Re: Much thicker lines by default

[sfeam <sf...@us...>]

On Monday, 28 April 2014 02:34:01 PM Ethan A Merritt wrote:
> On Monday, 28 April, 2014 14:10:59 Dima Kogan wrote:
> > Ethan A Merritt <sf...@us...> writes:
> > 
> > > On Monday, 28 April, 2014 13:30:18 Dima Kogan wrote:
> > >> Hi.
> > >> 
> > >> The default line width appears to have been affected in a recent commit:
> > >> 
> > >>  https://github.com/gnuplot/gnuplot/commit/b6c8dbfc63387be9e0c84d0d7b9ba6f480e5da8b
> > >> 
> > >> The commit notes don't say anything about it, so I'm wondering if this
> > >> change wasn't intentional. Is nobody else seeing this?
> > >
> > > Do you mean lines in the "test" command?  Which terminal?
> > 
> > I just ran a few more tests. Only the x11 terminal appears to be
> > affected. This explains why nobody complained yet. To reproduce, plot
> > anything 'with lines' in x11. Or "plot x".

Here is what is going on.

1) For a long time gnuplot has used the special linetype -1 to
indicate a solid black line.  This has been a convenient way to 
guarantee getting a black line even if the normal terminal color
sequence does not include black.  Most places in the code refer
to this linetype as LT_BLACK.

2) Since lt -1 was also guaranteed to be a solid line whatever the
terminal dash pattern sequence, it seemed logical to also special
case this linetype as LT_SOLID for the purpose of supporting 
dashtypes.  So far so good.

3) The glitch is that some of the oldest gnuplot terminals 
apparently treat lt -1  as a solid black _double thickness_ line.
This is true at least for x11 and postscript.  I have not yet
checked all the others.   So in revising the code to support
dashtypes, all the solid lines started being drawn with 
LT_SOLID, which for x11 and postscript is for some reason
drawn double thickness.

I see two possible fixes.

1) Change LT_SOLID to some other value.  The obvious value would
be linetype 1.  But this would mean you can never set a non-solid
dashpattern for linetype 1, so I don't like this idea.

2) Change x11 so that lt -1 is not drawn double thickness by default.
I don't see a problem there.   

What about postscript? The postscript code really does treat this
linetype differently, so there might be side effects from changing it
even aside from all those old postscript generating
gnuplot scripts out there that were written when lt -1 produced a 
thicker line.  On the other hand, unlike the x11 case the factor
of two in the default lt -1 linewidth does not affect any other
linetypes or linewidths.  So we could just leave it 


I'm leaning toward fix #2, either with or without making a 
change to postscript also.

	Ethan