Polishing the new PDF terminal (cairopdf)

[Ethan M. <merritt@u.washington.edu>]

I'd like to collect comments and suggestions on any rough edges
marring the new cairopdf terminal driver.

I know of 3 problems, 2 of which are illustrated by 
fillbetween.dem

1) The pattern fill scales as a bitmap rather than as
   a vector pattern.  This is ugly at high resolution.
   If we can't make the vector pattern scale correctly,
   then in monochrome mode we should probably replace
   the pattern fill with incremental solid shading.
   pattern 1 = no fill
   pattern 2 = black
   pattern 3 = 50% grey
   etc

2) The fill area is not clipped to the plot boundaries.
   This puzzles me, because I thought that the clipping
   was done by the core code.  But other terminals do not
   show this, so...

The 3rd problem may or may not be a gnuplot bug.

3) Under some conditions the entire plot has a black background.
   I only see this on machines with very different versions of
   cairo/pango/kde/kpdf/... so I'm having difficulty figuring
   out which program or library  is at fault.  But even if it is
   a viewer bug, there may still be a fix to gnuplot that would
   avoid triggering it

Missing features:

4) There should be a dashlength option (similar to postscript)

5) Circles (e.g. point types 6 and 7) look jagged.
   This is ultimately the fault of the cairo library, but perhaps
   we could work around it by scaling a well-hinted character
   glyph instead?

Any other observations?

-- 
Ethan A Merritt