Question

look at this simple procedure:

(defun test ()
  (interactive)
  (push-mark)
  (setq mark-active t)
  (search-forward "a" nil nil 1))

It moves cursor to the nearest ‘a’,and highlight the path.Of course,It’s obvious.

But it behaves differently depending on what’s your next input after this procedure’s execution,For example,you input a char,like ‘b’,or \C-g,the highlight disappeared,but if you input \C-f,or \C-e,the highlight keeps. So Here is my question: what makes these input behave differently?

Answer 1

From the Emacs manual:

Setting the mark at a position in the text also activates it. When the
mark is active, Emacs indicates the extent of the region by
highlighting the text within it, using the region face (see Face
Customization). After certain non-motion commands, including any
command that changes the text in the buffer, Emacs automatically
deactivates the mark; this turns off the highlighting. You can also
explicitly deactivate the mark at any time, by typing C-g (see
Quitting).