XLIB Programming Manual, Rel. 5, Third Edition

A.3 Scalable Fonts

Another new feature in R5 is font scaling. In previous releases, each font was available only in a limited number of standard point sizes and resolutions. In the MIT distribution of R5, both the X server and the font server implement a simple bitmap font-scaling algorithm that allows fonts to be obtained at any desired point size and resolution. Bitmap fonts are easily scalable, but the resulting scaled font is generally jagged and difficult to read. Fortunately, R5 also provides a set of outline fonts. Outline fonts scale nicely, but the scaling process requires significant computation, so an X server might freeze for several seconds while scaling a large Asian font. This is one of the problems that font servers are intended to address. The fonts and the scaling code were donated by Bitstream, Inc.

Until Release 5, X relied exclusively on non-scalable bitmap fonts. If there was no installed font in the point size and resolution you wanted, then you were out of luck—it is obviously not feasible to provide every font in every point size and for every possible resolution. Bitmap fonts do not scale well, because their pixel-by-pixel specification can only be made smaller by omitting pixels or made larger by making pixels bigger, resulting in a jagged, low-resolution font. The fonts shipped by MIT for Release 5 include several “outline fonts” which describe characters by their component curves rather than by individual pixels. This description allows for successful ...