> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf > Of Mark E. Shoulson
> I also agree, but I point out that the sufficiently perverse could come > up with some pretty tough examples. Applying color is a pretty benign > style, but what if I wanted a boldface circumflex on a normal letter? Shaping of diacritics where such styling differences (face, size or weight) occur is problematic to implement due to reasons related to design and also reasons related purely to the technologies involved: Diacritic positioning can be accomplished in a few different ways: - substitution of alternate glyphs that have metrics that result in different positioning of the outline, to correspond with different metrics of a base glyph - kerning rules (in this context adjust the glyph by x units horizontally and y units vertically) - attachment anchor points (adjust the glyph so that point i in the outline aligns with point j in the outline of the base glyph) Whichever approach is used in a font implementation, the implementation will have assumed equal point sizes (remember, the outline has no point size) and equal face and weight/style characteristics. If positioning by attachment point is used, it may be possible to produce somewhat tolerable results when the base and diacritic are different sizes, or one is (say) bold while the other is italic; but even then ideal results should not be expected, and might not even be clearly definable. (What's the correct positioning of a non-italic circumflex over an italic o?) Then there's the issue of the font technologies involved: whether we're talking about OpenType, AAT, Graphite, Pango or whatever, and no matter which approach to positioning described above is used, this kind of positioning is accomplished by rules within a given font (not typeface, but font) that describe how particular glyphs within that font should behave in relation to one another. There is absolutely no way to say that glyph x in font A should behave in a particular way when combined with glyph y in some different font B. In principle, these rules can still apply when there is a change in colour or point size, but as soon as you change between different font files (change in face or weight), no glyph processing is possible. > Or even more obnoxious, a 10-point circumflex on a an 8-point letter? > These could be tricky to compute. [then in a subsequent message] > (and now I contradict myself with a counterexample. In > http://omega.enstb.org/yannis/pdf/biblical-hebrew94.pdf, Yannis > Haralambous notes--correctly--that when typesetting the Hebrew Bible, > letters that are written small hang from the top line and have > normal-sized vowels below them (and the vowels are below the baseline of > the normal text)) It might be possible to develop technologies that allowed correct positioning in particular cases where different sizes were involved, but I think we still have some more basic problems to solve, like finishing getting implementations that offer basic support for all of the scripts in Unicode 4.0. Peter Peter Constable Globalization Infrastructure and Font Technologies Microsoft Windows Division
