Re: Emacs Mac port

[YAMAMOTO Mitsuharu <mituharu@math.s.chiba-u.ac.jp>]

>>>>> On Mon, 22 Apr 2013 09:54:33 +0100, Nix <nix@esperi.org.uk> said:

>>> Which window systems we support don't use "backing store"?
>> 
>> Some implementations of Xservers.  According to the manual, -bs
>> option seems to turn off the backing store support.

> This option does nothing nowadays, because backing store was
> entirely removed from the X.org X server implementation before X
> server 1.5, in 2007. The idea now is that if you want the same
> effect you have to use a compositing manager, which naturally
> provides double-buffering of everything anyway.

>> Mac does have "backing store".  I meant Xserver implementation
>> without "backing store".  I vaguely remember Xvnc didn't have one
>> and issued "expose" events every time a window is uncovered, but
>> I'm not sure about the recent situation of Xservers.

> Just use X.org and make sure your compositing manager is turned off
> :)

Thanks for the info.  With these hints, I could reproduce the problem
on CentOS 5.9, where no compositing manager seems to be used by
default and expose events are issued when a window is being uncovered.

1. Execute "emacs -Q -D &" from the terminal window.
2. Evaluate the following expression in the *scratch* buffer:

    (progn
      (sleep-for 5)
      (let ((cursor-in-echo-area t))
	(message "foo")
	(sit-for 0))
      (sleep-for 30))

3. Switch focus to the terminal window and wait 5 seconds for the
   message "foo" followed by the cursor to be displayed in the echo
   area.
4. Move the terminal window so it goes across the echo area.

Then the cursor in the echo area disappears.  If I try the same
experiment on Ubuntu 12.04 LTS, which has a compositing manager, then
the cursor does not disappear.

				     YAMAMOTO Mitsuharu
				mituharu@math.s.chiba-u.ac.jp