Allin:
Thanks for your solution for this 'gretl/gnuplot: "first-time" plots slow
on
Windows' problem. I had to note this "slow plot" problem in gretl when I
introduced gretl to my cleagues and students.
I've just downloaded cvs and tested it. It looks now no-delay at all on my
winXP+sp3 machine.
Great job and thanks again.
Yi-Nung Yang
Chair and Associate Professor
Dept. of International Business
Chung Yuan Christian University, Taiwan, ROC.
2011/1/19 Allin Cottrell <cottrell(a)wfu.edu>
Back in July 2010 we had an extensive discussion of this point:
the "first time" you generate a gnuplot graph via gretl on MS
Windows it can take an inordinate length of time for the plot to
appear. It wasn't clear that "first time" meant the same thing
thing in all reports, but the first plot after installing gretl +
gnuplot from scratch seemed most reliably problematic.
The discussion was inconclusive; we didn't up with a compelling
diagnosis.
I think I now have the answer: what's taking so long is the
fontconfig library building its initial font cache. This accounts
for the ambiguity over when exactly the problem arises, since
various system changes can provoke rebuilding of the cache
from time to time.
In the current Windows snapshot I've rebuilt gnuplot so that it
does not call fontconfig, and so cache-building time shouldn't be
a problem any more. Windows users, please test! We're looking for
(a) absence of any wait of more than a couple of seconds for a
plot to appear (should usually be faster than that) and (b) any
fallout from this change in the form of font-handling errors
(e.g. text on plots appears clipped, with bits of letters
missing).
For enquiring minds: gnuplot calls the cairo library in its
generation of PNG plots, and cairo has two different font-handling
"backends" that can be used on Windows: a native win32 one, and
FreeType plus fontconfig. In November 2009 gnuplot switched away
from using the cairo-win32 backend because it was found to be
buggy, with glyphs getting clipped. FreeType plus fontconfig
produces flawless plots, but the downside is an occasional long
wait as fontconfig (re-)builds its cache. By now, with cairo
1.10.2, the win32 bugs that were spoiling gnuplot PNG output seem
to be fixed, hence my experiment of going back to the win32
backend.
Allin Cottrell
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