From 796fdcf2d43569744f80c16ec29a2141da5700d8 Mon Sep 17 00:00:00 2001
From: Matthias Schmidt <gravatronics@live.com>
Date: Wed, 1 May 2013 12:37:34 +0200
Subject: [PATCH] Overhauls category implementation

Closes #1222
---
 .../template/categoryOptionList.tpl           |   4 +-
 .../files/acp/templates/categoryAdd.tpl       |   4 +-
 .../files/acp/templates/categoryList.tpl      | 193 ++++++++----------
 .../acp/templates/categoryOptionList.tpl      |   4 +-
 .../form/AbstractCategoryAddForm.class.php    |  33 ++-
 .../form/AbstractCategoryEditForm.class.php   |   6 +-
 .../page/AbstractCategoryListPage.class.php   |  12 +-
 .../AbstractDecoratedCategory.class.php       |  94 +++++++++
 .../lib/data/category/Category.class.php      |  56 ++++-
 .../lib/data/category/CategoryNode.class.php  |  53 ++---
 .../data/category/CategoryNodeList.class.php  |  84 --------
 .../data/category/CategoryNodeTree.class.php  | 148 ++++++++++++++
 .../UncachedCategoryNodeTree.class.php        |  67 ++++++
 .../data/category/ViewableCategory.class.php  |  96 ---------
 .../category/ViewableCategoryNode.class.php   |  31 ---
 .../ViewableCategoryNodeList.class.php        |  14 --
 .../category/AbstractCategoryType.class.php   |   2 +-
 .../system/category/CategoryHandler.class.php |  22 +-
 18 files changed, 506 insertions(+), 417 deletions(-)
 create mode 100644 wcfsetup/install/files/lib/data/category/AbstractDecoratedCategory.class.php
 delete mode 100644 wcfsetup/install/files/lib/data/category/CategoryNodeList.class.php
 create mode 100644 wcfsetup/install/files/lib/data/category/CategoryNodeTree.class.php
 create mode 100644 wcfsetup/install/files/lib/data/category/UncachedCategoryNodeTree.class.php
 delete mode 100644 wcfsetup/install/files/lib/data/category/ViewableCategory.class.php
 delete mode 100644 wcfsetup/install/files/lib/data/category/ViewableCategoryNode.class.php
 delete mode 100644 wcfsetup/install/files/lib/data/category/ViewableCategoryNodeList.class.php

diff --git a/com.woltlab.wcf/template/categoryOptionList.tpl b/com.woltlab.wcf/template/categoryOptionList.tpl
index 2e47acffa8..f362f14359 100644
--- a/com.woltlab.wcf/template/categoryOptionList.tpl
+++ b/com.woltlab.wcf/template/categoryOptionList.tpl
@@ -1,5 +1,5 @@
-{foreach from=$categoryNodeList item=category}
-	{if !$maximumNestingLevel|isset || $maximumNestingLevel == -2 || $categoryNodeList->getDepth() <= $maximumNestingLevel}
+{foreach from=$categoryNodeList item='category'}
+	{if !$maximumNestingLevel|isset || $maximumNestingLevel == -1 || $categoryNodeList->getDepth() <= $maximumNestingLevel}
 		<option value="{$category->categoryID}"{if $categoryID|isset && $categoryID == $category->categoryID} selected="selected"{/if}>{section name=i loop=$categoryNodeList->getDepth()}&nbsp;&nbsp;&nbsp;&nbsp;{/section}{$category->getTitle()}</option>
 	{/if}
 {/foreach}
\ No newline at end of file
diff --git a/wcfsetup/install/files/acp/templates/categoryAdd.tpl b/wcfsetup/install/files/acp/templates/categoryAdd.tpl
index 8796968bcc..383205d0b1 100644
--- a/wcfsetup/install/files/acp/templates/categoryAdd.tpl
+++ b/wcfsetup/install/files/acp/templates/categoryAdd.tpl
@@ -48,13 +48,13 @@
 		<fieldset>
 			<legend>{lang}wcf.global.form.data{/lang}</legend>
 			
-			{if $objectType->getProcessor()->getMaximumNestingLevel() && $categoryNodeList|count}
+			{if $categoryNodeList->hasChildren() && $objectType->getProcessor()->getMaximumNestingLevel()}
 				<dl{if $errorField == 'parentCategoryID'} class="formError"{/if}>
 					<dt><label for="parentCategoryID">{@$objectType->getProcessor()->getLanguageVariable('parentCategoryID')}</label></dt>
 					<dd>
 						<select id="parentCategoryID" name="parentCategoryID">
 							<option value="0"></option>
-							{include file='categoryOptionList' categoryID=$parentCategoryID maximumNestingLevel=$objectType->getProcessor()->getMaximumNestingLevel() - 1}
+							{include file='categoryOptionList' categoryID=$parentCategoryID maximumNestingLevel=$objectType->getProcessor()->getMaximumNestingLevel()}
 						</select>
 						{if $errorField == 'parentCategoryID'}
 							<small class="innerError">
diff --git a/wcfsetup/install/files/acp/templates/categoryList.tpl b/wcfsetup/install/files/acp/templates/categoryList.tpl
index eb69daba67..f84f3ef490 100644
--- a/wcfsetup/install/files/acp/templates/categoryList.tpl
+++ b/wcfsetup/install/files/acp/templates/categoryList.tpl
@@ -1,66 +1,65 @@
 {include file='header'}
 
-{if $categoryNodeList|count}
+{if $categoryNodeList->hasChildren()}
 	<script type="text/javascript">
 		//<![CDATA[
 		$(function() {
-			{if $collapsibleObjectTypeID && $categoryNodeList|count > 1}
+			{if $collapsibleObjectTypeID}
 				new WCF.ACP.Category.Collapsible('wcf\\data\\category\\CategoryAction', {@$collapsibleObjectTypeID});
 			{/if}
-			
+				
 			{if $objectType->getProcessor()->canDeleteCategory()}
 				new WCF.ACP.Category.Delete('wcf\\data\\category\\CategoryAction', $('.jsCategory'));
 			{/if}
 			{if $objectType->getProcessor()->canEditCategory()}
 				new WCF.Action.Toggle('wcf\\data\\category\\CategoryAction', '.jsCategory', '> .sortableNodeLabel > .buttons > .jsToggleButton');
 				
-				{if $categoryNodeList|count > 1}
-					var sortableNodes = $('.sortableNode');
-					sortableNodes.each(function(index, node) {
-						$(node).wcfIdentify();
-					});
-					
-					new WCF.Sortable.List('categoryList', 'wcf\\data\\category\\CategoryAction', 0{if $objectType->getProcessor()->getMaximumNestingLevel() != -1}, {
-						/**
-						 * Updates the sortable nodes after a sorting is started with
-						 * regard to their possibility to have child the currently sorted
-						 * category as a child category.
-						 */
-						start: function(event, ui) {
-							var sortedListItem = $(ui.item);
-							var itemNestingLevel = sortedListItem.find('.sortableList:has(.sortableNode)').length;
+				var sortableNodes = $('.sortableNode');
+				sortableNodes.each(function(index, node) {
+					$(node).wcfIdentify();
+				});
+				
+				new WCF.Sortable.List('categoryList', 'wcf\\data\\category\\CategoryAction', 0{if $objectType->getProcessor()->getMaximumNestingLevel() != -1}, {
+					/**
+					 * Updates the sortable nodes after a sorting is started with
+					 * regard to their possibility to have child the currently sorted
+					 * category as a child category.
+					 */
+					start: function(event, ui) {
+						var sortedListItem = $(ui.item);
+						var itemNestingLevel = sortedListItem.find('.sortableList:has(.sortableNode)').length;
+						
+						sortableNodes.each(function(index, node) {
+							node = $(node);
 							
-							sortableNodes.each(function(index, node) {
-								node = $(node);
-								
-								if (node.attr('id') != sortedListItem.attr('id')) {
-									if (node.parents('.sortableList').length + itemNestingLevel >= {@$objectType->getProcessor()->getMaximumNestingLevel() + 1}) {
-										node.addClass('sortableNoNesting');
-									}
-									else if (node.hasClass('sortableNoNesting')) {
-										node.removeClass('sortableNoNesting');
-									}
-								}
-							});
-						},
-						/**
-						 * Updates the sortable nodes after a sorting is completed with
-						 * regard to their possibility to have child categories.
-						 */
-						stop: function(event, ui) {
-							sortableNodes.each(function(index, node) {
-								node = $(node);
-								
-								if (node.parents('.sortableList').length == {@$objectType->getProcessor()->getMaximumNestingLevel() + 1}) {
+							if (node.attr('id') != sortedListItem.attr('id')) {
+								if (node.parents('.sortableList').length + itemNestingLevel >= {@$objectType->getProcessor()->getMaximumNestingLevel() + 1}) {
 									node.addClass('sortableNoNesting');
 								}
 								else if (node.hasClass('sortableNoNesting')) {
 									node.removeClass('sortableNoNesting');
 								}
-							});
-						}
-					}{/if});
-				{/if}
+							}
+						});
+					},
+					
+					/**
+					 * Updates the sortable nodes after a sorting is completed with
+					 * regard to their possibility to have child categories.
+					 */
+					stop: function(event, ui) {
+						sortableNodes.each(function(index, node) {
+							node = $(node);
+							
+							if (node.parents('.sortableList').length == {@$objectType->getProcessor()->getMaximumNestingLevel() + 1}) {
+								node.addClass('sortableNoNesting');
+							}
+							else if (node.hasClass('sortableNoNesting')) {
+								node.removeClass('sortableNoNesting');
+							}
+						});
+					}
+				}{/if});
 			{/if}
 		});
 		//]]>
@@ -80,80 +79,64 @@
 						<li><a href="{link controller=$addController application=$objectType->getProcessor()->getApplication()}{/link}" class="button"><span class="icon icon16 icon-plus"></span> <span>{@$objectType->getProcessor()->getLanguageVariable('add')}</span></a></li>
 					{/if}
 					
-					{event name='contentNavigationButtonsTop'}
+					{event name='contentNavigationButtons'}
 				{/content}
 			</ul>
 		</nav>
 	{/hascontent}
 </div>
 
-{if $categoryNodeList|count}
-	<section id="categoryList" class="container containerPadding marginTop{if $objectType->getProcessor()->canEditCategory() && $categoryNodeList|count > 1} sortableListContainer{/if}">
+{hascontent}
+	<section id="categoryList" class="container containerPadding marginTop{if $objectType->getProcessor()->canEditCategory()} sortableListContainer{/if}">
 		<ol class="categoryList sortableList" data-object-id="0">
-			{assign var=oldDepth value=0}
-			{foreach from=$categoryNodeList item=category}
-				{section name=i loop=$oldDepth-$categoryNodeList->getDepth()}</ol></li>{/section}
-				
-				<li class="{if $objectType->getProcessor()->canEditCategory() && $categoryNodeList|count > 1}sortableNode {if $categoryNodeList->getDepth() == $objectType->getProcessor()->getMaximumNestingLevel()}sortableNoNesting {/if}{/if}jsCategory" data-object-id="{@$category->categoryID}"{if $collapsedCategoryIDs|is_array} data-is-open="{if $collapsedCategoryIDs[$category->categoryID]|isset}0{else}1{/if}"{/if}>
-					<span class="sortableNodeLabel">
-						<span class="title">
-							{if $objectType->getProcessor()->canEditCategory()}
-								<a href="{link controller=$editController application=$objectType->getProcessor()->getApplication() id=$category->categoryID title=$category->getTitle()}{/link}">{$category->getTitle()}</a>
-							{else}
-								{$category->getTitle()}
-							{/if}
-						</span>
-						
-						<span class="statusDisplay buttons">
-							{if $objectType->getProcessor()->canEditCategory()}
-								<a href="{link controller=$editController application=$objectType->getProcessor()->getApplication() id=$category->categoryID title=$category->getTitle()}{/link}" title="{lang}wcf.global.button.edit{/lang}" class="jsTooltip"><span class="icon icon16 icon-pencil"></span></a>
-							{/if}
-							
-							{if $objectType->getProcessor()->canDeleteCategory()}
-								<span class="icon icon16 icon-remove jsDeleteButton jsTooltip pointer" title="{lang}wcf.global.button.delete{/lang}" data-object-id="{@$category->categoryID}" data-confirm-message="{@$objectType->getProcessor()->getLanguageVariable('delete.sure')}"></span>
-							{/if}
-							
-							{if $objectType->getProcessor()->canEditCategory()}
-								<span class="icon icon16 icon-{if !$category->isDisabled}circle-blank{else}off{/if} jsToggleButton jsTooltip pointer" title="{lang}wcf.global.button.{if !$category->isDisabled}disable{else}enable{/if}{/lang}" data-object-id="{@$category->categoryID}"></span>
-							{/if}
+			{content}
+				{assign var=oldDepth value=0}
+				{foreach from=$categoryNodeList item='category'}
+					{section name=i loop=$oldDepth-$categoryNodeList->getDepth()}</ol></li>{/section}
+					
+					<li class="{if $objectType->getProcessor()->canEditCategory()}sortableNode {if $categoryNodeList->getDepth() == $objectType->getProcessor()->getMaximumNestingLevel()}sortableNoNesting {/if}{/if}jsCategory" data-object-id="{@$category->categoryID}"{if $collapsedCategoryIDs|is_array} data-is-open="{if $collapsedCategoryIDs[$category->categoryID]|isset}0{else}1{/if}"{/if}>
+						<span class="sortableNodeLabel">
+							<span class="title">
+								{if $objectType->getProcessor()->canEditCategory()}
+									<a href="{link controller=$editController application=$objectType->getProcessor()->getApplication() id=$category->categoryID title=$category->getTitle()}{/link}">{$category->getTitle()}</a>
+								{else}
+									{$category->getTitle()}
+								{/if}
+							</span>
 							
-							{event name='itemButtons'}
+							<span class="statusDisplay buttons">
+								{if $objectType->getProcessor()->canEditCategory()}
+									<a href="{link controller=$editController application=$objectType->getProcessor()->getApplication() id=$category->categoryID title=$category->getTitle()}{/link}" title="{lang}wcf.global.button.edit{/lang}" class="jsTooltip"><span class="icon icon16 icon-pencil"></span></a>
+								{/if}
+								
+								{if $objectType->getProcessor()->canDeleteCategory()}
+									<span class="icon icon16 icon-remove jsDeleteButton jsTooltip pointer" title="{lang}wcf.global.button.delete{/lang}" data-object-id="{@$category->categoryID}" data-confirm-message="{@$objectType->getProcessor()->getLanguageVariable('delete.sure')}"></span>
+								{/if}
+								
+								{if $objectType->getProcessor()->canEditCategory()}
+									<span class="icon icon16 icon-{if !$category->isDisabled}circle-blank{else}off{/if} jsToggleButton jsTooltip pointer" title="{lang}wcf.global.button.{if !$category->isDisabled}disable{else}enable{/if}{/lang}" data-object-id="{@$category->categoryID}"></span>
+								{/if}
+								
+								{event name='itemButtons'}
+							</span>
 						</span>
-					</span>
-					
-					<ol class="categoryList sortableList" data-object-id="{@$category->categoryID}">
-				{if !$categoryNodeList->current()->hasChildren()}
-					</ol></li>
-				{/if}
-				{assign var=oldDepth value=$categoryNodeList->getDepth()}
-			{/foreach}
-			{section name=i loop=$oldDepth}</ol></li>{/section}
+						
+						<ol class="categoryList sortableList" data-object-id="{@$category->categoryID}">
+					{if !$categoryNodeList->current()->hasChildren()}
+						</ol></li>
+					{/if}
+					{assign var=oldDepth value=$categoryNodeList->getDepth()}
+				{/foreach}
+				{section name=i loop=$oldDepth}</ol></li>{/section}
+			{/content}
 		</ol>
-		
-		{if $objectType->getProcessor()->canEditCategory() && $categoryNodeList|count > 1}
-			<div class="formSubmit">
-				<button class="button buttonPrimary" data-type="submit">{lang}wcf.global.button.saveSorting{/lang}</button>
-			</div>
-		{/if}
 	</section>
 	
-	<div class="contentNavigation">
-		{hascontent}
-			<nav>
-				<ul>
-					{content}
-						{if $objectType->getProcessor()->canAddCategory()}
-							<li><a href="{link controller=$addController application=$objectType->getProcessor()->getApplication()}{/link}" class="button"><span class="icon icon16 icon-plus"></span> <span>{@$objectType->getProcessor()->getLanguageVariable('add')}</span></a></li>
-						{/if}
-						
-						{event name='contentNavigationButtonsBottom'}
-					{/content}
-				</ul>
-			</nav>
-		{/hascontent}
+	<div class="formSubmit">
+		<button class="button" data-type="submit">{lang}wcf.global.button.saveSorting{/lang}</button>
 	</div>
-{else}
+{hascontentelse}
 	<p class="info">{@$objectType->getProcessor()->getLanguageVariable('noneAvailable')}</p>
-{/if}
+{/hascontent}
 
 {include file='footer'}
\ No newline at end of file
diff --git a/wcfsetup/install/files/acp/templates/categoryOptionList.tpl b/wcfsetup/install/files/acp/templates/categoryOptionList.tpl
index 2e47acffa8..f362f14359 100644
--- a/wcfsetup/install/files/acp/templates/categoryOptionList.tpl
+++ b/wcfsetup/install/files/acp/templates/categoryOptionList.tpl
@@ -1,5 +1,5 @@
-{foreach from=$categoryNodeList item=category}
-	{if !$maximumNestingLevel|isset || $maximumNestingLevel == -2 || $categoryNodeList->getDepth() <= $maximumNestingLevel}
+{foreach from=$categoryNodeList item='category'}
+	{if !$maximumNestingLevel|isset || $maximumNestingLevel == -1 || $categoryNodeList->getDepth() <= $maximumNestingLevel}
 		<option value="{$category->categoryID}"{if $categoryID|isset && $categoryID == $category->categoryID} selected="selected"{/if}>{section name=i loop=$categoryNodeList->getDepth()}&nbsp;&nbsp;&nbsp;&nbsp;{/section}{$category->getTitle()}</option>
 	{/if}
 {/foreach}
\ No newline at end of file
diff --git a/wcfsetup/install/files/lib/acp/form/AbstractCategoryAddForm.class.php b/wcfsetup/install/files/lib/acp/form/AbstractCategoryAddForm.class.php
index df99bc6aab..d461b662b2 100644
--- a/wcfsetup/install/files/lib/acp/form/AbstractCategoryAddForm.class.php
+++ b/wcfsetup/install/files/lib/acp/form/AbstractCategoryAddForm.class.php
@@ -2,7 +2,7 @@
 namespace wcf\acp\form;
 use wcf\data\category\CategoryAction;
 use wcf\data\category\CategoryEditor;
-use wcf\data\category\CategoryNodeList;
+use wcf\data\category\UncachedCategoryNodeTree;
 use wcf\form\AbstractForm;
 use wcf\system\acl\ACLHandler;
 use wcf\system\category\CategoryHandler;
@@ -45,10 +45,10 @@ abstract class AbstractCategoryAddForm extends AbstractForm {
 	public $additionalData = array();
 	
 	/**
-	 * list with the category nodes
-	 * @var	wcf\data\category\CategoryNodeList
+	 * tree with the category nodes
+	 * @var	wcf\data\category\CategoryNodeTree
 	 */
-	public $categoryNodeList = null;
+	public $categoryNodeTree = null;
 	
 	/**
 	 * indicates if the category is disabled
@@ -146,7 +146,7 @@ abstract class AbstractCategoryAddForm extends AbstractForm {
 			'action' => 'add',
 			'addController' => $this->addController,
 			'additionalData' => $this->additionalData,
-			'categoryNodeList' => $this->categoryNodeList,
+			'categoryNodeList' => $this->categoryNodeTree->getIterator(),
 			'editController' => $this->editController,
 			'isDisabled' => $this->isDisabled,
 			'listController' => $this->listController,
@@ -173,13 +173,13 @@ abstract class AbstractCategoryAddForm extends AbstractForm {
 	 * Reads the categories.
 	 */
 	protected function readCategories() {
-		$this->categoryNodeList = new CategoryNodeList($this->objectType->objectType, 0, true);
+		$this->categoryNodeTree = new UncachedCategoryNodeTree($this->objectType->objectType, 0, true);
 	}
 	
 	/**
 	 * @see	wcf\page\IPage::readData()
 	 */
-	public function readData() {		
+	public function readData() {
 		$this->objectType = CategoryHandler::getInstance()->getObjectTypeByName($this->objectTypeName);
 		if ($this->objectType === null) {
 			throw new SystemException("Unknown category object type with name '".$this->objectTypeName."'");
@@ -204,9 +204,9 @@ abstract class AbstractCategoryAddForm extends AbstractForm {
 		}
 		I18nHandler::getInstance()->register('title');
 		
-		$this->readCategories();
-		
 		parent::readData();
+		
+		$this->readCategories();
 	}
 	
 	/**
@@ -330,19 +330,14 @@ abstract class AbstractCategoryAddForm extends AbstractForm {
 				return;
 			}
 			
-			if (CategoryHandler::getInstance()->getCategory($this->parentCategoryID) === null) {
-				throw new UserInputException('parentCategoryID', 'invalid');
+			$category = CategoryHandler::getInstance()->getCategory($this->parentCategoryID);
+			if ($category === null) {
+				throw new UserInputException('parentCategoryID', 'notValid');
 			}
 			
 			if ($this->objectType->getProcessor()->getMaximumNestingLevel() != -1) {
-				foreach ($this->categoryNodeList as $category) {
-					if ($category->categoryID == $this->parentCategoryID) {
-						if ($this->categoryNodeList->getDepth() > $this->objectType->getProcessor()->getMaximumNestingLevel() - 1) {
-							throw new UserInputException('parentCategoryID', 'invalid');
-						}
-						
-						break;
-					}
+				if (count($category->getParentCategories()) > $this->objectType->getProcessor()->getMaximumNestingLevel()) {
+					throw new UserInputException('parentCategoryID', 'notValid');
 				}
 			}
 		}
diff --git a/wcfsetup/install/files/lib/acp/form/AbstractCategoryEditForm.class.php b/wcfsetup/install/files/lib/acp/form/AbstractCategoryEditForm.class.php
index d3065c4d28..6301a65375 100644
--- a/wcfsetup/install/files/lib/acp/form/AbstractCategoryEditForm.class.php
+++ b/wcfsetup/install/files/lib/acp/form/AbstractCategoryEditForm.class.php
@@ -2,7 +2,7 @@
 namespace wcf\acp\form;
 use wcf\data\category\Category;
 use wcf\data\category\CategoryAction;
-use wcf\data\category\CategoryNodeList;
+use wcf\data\category\CategoryNodeTree;
 use wcf\form\AbstractForm;
 use wcf\system\acl\ACLHandler;
 use wcf\system\category\CategoryHandler;
@@ -63,7 +63,7 @@ class AbstractCategoryEditForm extends AbstractCategoryAddForm {
 	 * @see	wcf\acp\form\AbstractCategoryAddForm::readCategories()
 	 */
 	protected function readCategories() {
-		$this->categoryNodeList = new CategoryNodeList($this->objectType->objectType, 0, true, array($this->category->categoryID));
+		$this->categoryNodeTree = new CategoryNodeTree($this->objectType->objectType, 0, true, array($this->category->categoryID));
 	}
 	
 	/**
@@ -164,7 +164,7 @@ class AbstractCategoryEditForm extends AbstractCategoryAddForm {
 		parent::validateParentCategory();
 		
 		// check if new parent category is no child category of the category
-		$childCategories = CategoryHandler::getInstance()->getChildCategories($this->category);
+		$childCategories = CategoryHandler::getInstance()->getChildCategories($this->categoryID, $this->objectType->objectTypeID);
 		if (isset($childCategories[$this->parentCategoryID])) {
 			throw new UserInputException('parentCategoryID', 'invalid');
 		}
diff --git a/wcfsetup/install/files/lib/acp/page/AbstractCategoryListPage.class.php b/wcfsetup/install/files/lib/acp/page/AbstractCategoryListPage.class.php
index d816884dd6..58173c1a5d 100644
--- a/wcfsetup/install/files/lib/acp/page/AbstractCategoryListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/AbstractCategoryListPage.class.php
@@ -1,6 +1,6 @@
 <?php
 namespace wcf\acp\page;
-use wcf\data\category\CategoryNodeList;
+use wcf\data\category\CategoryNodeTree;
 use wcf\page\AbstractPage;
 use wcf\system\category\CategoryHandler;
 use wcf\system\exception\PermissionDeniedException;
@@ -28,10 +28,10 @@ abstract class AbstractCategoryListPage extends AbstractPage {
 	public $addController = '';
 	
 	/**
-	 * category node list
-	 * @var	wcf\data\category\CategoryNodeList
+	 * category node tree
+	 * @var	wcf\data\category\CategoryNodeTree
 	 */
-	public $categoryNodeList = null;
+	public $categoryNodeTree = null;
 	
 	/**
 	 * ids of collapsed categories
@@ -100,7 +100,7 @@ abstract class AbstractCategoryListPage extends AbstractPage {
 		
 		WCF::getTPL()->assign(array(
 			'addController' => $this->addController,
-			'categoryNodeList' => $this->categoryNodeList,
+			'categoryNodeList' => $this->categoryNodeTree->getIterator(),
 			'collapsedCategoryIDs' => $this->collapsedCategoryIDs,
 			'collapsibleObjectTypeID' => $this->collapsibleObjectTypeID,
 			'editController' => $this->editController,
@@ -125,7 +125,7 @@ abstract class AbstractCategoryListPage extends AbstractPage {
 	 * Reads the categories.
 	 */
 	protected function readCategories() {
-		$this->categoryNodeList = new CategoryNodeList($this->objectType->objectType, 0, true);
+		$this->categoryNodeTree = new CategoryNodeTree($this->objectType->objectType, 0, true);
 	}
 	
 	/**
diff --git a/wcfsetup/install/files/lib/data/category/AbstractDecoratedCategory.class.php b/wcfsetup/install/files/lib/data/category/AbstractDecoratedCategory.class.php
new file mode 100644
index 0000000000..5618735271
--- /dev/null
+++ b/wcfsetup/install/files/lib/data/category/AbstractDecoratedCategory.class.php
@@ -0,0 +1,94 @@
+<?php
+namespace wcf\data\category;
+use wcf\data\DatabaseObjectDecorator;
+use wcf\system\category\CategoryHandler;
+
+/**
+ * Abstract implementation of a decorated category.
+ * 
+ * @author	Matthias Schmidt
+ * @copyright	2001-2013 WoltLab GmbH
+ * @license	GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
+ * @package	com.woltlab.wcf
+ * @subpackage	data.category
+ * @category	Community Framework
+ */
+abstract class AbstractDecoratedCategory extends DatabaseObjectDecorator {
+	/**
+	 * list of all child categories of this category
+	 * @var	array<wcf\data\category\Category>
+	 */
+	protected $childCategories = null;
+	
+	/**
+	 * list of all parent category generations of this category
+	 * @var	array<wcf\data\category\AbstractDecoratedCategory>
+	 */
+	protected $parentCategories = null;
+	
+	/**
+	 * parent category of this category
+	 * @var	wcf\data\category\AbstractDecoratedCategory
+	 */
+	protected $parentCategory = null;
+	
+	/**
+	 * @see	wcf\data\DatabaseObjectDecorator::$baseClass
+	 */
+	protected static $baseClass = 'wcf\data\category\Category';
+	
+	/**
+	 * @see	wcf\data\category\Category::getChildCategories()
+	 */
+	public function getChildCategories() {
+		if ($this->childCategories === null) {
+			$this->childCategories = array();
+			foreach ($this->getDecoratedObject()->getChildCategories() as $category) {
+				$this->childCategories[$category->categoryID] = new static($category);
+			}
+		}
+		
+		return $this->childCategories;
+	}
+	
+	/**
+	 * @see	wcf\data\category\Category::getParentCategories()
+	 */
+	public function getParentCategories() {
+		if ($this->parentCategories === null) {
+			$this->parentCategories = array();
+			foreach ($this->getDecoratedObject()->getParentCategories() as $category) {
+				$this->parentCategories[$category->categoryID] = new static($category);
+			}
+		}
+		
+		return $this->parentCategories;
+	}
+	
+	/**
+	 * @see	wcf\data\category\Category::getParentCategory()
+	 */
+	public function getParentCategory() {
+		if ($this->parentCategoryID && $this->parentCategory === null) {
+			$this->parentCategory = new static($this->getDecoratedObject()->getParentCategory());
+		}
+		
+		return $this->parentCategory;
+	}
+	
+	/**
+	 * Returns the decorated category with the given id or null if no such
+	 * category exists.
+	 * 
+	 * @param	integer		$categoryID
+	 * @return	wcf\data\category\AbstractDecoratedCategory
+	 */
+	public static function getCategory($categoryID) {
+		$category = CategoryHandler::getInstance()->getCategory($categoryID);
+		if ($category) {
+			return new static($category);
+		}
+		
+		return null;
+	}
+}
diff --git a/wcfsetup/install/files/lib/data/category/Category.class.php b/wcfsetup/install/files/lib/data/category/Category.class.php
index cf1539fcda..2f84c8f056 100644
--- a/wcfsetup/install/files/lib/data/category/Category.class.php
+++ b/wcfsetup/install/files/lib/data/category/Category.class.php
@@ -1,7 +1,10 @@
 <?php
 namespace wcf\data\category;
+use wcf\data\IPermissionObject;
 use wcf\data\ProcessibleDatabaseObject;
 use wcf\system\category\CategoryHandler;
+use wcf\system\category\CategoryPermissionHandler;
+use wcf\system\exception\PermissionDeniedException;
 use wcf\system\request\IRouteController;
 use wcf\system\WCF;
 
@@ -15,7 +18,13 @@ use wcf\system\WCF;
  * @subpackage	data.category
  * @category	Community Framework
  */
-class Category extends ProcessibleDatabaseObject implements IRouteController {
+class Category extends ProcessibleDatabaseObject implements IPermissionObject, IRouteController {
+	/**
+	 * list of all child categories of this category
+	 * @var	array<wcf\data\category\Category>
+	 */
+	protected $childCategories = null;
+	
 	/**
 	 * list of all parent category generations of this category
 	 * @var	array<wcf\data\category\Category>
@@ -28,6 +37,12 @@ class Category extends ProcessibleDatabaseObject implements IRouteController {
 	 */
 	protected $parentCategory = null;
 	
+	/**
+	 * acl permissions for the active user of this category
+	 * @var	array<boolean>
+	 */
+	protected $permissions = null;
+	
 	/**
 	 * @see	wcf\data\DatabaseObject::$databaseTableIndexName
 	 */
@@ -64,6 +79,17 @@ class Category extends ProcessibleDatabaseObject implements IRouteController {
 		return $value;
 	}
 	
+	/**
+	 * @see	wcf\data\IPermissionObject::checkPermissions()
+	 */
+	public function checkPermissions(array $permissions) {
+		foreach ($permissions as $permission) {
+			if (!$this->getPermission($permission)) {
+				throw new PermissionDeniedException();
+			}
+		}
+	}
+	
 	/**
 	 * Returns the category object type of the category.
 	 * 
@@ -73,6 +99,19 @@ class Category extends ProcessibleDatabaseObject implements IRouteController {
 		return CategoryHandler::getInstance()->getObjectType($this->objectTypeID);
 	}
 	
+	/**
+	 * Returns the child categories of this category.
+	 * 
+	 * @return	array<wcf\data\category\Category>
+	 */
+	public function getChildCategories() {
+		if ($this->childCategories === null) {
+			$this->childCategories = CategoryHandler::getInstance()->getChildCategories($this->categoryID);
+		}
+		
+		return $this->childCategories;
+	}
+	
 	/**
 	 * Returns the parent category of this category.
 	 * 
@@ -105,6 +144,21 @@ class Category extends ProcessibleDatabaseObject implements IRouteController {
 		return $this->parentCategories;
 	}
 	
+	/**
+	 * @see	wcf\data\IPermissionObject::getPermission()
+	 */
+	public function getPermission($permission) {
+		if ($this->permissions === null) {
+			$this->permissions = CategoryPermissionHandler::getInstance()->getPermissions($this);
+		}
+		
+		if (isset($this->permissions[$permission])) {
+			return $this->permissions[$permission];
+		}
+		
+		return false;
+	}
+	
 	/**
 	 * @see	wcf\data\ITitledObject::getTitle()
 	 */
diff --git a/wcfsetup/install/files/lib/data/category/CategoryNode.class.php b/wcfsetup/install/files/lib/data/category/CategoryNode.class.php
index 4a154a3feb..cb8331ec01 100644
--- a/wcfsetup/install/files/lib/data/category/CategoryNode.class.php
+++ b/wcfsetup/install/files/lib/data/category/CategoryNode.class.php
@@ -1,8 +1,6 @@
 <?php
 namespace wcf\data\category;
-use wcf\data\DatabaseObject;
 use wcf\data\DatabaseObjectDecorator;
-use wcf\system\category\CategoryHandler;
 
 /**
  * Represents a category node.
@@ -19,19 +17,13 @@ class CategoryNode extends DatabaseObjectDecorator implements \RecursiveIterator
 	 * child category nodes
 	 * @var	array<wcf\data\category\CategoryNode>
 	 */
-	protected $childCategories = array();
+	protected $children = array();
 	
 	/**
-	 * indicates if disabled categories are included
+	 * current iterator key
 	 * @var	integer
 	 */
-	protected $includeDisabledCategories = false;
-	
-	/**
-	 * list of object type category ids of excluded categories
-	 * @var	array<integer>
-	 */
-	protected $excludedCategoryIDs = false;
+	protected $index = 0;
 	
 	/**
 	 * @see	wcf\data\DatabaseObjectDecorator::$baseClass
@@ -39,59 +31,40 @@ class CategoryNode extends DatabaseObjectDecorator implements \RecursiveIterator
 	protected static $baseClass = 'wcf\data\category\Category';
 	
 	/**
-	 * @see	wcf\data\DatabaseObjectDecorator::__construct()
+	 * Adds the given category node as child node.
+	 * 
+	 * @param	wcf\data\category\CategoryNode		$categoryNode
 	 */
-	public function __construct(DatabaseObject $object, $includeDisabledCategories = false, array $excludedCategoryIDs = array()) {
-		parent::__construct($object);
-		
-		$this->includeDisabledCategories = $includeDisabledCategories;
-		$this->excludedCategoryIDs = $excludedCategoryIDs;
-		
-		$className = get_called_class();
-		foreach (CategoryHandler::getInstance()->getChildCategories($this->getDecoratedObject()) as $category) {
-			if ($this->fulfillsConditions($category)) {
-				$this->childCategories[] = new $className($category, $includeDisabledCategories, $excludedCategoryIDs);
-			}
-		}
+	public function addChild(CategoryNode $categoryNode) {
+		$this->children[] = $categoryNode;
 	}
 	
 	/**
 	 * @see	\Countable::count()
 	 */
 	public function count() {
-		return count($this->childCategories);
+		return count($this->children);
 	}
 	
 	/**
 	 * @see	\Iterator::current()
 	 */
 	public function current() {
-		return $this->childCategories[$this->index];
-	}
-	
-	/**
-	 * Returns true if the given category fulfills all needed conditions to
-	 * be included in the list.
-	 * 
-	 * @param	wcf\data\DatabaseObject	$category
-	 * @return	boolean
-	 */
-	protected function fulfillsConditions(DatabaseObject $category) {
-		return !in_array($category->categoryID, $this->excludedCategoryIDs) && ($this->includeDisabledCategories || !$category->isDisabled);
+		return $this->children[$this->index];
 	}
 	
 	/**
 	 * @see	\RecursiveIterator::getChildren()
 	 */
 	public function getChildren() {
-		return $this->childCategories[$this->index];
+		return $this->children[$this->index];
 	}
 	
 	/**
 	 * @see	\RecursiveIterator::getChildren()
 	 */
 	public function hasChildren() {
-		return !empty($this->childCategories);
+		return !empty($this->children);
 	}
 	
 	/**
@@ -119,6 +92,6 @@ class CategoryNode extends DatabaseObjectDecorator implements \RecursiveIterator
 	 * @see	\Iterator::valid()
 	 */
 	public function valid() {
-		return isset($this->childCategories[$this->index]);
+		return isset($this->children[$this->index]);
 	}
 }
diff --git a/wcfsetup/install/files/lib/data/category/CategoryNodeList.class.php b/wcfsetup/install/files/lib/data/category/CategoryNodeList.class.php
deleted file mode 100644
index 0f2fbf3fbf..0000000000
--- a/wcfsetup/install/files/lib/data/category/CategoryNodeList.class.php
+++ /dev/null
@@ -1,84 +0,0 @@
-<?php
-namespace wcf\data\category;
-use wcf\system\category\CategoryHandler;
-use wcf\system\exception\SystemException;
-
-/**
- * Represents a category node list.
- * 
- * @author	Matthias Schmidt
- * @copyright	2001-2012 WoltLab GmbH
- * @license	GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
- * @package	com.woltlab.wcf
- * @subpackage	data.category
- * @category	Community Framework
- */
-class CategoryNodeList extends \RecursiveIteratorIterator implements \Countable {
-	/**
-	 * number of (real) category nodes in this list
-	 * @var	integer
-	 */
-	protected $count = null;
-	
-	/**
-	 * name of the category node class
-	 * @var	string
-	 */
-	protected $nodeClassName = '';
-	
-	/**
-	 * id of the parent category
-	 * @var	integer
-	 */
-	protected $parentCategoryID = 0;
-	
-	/**
-	 * Creates a new CategoryNodeList instance.
-	 * 
-	 * @param	string		$objectType
-	 * @param	integer		$parentCategoryID
-	 * @param	boolean		$includeDisabledCategories
-	 * @param	array<integer>	$excludedCategoryIDs
-	 */
-	public function __construct($objectType, $parentCategoryID = 0, $includeDisabledCategories = false, array $excludedCategoryIDs = array()) {
-		if (empty($this->nodeClassName)) {
-			$this->nodeClassName = str_replace('List', '', get_class($this));
-			if (!class_exists($this->nodeClassName)) {
-				throw new SystemException("Unknown category node class '".$this->nodeClassName."'.");
-			}
-		}
-		
-		$this->parentCategoryID = $parentCategoryID;
-		
-		// get parent category
-		if (!$this->parentCategoryID) {
-			// empty node
-			$parentCategory = new Category(null, array(
-				'categoryID' => 0,
-				'objectTypeID' => CategoryHandler::getInstance()->getObjectTypeByName($objectType)->objectTypeID
-			));
-		}
-		else {
-			$parentCategory = CategoryHandler::getInstance()->getCategory($this->parentCategoryID);
-			if ($parentCategory === null) {
-				throw new SystemException("There is no category with id '".$this->parentCategoryID."'");
-			}
-		}
-		
-		parent::__construct(new $this->nodeClassName($parentCategory, $includeDisabledCategories, $excludedCategoryIDs), \RecursiveIteratorIterator::SELF_FIRST);
-	}
-	
-	/**
-	 * @see	\Countable::count()
-	 */
-	public function count() {
-		if ($this->count === null) {
-			$this->count = 0;
-			foreach ($this as $categoryNode) {
-				$this->count++;
-			}
-		}
-		
-		return $this->count;
-	}
-}
diff --git a/wcfsetup/install/files/lib/data/category/CategoryNodeTree.class.php b/wcfsetup/install/files/lib/data/category/CategoryNodeTree.class.php
new file mode 100644
index 0000000000..50312f14f3
--- /dev/null
+++ b/wcfsetup/install/files/lib/data/category/CategoryNodeTree.class.php
@@ -0,0 +1,148 @@
+<?php
+namespace wcf\data\category;
+use wcf\system\category\CategoryHandler;
+use wcf\system\exception\SystemException;
+
+/**
+ * Represents a tree of category nodes.
+ * 
+ * @author	Matthias Schmidt
+ * @copyright	2001-2013 WoltLab GmbH
+ * @license	GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
+ * @package	com.woltlab.wcf
+ * @subpackage	data.category
+ * @category	Community Framework
+ */
+class CategoryNodeTree implements \IteratorAggregate {
+	/**
+	 * name of the category node class
+	 * @var	string
+	 */
+	protected $nodeClassName = 'wcf\data\category\CategoryNode';
+	
+	/**
+	 * id of the parent category
+	 * @var	integer
+	 */
+	protected $parentCategoryID = 0;
+	
+	/**
+	 * parent category node
+	 * @var	wcf\data\category\CategoryNode
+	 */
+	protected $parentNode = null;
+	
+	/**
+	 * Creates a new instance of CategoryNodeTree.
+	 * 
+	 * @param	string			$objectType
+	 * @param	integer			$parentCategoryID
+	 * @param	boolean			$includeDisabledCategories
+	 * @param	array<integer>		$excludedCategoryIDs
+	 */
+	public function __construct($objectType, $parentCategoryID = 0, $includeDisabledCategories = false, array $excludedCategoryIDs = array()) {
+		$this->objectType = $objectType;
+		$this->parentCategoryID = $parentCategoryID;
+		$this->includeDisabledCategories = $includeDisabledCategories;
+		$this->excludedCategoryIDs = $excludedCategoryIDs;
+		
+		// validate category object type
+		if (CategoryHandler::getInstance()->getObjectTypeByName($this->objectType) === null) {
+			throw new SystemException("Unknown category object type '".$this->objectType."'");
+		}
+	}
+	
+	/**
+	 * Builds the category node tree.
+	 */
+	protected function buildTree() {
+		$this->parentNode = $this->getNode($this->parentCategoryID);
+		$this->buildTreeLevel($this->parentNode);
+	}
+	
+	/**
+	 * Builds a certain level of the tree.
+	 * 
+	 * @param	wcf\data\category\CategoryNode	$parentNode
+	 */
+	protected function buildTreeLevel(CategoryNode $parentNode) {
+		foreach ($this->getChildCategories($parentNode) as $childCategory) {
+			$childNode = $this->getNode($childCategory->categoryID);
+			
+			if ($this->isIncluded($childNode)) {
+				$parentNode->addChild($childNode);
+				
+				// build next level
+				$this->buildTreeLevel($childNode);
+			}
+		}
+	}
+	
+	/**
+	 * Returns the category with the given id.
+	 * 
+	 * @param	integer		$categoryID
+	 * @return	wcf\data\category\Category
+	 */
+	protected function getCategory($categoryID) {
+		return CategoryHandler::getInstance()->getCategory($categoryID);
+	}
+	
+	/**
+	 * Returns the child categories of the given category node.
+	 * 
+	 * @param	wcf\data\category\CategoryNode		$parentNode
+	 * @return	array<wcf\data\category\Category>
+	 */
+	protected function getChildCategories(CategoryNode $parentNode) {
+		return CategoryHandler::getInstance()->getChildCategories($parentNode->categoryID, $parentNode->objectTypeID);
+	}
+	
+	/**
+	 * @see	\IteratorAggregate::getIterator()
+	 */
+	public function getIterator() {
+		if ($this->parentNode === null) {
+			$this->buildTree();
+		}
+		
+		return new \RecursiveIteratorIterator($this->parentNode, \RecursiveIteratorIterator::SELF_FIRST);
+	}
+	
+	/**
+	 * Returns the category node for the category with the given id.
+	 * 
+	 * @param	integer		$categoryID
+	 * @return	wcf\data\category\CategoryNode
+	 */
+	protected function getNode($categoryID) {
+		if (!$categoryID) {
+			$category = new Category(null, array(
+				'categoryID' => 0,
+				'objectTypeID' => CategoryHandler::getInstance()->getObjectTypeByName($this->objectType)->objectTypeID
+			));
+		}
+		else {
+			$category = $this->getCategory($categoryID);
+		}
+		
+		// decorate category if necessary
+		$decoratorClassName = call_user_func(array($this->nodeClassName, 'getBaseClass'));
+		if ($decoratorClassName != 'wcf\data\category\Category') {
+			$category = new $decoratorClassName($category);
+		}
+		
+		return new $this->nodeClassName($category);
+	}
+	
+	/**
+	 * Returns true if the given category node fulfils all relevant conditions
+	 * to be included in this tree.
+	 * 
+	 * @param	wcf\data\category\CategoryNode		$categoryNode
+	 * @return	boolean
+	 */
+	protected function isIncluded(CategoryNode $categoryNode) {
+		return (!$categoryNode->isDisabled || $this->includeDisabledCategories) && !in_array($categoryNode->categoryID, $this->excludedCategoryIDs);
+	}
+}
diff --git a/wcfsetup/install/files/lib/data/category/UncachedCategoryNodeTree.class.php b/wcfsetup/install/files/lib/data/category/UncachedCategoryNodeTree.class.php
new file mode 100644
index 0000000000..a7b8a69f61
--- /dev/null
+++ b/wcfsetup/install/files/lib/data/category/UncachedCategoryNodeTree.class.php
@@ -0,0 +1,67 @@
+<?php
+namespace wcf\data\category;
+use wcf\system\category\CategoryHandler;
+
+/**
+ * Represents an uncached tree of category nodes.
+ * 
+ * @author	Matthias Schmidt
+ * @copyright	2001-2013 WoltLab GmbH
+ * @license	GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
+ * @package	com.woltlab.wcf
+ * @subpackage	data.category
+ * @category	Community Framework
+ */
+class UncachedCategoryNodeTree extends CategoryNodeTree {
+	/**
+	 * locally cached categories
+	 * @var	array<wcf\data\category\Category>
+	 */
+	protected $categoryCache = array();
+	
+	/**
+	 * locally cached category ids grouped by the id of their parent category
+	 * @var	array
+	 */
+	protected $categoryStructureCache = array();
+	
+	/**
+	 * @see	wcf\data\category\CategoryNodeTree::buildTree()
+	 */
+	protected function buildTree() {
+		$categoryList = new CategoryList();
+		$categoryList->getConditionBuilder()->add('category.objectTypeID = ?', array(CategoryHandler::getInstance()->getObjectTypeByName($this->objectType)->objectTypeID));
+		$categoryList->readObjects();
+		foreach ($categoryList as $category) {
+			if (!isset($this->categoryStructureCache[$category->parentCategoryID])) {
+				$this->categoryStructureCache[$category->parentCategoryID] = array();
+			}
+			
+			$this->categoryStructureCache[$category->parentCategoryID][] = $category->categoryID;
+			$this->categoryCache[$category->categoryID] = $category;
+		}
+		
+		parent::buildTree();
+	}
+	
+	/**
+	 * @see	wcf\data\category\CategoryNodeTree::getCategory()
+	 */
+	protected function getCategory($categoryID) {
+		return $this->categoryCache[$categoryID];
+	}
+	
+	/**
+	 * @see	wcf\data\category\CategoryNodeTree::getChildCategories()
+	 */
+	protected function getChildCategories(CategoryNode $parentNode) {
+		$categories = array();
+		if (isset($this->categoryStructureCache[$parentNode->categoryID])) {
+			foreach ($this->categoryStructureCache[$parentNode->categoryID] as $categoryID) {
+				$categories[$categoryID] = $this->getCategory($categoryID);
+			}
+		}
+		
+		return $categories;
+	}
+}
diff --git a/wcfsetup/install/files/lib/data/category/ViewableCategory.class.php b/wcfsetup/install/files/lib/data/category/ViewableCategory.class.php
deleted file mode 100644
index 27a1feaa56..0000000000
--- a/wcfsetup/install/files/lib/data/category/ViewableCategory.class.php
+++ /dev/null
@@ -1,96 +0,0 @@
-<?php
-namespace wcf\data\category;
-use wcf\data\DatabaseObjectDecorator;
-use wcf\data\IPermissionObject;
-use wcf\system\category\CategoryPermissionHandler;
-use wcf\system\exception\PermissionDeniedException;
-
-/**
- * Represents a viewable category.
- * 
- * @author	Matthias Schmidt
- * @copyright	2001-2012 WoltLab GmbH
- * @license	GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
- * @package	com.woltlab.wcf
- * @subpackage	data.category
- * @category	Community Framework
- */
-class ViewableCategory extends DatabaseObjectDecorator implements IPermissionObject {
-	/**
-	 * list of all parent category generations of this category
-	 * @var	array<wcf\data\category\ViewableCategory>
-	 */
-	protected $parentCategories = null;
-	
-	/**
-	 * parent category of this category
-	 * @var	wcf\data\category\ViewableCategory
-	 */
-	protected $parentCategory = null;
-	
-	/**
-	 * @see	wcf\data\DatabaseObjectDecorator::$baseClass
-	 */
-	protected static $baseClass = 'wcf\data\category\Category';
-	
-	/**
-	 * acl permissions for the active user of this category
-	 * @var	array<boolean>
-	 */
-	protected $permissions = null;
-	
-	/**
-	 * @see	wcf\data\IPermissionObject::checkPermissions()
-	 */
-	public function checkPermissions(array $permissions) {
-		foreach ($permissions as $permission) {
-			if (!$this->getPermission($permission)) {
-				throw new PermissionDeniedException();
-			}
-		}
-	}
-	
-	/**
-	 * @see	wcf\data\category\Category::getParentCategories()
-	 */
-	public function getParentCategories() {
-		if ($this->parentCategories === null) {
-			$this->parentCategories = array();
-			$className = get_class($this);
-			
-			foreach ($this->getDecoratedObject()->getParentCategories() as $category) {
-				$this->parentCategories[$category->categoryID] = new $className($category);
-			}
-		}
-		
-		return $this->parentCategories;
-	}
-	
-	/**
-	 * @see	wcf\data\category\Category::getParentCategory()
-	 */
-	public function getParentCategory() {
-		if ($this->parentCategoryID && $this->parentCategory === null) {
-			$className = get_class($this);
-			
-			$this->parentCategory = new $className($this->getDecoratedObject()->getParentCategory());
-		}
-		
-		return $this->parentCategory;
-	}
-	
-	/**
-	 * @see	wcf\data\IPermissionObject::getPermission()
-	 */
-	public function getPermission($permission) {
-		if ($this->permissions === null) {
-			$this->permissions = CategoryPermissionHandler::getInstance()->getPermissions($this->getDecoratedObject());
-		}
-		
-		if (isset($this->permissions[$permission])) {
-			return $this->permissions[$permission];
-		}
-		
-		return false;
-	}
-}
diff --git a/wcfsetup/install/files/lib/data/category/ViewableCategoryNode.class.php b/wcfsetup/install/files/lib/data/category/ViewableCategoryNode.class.php
deleted file mode 100644
index 0727611635..0000000000
--- a/wcfsetup/install/files/lib/data/category/ViewableCategoryNode.class.php
+++ /dev/null
@@ -1,31 +0,0 @@
-<?php
-namespace wcf\data\category;
-use wcf\data\DatabaseObject;
-
-/**
- * Represents a viewable category node.
- * 
- * @author	Matthias Schmidt
- * @copyright	2001-2012 WoltLab GmbH
- * @license	GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
- * @package	com.woltlab.wcf
- * @subpackage	data.category
- * @category	Community Framework
- */
-class ViewableCategoryNode extends CategoryNode {
-	/**
-	 * @see	wcf\data\DatabaseObjectDecorator::$baseClass
-	 */
-	protected static $baseClass = 'wcf\data\category\ViewableCategory';
-	
-	/**
-	 * @see	wcf\data\DatabaseObjectDecorator::__construct()
-	 */
-	public function __construct(DatabaseObject $object, $includeDisabledCategories = false, array $excludedCategoryIDs = array()) {
-		if (!($object instanceof static::$baseClass)) {
-			$object = new static::$baseClass($object);
-		}
-		
-		parent::__construct($object, $includeDisabledCategories, $excludedCategoryIDs);
-	}
-}
diff --git a/wcfsetup/install/files/lib/data/category/ViewableCategoryNodeList.class.php b/wcfsetup/install/files/lib/data/category/ViewableCategoryNodeList.class.php
deleted file mode 100644
index deee714614..0000000000
--- a/wcfsetup/install/files/lib/data/category/ViewableCategoryNodeList.class.php
+++ /dev/null
@@ -1,14 +0,0 @@
-<?php
-namespace wcf\data\category;
-
-/**
- * Represents a list of viewable category nodes.
- * 
- * @author	Matthias Schmidt
- * @copyright	2001-2013 WoltLab GmbH
- * @license	GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
- * @package	com.woltlab.wcf
- * @subpackage	data.category
- * @category	Community Framework
- */
-class ViewableCategoryNodeList extends CategoryNodeList { }
diff --git a/wcfsetup/install/files/lib/system/category/AbstractCategoryType.class.php b/wcfsetup/install/files/lib/system/category/AbstractCategoryType.class.php
index 4889d09a96..bcae5d6db1 100644
--- a/wcfsetup/install/files/lib/system/category/AbstractCategoryType.class.php
+++ b/wcfsetup/install/files/lib/system/category/AbstractCategoryType.class.php
@@ -63,7 +63,7 @@ abstract class AbstractCategoryType extends SingletonFactory implements ICategor
 	 * @see	wcf\system\category\ICategoryType::afterDeletion()
 	 */
 	public function afterDeletion(CategoryEditor $categoryEditor) {
-		$categoryIDs = array_keys(CategoryHandler::getInstance()->getChildCategories($categoryEditor->getDecoratedObject()));
+		$categoryIDs = array_keys(CategoryHandler::getInstance()->getChildCategories($categoryEditor->categoryID));
 		
 		if (!empty($categoryIDs)) {
 			// move child categories to parent category
diff --git a/wcfsetup/install/files/lib/system/category/CategoryHandler.class.php b/wcfsetup/install/files/lib/system/category/CategoryHandler.class.php
index 6e76794a59..64d718e9ba 100644
--- a/wcfsetup/install/files/lib/system/category/CategoryHandler.class.php
+++ b/wcfsetup/install/files/lib/system/category/CategoryHandler.class.php
@@ -1,9 +1,6 @@
 <?php
 namespace wcf\system\category;
-use wcf\data\category\Category;
 use wcf\data\object\type\ObjectTypeCache;
-use wcf\data\DatabaseObject;
-use wcf\data\DatabaseObjectDecorator;
 use wcf\system\cache\builder\CategoryCacheBuilder;
 use wcf\system\exception\SystemException;
 use wcf\system\SingletonFactory;
@@ -81,20 +78,23 @@ class CategoryHandler extends SingletonFactory {
 	}
 	
 	/**
-	 * Returns the child categories of the given category.
+	 * Returns the child categories of the category with the given id.
 	 * 
-	 * @param	wcf\data\DatabaseObject		$category
+	 * The second parameter is only needed if $categoryID is 0.
+	 * 
+	 * @param	integer		$categoryID
+	 * @param	integer		$objectTypeID
 	 * @return	array<wcf\data\category\Category>
 	 */
-	public function getChildCategories(DatabaseObject $category) {
-		if (!($category instanceof Category) && (!($category instanceof DatabaseObjectDecorator) || !($category->getDecoratedObject() instanceof Category))) {
-			throw new SystemException("Invalid object given (class: ".get_class($category).")");
+	public function getChildCategories($categoryID, $objectTypeID = null) {
+		if (!$categoryID && $objectTypeID === null) {
+			throw new SystemException("Missing object type id");
 		}
 		
 		$categories = array();
-		foreach ($this->categories as $__category) {
-			if ($__category->parentCategoryID == $category->categoryID && ($category->categoryID || $category->objectTypeID == $__category->objectTypeID)) {
-				$categories[$__category->categoryID] = $__category;
+		foreach ($this->categories as $category) {
+			if ($category->parentCategoryID == $categoryID && ($categoryID || $category->objectTypeID == $objectTypeID)) {
+				$categories[$category->categoryID] = $category;
 			}
 		}
 		
-- 
2.20.1