diff -r 6c2b4b5c2cf4 Lib/idlelib/CodeContext.py
--- a/Lib/idlelib/CodeContext.py	Mon Apr 29 01:17:54 2013 +0530
+++ b/Lib/idlelib/CodeContext.py	Mon Apr 29 02:10:50 2013 +0530
@@ -50,7 +50,7 @@
             self.editwin.setvar('<<toggle-code-context>>', True)
         # Start two update cycles, one for context lines, one for font changes.
         self.text.after(UPDATEINTERVAL, self.timer_event)
-        self.text.after(FONTUPDATEINTERVAL, self.font_timer_event)
+	self.font_timer_event()
 
     def toggle_code_context_event(self, event=None):
         if not self.label:
@@ -173,4 +173,4 @@
         if self.label and newtextfont != self.textfont:
             self.textfont = newtextfont
             self.label["font"] = self.textfont
-        self.text.after(FONTUPDATEINTERVAL, self.font_timer_event)
+
diff -r 6c2b4b5c2cf4 Lib/idlelib/ZoomFont.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Lib/idlelib/ZoomFont.py	Mon Apr 29 02:10:50 2013 +0530
@@ -0,0 +1,134 @@
+# Python 2/3 compatibility
+import sys
+if sys.version < '3':
+    import Tkinter as tk
+    import tkFont
+else:
+    import tkinter as tk
+    import tkinter.font as tkFont
+
+
+# get the IDLE configuration handler
+from idlelib.configHandler import idleConf
+
+from pprint import pprint
+
+def printit(func):
+    def f(*args, **kw):
+        return func(*args, **kw)
+    return f
+
+
+
+jn = lambda x,y: '%i.%i' % (x,y)        # join integers to text coordinates
+sp = lambda x: list(map(int, x.split('.')))   # convert tkinter Text coordinate to a line and column tuple
+
+class ZoomFont:   # must be the same name as the file for EditorWindow.py
+                    # to load it.
+
+    menudefs = [
+        ('options', [
+                None,
+               ('Increase Font Size', '<<zoomfont-increase>>'),
+               ('Default Font Size', '<<zoomfont-default>>'),
+               ('Decrease Font Size', '<<zoomfont-decrease>>'),
+       ]),]
+
+    def __init__(self, editwin):
+        self.editwin = editwin      # reference to the editor window
+        self.text = text = self.editwin.text
+        self.text.bind('<Control-4>', self.zoomfont_increase_event)
+        self.text.bind('<Control-5>', self.zoomfont_decrease_event)
+        self.text.bind('<Control-KeyRelease>', self.control_release, '+')
+        self.text.bind('<Control-Key-0>', self.zoomfont_default_event)
+        self._ratio = 0
+        self._zero_pause = False
+        self._pause_id = None
+
+    def set_font(self, fontSize=0):
+        if fontSize:
+            idleConf.userCfg['main'].SetOption('EditorWindow','font-size',
+                                            str(fontSize))
+        else:
+            #set to default
+            idleConf.userCfg['main'].RemoveOption('EditorWindow','font-size')
+
+        winInstances = self.editwin.top.instance_dict.keys()
+        for instance in winInstances:
+            instance.ResetFont()
+            # This is a hack to work with LineNumbers and CodeContext
+            C = instance.extensions.get('CodeContext', None)
+            if C:
+                C.font_timer_event()
+            L = self.editwin.extensions.get('LineNumbers', None)
+            if L:
+                L.adjust_font() 
+        return 
+
+    def store_cursor(self, event):
+        x, y = event.x, event.y
+        text = self.text
+        line, col = sp(text.index('@%d,%d' % (x,y)))
+        top, bot = self.editwin.getwindowlines()
+        self._store = (line, top, bot)
+
+    def restore_cursor(self):
+        line, top, bot = self._store
+        new_top, new_bot = self.editwin.getwindowlines()
+        new_h = max([new_bot - new_top - 1, 1])
+
+        h = max([bot - top, 1])
+
+        ratio = (line - top) / (1.0 * h)
+        top2 = int(line - new_h * ratio)
+        top2 = max([top2, 0])
+
+        self.text.yview(jn(top2, 0))
+
+    def cursor(func):
+        # Decorator function for handling yview
+        def f(self, event):
+            if self._zero_pause:
+                self.pause_at_default()
+                return "break"
+            self.store_cursor(event)
+            ret = func(self, event)
+            self.restore_cursor()
+            return ret
+        return f
+
+    @cursor
+    def zoomfont_increase_event(self, event=None):
+        fontSize=int(idleConf.GetOption('main', 'EditorWindow', 'font-size',
+                                    type='int', default='10'))
+        if fontSize<22:
+            self.set_font(fontSize+1)
+        return "break"
+
+    @cursor
+    def zoomfont_decrease_event(self, event=None):
+        fontSize=int(idleConf.GetOption('main', 'EditorWindow', 'font-size',
+                                    type='int', default='10'))
+        if fontSize>7:
+            self.set_font(fontSize-1)
+        return "break"
+
+    @cursor
+    def zoomfont_default_event(self, event=None):
+        if idleConf.defaultCfg['main'].has_option('EditorWindow','font-size'):
+            self.set_font(0)
+        return "break"
+
+    def control_release(self, event=None):
+        self._zero_pause = False
+
+    def pause_at_default(self, event=None):
+        self._zero_pause = True
+        if self._pause_id:
+            self.text.after_cancel(self._pause_id)
+
+        def unpause():
+            self._zero_pause = False
+
+        self._pause_id = self.text.after(250, unpause)
+
diff -r 6c2b4b5c2cf4 Lib/idlelib/config-extensions.def
--- a/Lib/idlelib/config-extensions.def	Mon Apr 29 01:17:54 2013 +0530
+++ b/Lib/idlelib/config-extensions.def	Mon Apr 29 02:10:50 2013 +0530
@@ -94,3 +94,13 @@
 enable_shell=0
 enable_editor=1
 
+[ZoomFont]
+enable=1
+enable_editor=1
+enable_shell=1
+
+[ZoomFont_cfgBindings]
+zoomfont-default=<Control-Key-0> <Control-Shift-Key-0>
+zoomfont-increase=<Control-Key-plus> <Control-Key-equal> <Control-Shift-Key-equal> <Control-Shift-Key-plus>
+zoomfont-decrease=<Control-Key-minus> <Control-Shift-Key-minus>
+
diff -r 6c2b4b5c2cf4 Lib/idlelib/configDialog.py
--- a/Lib/idlelib/configDialog.py	Mon Apr 29 01:17:54 2013 +0530
+++ b/Lib/idlelib/configDialog.py	Mon Apr 29 02:10:50 2013 +0530
@@ -1122,6 +1122,12 @@
             instance.set_notabs_indentwidth()
             instance.ApplyKeybindings()
             instance.reset_help_menu_entries()
+            C = instance.extensions.get('CodeContext', None)
+            if C:
+                C.font_timer_event()
+            L = instance.extensions.get('LineNumbers', None)
+            if L:
+                L.adjust_font() 
 
     def Cancel(self):
         self.destroy()