Standard icon - %nsisymbol
Defines a standard icon that is to be placed to the left of the block of text
that follows the format code. symbol is one of "?", "*", "!", and "#".
The icons given by these symbols are illustrated below.
i=winio@('%2nlThese are all the standard icons.&')
The symbol is vertically centred to the left of n lines of text (the
parameter n defaults to 1), and a half icon width is left blank to the
right so as to leave an appropriate gap between the icon and subsequent text.
Sound is added by attaching the "BEEP" call-back (see
BEEP). Alternatively, you can call the API function MessageBeep before
creating the format window.
The caret character (^) is used with %si in order to attach a call-back
function. This function is called each time the user clicks on the icon. In the
above example the '!' icon uses the call-back function cb_icon.