Re: Square pens and dash pattern

[luigi scarso <luigi.scarso@gmail.com>]

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On Wed, Apr 6, 2016 at 9:52 AM, Hans Hagen <pragma@wxs.nl> wrote:

> On 4/6/2016 1:44 AM, Aditya Mahajan wrote:
>
>> Hi,
>>
>> There appears to be a metapost bug with square pens and dash patterns:
>>
>> \starttext
>>
>> \startMPcode
>>      pickup pencircle scaled 1bp;
>>      drawarrow origin -- (5cm, 4cm) dashed evenly;
>>      pickup pensquare scaled 1bp;
>>      drawarrow origin -- (5cm,-4cm) dashed evenly;
>> \stopMPcode
>>
>> \stoptext
>>
>> Note that the second arrow is not dashed at all! This is not due to the
>> thick pen.
>>
>
> pencircles make simple round pens that are mapped directly onto ps
> primitives and there dashing applies (dashing is just passing data to the
> backend) ... afaik other penshapes can result in a filled path so no
> dashing applies
>
> (but mp master luigi will tripple check it in the source for you so he
> might come up with another answer)
>
> (and after that, as mathematical challenge, alan will write a mp macro
> that fakes the dashing)
>
> Hans
>
>


 # cat test-square.mp test-circle.mp
beginfig(1);
tracingall;
%pickup pencircle scaled 1bp;
%drawarrow origin -- (5cm, 4cm) dashed evenly;
pickup pensquare scaled 1bp;
drawarrow origin -- (5cm,-4cm) dashed evenly;
endfig;
end.



beginfig(1);
tracingall;
pickup pencircle scaled 1bp;
drawarrow origin -- (5cm, 4cm) dashed evenly;
%pickup pensquare scaled 1bp;
%drawarrow origin -- (5cm,-4cm) dashed evenly;
endfig;
end.

 # mpost test-square.mp
says, near the end,


Edge structure at line 7 (just shipped out):
Filled pen stroke :
(0,0)..controls (47.24408,-37.79527) and (94.48817,-75.59053)
 ..(141.73225,-113.3858)
dashed (on 3 off 3) shifted 0 (this will be ignored)


while
# mpost test-circle.mp
says

Edge structure at line 7 (just shipped out):
Filled pen stroke :
(0,0)..controls (47.24408,37.79527) and (94.48817,75.59053)
 ..(141.73225,113.3858)
dashed (on 3 off 3) shifted 0

So it doesn't look  a mpost bug .

-- 
luigi

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