Hi Karl, Sorry to take so long to answer. Karl Tomlinson wrote:> I'm looking for comments on how fontconfig users would prefer font> families defined in web documents through @font-face (or defined> by other means in other documents) to be presented in FcPattern *p> for FcConfigSubstitute(FcConfig*, p, FcMatchPattern).> > The question basically comes down to whether> author-defined/provided fonts should be treated in the same way as> locally installed fonts, or whether they should be considered> special. My take on it is that they should be considered special. And that's the APII'm going to implement in Pango. Actually the proposed Pango API is veryclose to CSS. Or I think it is. Anyway, the bug to track it is here: http://bugzilla.gnome.org/show_bug.cgi?id=347237 > Locally installed fonts only:> ----------------------------> > For web documents using only locally installed font families> through CSS 2.1, there is a reasonably well defined algorithm for> prioritizing fonts according to the font-family property, which is> a list of family names, and other style properties.> > In the spirit of giving the user the final say, the CSS properties> are converted to an FcPattern and presented to> FcConfigSubstitute(,,FcMatchPattern), and the result is used in> the equivalent of an FcFontSetSort.> > For example, with> > <p lang="en" style="font-family: Helvetica, sans-serif">> Paragraph.> </p>> > After FcConfigSubstitute, the FC_FAMILY property for the element> might be something like "Helvetica(s), Nimbus Sans L(s), Bitstream> Vera Sans(w)" (followed by several other family names). Here> Nimbus Sans L is a possible close-match to the author-requested> Helvetica (for use when Helvetica is not installed), and> Bitstream Vera Sans is the default font for lang="en". These> families are considered in this order when finding glyphs for> characters. You do a FcConfigSubstitute(,,FcMatchFont) in the resulting fonts too, right? > @font-face:> ----------> > What the @font-face CSS rule adds is the ability for the author to describe> the properties of a automatically-downloadable font face and the family to> which it belongs. This font face is only available to the document(s) that> use this style rule. The following web page contains an example, which uses> the BPG Ucnobi U font:> > http://www.w3.org/International/tests/test-webfonts/test-georgian-ucnobi.html> > Consider now if the author had included this style rule:> > @font-face {> font-family: "BPG Ucnobi U";> font-style: normal;> font-weight: normal;> src: url(http://www.w3.org/International/tests/test-webfonts/BPG-Ucnobi-U.ttf);> }> > Note that the value of the font-family descriptor here may or may> not be the same as the family name in the font referenced by the> src descriptor. It is the value in the @font-face rule, not the> name from the font, that is matched against any HTML element's> font-family style properties, when deciding whether to use this> font-face. Equivalently the family name in font pattern> constructed to represent this face comes from the @font-face rule> not the font.> > (In the @font-face rule above the descriptor value is the same as> the font family name, but the page referenced above actually used> a different font-family value.)> > Now consider if a user has the following fontconfig rule:> > <alias>> <family>sans-serif</family>> <prefer>> <family>BPG Ucnobi U</family>> </prefer>> </alias>> > so that FcConfigSubstitute turns font-family:sans-serif into> "Bitstream Vera Sans(w), BPG Ucnobi U(w)", which roughly means use> Bitstream Vera Sans for Latin languages and BPG Ucnobi U for the> Georgian language.> > Now, if no BPG Ucnobi U font is installed locally, and a page> includes an @font-face rule with family BPG Ucnobi U, should the> element> > <p lang="ka" style="font-family:sans-serif">უნიკოდის</p>> > be rendered with the font from> http://www.w3.org/International/tests/test-webfonts/BPG-Ucnobi-U.ttf> or with a locally installed fallback font? I'd say the locally installed font. > And, if there were a locally installed version of BPG Ucnobi U,> how would the user choose between the document font and the> locally installed font? (Currently this is decided by the web> browser. The spec is changing and currently contradictory.) The document one used if user specified that font family explicitly. Thesystem one used as a result of fontconfig configuration. I always think ofthe @font-face families as living in separate namespace. > Discussion:> ----------> > Part of me would like to think that document fonts are just like> any other fonts but I think there are differences.> > * The user has control over locally installed fonts, and can set> up fontconfig rules appropriately. Document fonts change as> often as users view different documents and do not get parsed by> acceptfont/rejectfont rules.> > * Document fonts may not be what they seem.> > * The font-family descriptor may have little to do with the font> itself.> > * The document font may be a trimmed down version of the font> with only enough glyphs to display a heading, for example. Exactly. A good way to think about them is like fonts embedded in a PDF, or aSVG. Do you expect your PDF/SVG. That makes things much easier. > Document fonts are already treated differently in that they are> not considered for fallback when looking for support for> characters not supported by the specified fonts.> (The draft spec http://dev.w3.org/csswg/css3-fonts/#font-matching> is changing but currently says "the user agent performs a system> font fallback procedure to find the best match for the character> to be rendered".) I imagine the reason for not considering> document fonts is that the author may (dare I mention it) play> tricks using Unicode code point assignments for unrelated glyphs.> > > My current thinking is that the FC_FAMILY value in the font> pattern representing fonts from document @font-face rules would> have a namespace. e.g.> > family: "@font-face:BPG Ucnobi U" Exactly my thinking in the context of how this will be used with Pango. > and, when the CSS style for an HTML element requests> "font-family:BPG Ucnobi U" (and an @font-face rule exists), the> FC_FAMILY property of the pattern passed to> FcConfigSubstitute(,,FcMatchPattern) would include> "@font-face:BPG Ucnobi U". You sure can do that. But I'm not sure how useful that would be. behdad_______________________________________________Fontconfig mailing listFontconfig@xxxxxxxxxxxxxxxxxxxxxxxxx://lists.freedesktop.org/mailman/listinfo/fontconfig
