On Saturday, September 28, 2002, at 03:19 PM, David Starner wrote:
> On Sat, Sep 28, 2002 at 01:19:58PM -0700, Murray Sargent wrote: >> 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. > > Try, for example, opening a file for which you have no font coverage in > Mozilla on Linux. It will open every font on the system looking for the > missing characters, and it will take quite a while, accompanied by much > disk thrashing to find they aren't there. > This just seems wildly inefficient to me, but then I'm coming from an OS where this isn't done. The app doesn't keep track of whether or not a particular font can draw a particular character; that's handled at display time. If a particular font doesn't handle a particular character, then a fallback mechanism is invoked by the system, which caches the necessary data. I really don't see why an application needs to check every character as it reads in a file to make sure it can be drawn with the set font. ========== John H. Jenkins [EMAIL PROTECTED] [EMAIL PROTECTED] http://www.tejat.net/
