAL should be a terminal object, a frame or a display name (a string).
If omitted or nil, that stands for the selected frame's display.