[3.1.0] Implement DenyElementDecorator for imagecrash-protection against CSS width/height

- Misc doc changes
- Add missing inheritance for AttrDef_CSS decorators


git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@1684 48356398-32a2-884e-a903-53898d9a118a

library/HTMLPurifier/AttrDef/CSS/DenyElementDecorator.php

@@ -0,0 +1,26 @@
+<?php
+
+/**
+ * Decorator which enables CSS properties to be disabled for specific elements.
+ */
+class HTMLPurifier_AttrDef_CSS_DenyElementDecorator extends HTMLPurifier_AttrDef
+{
+    protected $def, $element;
+    
+    /**
+     * @param $def Definition to wrap
+     * @param $element Element to deny
+     */
+    public function __construct($def, $element) {
+        $this->def = $def;
+        $this->element = $element;
+    }
+    /**
+     * Checks if CurrentToken is set and equal to $this->element
+     */
+    public function validate($string, $config, $context) {
+        $token = $context->get('CurrentToken', true);
+        if ($token && $token->name == $this->element) return false;
+        return $this->def->validate($string, $config, $context);
+    }
+}

library/HTMLPurifier/AttrDef/CSS/ImportantDecorator.php

@@ -3,7 +3,7 @@
 /**
  * Decorator which enables !important to be used in CSS values.
  */
-class HTMLPurifier_AttrDef_CSS_ImportantDecorator
+class HTMLPurifier_AttrDef_CSS_ImportantDecorator extends HTMLPurifier_AttrDef
 {
     protected $def, $allow;