Another alternative is to check the font at install time, and then make sure that the bits are set correctly.
Mark __________________________________ http://www.macchiato.com ► “Eppur si muove” ◄ ----- Original Message ----- From: "Murray Sargent" <[EMAIL PROTECTED]> To: "Michael Everson" <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> Sent: Saturday, September 28, 2002 13:19 Subject: RE: script or block detection needed for Unicode fonts > Michael Everson said: > > I don't understand why a particular bit has to be set in > > some table. Why can't the OS just accept what's in the font? > > The main reason is performance. If an application has to check the font > cmap for every character in a file, it slows down reading the file. > Accordingly programs typically check the script bits of a font to see if > the font claims to support a script. If so, the font is accepted. Else > another font that has the appropriate bit is accepted. This info is > cached, so it's very fast. > > A problem occurs more often with fonts that claim to support say Greek > or Cyrillic, but only support the most common characters in these > scripts. In RichEdit we now check the cmap for the less common Greek, > Cyrillic, Arabic, etc., characters to ensure that they are in fact in > the font. If not, we switch to some other font that has them. > > The problem with a font setting a script bit when the font only has a > single glyph is that that font may then be used for other common > characters in the script, thereby resulting in a missing-character glyph > at display time. > > I suppose one could have it both ways by instructing a program to always > check the cmap for a given font, thereby bypassing the more streamlined > algorithms. This would be a handy option for specialized fonts. We'd > need some font convention to turn on this behavior. > > Thanks > Murray > >
