symbols-a4

font identifier := "LightBulb10"; % Name the font.
font size 10pt # ; % Specify the design size.
em # := 10pt # ; % “M” width is 10 points.
cap # := 7pt # ; % Capital letter height is 7 points above the baseline.
sb # := 1/4pt # ; % Leave this much space on the side of each character.
o # := 1/16pt # ; % Amount that curves overshoot borders.
input lightbulb % Load the file that draws the actual glyph.
Figure 2: Sample METAFONT size-specific file (lightbulb10.mf)
mode setup; % Target a given printer.
define pixels(em, cap, sb); % Convert to device-specific units.
define corrected pixels(o); % Same, but add a device-specific fudge factor.
%% Define a light bulb at the character position for “A”
%% with width 1/2em # , height cap # , and depth 1pt # .
beginchar("A", 1/2em # , cap # , 1pt # ); "A light bulb";
pickup pencircle scaled 1/2pt; % Use a pen with a small, circular tip.
%% Define the points we need.
top z1 = (w/2, h + o); % z1 is at the top of a circle.
rt z2 = (w + sb + o − x4, y4); % z2 is at the same height as z4 but the opposite side.
bot z3 = (z1 − (0, w − sb − o)); % z3 is at the bottom of the circle.
lft z4 = (sb − o, 1/2[y1, y3]); % z4 is on the left of the circle.
path bulb; % Define a path for the bulb itself.
bulb = z1 . . z2 . . z3 . . z4 . . cycle; % The bulb is a closed path.
z5 = point 2 − 1/3 of bulb; % z5 lies on the bulb, a little to the right of z3.
z6 = (x5, 0); % z6 is at the bottom, directly under z5.
z7 = (x8, 0); % z7 is at the bottom, directly under z8.
z8 = point 2 + 1/3 of bulb; % z8 lies on the bulb, a little to the left of z3.
bot z67 = ( 1/2[x6, x7], pen bot − o − 1/8pt); % z67 lies halfway between z6 and z7 but a jot lower.
%% Draw the bulb and the base.
draw bulb; % Draw the bulb proper.
draw z5 - - z6 . . z67 . . z7 - - z8; % Draw the base of the bulb.
%% Display key positions and points to help us debug.
makegrid(0, sb, w/2, w − sb)(0, −1pt, y2, h); % Label “interesting” x and y coordinates.
penlabels(1, 2, 3, 4, 5, 6, 67, 7, 8); % Label control points for debugging.
endchar;
end
Figure 3: Sample METAFONT size-independent file (lightbulb.mf)
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