Hi,

My vim seems to flicker on big terminals because the output buffer is
limited to 2K. Outputting a full redraw of large screen needs much more
characters (especially if it has lots of colors). Currently it is
distributed to several writes (separated by several milliseconds on my
slow machine). This causes that when I press Page Down for example I can
see the black flicker in bottom part of the terminal.

I propose increasing this buffer to 64K. So in src/term.c:
-#  define OUT_SIZE     2047
+#  define OUT_SIZE     65535

Thanks!

Balazs

On 29/07/12 11:41 PM, Balazs Kezes wrote:

This sounds like a good idea to me.

Ben.

The purpose of the output buffer is not to avoid flicker.  It's to avoid
many small updates, which is slow.

Computers have much more memory now, thus we could make the buffer
bigger.  But they are also much faster, thus the need for reducing the
number of calls is smaller.  I suppose making it 8K would be OK.

I'm mainly worried about slow remote connections.  Personally that's
where I sometimes have problems (ssh over GPRS).  I'm not sure what the
relation is between the buffer size and responsiveness.  While typing
out_flush() should be called quite often.

--
% cat /usr/include/sys/errno.h
#define EPERM           1               /* Operation not permitted */
#define ENOENT          2               /* No such file or directory */
#define ESRCH           3               /* No such process */
[...]
#define EMACS           666             /* Too many macros */
%

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I'm even doubting a bit that 64K is enough for all cases. Maybe a
configuration option for this size would be better (defaulting to 64K
but others can reduce/increase the size depending on their needs)?

Yeah, they are faster, but mine is slow enough that I see the partial
update on most terminals. :(

I think that's where this change would shine! Suppose that vim does a
full screen update (e.g. you press page down) and this means outputting
13K bytes to the terminal. Vim does the update quite quickly but
depending on your TCP settings and the time between the actual writes
this might happen: In the 2K buffer size case the operating system sees
a bunch of 2K buffers and this might result a bunch of partial packets
whereas 13K would ensure that the packets are always full length thus it
should need less packets to transmit the full update.

It is called quite often already. Vim won't wait for the buffer to fill
when you append a character to a line. That's only a several character
update and because you can see that the character is immediately
outputted it means the output buffer is flushed often.

My only problem is when vim does a full screen update, that's the only
case when a 2K buffer is not enough (it is enough for any other update).

Thanks!

Balazs