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%% sgbx0015.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_lefthalfarrow (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, monospace, fudge, crisp, hair;" &
"boolean monospace;" &
"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 & ";" &
"monospace :=" & if monospace: "true" else: "false" fi & ";" &
"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#;
penpos1(rule_thickness#, 90); penpos2(rule_thickness#, 90);
penpos3(rule_thickness#, 0); penpos4(rule_thickness#, 0);
y0=y1=y2=math_axis#; x1-.5rule_thickness#=u#; rt x0=w-u#;
y3-y0=y0-y4=.36asc_height#+eps;
x3=x4=x0-4u#-eps;
penpos5(rule_thickness#, angle(z4-z0)); z5l=z0;
penpos6(rule_thickness#, angle(z3-z0)); z6l=z0;
save t; numeric t;
save pq; path pq; pq = z4l..{2(x0-x4),y0-y4}z6r;
t=xpart(pq intersectiontimes ((0,y2l)--(w,y2l))); x2=xpart point t of pq;
z9=.2[.5[z3,z4],z0];
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;
save T; transform T;
save tt; numeric tt; tt = arctime(arclength apth - (x0-x9)) of apth;
save ttt; numeric ttt; ttt = arctime(arclength apth - (x0-x2)) of apth;
% Draw the arrow head
save pp; path pp; pp := (z3l..{2(x0-x3),y0-y3}z5r);
save pq; path pq; pq := (z3r..{2(x0-x3),y0-y3}z5l);
save halfarrowhead, pa;
vardef halfarrowhead(expr T, s) =
(z0--(x0,y2l)--z2l--z2r
..subpath(t,s) of pp
--subpath(xpart( pq intersectiontimes
(point s of pp -- point s of pp +(2rule_thickness#,0))),
length (z3r..{2(x0-x3),y0-y3}z5l)) of pq --cycle)
transformed T
enddef;
if arclength apth = 0:
T:=identity shifted (point (length apth) of apth - z0);
elseif arclength apth < x0-x3l:
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,
z2,
point ttt of apth,
z9+(0,3rule_thickness#),
point tt of apth + 3rule_thickness#*
(unitvector (direction tt of apth) rotated 90));
fi
save f,s;
vardef f(expr s) =
length(point s of (pp transformed T) - point tt 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
filldraw halfarrowhead(T,s) text_;
% Draw the path
if arclength apth > x0-x2: draw subpath(0,ttt) of apth
withpen pencircle scaled rule_thickness# text_;
fi
pickup prevpen;
enddef;
enddef;
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