Document when config can be NULL (#17105)

Note that this also fixes a bug with FcFontList() where previously
it was NOT checking whether the config is up-to-date.  May want to
keep the old behavior and document that ScanInterval is essentially
unused internally (FcFontSetList uses it, but we can remove that
too).

doc/fcconfig.fncs

@@ -63,6 +63,7 @@ Returns the current default configuration.
 @DESC@
 Checks all of the files related to <parameter>config</parameter> and returns
 whether any of them has been modified since the configuration was created.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@		FcChar8 *
@@ -95,6 +96,7 @@ disabled. The previous setting of the value is returned.
 Builds the set of available fonts for the given configuration.  Note that
 any changes to the configuration after this call have indeterminate effects.
 Returns FcFalse if this operation runs out of memory.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           FcStrList *
@@ -104,6 +106,7 @@ Returns FcFalse if this operation runs out of memory.
 @DESC@
 Returns the list of font directories specified in the configuration files
 for <parameter>config</parameter>.  Does not include any subdirectories.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           FcStrList *
@@ -114,6 +117,7 @@ for <parameter>config</parameter>.  Does not include any subdirectories.
 Returns the list of font directories in <parameter>config</parameter>. This includes the
 configured font directories along with any directories below those in the
 filesystem.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           FcStrList *
@@ -122,6 +126,7 @@ filesystem.
 @PURPOSE@	Get config files
 @DESC@
 Returns the list of known configuration files used to generate <parameter>config</parameter>.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           FcChar8 *
@@ -141,6 +146,7 @@ simply returns NULL to indicate that no per-user file exists.
 <function>FcConfigGetCacheDirs</function> returns a string list containing
 all of the directories that fontconfig will search when attempting to load a
 cache file for a font directory.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           FcFontSet *
@@ -152,6 +158,7 @@ cache file for a font directory.
 Returns one of the two sets of fonts from the configuration as specified
 by <parameter>set</parameter>. This font set is owned by the library and must
 not be freed.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           FcBlanks *
@@ -161,6 +168,9 @@ not be freed.
 @DESC@
 Returns the FcBlanks object associated with the given configuration, if no
 blanks were present in the configuration, this function will return 0.
+The returned FcBlanks object if not NULL, is valid as long as the owning
+FcConfig is alive.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           int
@@ -172,6 +182,7 @@ Returns the interval between automatic checks of the configuration (in
 seconds) specified in <parameter>config</parameter>.  The configuration is checked during
 a call to FcFontList when this interval has passed since the last check.
 An interval setting of zero disables automatic checks.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           FcBool
@@ -183,6 +194,7 @@ An interval setting of zero disables automatic checks.
 Sets the rescan interval. Returns FcFalse if the interval cannot be set (due
 to allocation failure). Otherwise returns FcTrue.
 An interval setting of zero disables automatic checks.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           FcBool
@@ -193,6 +205,7 @@ An interval setting of zero disables automatic checks.
 @DESC@
 Adds an application-specific font to the configuration. Returns FcFalse
 if the fonts cannot be added (due to allocation failure). Otherwise returns FcTrue.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           FcBool
@@ -204,6 +217,7 @@ if the fonts cannot be added (due to allocation failure). Otherwise returns FcTr
 Scans the specified directory for fonts, adding each one found to the
 application-specific set of fonts. Returns FcFalse
 if the fonts cannot be added (due to allocation failure). Otherwise returns FcTrue.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           void
@@ -212,6 +226,7 @@ if the fonts cannot be added (due to allocation failure). Otherwise returns FcTr
 @PURPOSE@	Remove all app fonts from font database
 @DESC@
 Clears the set of application-specific fonts.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           FcBool
@@ -227,6 +242,7 @@ FcMatchPattern, then those tagged as pattern operations are applied, else
 if <parameter>kind</parameter> is FcMatchFont, those tagged as font operations are applied and
 p_pat is used for &lt;test&gt; elements with target=pattern. Returns FcFalse
 if the substitution cannot be performed (due to allocation failure). Otherwise returns FcTrue.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           FcBool
@@ -238,6 +254,7 @@ if the substitution cannot be performed (due to allocation failure). Otherwise r
 @DESC@
 Calls FcConfigSubstituteWithPat setting p_pat to NULL. Returns FcFalse
 if the substitution cannot be performed (due to allocation failure). Otherwise returns FcTrue.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           FcPattern *
@@ -254,6 +271,7 @@ pattern. This function should be called only after
 <function>FcConfigSubstitute</function> and
 <function>FcDefaultSubstitute</function> have been called for
 <parameter>p</parameter>; otherwise the results will not be correct.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           FcFontSet *
@@ -278,6 +296,7 @@ modify these patterns.  Instead, they should be passed, along with <parameter>p<
 <function>FcFontRenderPrepare</function> which combines them into a complete pattern.
     </para><para>
 The FcFontSet returned by FcFontSort is destroyed by caling FcFontSetDestroy.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 @@
 
 @RET@           FcPattern *
@@ -302,6 +321,8 @@ FcConfigSubstituteWithPat with <parameter>kind</parameter> FcMatchFont and then
 @DESC@
 Selects fonts matching <parameter>p</parameter>, creates patterns from those fonts containing
 only the objects in <parameter>os</parameter> and returns the set of unique such patterns.
+If <parameter>config</parameter> is NULL, the default configuration is checked
+to be up to date, and used.
 @@
 
 @RET@           FcChar8 *

doc/fcfontset.fncs

@@ -62,6 +62,8 @@ Selects fonts matching <parameter>pattern</parameter> from
 <parameter>sets</parameter>, creates patterns from those
 fonts containing only the objects in <parameter>object_set</parameter> and returns
 the set of unique such patterns.
+If <parameter>config</parameter> is NULL, the default configuration is checked
+to be up to date, and used.
 @@
 
 @RET@		FcPattern *
@@ -80,6 +82,7 @@ pattern. This function should be called only after
 <function>FcConfigSubstitute</function> and
 <function>FcDefaultSubstitute</function> have been called for
 <parameter>pattern</parameter>; otherwise the results will not be correct.
+If <parameter>config</parameter> is NULL, the current configuration is used.
 Returns NULL if an error occurs during this process.
 @@
 

src/fclist.c

@@ -555,6 +555,9 @@ FcFontList (FcConfig	*config,
 
     if (!config)
     {
+	if (!FcInitBringUptoDate ())
+	    return 0;
+
 	config = FcConfigGetCurrent ();
 	if (!config)
 	    return 0;