The variable double-click-fuzz specifies how much the mouse can move between clicks still allow them to be grouped as a multiple click. Its value is in units of pixels on windowed displays and in units of 1/8 of a character cell on text-mode terminals; the default is 3.
The symbols for mouse events also indicate the status of the modifier keys, with the usual prefixes C-, M-, H-, s-, A- and S-. These always precede double- or triple-, which always precede drag- or down-.
A frame includes areas that don't show text from the buffer, such as the mode line and the scroll bar. You can tell whether a mouse button comes from a special area of the screen by means of dummy "prefix keys." For example, if you click the mouse in the mode line, you get the prefix key mode-line before the ordinary mouse-button symbol. Thus, here is how to define the command for clicking the first button in a mode line to run scroll-up:
(global-set-key [mode-line mouse-1] 'scroll-up)
Here is the complete list of these dummy prefix keys and their meanings:
- mode-line
The mouse was in the mode line of a window. - vertical-line
The mouse was in the vertical line separating side-by-side windows. (If you use scroll bars, they appear in place of these vertical lines.) - vertical-scroll-bar
The mouse was in a vertical scroll bar. (This is the only kind of scroll bar Emacs currently supports.)
You can put more than one mouse button in a key sequence, but it isn't usual to do so.
