From 6a2490005cfb45df719a6715d09e414dbb4a54a4 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Mon, 5 Jan 2015 10:46:18 +0530
Subject: [PATCH] ...

---
 src/calibre/gui2/tweak_book/editor/__init__.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/calibre/gui2/tweak_book/editor/__init__.py b/src/calibre/gui2/tweak_book/editor/__init__.py
index d461cc9f4e..18c9ca3359 100644
--- a/src/calibre/gui2/tweak_book/editor/__init__.py
+++ b/src/calibre/gui2/tweak_book/editor/__init__.py
@@ -29,8 +29,10 @@ def syntax_from_mime(name, mime):
     if mime.endswith('+xml'):
         return 'xml'
 
+all_text_syntaxes = frozenset({'text', 'html', 'xml', 'css', 'javascript'})
+
 def editor_from_syntax(syntax, parent=None):
-    if syntax in {'text', 'html', 'css', 'xml', 'javascript'}:
+    if syntax in all_text_syntaxes:
         from calibre.gui2.tweak_book.editor.widget import Editor
         return Editor(syntax, parent=parent)
     elif syntax == 'raster_image':