Re: The WHY of Xft

[James Cloos <cloos@jhcloos.com>]

>>>>> “Miles” == Miles Bader <snogglethorpe@gmail.com> writes:

>> The other benefits are just as important.  Control and installation
>> of fonts are easier for most users

Miles> Can you explain in more detail?  I use debian, and Emacs
Miles> already seems able to use the same fonts as xft-using programs,
Miles> albeit not in anti-aliased form.

That is becasue debian did the hard work for those fonts that it
includes as part of the distribution.  The hard part for users
comes when they want to install a font not part of the dist,
whether one they've purchased or otherwise acquired.

It is much easier to just drop a font into ~/.fonts than to mess
with fonts.dir and fonts.scale files, etc.  At least for those
who've not been doing so for a couple of decades....  ☺

fc-cache should be run when the contents of the searched directories
change, but cli-averse users will probably use a gui not unlike that
on doze or macs which can do that for them.  mkfontscale has helped
ease installation of server-side fonts, but it is still not as easy.

Obviously for emacs it is less of an issue than for something like
gimp, but I’m sure it will come up for some.  Especially if packages
like preview-latex can use the client-side fonts to preview the entire
document as it is being edited rather than just selected portions.

>> fonts with large encodings -- such as CJKV fonts or any
>> iso10646-encoded font -- use *much* less vm and data transfer
>> between client and server is reduced for most workloads.

Miles> Doesn’t the X server already support partial loading of large
Miles> fonts?  [I mean the “-deferglyphs 16” in the X startup
Miles> options.]

I’m not familiar with deferglyphs; I don't remember it from any of
the discussions I read or participated in on the fontconfig, xfree
or freedesktop lists.  And I cannot find it in X(7x) or Xorg(1x).

My understanding is that when a (server-side) font is opened by the
X server it must determine all of the glyphs’ metrics, which requires
rendering all of them.

There are also still at least a couple of things I forgot to mention.
Server-side unicode fonts are limited to the bmp, so one cannot edit
scripts that use non-bmp characters w/o switching to client-side
fonts.  Client-side fonts are also necessary to take full advantage
of opentype features.

-JimC
-- 
James H. Cloos, Jr. <cloos@jhcloos.com>