Paul Nelson (ATC) wrote: > CSS is a higher level protocol. There is room for a higher level protocol to > override things, for example, by specifying the PRE. CSS is indeed a higher-level protocol. However, UAX14 sets explicit limits on what a higher-level protocol can do: http://unicode.org/reports/tr14/#ConfProtocols >> 1. Spaces are a non-tailorable line breaking class. The description of its >> behavior also includes prescriptions on presentation that are not >> compatible with what CSS prescribes. > > The only place where I see problems with the SP definition are in the PRE > situation where we are keeping the widths of all spaces explicitly. In this > case are we really tailoring the line breaking class of the character? AFAICT, there's only two ways of tailoring a class: changing its membership (which is forbidden for SP), or changing the rules in 6.2. The statements governing the presentation of spaces are in 5.1... >> 2. CSS has a line breaking mode that forbids all breaks. This needs to >> override the non-tailorable behavior of the ZW (and SP?) classes. > > In this case, CSS is simply saying that the line has no end, and therefore > there is no wrapping point. We are not overriding the behavior of the ZW and > SP classes. Hm, good point. :) >> 3. CSS3 Text introduces an 'unrestricted' line breaking mode. In this mode, >> line breaking restrictions are ignored completely, (except for the CM >> class). > > One way to look at the 'unrestricted' line breaking is that we are forcing > emergency line breaking to happen at the end of every line. Emergency line breaking is only allowed "if a legal line break cannot be found". We could tailor everything tailorable into the AL class, but ZWSP is still defined to always provide a legal line break. SP also can't be altered. ~fantasaiReceived on Tuesday, 20 February 2007 13:11:15 UTC
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