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From: karl AT aspodata DOT se
To: geda-user AT delorie DOT com
Subject: Re: [geda-user] adventures using arrows (for documentation), or cross my lines
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Comments: In-reply-to "Sergey Stepanov (no DOT such DOT process AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
   message dated "Fri, 13 Jul 2018 20:29:36 +0500."
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Date: Fri, 13 Jul 2018 19:14:44 +0200 (CEST)
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Sergey:
> > That arrow could be done right there in the sch-file, like
> You are perfectly right, this is it:
> H 3 0 1 0 -1 -1 1 -1 -1 -1 -1 -1 4
> M 220,132
> C 205,115 205,85 220,68
> L 100,100
> z
> 
> But still:
> - thick line overwrites sharp end of arrow

Yes, that is why I want to be able to do filled arrowheads with line 
width = 0.
 or...
round line joins so that when the (now round) tip intersects with a 
line (and they have the line widths) the tip doesn't go beyound the 
line.

> - every editing mistake makes this arrow broken
> - gEDA is lack of precise editing of symbol elements, like rotating by
> arbitrary (or at least, 30^o, 45^o) angle or shifting, or scaling,
> etc.

Very much so, it would be nice if you could select things and scale and 
rotate the selected.

> So one have to write some scripts to do these things.

Meetoo... I did a scaling script that can scale symbols and schematis;
perhaps I should do rotations also.

> The solution for my code (and to this ^^^) is to not draw arrow's line
> from the tip, but from the opposite side from the arrow triangle, like
> I do in this horizontal arrow from (0,0) to (5,0) with tip at (0,0):

Yes, I noticed. Since the arrow tip is very thin at the tip with miter 
joins, the line end (which i "width" wide) would interfere with the tip.

But if you are useing round caps and joins, the arrow tip and line end
would follow the same roundish form. So if you are set to round cap
and round joins the work to make suitable graphics is easier.

> // Arrow
> cairo_move_to(cr, to_device_x(0.0), to_device_y(0.0));
> cairo_arc(cr, to_device_x(3.8038), to_device_y(0.0),
> to_device(1.1368), to_radians(135.), to_radians(135.+90.));
> cairo_close_path(cr);
> cairo_fill(cr);
> // Bar
> cairo_move_to(cr, to_device_x(2.667), to_device_y(0.0));
> cairo_line_to(cr, to_device_x(5.0), to_device_y(0.0));
> cairo_set_line_width(cr, to_device(0.25));
> cairo_stroke(cr);

What is "Bar" here ?

> But this need some changes in line drawing in gedacairo, so I gave up.

Lines with arrow heads are so much used, it would be really nice if one 
could just flip a flag value and have a arrow head attached to the line,
obeying any angle the line has.

... and since every one has their own preference how the arrow should
look like, it would be nice if the arrow head style could be 
configurable. Possible settings are:
 arrow head length
 width
 possible arc at thick end
 filled or open
so three, four settings would perhaps suffice.

Regards,
/Karl Hammar

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