FontSelect: A Tkinter widget to select fonts

The constructor for a class that inherits from Frame is pretty stereotyped: call the parent class's constructor, then create the widgets.

    def __init__ ( self, master=None, font=None, listCount=None,
                   observer=None ):
        """Constructor for the FontSelect widget.
        """

        #-- 1 --
        # [ master  :=  master with a new Frame widget added
        #   self    :=  that Frame ]
        Frame.__init__ ( self, master, relief=RIDGE,
                         borderwidth=4 )

We export the usual font for controls as the .regularFont attribute.

        #-- 2 --
        self.regularFont  =  tkFont.Font (
            family="new century schoolbook", size="13" )

Next, we process the various constructor arguments. If a font was passed in, we store it in self.listFont; the default value is the regular font.

        #-- 3 --
        # [ if font is None ->
        #     self.listFont  :=  self.regularFont
        #   else ->
        #     self.listFont  :=  font ]
        self.listFont   =  font or self.regularFont

        #-- 4 --
        # [ if listCount is None ->
        #     self.__listCount  :=  LISTBOX_HEIGHT
        #   else ->
        #     self.__listCount  :=  listCount ]
        self.__listCount  =  listCount or LISTBOX_HEIGHT

If an observer function was passed in, put it in self.__observerList.

        #-- 5 --
        # [ if observer is not None ->
        #     self.__observerList  :=  [ observer ]
        #   else ->
        #     self.__observerList  :=  an empty list ]
        self.__observerList  =  []
        if  observer:
            self.__observerList.append ( observer )

For widget creation, see Section 5.3, “FontSelect.__createWidgets(): Widget placement”.

        #-- 6 --
        # [ self  :=  self with all widgets and control linkages ]
        self.__createWidgets()