16 Facts About Metafont

Metafont is a description language used to define raster fonts.

Metafont was devised by Donald Knuth as a companion to his TeX typesetting system.

One of the characteristics of Metafont is that the points defining the shapes of the glyphs—for example top of a stem, or intersection of a stem and crossbar—are defined with geometrical equations; the intent that the three stems of an 'm' are equally spaced horizontally might be expressed as if points 1,2, and 3 are at the bottom ends of the three stems, whereas the intent that they all end on the same vertical position would be.

Metafont is a macro language, where operations such as "draw a lower case top of stem serif at point 4" might appear as one macro instruction in the program for a letter.

For describing shapes, Metafont has a rich set of path construction operations that mostly relieves the user of having to calculate control points.

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Metafont is most often run as a helper to output device drivers; in those cases, its job is to generate bitmaps for a font for a specific combination of output device and resolution.

Equally important, but not as common, is running Metafont to generate a font metric file; a TFM file is only generated if the fontmaking variable is positive.

Third way of operating Metafont is proof mode: if the proofing variable is positive then the bitmap font file contains additional information provided via special commands, in particular the positions and names of points the font designer considered important for the design.

Metafont can be run interactively, and has commands for displaying on the screen the images it produces.

Metafont can render any kind of graphical output, not just glyphs.

Metafont is most commonly invoked without a direct request from the user.

Metafont language is an interpreted language for programs that are essentially declarative rather than imperative.

When Metafont executes an equation statement, it turns one of the independents involved into a dependent and eliminates it from the expressions for all other dependents; when no independents remain in the expression for a dependent variable, that variable becomes known.

Curves in Metafont are defined as cubic splines rather than quadratic, for greater versatility at the cost of more complex arithmetic.

Unlike more common outline font formats, a Metafont font is primarily made up of strokes with finite-width "pens", along with filled regions.

Metafont system allows fonts to be processed in unusual ways; in 1982 Knuth showed how it could be used to morph fonts, with a serif font slowly transitioning into a sans-serif design over the course of a text.