Re: special behavior of postscript terminal? (again)

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

On Thursday 23 October 2008 16:31:01 Allin Cottrell wrote:
> On Thu, 23 Oct 2008, Ethan Merritt wrote:
> 
> > On Thursday 23 October 2008 12:30:21 Allin Cottrell wrote:
> > > It seems to me that a nice solution would be if "set style line" 
> > > were extended to include a "dashtype/dt" option, in the same way 
> > > that pointtype can be selected independently of other features of 
> > > the line.  
> > 
> > Isn't that what it does now?
> > Each line type has an explicit dash pattern, selected by saying "lt N",
> > analogous to selecting point type by saying "pt N".
> 
> Yes, but this depends on the terminal type, making it more or less 
> impossible to produce a "portable" gnuplot command file which will 
> produce similar effects (modulo inevitable differences in 
> capabilities) across the various terminals.

Ah, I misunderstood.
That's an entirely different issue.

We made a concerted effort for 4.2 to bring the sequence of point types
into conformity across terminals.  So far as I recall, no one argued for
doing the same to dash patterns. I have no objections to someone offering
a series of patches that re-orders the sequence of dash patterns to
achieve some level of cross-terminal agreement.

I don't particularly like the sequence used by postscript, but I guess
it is the most likely terminal for which we would have to worry about
compatibility with existing scripts.

Perhaps a more interesting question is how many of the terminals could
support user-defined dash patterns?

  set style dash 1  2,4,2,4      # short-dashes
  set style dash 2  8,4,1,4      # long-dash, dot

  plot sin(x) lc rgb "blue" dashstyle 2, ...
 
> I'm particularly interested in eps, pdf(cairo), png(cairo) and emf 
> (on behalf of Windows users).  To get any dashes you have to set 
> the "dashed" option for these terminals (except for postscript, 
> which as I noted is exceptional in doing dashes by default).  But 
> the "linetype" numbers in dashed mode produce different effects 
> as noted below:
> 
> In postscript, dashed mode:
> 
>  solid lines: 1, 10, 19, 28
>  regular dash: 2, 11, 20, 29
>  short dash: 3, 12, 21, 30
> 
> in pngcairo, pdfcairo, dashed mode:
> 
>  solid lines: 1, 6, 11, 16, 21
>  regular dash: 2, 7, 12, 17, 22
>  short dash: 3, 8, 13, 18
> 
> in emf, dashed mode:
> 
>  solid lines: 1 to 15
>  regular dash: 16 to 30
>  short dash: 31 to 33
> 
> This is a total nightmare with regard to portability.  
> 
> Allin Cottrell
> 



-- 
Ethan A Merritt