hook up latex tools config to global instance

instead of instantiation on shell init

- removes unnecessary instantiation of unused object
- fixes config loading in qtconsole

IPython/core/interactiveshell.py

@@ -54,7 +54,6 b' from IPython.core.prefilter import PrefilterManager'
 from IPython.core.profiledir import ProfileDir
 from IPython.core.prompts import PromptManager
 from IPython.core.usage import default_banner
-from IPython.lib.latextools import LaTeXTool
 from IPython.testing.skipdoctest import skip_doctest
 from IPython.utils import PyColorize
 from IPython.utils import io
@@ -521,7 +520,6 b' class InteractiveShell(SingletonConfigurable):'
         self.init_display_pub()
         self.init_data_pub()
         self.init_displayhook()
-        self.init_latextool()
         self.init_magics()
         self.init_alias()
         self.init_logstart()
@@ -715,12 +713,6 b' class InteractiveShell(SingletonConfigurable):'
         # the appropriate time.
         self.display_trap = DisplayTrap(hook=self.displayhook)
 
-    def init_latextool(self):
-        """Configure LaTeXTool."""
-        cfg = LaTeXTool.instance(parent=self)
-        if cfg not in self.configurables:
-            self.configurables.append(cfg)
-
     def init_virtualenv(self):
         """Add a virtualenv to sys.path so the user can import modules from it.
         This isn't perfect: it doesn't use the Python interpreter with which the

IPython/lib/latextools.py

@@ -12,7 +12,7 b' import shutil'
 import subprocess
 
 from IPython.utils.process import find_cmd, FindCmdError
-from IPython.config.application import Application
+from IPython.config import get_config
 from IPython.config.configurable import SingletonConfigurable
 from IPython.utils.traitlets import List, Bool, Unicode
 from IPython.utils.py3compat import cast_unicode, cast_unicode_py2 as u
@@ -20,7 +20,9 b' from IPython.utils.py3compat import cast_unicode, cast_unicode_py2 as u'
 
 class LaTeXTool(SingletonConfigurable):
     """An object to store configuration of the LaTeX tool."""
-
+    def _config_default(self):
+        return get_config()
+    
     backends = List(
         Unicode, ["matplotlib", "dvipng"],
         help="Preferred backend to draw LaTeX math equations. "
@@ -93,11 +95,12 b' def latex_to_png_mpl(s, wrap):'
         from matplotlib import mathtext
     except ImportError:
         return None
-
+    
     # mpl mathtext doesn't support display math, force inline
     s = s.replace('$$', '$')
     if wrap:
         s = u'${0}$'.format(s)
+    
     mt = mathtext.MathTextParser('bitmap')
     f = BytesIO()
     mt.to_png(f, s, fontsize=12)