[Therion] Symbol for fixed ladder

[rowena_l at tpg.com.au]

Hi, 
I did an alternative ladder symbol like this for my own purposes,
which I can post - tho not till Monday. It is a public Holiday and I
am off for 4 days caving/surveying with no network connectivity. 

----- Original Message -----
From: "List for Therion users" 
To:"List for Therion users" 
Cc:"Benedikt Hallinger" 
Sent:Wed, 25 Jan 2017 00:51:02 +0200
Subject:[Therion] Symbol for fixed ladder

 Hello,
 i get gray hair with metapost while i want to make a line symbol for 
 ladders, so i can nicely draw them in my maps as the cave have alot
of them.

 The basic idea i had was, t define a symbol of one "rung" segment
(rung and 
 a little of either sides, like the letter "H") as a symbol picture.
Then i 
 wanted to apply this image seamlessly over the length of the given
path 
 (straight lines)
 What i have for now is the following, however it does not show at all
(still 
 shows a red line with symbol set AUT in effect), so i have no clue
how to 
 even debug this.

 I tried to start with the example from thbook salted a little with
peeks to 
 the internal metapost codes.

 Can someone assist please?

 Thank you very much!

 # Symbol for fixed ladder
 def l_fixedladder_SKBB (expr P) =
 T:=identity;
 cas := 0;
 dlzka := arclength P;
 mojkrok:=adjust_step(dlzka, 1.0u);

 pickup PenC;
 sideL := (-.20u,0)--(-.20u,0.20u);
 sideR := (.20u,0)--(.20u,0.20u);
 rung := (-.20u,0.10u)--(.20u,0.10u);

 picture symbol,test_symbol;
 symbol:= image (
 thdraw sideL;
 thdraw sideR;
 thdraw rung;
 );

 forever:
 t := arctime cas of P;
 thdraw symbol shifted (point t of P) withcolor black;
 cas := cas + mojkrok;
 exitif cas > dlzka + (mojkrok / 3); % for rounding errors
 endfor;

 enddef;

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