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hmetafont

Hmetafont is a DSL (Domain Specific Language) for creating variable fonts in haskell. It's inspired by metafont, but adapted to modern technologies (Opentype). It's written as a library for haskell, with a syntax that closely resembles metafont. It's distinguishes itself from existing methods that generate outline fonts from metafont:

  • supports all of metafont, including calligraphic strokes, arbitrary pen shapes, filldrawing, solving equations
  • supports the full unicode point range
  • generates clean opentype fonts
  • analytical aproach generates precise outlines, without artifacts (as in autotracing).
  • supports composite glyphs

It's work in progress. Most of the work right now has gone into the support libraries, which can be found here:

  • cubicbezier: bezier intersections, boolean path operations, hobby splines, curve approximation, caligraphic strokes
  • MFSolve: A linear equation solver, with the ability to calculate non-linear expressions on the fly.
  • Opentype: Reading and writing of Opentype files into haskell

These packages can also be found on hackage:

Example Program:

For example take the lowercase letter c from a metafont (walbaum):

beginchar("c", 12u#, x_height#, dp#);
  pickup tiny.nib;
  pos1(vair, 158);
  pos3(curve, 0);
  pos4(vair, -90);
  pos5(flare, flareangle);
  
  top y1r = 0.35x_height;
  rt x1l = x5r + 0.04w;
  
  x2r = 0.5[rt x3r, lft x1r];
  bot y2l = -o;
  top y2r = bot y2l + 0.05 [hair, stem];

  lft x3l = 0;
  y3 = x_height/2;

  x4 = x2l = w/2;
  top y4l = x_height + o;

  z2mid = 0.78[(x2r,y3r), (x3r,y2r)];
  
  lft x5l = 0.2[w - curve, x4r];
  bot y6 = 0.66h;
  z6 = z5 + whatever*dir (flareangle - 85);
  y5 = 2/3[y4, y6];

  penlabels(1,2,3,4,5,6);

  filldraw z1l{dir -100}..tension 0.75 and 0.78..
  z2l{left}..tension 0.88..
  z3l{up}..tension 0.88..
  z4l{right}..tension 1 and 1..
  z5r{dir (flareangle - 90)}..tension 0.85..
  z6{dir(flareangle - 180)}.. tension 0.8..
  z5l{dir (flareangle + 90)}..tension 0.85..
  z4r{left}..tension 0.88..
  z3r{down}..
  z2mid{z2r-z3r}..
  z2r{right}..tension 0.9 and 0.75 ..{dir 80}
  z1r--cycle;
endchar;

In hmetafont this becomes:

lowerC :: Glyph ()
lowerC = glyph "c" (return w) &
  contours $=
  do pickup tinyNib
     pos 1 vair 158
     pos 2 curve 0
     pos 4 vair (-90)
     pos 5 flare flareangle

     w === 12*u
     top y1r === 0.35*x_height
     rt x1l === x5r + 0.04*w

     x2r === between 0.5 (rt x3r) (lft x1r)
     bot y2l === -o
     top y2r === bot y2l + between 0.5 hair stem

     lft x3l === 0
     y3 === x_height/2

     x4 === x2l
     x2l === x/2
     top y4l === x_height + o

     z"2mid" === between 0.78 (x2r, y3r) (x3r, y2r)
     
     lft x5l === between 0.2 (w - curve) x4r
     bot y6 === 0.66*h
     z6 === z5 + whatever*dir (flareangle - 85)
     y5 === between (2/3) y4 y6

	 penlabels [1, 2, 3, 4, 5, 6]

     filldraw $ z1l .- leaving (dir (-100)) <> tensions 0.75 0.78 -.
       z2l .- leaving left <> tension 0.88 -.
	   z3l .- leaving up <> tension 0.88 -.
	   z4l .- leaving right -.
	   z5r .- leaving (dir (flareangle - 90)) <> tension 0.85 -.
	   z6 .- leaving (dir(flareangle - 180)) <> tension 0.8 -.
       z5l .- leaving (dir (flareangle + 90)) <> tension 0.85 -.
	   z4r .- leaving left <> tension 0.88 -.
	   z3r -. leaving down -.
	   z"2mid" .- leaving (z2r-z3r) -.
	   z2r .- leaving right <> tensions 0.9 0.75 <> arriving (dir 80) -.
	   z1r .--. cyclePath