Re: Should 'dashlength' affect only builtin or also custom dash patterns?

[Mojca M. <moj...@gm...>]

On Mon, Jun 2, 2014 at 5:39 PM, sfeam wrote:
> On Monday, 02 June 2014 11:18:08 AM Christoph Bersch wrote:
>>
>> Zitat von sfeam <sf...@us...>:
>>
>> > On Sunday, 01 June 2014 07:34:53 PM Christoph Bersch wrote:
>> >
>> >> I've seen, that different terminals handle the `dashlength` option
>> >> differently:
>> >>
>> >> set termoption dashlength 1
>> >> plot x dt 2, 2*x dt '.-'
>> >> pause -1
>> >>
>> >> set termoption dashlength 3
>> >> replot
>> >>
>> >> `qt`: dashlength affects only the custom dash pattern
>> >> `wxt`: both patterns are stretched
>> >> `post`: only the builtin patterns are affected
>> >>
>> >> This behaviour should be equal for all terminals.
>> >
>> > Good point.
>>
>> I've had a quick look at the Qt-documentation, but I couldn't find an
>> option to change the dash length for the builtin patterns.
>
> Correct.
>
>> Another thing I've seen is, that for some terminals the dash pattern
>> length depends on the linewidth, e.g. for the `qt` terminal. For
>> others, like the `wxt` terminal it doesn't.
>
> Qt docs:  "the dash pattern is specified in units of the pens width"
>
>> [...] we should try to have similar
>> behavior across the terminals, or at least try to.
>
> For output devices that really do provide their own dash types
> we can't do much other than use them as provided.

But wxt isn't a black box that simply draws dashed lines with "please
give me dash type 3" and could probably be fixed. I'm attaching an
example of a patch that fixes at least some cases (please note that
I'm not familiar with wxt code, I haven't verified or tested the patch
extensively, it's just a quick hack and it's possible that I made
mistakes; use it only as a proof-of-principle for now).

> But we can aim for consistent behavior of the new "custom"
> dashtypes.  I kind of like the Qt approach of scaling the
> dashlength with the line width.  I'm not certain that would
> work for all terminal types but it's something to think about.

I agree. Scaling the dash length with the pen width certainly makes
sense. In all terminals where this can be supported.

Mojca