Patch #764217: Add nametofont function, exists parameter.

Lib/lib-tk/tkFont.py

@@ -25,6 +25,11 @@ ROMAN = "roman"
 BOLD   = "bold"
 ITALIC = "italic"
 
+def nametofont(name):
+    """Given the name of a tk named font, returns a Font representation.
+    """
+    return Font(name=name, exists=True)
+    
 class Font:
 
     """Represents a named font.
@@ -32,8 +37,12 @@ class Font:
     Constructor options are:
 
     font -- font specifier (name, system font, or (family, size, style)-tuple)
+    name -- name to use for this font configuration (defaults to a unique name)
+    exists -- does a named font by this name already exist?
+       Creates a new named font if False, points to the existing font if True.
+       Raises _tkinter.TclError if the assertion is false.
 
-       or any combination of
+       the following are ignored if font is specified:
 
     family -- font 'family', e.g. Courier, Times, Helvetica
     size -- font size in points
@@ -41,7 +50,7 @@ class Font:
     slant -- font slant: ROMAN, ITALIC
     underline -- font underlining: false (0), true (1)
     overstrike -- font strikeout: false (0), true (1)
-    name -- name to use for this font configuration (defaults to a unique name)
+        
     """
 
     def _set(self, kw):
@@ -63,7 +72,7 @@ class Font:
             options[args[i][1:]] = args[i+1]
         return options
 
-    def __init__(self, root=None, font=None, name=None, **options):
+    def __init__(self, root=None, font=None, name=None, exists=False, **options):
         if not root:
             root = Tkinter._default_root
         if font:
@@ -74,7 +83,20 @@ class Font:
         if not name:
             name = "font" + str(id(self))
         self.name = name
-        root.tk.call("font", "create", name, *font)
+
+        if exists:
+            self.delete_font = False
+            # confirm font exists
+            if self.name not in root.tk.call("font", "names"):
+                raise Tkinter._tkinter.TclError, "named font %s does not already exist" % (self.name,)
+            # if font config info supplied, apply it
+            if font:
+            	print "font=%r" % font
+                root.tk.call("font", "configure", self.name, *font)
+        else:
+            # create new font (raises TclError if the font exists)
+            root.tk.call("font", "create", self.name, *font) 
+            self.delete_font = True
         # backlinks!
         self._root  = root
         self._split = root.tk.splitlist
@@ -83,12 +105,22 @@ class Font:
     def __str__(self):
         return self.name
 
+    def __eq__(self, other):
+        return self.name == other.name and isinstance(other, Font)
+
+    def __getitem__(self, key):
+        return self.cget(key)
+
+    def __setitem__(self, key, value):
+        self.configure(**{key: value})
+
     def __del__(self):
         try:
-            self._call("font", "delete", self.name)
+            if self.delete_font:
+                self._call("font", "delete", self.name)
         except (AttributeError, Tkinter.TclError):
             pass
-
+  
     def copy(self):
         "Return a distinct copy of the current font"
         return Font(self._root, **self.actual())

Misc/NEWS

@@ -44,6 +44,11 @@ Extension modules
 Library
 -------
 
+- A new function tkFont.nametofont was added to return an existing
+  font. The Font class constructor now has an additional exists argument
+  which, if True, requests to return/configure an existing font, rather
+  than creating a new one. 
+
 - Updated the decimal package's min() and max() methods to match the
   latest revision of the General Decimal Arithmetic Specification.
   Quiet NaNs are ignored and equal values are sorted based on sign