diff --git a/src/calibre/gui2/dialogs/template_dialog.py b/src/calibre/gui2/dialogs/template_dialog.py
index 60d4025ef9..62accdc842 100644
--- a/src/calibre/gui2/dialogs/template_dialog.py
+++ b/src/calibre/gui2/dialogs/template_dialog.py
@@ -3,8 +3,11 @@ __copyright__ = '2008, Kovid Goyal kovid@kovidgoyal.net'
 __docformat__ = 'restructuredtext en'
 __license__   = 'GPL v3'
 
+import json
+
 from PyQt4.Qt import Qt, QDialog, QDialogButtonBox
 from calibre.gui2.dialogs.template_dialog_ui import Ui_TemplateDialog
+from calibre.utils.formatter_functions import formatter_functions
 
 class TemplateDialog(QDialog, Ui_TemplateDialog):
 
@@ -17,9 +20,44 @@ class TemplateDialog(QDialog, Ui_TemplateDialog):
         self.setWindowFlags(self.windowFlags()&(~Qt.WindowContextHelpButtonHint))
         self.setWindowIcon(icon)
 
+        self.textbox.setTabStopWidth(10)
+        self.source_code.setTabStopWidth(10)
+        self.documentation.setReadOnly(True)
+        self.source_code.setReadOnly(True)
+
         if text is not None:
             self.textbox.setPlainText(text)
-        self.textbox.setTabStopWidth(50)
         self.buttonBox.button(QDialogButtonBox.Ok).setText(_('&OK'))
         self.buttonBox.button(QDialogButtonBox.Cancel).setText(_('&Cancel'))
 
+        try:
+            with open(P('template-functions.json'), 'rb') as f:
+                self.builtin_source_dict = json.load(f, encoding='utf-8')
+        except:
+            self.builtin_source_dict = {}
+
+        self.funcs = formatter_functions.get_functions()
+        self.builtins = formatter_functions.get_builtins()
+
+        func_names = sorted(self.funcs)
+        self.function.clear()
+        self.function.addItem('')
+        self.function.addItems(func_names)
+        self.function.setCurrentIndex(0)
+        self.function.currentIndexChanged[str].connect(self.function_changed)
+
+        print self.textbox.tabStopWidth()
+        print self.source_code.tabStopWidth()
+
+    def function_changed(self, toWhat):
+        name = unicode(toWhat)
+        self.source_code.clear()
+        self.documentation.clear()
+        if name in self.funcs:
+            self.documentation.setPlainText(self.funcs[name].doc)
+            if name in self.builtins:
+                if name in self.builtin_source_dict:
+                    self.source_code.setPlainText(self.builtin_source_dict[name])
+            else:
+                self.source_code.setPlainText(self.funcs[name].program_text)
+
diff --git a/src/calibre/gui2/dialogs/template_dialog.ui b/src/calibre/gui2/dialogs/template_dialog.ui
index a30d6ef273..e1980a8397 100644
--- a/src/calibre/gui2/dialogs/template_dialog.ui
+++ b/src/calibre/gui2/dialogs/template_dialog.ui
@@ -6,8 +6,8 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>500</width>
-    <height>235</height>
+    <width>588</width>
+    <height>546</height>
    </rect>
   </property>
   <property name="sizePolicy">
@@ -19,21 +19,68 @@
   <property name="windowTitle">
    <string>Edit Comments</string>
   </property>
-   <layout class="QVBoxLayout" name="verticalLayout">
-    <item>
-     <widget class="QPlainTextEdit" name="textbox"/>
-    </item>
-    <item>
-     <widget class="QDialogButtonBox" name="buttonBox">
-      <property name="orientation">
-       <enum>Qt::Horizontal</enum>
-      </property>
-      <property name="standardButtons">
-       <set>QDialogButtonBox::Cancel|QDialogButtonBox::Ok</set>
-      </property>
-     </widget>
-    </item>
-   </layout>
+  <layout class="QVBoxLayout" name="verticalLayout">
+   <item>
+    <widget class="QPlainTextEdit" name="textbox"/>
+   </item>
+   <item>
+    <widget class="QDialogButtonBox" name="buttonBox">
+     <property name="orientation">
+      <enum>Qt::Horizontal</enum>
+     </property>
+     <property name="standardButtons">
+      <set>QDialogButtonBox::Cancel|QDialogButtonBox::Ok</set>
+     </property>
+    </widget>
+   </item>
+   <item>
+    <layout class="QGridLayout" name="gridLayout">
+     <item row="0" column="0">
+      <widget class="QLabel" name="label">
+       <property name="text">
+        <string>Function name:</string>
+       </property>
+      </widget>
+     </item>
+     <item row="0" column="1">
+      <widget class="QComboBox" name="function"/>
+     </item>
+     <item row="1" column="0">
+      <widget class="QLabel" name="label_2">
+       <property name="text">
+        <string>Documentation:</string>
+       </property>
+       <property name="alignment">
+        <set>Qt::AlignLeading|Qt::AlignLeft|Qt::AlignTop</set>
+       </property>
+      </widget>
+     </item>
+     <item row="2" column="0">
+      <widget class="QLabel" name="label_3">
+       <property name="text">
+        <string>Python code:</string>
+       </property>
+       <property name="alignment">
+        <set>Qt::AlignLeading|Qt::AlignLeft|Qt::AlignTop</set>
+       </property>
+      </widget>
+     </item>
+     <item row="1" column="1">
+      <widget class="QPlainTextEdit" name="documentation">
+       <property name="maximumSize">
+        <size>
+         <width>16777215</width>
+         <height>75</height>
+        </size>
+       </property>
+      </widget>
+     </item>
+     <item row="2" column="1">
+      <widget class="QPlainTextEdit" name="source_code"/>
+     </item>
+    </layout>
+   </item>
+  </layout>
  </widget>
  <resources/>
  <connections>