Changeset 7457dcb for x/installing

Timestamp:

08/30/2023 04:45:59 PM (9 months ago)

Author:

Xi Ruoyao <xry111@…>

Branches:

12.0, 12.1, ken/TL2024, ken/tuningfonts, lazarus, plabs/newcss, python3.11, rahul/power-profiles-daemon, renodr/vulkan-addition, trunk, xry111/llvm18

Children:

bec34e0

Parents:

7c60108

git-author:

Xi Ruoyao <xry111@…> (08/30/2023 04:35:33 PM)

git-committer:

Xi Ruoyao <xry111@…> (08/30/2023 04:45:59 PM)

Message:

TTF-and-OTF-fonts: Expand and correct the info about variable fonts

I'm pretty sure most desktop apps can use variable fonts today (even
Xterm renders variable fonts fine). But there is indeed something not
working, notably xelatex.

File:

• x/installing/TTF-and-OTF-fonts.xml (modified) (1 diff)

x/installing/TTF-and-OTF-fonts.xml

@@ -47 +47 @@
       If a font provides both TTF and OTF forms, you should prefer the OTF form
       in Linux, as it may provide more features for programs which know how to
-      use them (such as xelatex). But if a font is supplied with one or more
-      variable fonts, you should not use them. Desktop applications need static
-      fonts. For information about variable fonts, please see <ulink
+      use them (such as xelatex).
+    </para>
+
+    <para>
+      A font may have multiple variations.  For example, Noto Sans
+      has 9 weights (ExtraLight, Light, Thin, Normal, Medium, SemiBold,
+      Bold, ExtraBold, and Black) and 2 styles (Regular and Italic), thus
+      18 variations in total.  Normally each variation is provided as a
+      separate TTF or OTF file.  For full coverage you need to install
+      all these TTF or OTF files.  Even if you are low on disk space, you
+      should still install two weights (Regular and Bold) by two styles
+      (Normal and Italic) if the font has these variations.  Some fonts
+      do not have Italic style (for example most CJK fonts and some
+      monospace fonts), and some fonts only have one variation (for example
+      Noto Sans Math, it only provides the glyph of some mathematic
+      symbols).
+    </para>
+
+    <para>
+      Some fonts are also available as <emphasis>variable</emphasis> font
+      files.  Unlike a normal font file which only contains one variation,
+      a variable font file contains infinite variations.  Each variation
+      can be defined by the application using this font by assigning
+      number(s) to one or more variables.  There are also pre-defined
+      <emphasis>named instances</emphasis> analogous to the traditional
+      variations.  For example, with the variable version of Noto Sans, the
+      weight variable can be assigned any number not less than 100 and not
+      greater than 900, and 9 named instances are pre-defined: ExtraLight
+      for weight=100, Regular for weight=400, Bold for weight=700, etc.  So
+      once a variable variable font file for Noto Sans is installed, all the
+      9 named instances (or <quote>variations</quote>) are available.  Note
+      that the slope is not defined as a variable in the variable version
+      of Noto Sans, so Regular and Italic are still traditional variations
+      and a separate variable font file is needed for the Italic variation.
+    </para>
+
+    <para>
+      A variable font file is obviously more flexiable than the normal
+      (static) font files.  It's extremely useful for fine tuning the
+      font for Web pages or publications.  And, the size of a variable font
+      file is usually significantly smaller than the total size of several
+      static font files for multiple variations.  For example, the variable
+      font file for Noto Sans SC is only 11M, while the total size of 9
+      static font files for Noto Sans SC is 91M.  But you must make sure
+      your applications really support variable fonts before installing one.
+      For example, <command>lualatex</command> supports variable font but
+      <command>xelatex</command> does not.  So if you want to use a font for
+      an article and use <command>xelatex</command> for typesetting, you
+      must not install the variable font files.
+    </para>
+
+    <para>
+      For information about variable fonts, please see <ulink
       url="https://fonts.google.com/knowledge/introducing_type/introducing_variable_fonts/">
-      Variable Fonts</ulink>, as they are particularly useful where a web page
-      forces one of these fonts and sets details in its CSS.
+      Variable Fonts</ulink>.
     </para>