A note on missing glyphs.

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@722474 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 15 insertions, 1 deletions

diff --git a/src/documentation/content/xdocs/trunk/fonts.xml b/src/documentation/content/xdocs/trunk/fonts.xml
index 5eb3463c8..758a537cc 100644
--- a/src/documentation/content/xdocs/trunk/fonts.xml
+++ b/src/documentation/content/xdocs/trunk/fonts.xml
@@ -168,7 +168,7 @@
         the target document.
       </p>
     </section>
-    <section>
+    <section id="missing-fonts">
       <title>Missing Fonts</title>
       <p>
         When FOP does not have a specific font at its disposal (because it's 
@@ -177,6 +177,20 @@
         Base-14 font "Times" (see above).
       </p>
     </section>
+    <section id="missing-glyphs">
+      <title>Missing Glyphs</title>
+      <p>
+        Every font contains a particular set of
+        <a href="http://en.wikipedia.org/wiki/Glyph">glyphs</a>. If no glyph can be found for
+        a given character, FOP will issue a warning and use the glpyh for "#" (if available)
+        instead. Before it does that, it consults a (currently hard-coded) registry of
+        glyph substitution groups (see Glyphs.java in Apache XML Graphics Commons).
+        This registry can supply alternative glyphs in some cases (like using space when a no-break
+        space is requested). But there's no guarantee that the result will be as expected (for
+        example, in the case of hyphens and similar glyphs). A better way is to use a font that
+        has all the necessary glyphs. This glyph substitution is only a last resort.
+      </p>
+    </section>
     <section id="awt">
       <title>Java2D/AWT/Operating System Fonts</title>
       <p>