Mini Shell

"""Switchboard class.

This class is used to coordinate updates among all Viewers.  Every Viewer must
conform to the following interface:

    - it must include a method called update_yourself() which takes three
      arguments; the red, green, and blue values of the selected color.

    - When a Viewer selects a color and wishes to update all other Views, it
      should call update_views() on the Switchboard object.  Note that the
      Viewer typically does *not* update itself before calling update_views(),
      since this would cause it to get updated twice.

Optionally, Viewers can also implement:

    - save_options() which takes an optiondb (a dictionary).  Store into this
      dictionary any values the Viewer wants to save in the persistent
      ~/.pynche file.  This dictionary is saved using marshal.  The namespace
      for the keys is ad-hoc; make sure you don't clobber some other Viewer's
      keys!

    - withdraw() which takes no arguments.  This is called when Pynche is
      unmapped.  All Viewers should implement this.

    - colordb_changed() which takes a single argument, an instance of
      ColorDB.  This is called whenever the color name database is changed and
      gives a chance for the Viewers to do something on those events.  See
      ListViewer for details.

External Viewers are found dynamically.  Viewer modules should have names such
as FooViewer.py.  If such a named module has a module global variable called
ADDTOVIEW and this variable is true, the Viewer will be added dynamically to
the `View' menu.  ADDTOVIEW contains a string which is used as the menu item
to display the Viewer (one kludge: if the string contains a `%', this is used
to indicate that the next character will get an underline in the menu,
otherwise the first character is underlined).

FooViewer.py should contain a class called FooViewer, and its constructor
should take two arguments, an instance of Switchboard, and optionally a Tk
master window.

"""

import sys
from types import DictType
import marshal



class Switchboard:
    def __init__(self, initfile):
        self.__initfile = initfile
        self.__colordb = None
        self.__optiondb = {}
        self.__views = []
        self.__red = 0
        self.__green = 0
        self.__blue = 0
        self.__canceled = 0
        # read the initialization file
        fp = None
        if initfile:
            try:
                try:
                    fp = open(initfile)
                    self.__optiondb = marshal.load(fp)
                    if not isinstance(self.__optiondb, DictType):
                        print >> sys.stderr, \
                              'Problem reading options from file:', initfile
                        self.__optiondb = {}
                except (IOError, EOFError, ValueError):
                    pass
            finally:
                if fp:
                    fp.close()

    def add_view(self, view):
        self.__views.append(view)

    def update_views(self, red, green, blue):
        self.__red = red
        self.__green = green
        self.__blue = blue
        for v in self.__views:
            v.update_yourself(red, green, blue)

    def update_views_current(self):
        self.update_views(self.__red, self.__green, self.__blue)

    def current_rgb(self):
        return self.__red, self.__green, self.__blue

    def colordb(self):
        return self.__colordb

    def set_colordb(self, colordb):
        self.__colordb = colordb
        for v in self.__views:
            if hasattr(v, 'colordb_changed'):
                v.colordb_changed(colordb)
        self.update_views_current()

    def optiondb(self):
        return self.__optiondb

    def save_views(self):
        # save the current color
        self.__optiondb['RED'] = self.__red
        self.__optiondb['GREEN'] = self.__green
        self.__optiondb['BLUE'] = self.__blue
        for v in self.__views:
            if hasattr(v, 'save_options'):
                v.save_options(self.__optiondb)
        # save the name of the file used for the color database.  we'll try to
        # load this first.
        self.__optiondb['DBFILE'] = self.__colordb.filename()
        fp = None
        try:
            try:
                fp = open(self.__initfile, 'w')
            except IOError:
                print >> sys.stderr, 'Cannot write options to file:', \
                      self.__initfile
            else:
                marshal.dump(self.__optiondb, fp)
        finally:
            if fp:
                fp.close()

    def withdraw_views(self):
        for v in self.__views:
            if hasattr(v, 'withdraw'):
                v.withdraw()

    def canceled(self, flag=1):
        self.__canceled = flag

    def canceled_p(self):
        return self.__canceled