+ XM <I>string</I>, override ncurses's built-in string which enables/disables
+ <B>xterm</B> mouse mode.
+
+ ncurses sends a character sequence to the terminal to initialize
+ mouse mode, and when the user clicks the mouse buttons or (in
+ certain modes) moves the mouse, handles the characters sent back
+ by the terminal to tell it what was done with the mouse.
+
+ The mouse protocol is enabled when the <I>mask</I> passed in the
+ <B>mousemask</B> function is nonzero. By default, ncurses handles the
+ responses for the X11 xterm mouse protocol. It also knows about
+ the <I>SGR</I> <I>1006</I> xterm mouse protocol, but must to be told to look
+ for this specifically. It will not be able to guess which mode
+ is used, because the responses are enough alike that only
+ confusion would result.
+
+ The <B>XM</B> capability has a single parameter. If nonzero, the mouse
+ protocol should be enabled. If zero, the mouse protocol should
+ be disabled. ncurses inspects this capability if it is present,
+ to see whether the 1006 protocol is used. If so, it expects the
+ responses to use the <I>SGR</I> <I>1006</I> xterm mouse protocol.
+
+ The xterm mouse protocol is used by other terminal emulators.
+ The terminal database uses building-blocks for the various xterm
+ mouse protocols which can be used in customized terminal
+ descriptions.
+
+ The terminal database building blocks for this mouse feature also
+ have an experimental capability <I>xm</I>. The "xm" capability
+ describes the mouse response. Currently there is no interpreter
+ which would use this information to make the mouse support
+ completely data-driven.
+
+ <I>xm</I> shows the format of the mouse responses. In this experimental
+ capability, the parameters are
+
+ <I>p1</I> y-ordinate
+
+ <I>p2</I> x-ordinate
+
+ <I>p3</I> button
+
+ <I>p4</I> state, e.g., pressed or released
+
+ <I>p5</I> y-ordinate starting region
+
+ <I>p6</I> x-ordinate starting region
+
+ <I>p7</I> y-ordinate ending region
+
+ <I>p8</I> x-ordinate ending region
+
+ Here are examples from the terminal database for the most
+ commonly used xterm mouse protocols:
+
+ xterm+x11mouse|X11 xterm mouse protocol,
+ kmous=\E[M, XM=\E[?1000%?%p1%{1}%=%th%el%;,
+ xm=\E[M
+ %?%p4%t%p3%e%{3}%;%' '%+%c
+ %p2%'!'%+%c
+ %p1%'!'%+%c,
+
+ xterm+sm+1006|xterm SGR-mouse,
+ kmous=\E[<, XM=\E[?1006;1000%?%p1%{1}%=%th%el%;,
+ xm=\E[<%i%p3%d;
+ %p1%d;
+ %p2%d;
+ %?%p4%tM%em%;,