+<refsect1><title>Debugging Applications</title>
+ <para>
+To help diagnose font and applications problems, fontconfig is built with a
+large amount of internal debugging left enabled. It is controlled by means
+of the FC_DEBUG environment variable. The value of this variable is
+interpreted as a number, and each bit within that value controls different
+debugging messages.
+ </para>
+ <programlisting>
+ Name Value Meaning
+ ---------------------------------------------------------
+ MATCH 1 Brief information about font matching
+ MATCHV 2 Extensive font matching information
+ EDIT 4 Monitor match/test/edit execution
+ FONTSET 8 Track loading of font information at startup
+ CACHE 16 Watch cache files being written
+ CACHEV 32 Extensive cache file writing information
+ PARSE 64 (no longer in use)
+ SCAN 128 Watch font files being scanned to build caches
+ SCANV 256 Verbose font file scanning information
+ MEMORY 512 Monitor fontconfig memory usage
+ CONFIG 1024 Monitor which config files are loaded
+ LANGSET 2048 Dump char sets used to construct lang values
+ OBJTYPES 4096 Display message when value typechecks fail
+ </programlisting>
+ <para>
+Add the value of the desired debug levels together and assign that (in
+base 10) to the FC_DEBUG environment variable before running the
+application. Output from these statements is sent to stdout.
+ </para>
+</refsect1>