% My MetaPost macros
%

% labeling lengths (as in drafting), e.g.  |<---- 2 in ---->|

def drawopaque(expr p)=
drawopaqueraw(p,0);
enddef;

def drawopaquecolor(expr p, c)=
begingroup
interim bboxmargin := 0;
fill if path p: else: bbox fi p withcolor white;
draw p withcolor c;
endgroup
enddef;

def drawopaqueusebox (expr p, b) = 
fill b withcolor white;
draw p;
enddef;

% draw a picture, but first erase what's underneath it (for perspecives)
def drawopaqueraw(expr p, margin)=
begingroup
interim bboxmargin := margin;
fill if path p: else: bbox fi p withcolor white;
draw p;
endgroup
enddef;

def endpoint(expr p)=
begingroup
save len; numeric len; len:=length(p);
point len of p
endgroup
enddef;

def drawbound(expr where, ldir)=
begingroup 
  save a,b;
  pair a,b;
  a := where + ldir*5pt;
  where = 0.5[a,b];
  draw a--b;
endgroup
enddef;

def draftlabel(expr g, ex)=
begingroup
  save ldir;
  pair ldir;
  ldir = direction 0 of g; ldir := ldir/length(ldir);
  draftlabelraw(g, ex,(ldir rotated 90));
endgroup
enddef;

def draftlabelraw(expr g, ex, tdir) = 
begingroup
  save magic; numeric magic; save pict;

  magic := angle(tdir);
  drawdblarrow g;
  drawbound((point 0 of g), tdir);
  drawbound((endpoint(g)), tdir);
  picture pict; pict := nullpicture;
  save where; pair where; 
  where = 0.5[point 0 of g,endpoint(g)];
  pict := thelabel(ex, where);
  drawopaqueraw(pict, 2pt);
endgroup
enddef;

%
% labeling angles
%

howwide=30;
tall=2in;

marksize=4pt;
angle_radius=tall/4;
bobradius=tall/10;
path lastarrow;

def draw_mark(expr p, a, x) =
  begingroup
  save t, dm; pair dm;
  t = arctime a of p;
  label.bot(x, point t of p);
  endgroup
enddef;

def draw_mark_outside(expr p, a, x) =
  begingroup
  save t, dm; pair dm;
  t = arctime a of p;
  label.top(x, point t of p);
  endgroup
enddef;

def draw_marked(expr p, x) =
  begingroup
  save amid;
  amid = .5*arclength p;
  draw_mark(p, amid, x);
  draw p thinpen;
  endgroup
enddef;

def draw_marked_outside(expr p, x) =
  begingroup
  save amid;
  amid = .5*arclength p;
  draw_mark_outside(p, amid, x);
  draw p thinpen;
  endgroup
enddef;

def mark_angle(expr a, b, c, x) =
  begingroup
  save s, p; path p;
  p = unitvector(a-b){(a-b)rotated 90}..{(c-b)rotated 90}unitvector(c-b);
  s = .9marksize/length(point 1 of p - point 0 of p);
  if s<angle_radius: s:=angle_radius; fi
  draw_marked(p scaled s shifted b, x);
  endgroup
enddef;

def mark_angle_outside(expr a, b, c, x) =
  begingroup
  save s, p; path p;
  p = unitvector(a-b){(a-b)rotated 90}..{(c-b)rotated 90}unitvector(c-b);
  s = .9marksize/length(point 1 of p - point 0 of p);
  if s<angle_radius: s:=angle_radius; fi
  draw_marked_outside(p scaled s shifted b, x);
  endgroup
enddef;

def mark_rt_angle(expr a, b, c) =
  draw ((1,0)--(1,1)--(0,1))
       zscaled (angle_radius*unitvector(a-b)) shifted b
enddef;

def verythinpen =  withpen pencircle scaled 0.125pt enddef;
def thinpen     =  withpen pencircle scaled 0.250pt enddef;
def thickpen    =  withpen pencircle scaled 1.000pt enddef;

color figlabelcolor;
figlabelcolor := black;

def emphasize = thickpen enddef;
def labelpen =  thinpen  enddef;
def labelcolor = withcolor figlabelcolor enddef;
def labelmode = labelpen labelcolor enddef;




def circle(expr r) = fullcircle scaled (2*(r)) enddef;

% draw arrow on path P, labeling it with WHAT
def labelarrow(expr p, what) =
begingroup
  draw p;
  label.top ();
endgroup
enddef;

% spring path, with n complete periods, horizontal

def spring(expr n) = 
begingroup
path cell;
path q;

cell := (0,0)--(0.25,-1)--(0.75,1)--(1,0);
q := cell;
for i = 2 upto n : 
   q := q--(cell shifted (i-1,0));
endfor
q
endgroup
enddef;

% a+b for paths
def link(expr a, b) =
  a--(b shifted (endpoint(a) - point 0 of b))
enddef;

pi := 3.1415926535;