Fix for FS#1598 - allow a plugin to be a singleton if it so desires

DokuWiki typically instantiates a plugin once and reuses
that instance whenever the plugin is required. However on
some occasions DokuWiki will request a new instantiation of
a plugin.  This particularly applies to render plugins.  This
patch allows a plugin to force DokuWiki to reuse the existing
instance.

If a plugin wishes to only be instantiated once then it
should implement an "isSingleton()" method and that
method should return boolean true.

darcs-hash:20090211143520-f07c6-5c1a33dbed55f0b196a204745fe3139f3c7c0aa9.gz

inc/plugin.php

@@ -215,6 +215,15 @@ class DokuWiki_Plugin {
     return p_render($format, p_get_instructions($text),$info);
   }
 
+  /**
+   * Allow the plugin to prevent DokuWiki creating a second instance of itself
+   *
+   * @return bool   true if the plugin can not be instantiated more than once
+   */
+  function isSingleton() {
+    return false;
+  }
+
   // deprecated functions
   function plugin_localFN($id) { return $this->localFN($id); }
   function plugin_locale_xhtml($id) { return $this->locale_xhtml($id); }

inc/plugincontroller.class.php

@@ -66,7 +66,7 @@ class Doku_Plugin_Controller {
 
     //plugin already loaded?
     if(!empty($DOKU_PLUGINS[$type][$name])){
-      if ($new) {
+      if ($new  && !$DOKU_PLUGINS[$type][$name]->isSingleton()) {
         $class = $type.'_plugin_'.$name;
         return class_exists($class) ? new $class : null;
       } else {

lib/plugins/syntax.php

@@ -266,5 +266,13 @@ class DokuWiki_Syntax_Plugin extends Doku_Parser_Mode {
     return $conf;
   }
 
+  /**
+   * Allow the plugin to prevent DokuWiki creating a second instance of itself
+   *
+   * @return bool   true if the plugin can not be instantiated more than once
+   */
+  function isSingleton() {
+    return false;
+  }
 }
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