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%% sgbx0011.mp
%% Copyright 2006 Tommy Ekola <tek@kth.se>
%
% This work may be distributed and/or modified under the conditions of
% the LaTeX Project Public License, either version 1.3 of this license
% or (at your option) any later version. The latest version of this
% license is in http://www.latex-project.org/lppl.txt
%
% This work has the LPPL maintenance status `maintained'. The Current
% Maintainer of this work is Tommy Ekola. The Base Interpreter is
% MetaPost.
vardef setup_twowaydoublearrow (expr source_file, cmdname) =
scantokens ("input tgbx0000");
scantokens ("input " & source_file);
expandafter def scantokens cmdname expr p =
scantokens (cmdname & "__sgbxww")(p)
enddef;
expandafter vardef scantokens (cmdname & "__sgbxww " & "(expr apth) " &
"text text_ = " &
"save math_spread, x_height, u, rule_thickness, bar, math_axis," &
" asc_height, eps, fudge, crisp, hair;" &
"math_spread :=" & decimal math_spread & ";" &
"x_height# :=" & decimal x_height# & ";" &
"u# :=" & decimal u# & ";" &
"rule_thickness# :=" & decimal rule_thickness# & ";" &
"bar# :=" & decimal bar# & ";" &
"math_axis# :=" & decimal math_axis# & ";" &
"asc_height# :=" & decimal asc_height# & ";" &
"eps :=" & decimal eps & ";" &
"fudge :=" & decimal fudge & ";" &
"crisp# :=" & decimal crisp# & ";" &
"hair# :=" & decimal hair# & ";")
save prevpen;
prevpen:=savepen;
save x,y;
numeric x[], x[]', x[]l, x[]'l, x[]r, x[]'r,
y[], y[]', y[]l, y[]'l, y[]r, y[]'r;
save spread, w;
numeric spread, w;
if crisp#>fudge*hair#:
crisp#:=fudge*hair#;
fi
pickup if crisp#=0: nullpen else: pencircle scaled crisp# fi;
spread = math_spread[.45x_height#,.55x_height#];
w:=18u#;
lft x1 = u#-eps; x2=x1; x7=x8=w-x1;
y1=y7; y2=y8; y1-y2=spread; .5[y1,y2]=math_axis#;
rt x0 = w-u#+eps; y0 = math_axis#;
penpos3(rule_thickness#,0); penpos4(rule_thickness#,0);
y3-y1 = y2-y4 = .24asc_height#+eps; x3=x4=x0-6u#-eps;
penpos5(rule_thickness#, angle(z4-z0)); z5l=z0;
penpos6(rule_thickness#, angle(z3-z0)); z6l=z0;
z9 = .381966[.5[z3,z4],z0];
save pp;
path pp; pp = z4l{z9-z4}..z6r;
save t;
numeric t; t = xpart(pp intersectiontimes ((0,y0)--(w,y0)));
numeric t[]; t1 = xpart(pp intersectiontimes ( (0,y2-rule_thickness#/2)
--(w,y2-rule_thickness#/2)));
t2 = xpart(pp intersectiontimes ( (0,y2+rule_thickness#/2)
--(w,y2+rule_thickness#/2)));
save qq;
path qq; qq = z3l{z9-z3}..z5r;
save parallelline;
vardef parallelline expr ppp =
save s, stp;
numeric s, stp; stp:=(arclength ppp) div 5pt;
if stp=0: stp:=1; fi
stp:=(arclength ppp)/stp;
if arclength apth > 0:
draw for s=0 step stp until arclength ppp - stp:
point (arctime s of ppp) of ppp +
spread/2*(unitvector direction (arctime s of ppp)
of ppp rotated 90)
{direction (arctime s of ppp) of ppp}..
endfor
{direction (length ppp) of ppp}
point (length ppp) of ppp +
spread/2*(unitvector direction (length ppp) of ppp rotated 90)
withpen pencircle scaled rule_thickness#
text_;
draw for s=0 step stp until arclength ppp - stp:
point (arctime s of ppp) of ppp -
spread/2*(unitvector direction (arctime s of ppp)
of ppp rotated 90)
{direction (arctime s of ppp) of ppp}..
endfor
{direction (length ppp) of ppp}
point (length ppp) of ppp -
spread/2*(unitvector direction (length ppp) of ppp rotated 90)
withpen pencircle scaled rule_thickness#
text_;
fi
enddef;
save mapto, n;
vardef mapto(text t) =
hide(numeric n; n:=0;
numeric x,x_[],y,y_[];
for z=t: z_[incr n]:=z; endfor;
transform T;
z_2 = z_1 transformed T;
z_4 = z_3 transformed T;
z_6 = z_5 transformed T;)
T
enddef;
% Draw the front arrow head
save doublearrowhead;
vardef doublearrowhead(expr T, s, ss) =
(subpath(0, xpart((z0..{z4-z9}z4r) intersectiontimes
(point s of pp -- point s of pp + (2rule_thickness#,0))))
of (z0..{z4-z9}z4r)
--subpath(s,t1) of pp
--(xpart point t1 of pp, ypart point t2 of pp)
--subpath(t2,t) of pp
--subpath(t,t2) of qq
--(xpart point t1 of qq, ypart point t2 of qq)
--subpath(t1,ss) of qq
--subpath(xpart ((z3r{z9-z3}..z0) intersectiontimes
(point ss of qq -- point ss of qq + (2rule_thickness#,0))),1)
of (z3r{z9-z3}..z0)
& cycle) transformed T
enddef;
save T; transform T;
save tt; numeric tt;
tt = arctime (arclength apth - (x0 - xpart point t1 of pp)) of apth;
if arclength apth = 0:
T:=identity shifted (point (length apth) of apth - z0);
elseif arclength apth < x0-xpart(point t2 of pp):
T:=identity rotatedaround(z0,angle (direction (length apth) of apth))
shifted (point (length apth) of apth - z0);
else:
T := mapto(
z0,
point (length apth) of apth,
point t1 of pp + (0,rule_thickness#/2),
point tt of apth +
spread/2*(unitvector direction tt of apth rotated 90),
point t1 of qq - (0,rule_thickness#/2),
point tt of apth -
spread/2*(unitvector direction tt of apth rotated 90));
fi
save f,s,ss,ttt;
ttt = arctime(arclength apth - (x0-x9)) of apth;
vardef f(expr s) =
length(point s of (pp transformed T) - point ttt of apth)
< length(point 0 of pp - z9)
enddef;
if f(0) or (arclength apth < x0-x3l): s := 0;
else: s := solve f(length pp, 0);
fi
vardef f(expr ss) =
length(point ss of (qq transformed T) - point ttt of apth)
< length(point 0 of qq - z9)
enddef;
if f(0) or (arclength apth < x0-x3l): ss := 0;
else: ss := solve f(length qq, 0);
fi
filldraw doublearrowhead(T,s,ss) text_;
% Draw the back arrow head
save ttt; numeric ttt;
ttt = arctime (x0 - xpart point t1 of pp) of apth;
if arclength apth = 0:
T:=identity rotatedaround(z0, 180)
shifted (point (length apth) of apth - z0);
elseif arclength apth < x0-xpart(point t2 of pp):
T:=identity rotatedaround(z0,angle (direction 0 of apth)+180)
shifted (point 0 of apth - z0);
else:
T := mapto(
z0,
point 0 of apth,
point t1 of pp + (0,rule_thickness#/2),
point ttt of apth +
spread/2*(unitvector direction ttt of apth rotated 90),
point t1 of qq - (0,rule_thickness#/2),
point ttt of apth -
spread/2*(unitvector direction ttt of apth rotated 90));
fi
ttt := arctime(x0-x9) of apth;
vardef f(expr s) =
length(point s of (pp transformed T) - point ttt of apth)
< length(point 0 of pp - z9)
enddef;
if f(0) or (arclength apth < x0-x3l): s := 0;
else: s := solve f(length pp, 0);
fi
vardef f(expr ss) =
length(point ss of (qq transformed T) - point ttt of apth)
< length(point 0 of qq - z9)
enddef;
if f(0) or (arclength apth < x0-x3l): ss := 0;
else: ss := solve f(length qq, 0);
fi
filldraw doublearrowhead(T,s,ss) text_;
% Draw the path
if arclength apth > 2(x0-xpart(point t1 of pp)):
parallelline (subpath(ttt,tt) of apth);
fi
pickup prevpen;
enddef;
enddef;
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