Emacs minibuffer message when typing C-x

Question

Well. When I type some first keys of the key series, emacs write those keys in minibuffer after some interval of time. Like that: Typing C-x 4 will make C-x 4- visible in minibuffer.

The question is: can this be modified? I was thinking about making something like combining part of key-help (generated by C-h when type some keys) with this string. Can interval for waiting this message be shorten too? Is it subroutine?

Edited, new question

There is a message when I quit emacs with C-x C-c and have modified buffers, that ask me if I want to save them. How can I know that this message is here? I tried to look in (minibuffer-prompt) (minibuffer-contents) (buffer-substring (point-min) (point-max)), selecting (select-window (minibuffer-window)). Nothing gives me results.

Answer 1

Yes, the user option echo-keystrokes controls how much time elapses before the prefix key is shown in the minibuffer. From (emacs) Echo Area Customization:

User Option: echo-keystrokes
     This variable determines how much time should elapse before command
     characters echo.  Its value must be an integer or floating point
     number, which specifies the number of seconds to wait before
     echoing.  If the user types a prefix key (such as `C-x') and then
     delays this many seconds before continuing, the prefix key is
     echoed in the echo area.  (Once echoing begins in a key sequence,
     all subsequent characters in the same key sequence are echoed
     immediately.)

     If the value is zero, then command input is not echoed.