Unicode Explained

Unicode line-breaking rules are mostly oriented toward handling Western, Symbolic,

and East Asian modes. Thus, the rules address just a relatively small part of the problem.

On the other hand, being defined in a uniform manner, they let you work with docu-

ments containing a mixture of scripts and languages. This has partly been achieved by

somewhat artificial decisions. It is easy to start defining line-breaking rules so that Latin

letters and other characters used in Western scripts have properties suitable for the

Western mode, etc., but there are many borderline cases, especially since many char-

acters are used in several scripts, or for several essentially different purposes within a

script.

Emergency Breaks

The oldest forms of alphabetic writing can be described as using emergency breaks as

the normal mode. Words were written with no space between them, and the entire

available writing width was used, with no regard to word boundaries. This saved writ-

ing material, which was very expensive (e.g., parchment). We can see such things (al-

though with spaces between words) happen again, for example, on small devices where

the line length is small. Applying emergency break mode throughout makes things

unambiguous, if readers know about it and if a space is written even when a line break

occurs between words. Applying emergency breaks as the last resort may introduce

ambiguity. In particular, ...