Fonts & Encodings

8.1. Special Characteristics of X Window

First, we must point out that the overall ergonomic approach of Unix is based on the use of a terminal. This may seem to be a disadvantage to those who are accustomed to a completely graphical interface, such as that of Mac OS 9; however, to those who like to "retain control" over their machine, it is rather an advantage. In any event, with regard to fonts, the terminal is clearly less demanding than a graphical application. In particular, since we tend to use only one font size at a time on a terminal, it is not surprising that our good old-fashioned bitmap fonts (in the formats PSF, BDF, and PCF, etc.; see §A.4) are quite adequate for the terminal's needs and that font management under X is based almost entirely on bitmap fonts—at least until recent times, when vector fonts finally made their debut under X.

But let us be clear on one point: while Mac OS and Windows had only two or three bitmap fonts—relics from their infancy—in only two or three point sizes and with no attempt at grandeur, X provides a sophisticated system for font classification, with a substitution mechanism that keeps us from ever running short of fonts. This system is called XLFD (an unpronounceable acronym that stands for X Logical Font Description), and we shall describe it below.

As for the notorious fragility of fonts under Mac OS and Windows, it stemmed primarily from the fact that the files in question were left continuously open by the operating system. Under ...