Re: [AGG] Drawing dashed double-lines

[Pete B. <pet...@ge...>]

Maybe a bad suggestion (in DRY terms), but you make a custom stroker by 
cloning the conv_stroke and vcgen_stroke code, then in vcgen_stroke, 
change the path command returned in vertex(...) to path_cmd_move_to for 
the line caps?


Phil Endecott wrote:
> Dear Experts,
>
> I am attempting to draw a simple dashed double line, i.e. something like
>
>      - - - - - - - - - - - - -
>      - - - - - - - - - - - - -
>
> My first attempt used stroke -> dash -> stroke.  This has two problems: 
> the lines wrap around the ends, and the dashes on the sides are not 
> aligned especially if the line is not straight:
>
>       - - - - - - - - - - - - - - - - -|
>      | - - - - - - - - - - - - - - - - -
>
> Then I tried dash -> stroke -> stroke.  This makes the two sides 
> aligned, but of course it adds ends to each segment:
>
>      +--+ +--+ +--+ +--+ +--+
>      |  | |  | |  | |  | |  |
>      +--+ +--+ +--+ +--+ +--+
>
> My final attempt was using contour to make a "left path" and a "right 
> path", and to dash and stroke them separately:
>
> contour(width=+n) -> dash -> stroke
> contour(width=-n) -> dash -> stroke
>
> This doesn't work either, and I think I am probably misunderstanding 
> what contour should do to a non-closed path.
>
> Alignment of the dashes on each side would be good but is not 
> essential.  What is essential is not having stuff that wraps around the ends.
>
> I think the easiest way to make this work would be if stroke had a way 
> to specify "none" as the cap style.  Then I could do dash -> 
> stroke(cap=none) -> stroke.  Is there some way to achieve that?  Or can 
> someone suggest another way to do this?
>
>
> Thanks,  Phil.
>
>
>
>
>
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