This bug is related with bug 91190, but is different. Currently, unrecognized lang tags are regarded as x-western [1]. Howeer, I think it's better to regard them as x-unicode because most, if not all, languages covered by ISO-8859-1/ISO-8859-15 are listed in http://lxr.mozilla.org/seamonkey/source/intl/locale/src/langGroups.properties When a lang tag is not listed there, it's much more likely that it's only supported by Unicode than that it's supported by ISO 8859-1/15. Now that Mozilla-Win can properly display Indic scripts (and Mozilla-Xft will follow it soon : see bug 204439, bug 204286), there should be ways to designate separate fonts for those scripts. At the moment, when a page is tagged as 'ta' (Tamil), fonts to render the page come from fonts for x-western (only if the coverage of western fonts is not sufficient, other fonts are searched for). Therefore, Tamil speakers have to set fonts for Western to specify fonts to render Tamil pages (tagged with 'ta') with. It's not very intuitive. There are three ways to solve this problem. 1. Add a whole bunch of lang tags to langGroups.properties mapping them to x-unicode lang group. This is not such a good idea because eventually (#3 below) we have to map them to their own langgroup. [0] 2. Fix http://lxr.mozilla.org/seamonkey/source/intl/locale/src/nsLanguageAtomService.cpp#187 [1] to assign x-unicode to unrecognized lang tags instead of x-western. It has to be checked whether this has any unexpected result somewhere. 3. Add new lang tags to pref-fonts.xul and pref-fonts.dtd [2] as support for them are added. This is a bit tricky because the list of supported scripts are platform-dependent. On Win2k/XP, virtually all scripts supported by Win2k/XP are also supported by Mozilla. On other platforms, Mozilla is not quite there yet. I think we have to push forward #2 and #3 in parallel. [0] IMHO, 'script(name/group)' would have been a better choice than 'langgroup'. 'x-dv' would be a scriptgroup not just for Hindi(hi) but also for other languages written with Devanagari just as 'x-western'(latin1), 'x-baltic', 'x-centraleuro', and 'x-cyrillic' are for a number of European languages. [1] http://lxr.mozilla.org/seamonkey/source/intl/locale/src/nsLanguageAtomService.cpp#197 197 res = mLangGroups->GetStringFromName(lowered.get(), getter_Copies(langGroupStr)); 198 if (NS_FAILED(res)) { 199 PRInt32 hyphen = lowered.FindChar('-'); 200 if (hyphen >= 0) { 201 nsAutoString truncated(lowered); 202 truncated.Truncate(hyphen); 203 res = mLangGroups->GetStringFromName(truncated.get(), getter_Copies(langGroupStr)); 204 if (NS_FAILED(res)) { 205 langGroupStr.Assign(NS_LITERAL_STRING("x-western")); 206 } 207 } else { 208 langGroupStr.Assign(NS_LITERAL_STRING("x-western")); 209 } [2] http://lxr.mozilla.org/seamonkey/source/xpfe/components/prefwindow/resources/content/pref-fonts.xul#66 http://lxr.mozilla.org/seamonkey/source/xpfe/components/prefwindow/resources/locale/en-US/pref-fonts.dtd

I added several European and African languages supported by X-Western langgroup to langGroups.properties file. I also changed the default langGroup for unrecognized lang tags to x-unicode. As I mentioned earlier, this will enable speakers of those languages to set fonts to use when viewing lang-tagged web pages in UTF-8 by setting fonts for X-unicode (instead of x-western) until we add them to font preference menu.

If this changes get in, we have to release-note that 'Unicode' fonts have to be set to controll fonts for pages lang-tagged with languages not belonging to those covered by font-pref. menu. They include but not are limited to languages written with Tamil, Bengali, and other Indic scripts. Otherwise, they have to change Western fonts, which is not desriable in most cases because Western European text had better be rendered with high-quality Latin fonts refined over the years instead of non-Latin fonts that happen to cover Latin letters. Needless to say, as more and more web pages are put up in Unicode, this is not the best either (because European text in Unicode will be rendered with less-than-optimal fonts). Therefore, we have to implement item #3 soon. The only roadblock is the platform-dependent coverage of scripts. I wnoder if platform-dependent xul overlay can solve this problem.

Implementing #1 and #3 alone doesn't work. Gfx ports for different platforms have different ways of selecting fonts based on langGroup and currently most of Gfx ports support only 'major' scripts (Latin, Greek, Cyrillic, CJK, Thai, Hebrew and Arabic). I filed bug 206123 for Gfx-Win on this issue. In my patch to bug 204039, I partly fixed it for Tamil and Devanagari.

langGroups.properties changes were already checked in. I forgot I had filed this bug and filed bug 256383 where I uploaded a patch and asked for r/sr. *** This bug has been marked as a duplicate of 256383 ***