Lib/idlelib/configdialog.py

"""IDLE Configuration Dialog: support user customization of IDLE by GUI

Customize font faces, sizes, and colorization attributes.  Set indentation
defaults.  Customize keybindings.  Colorization and keybindings can be
saved as user defined sets.  Select startup options including shell/editor
and default window size.  Define additional help sources.

Note that tab width in IDLE is currently fixed at eight due to Tk issues.
Refer to comments in EditorWindow autoindent code for details.

"""
from tkinter import (Toplevel, Frame, LabelFrame, Listbox, Label, Button,
                     Entry, Text, Scale, Radiobutton, Checkbutton, Canvas,
                     StringVar, BooleanVar, IntVar, TRUE, FALSE,
                     TOP, BOTTOM, RIGHT, LEFT, SOLID, GROOVE, NORMAL, DISABLED,
                     NONE, BOTH, X, Y, W, E, EW, NS, NSEW, NW,
                     HORIZONTAL, VERTICAL, ANCHOR, ACTIVE, END)
from tkinter.ttk import Notebook, Scrollbar
import tkinter.colorchooser as tkColorChooser
import tkinter.font as tkFont
import tkinter.messagebox as tkMessageBox

from idlelib.config import idleConf, ConfigChanges
from idlelib.config_key import GetKeysDialog
from idlelib.dynoption import DynOptionMenu
from idlelib import macosx
from idlelib.query import SectionName, HelpSource
from idlelib.tabbedpages import TabbedPageSet
from idlelib.textview import view_text

changes = ConfigChanges()


class ConfigDialog(Toplevel):
    """Config dialog for IDLE.
    """

    def __init__(self, parent, title='', _htest=False, _utest=False):
        """Show the tabbed dialog for user configuration.

        Args:
            parent - parent of this dialog
            title - string which is the title of this popup dialog
            _htest - bool, change box location when running htest
            _utest - bool, don't wait_window when running unittest

        Note: Focus set on font page fontlist.

        Methods:
            create_widgets
            cancel: Bound to DELETE_WINDOW protocol.
        """
        Toplevel.__init__(self, parent)
        self.parent = parent
        if _htest:
            parent.instance_dict = {}
        if not _utest:
            self.withdraw()

        self.configure(borderwidth=5)
        self.title(title or 'IDLE Preferences')
        x = parent.winfo_rootx() + 20
        y = parent.winfo_rooty() + (30 if not _htest else 150)
        self.geometry(f'+{x}+{y}')
        # Each theme element key is its display name.
        # The first value of the tuple is the sample area tag name.
        # The second value is the display name list sort index.
        self.create_widgets()
        self.resizable(height=FALSE, width=FALSE)
        self.transient(parent)
        self.protocol("WM_DELETE_WINDOW", self.cancel)
        self.fontpage.fontlist.focus_set()
        # XXX Decide whether to keep or delete these key bindings.
        # Key bindings for this dialog.
        # self.bind('<Escape>', self.Cancel) #dismiss dialog, no save
        # self.bind('<Alt-a>', self.Apply) #apply changes, save
        # self.bind('<F1>', self.Help) #context help
        self.load_configs()
        # Avoid callbacks during load_configs.
        tracers.attach()

        if not _utest:
            self.grab_set()
            self.wm_deiconify()
            self.wait_window()


    def create_widgets(self):
        """Create and place widgets for tabbed dialog.

        Widgets Bound to self:
            tab_pages: TabbedPageSet

        Methods:
            create_page_font_tab
            create_page_highlight
            create_page_keys
            create_page_general
            create_page_extensions
            create_action_buttons
            load_configs: Load pages except for extensions.
            activate_config_changes: Tell editors to reload.
        """
        self.note = note = Notebook(self, width=450, height=450)
        self.highpage = self.create_page_highlight()
        self.fontpage = FontPage(note, self.highpage)
        self.keyspage = self.create_page_keys()
        self.genpage = self.create_page_general()
        self.extpage = self.create_page_extensions()
        note.add(self.fontpage, text='Fonts/Tabs')
        note.add(self.highpage, text='Highlights')
        note.add(self.keyspage, text=' Keys ')
        note.add(self.genpage, text=' General ')
        note.add(self.extpage, text='Extensions')
        note.enable_traversal()
        note.pack(side=TOP, expand=TRUE, fill=BOTH)
        self.create_action_buttons().pack(side=BOTTOM)

    def load_configs(self):
        """Load configuration for each page.

        Load configuration from default and user config files and populate
        the widgets on the config dialog pages.

        Methods:
            load_font_cfg
            load_tab_cfg
            load_theme_cfg
            load_key_cfg
            load_general_cfg
        """
        #self.load_font_cfg()
        #self.load_tab_cfg()
        self.load_theme_cfg()
        self.load_key_cfg()
        self.load_general_cfg()
        # note: extension page handled separately

    def create_action_buttons(self):
        """Return frame of action buttons for dialog.

        Methods:
            ok
            apply
            cancel
            help

        Widget Structure:
            outer: Frame
                buttons: Frame
                    (no assignment): Button (ok)
                    (no assignment): Button (apply)
                    (no assignment): Button (cancel)
                    (no assignment): Button (help)
                (no assignment): Frame
        """
        if macosx.isAquaTk():
            # Changing the default padding on OSX results in unreadable
            # text in the buttons.
            padding_args = {}
        else:
            padding_args = {'padx':6, 'pady':3}
        outer = Frame(self, pady=2)
        buttons = Frame(outer, pady=2)
        for txt, cmd in (
            ('Ok', self.ok),
            ('Apply', self.apply),
            ('Cancel', self.cancel),
            ('Help', self.help)):
            Button(buttons, text=txt, command=cmd, takefocus=FALSE,
                   **padding_args).pack(side=LEFT, padx=5)
        # Add space above buttons.
        Frame(outer, height=2, borderwidth=0).pack(side=TOP)
        buttons.pack(side=BOTTOM)
        return outer

    def ok(self):
        """Apply config changes, then dismiss dialog.

        Methods:
            apply
            destroy: inherited
        """
        self.apply()
        self.destroy()

    def apply(self):
        """Apply config changes and leave dialog open.

        Methods:
            deactivate_current_config
            save_all_changed_extensions
            activate_config_changes
        """
        self.deactivate_current_config()
        changes.save_all()
        self.save_all_changed_extensions()
        self.activate_config_changes()

    def cancel(self):
        """Dismiss config dialog.

        Methods:
            destroy: inherited
        """
        self.destroy()

    def help(self):
        """Create textview for config dialog help.

        Attrbutes accessed:
            tab_pages

        Methods:
            view_text: Method from textview module.
        """
        page = self.tab_pages._current_page
        view_text(self, title='Help for IDLE preferences',
                 text=help_common+help_pages.get(page, ''))


    def create_page_highlight(self):
        """Return frame of widgets for Highlighting tab.

        Tk Variables:
            color: Color of selected target.
            builtin_theme: Menu variable for built-in theme.
            custom_theme: Menu variable for custom theme.
            fg_bg_toggle: Toggle for foreground/background color.
                Note: this has no callback.
            is_builtin_theme: Selector for built-in or custom theme.
            highlight_target: Menu variable for the highlight tag target.

        Instance Data Attributes:
            theme_elements: Dictionary of tags for text highlighting.
                The key is the display name and the value is a tuple of
                (tag name, display sort order).

        Methods [attachment]:
            load_theme_cfg: Load current highlight colors.
            get_color: Invoke colorchooser [button_set_color].
            set_color_sample_binding: Call set_color_sample [fg_bg_toggle].
            set_highlight_target: set fg_bg_toggle, set_color_sample().
            set_color_sample: Set frame background to target.
            on_new_color_set: Set new color and add option.
            paint_theme_sample: Recolor sample.
            get_new_theme_name: Get from popup.
            create_new_theme: Combine theme with changes and save.
            save_as_new_theme: Save [button_save_custom_theme].
            set_theme_type: Command for [is_builtin_theme].
            delete_custom_theme: Ativate default [button_delete_custom_theme].
            save_new_theme: Save to userCfg['theme'] (is function).

        Widget Structure:  (*) widgets bound to self
            frame
                frame_custom: LabelFrame
                    (*)highlight_sample: Text
                    (*)frame_color_set: Frame
                        button_set_color: Button
                        (*)opt_menu_highlight_target: DynOptionMenu - highlight_target
                    frame_fg_bg_toggle: Frame
                        (*)radio_fg: Radiobutton - fg_bg_toggle
                        (*)radio_bg: Radiobutton - fg_bg_toggle
                    button_save_custom_theme: Button
                frame_theme: LabelFrame
                    theme_type_title: Label
                    (*)radio_theme_builtin: Radiobutton - is_builtin_theme
                    (*)radio_theme_custom: Radiobutton - is_builtin_theme
                    (*)opt_menu_theme_builtin: DynOptionMenu - builtin_theme
                    (*)opt_menu_theme_custom: DynOptionMenu - custom_theme
                    (*)button_delete_custom_theme: Button
                    (*)new_custom_theme: Label
        """
        self.theme_elements={
            'Normal Text': ('normal', '00'),
            'Python Keywords': ('keyword', '01'),
            'Python Definitions': ('definition', '02'),
            'Python Builtins': ('builtin', '03'),
            'Python Comments': ('comment', '04'),
            'Python Strings': ('string', '05'),
            'Selected Text': ('hilite', '06'),
            'Found Text': ('hit', '07'),
            'Cursor': ('cursor', '08'),
            'Editor Breakpoint': ('break', '09'),
            'Shell Normal Text': ('console', '10'),
            'Shell Error Text': ('error', '11'),
            'Shell Stdout Text': ('stdout', '12'),
            'Shell Stderr Text': ('stderr', '13'),
            }
        parent = self.parent
        self.builtin_theme = tracers.add(
                StringVar(parent), self.var_changed_builtin_theme)
        self.custom_theme = tracers.add(
                StringVar(parent), self.var_changed_custom_theme)
        self.fg_bg_toggle = BooleanVar(parent)
        self.color = tracers.add(
                StringVar(parent), self.var_changed_color)
        self.is_builtin_theme = tracers.add(
                BooleanVar(parent), self.var_changed_is_builtin_theme)
        self.highlight_target = tracers.add(
                StringVar(parent), self.var_changed_highlight_target)

        # Widget creation:
        # body frame and section frames
        frame = Frame(self.note)
        frame_custom = LabelFrame(frame, borderwidth=2, relief=GROOVE,
                                 text=' Custom Highlighting ')
        frame_theme = LabelFrame(frame, borderwidth=2, relief=GROOVE,
                                text=' Highlighting Theme ')
        #frame_custom
        text = self.highlight_sample = frame.highlight_sample = Text(
                frame_custom, relief=SOLID, borderwidth=1,
                font=('courier', 12, ''), cursor='hand2', width=21, height=13,
                takefocus=FALSE, highlightthickness=0, wrap=NONE)
        text=self.highlight_sample
        text.bind('<Double-Button-1>', lambda e: 'break')
        text.bind('<B1-Motion>', lambda e: 'break')
        text_and_tags=(('\n', 'normal'),
            ('#you can click here', 'comment'), ('\n', 'normal'),
            ('#to choose items', 'comment'), ('\n', 'normal'),
            ('def', 'keyword'), (' ', 'normal'),
            ('func', 'definition'), ('(param):\n  ', 'normal'),
            ('"""string"""', 'string'), ('\n  var0 = ', 'normal'),
            ("'string'", 'string'), ('\n  var1 = ', 'normal'),
            ("'selected'", 'hilite'), ('\n  var2 = ', 'normal'),
            ("'found'", 'hit'), ('\n  var3 = ', 'normal'),
            ('list', 'builtin'), ('(', 'normal'),
            ('None', 'keyword'), (')\n', 'normal'),
            ('  breakpoint("line")', 'break'), ('\n\n', 'normal'),
            (' error ', 'error'), (' ', 'normal'),
            ('cursor |', 'cursor'), ('\n ', 'normal'),
            ('shell', 'console'), (' ', 'normal'),
            ('stdout', 'stdout'), (' ', 'normal'),
            ('stderr', 'stderr'), ('\n\n', 'normal'))
        for texttag in text_and_tags:
            text.insert(END, texttag[0], texttag[1])
        for element in self.theme_elements:
            def tem(event, elem=element):
                event.widget.winfo_toplevel().highlight_target.set(elem)
            text.tag_bind(
                    self.theme_elements[element][0], '<ButtonPress-1>', tem)
        text['state'] = DISABLED
        self.frame_color_set = Frame(frame_custom, relief=SOLID, borderwidth=1)
        frame_fg_bg_toggle = Frame(frame_custom)
        button_set_color = Button(
                self.frame_color_set, text='Choose Color for :',
                command=self.get_color, highlightthickness=0)
        self.opt_menu_highlight_target = DynOptionMenu(
                self.frame_color_set, self.highlight_target, None,
                highlightthickness=0) #, command=self.set_highlight_targetBinding
        self.radio_fg = Radiobutton(
                frame_fg_bg_toggle, variable=self.fg_bg_toggle, value=1,
                text='Foreground', command=self.set_color_sample_binding)
        self.radio_bg=Radiobutton(
                frame_fg_bg_toggle, variable=self.fg_bg_toggle, value=0,
                text='Background', command=self.set_color_sample_binding)
        self.fg_bg_toggle.set(1)
        button_save_custom_theme = Button(
                frame_custom, text='Save as New Custom Theme',
                command=self.save_as_new_theme)
        #frame_theme
        theme_type_title = Label(frame_theme, text='Select : ')
        self.radio_theme_builtin = Radiobutton(
                frame_theme, variable=self.is_builtin_theme, value=1,
                command=self.set_theme_type, text='a Built-in Theme')
        self.radio_theme_custom = Radiobutton(
                frame_theme, variable=self.is_builtin_theme, value=0,
                command=self.set_theme_type, text='a Custom Theme')
        self.opt_menu_theme_builtin = DynOptionMenu(
                frame_theme, self.builtin_theme, None, command=None)
        self.opt_menu_theme_custom=DynOptionMenu(
                frame_theme, self.custom_theme, None, command=None)
        self.button_delete_custom_theme=Button(
                frame_theme, text='Delete Custom Theme',
                command=self.delete_custom_theme)
        self.new_custom_theme = Label(frame_theme, bd=2)

        ##widget packing
        #body
        frame_custom.pack(side=LEFT, padx=5, pady=5, expand=TRUE, fill=BOTH)
        frame_theme.pack(side=LEFT, padx=5, pady=5, fill=Y)
        #frame_custom
        self.frame_color_set.pack(side=TOP, padx=5, pady=5, expand=TRUE, fill=X)
        frame_fg_bg_toggle.pack(side=TOP, padx=5, pady=0)
        self.highlight_sample.pack(
                side=TOP, padx=5, pady=5, expand=TRUE, fill=BOTH)
        button_set_color.pack(side=TOP, expand=TRUE, fill=X, padx=8, pady=4)
        self.opt_menu_highlight_target.pack(
                side=TOP, expand=TRUE, fill=X, padx=8, pady=3)
        self.radio_fg.pack(side=LEFT, anchor=E)
        self.radio_bg.pack(side=RIGHT, anchor=W)
        button_save_custom_theme.pack(side=BOTTOM, fill=X, padx=5, pady=5)
        #frame_theme
        theme_type_title.pack(side=TOP, anchor=W, padx=5, pady=5)
        self.radio_theme_builtin.pack(side=TOP, anchor=W, padx=5)
        self.radio_theme_custom.pack(side=TOP, anchor=W, padx=5, pady=2)
        self.opt_menu_theme_builtin.pack(side=TOP, fill=X, padx=5, pady=5)
        self.opt_menu_theme_custom.pack(side=TOP, fill=X, anchor=W, padx=5, pady=5)
        self.button_delete_custom_theme.pack(side=TOP, fill=X, padx=5, pady=5)
        self.new_custom_theme.pack(side=TOP, fill=X, pady=5)
        return frame

    def load_theme_cfg(self):
        """Load current configuration settings for the theme options.

        Based on the is_builtin_theme toggle, the theme is set as
        either builtin or custom and the initial widget values
        reflect the current settings from idleConf.

        Attributes updated:
            is_builtin_theme: Set from idleConf.
            opt_menu_theme_builtin: List of default themes from idleConf.
            opt_menu_theme_custom: List of custom themes from idleConf.
            radio_theme_custom: Disabled if there are no custom themes.
            custom_theme: Message with additional information.
            opt_menu_highlight_target: Create menu from self.theme_elements.

        Methods:
            set_theme_type
            paint_theme_sample
            set_highlight_target
        """
        # Set current theme type radiobutton.
        self.is_builtin_theme.set(idleConf.GetOption(
                'main', 'Theme', 'default', type='bool', default=1))
        # Set current theme.
        current_option = idleConf.CurrentTheme()
        # Load available theme option menus.
        if self.is_builtin_theme.get():  # Default theme selected.
            item_list = idleConf.GetSectionList('default', 'highlight')
            item_list.sort()
            self.opt_menu_theme_builtin.SetMenu(item_list, current_option)
            item_list = idleConf.GetSectionList('user', 'highlight')
            item_list.sort()
            if not item_list:
                self.radio_theme_custom['state'] = DISABLED
                self.custom_theme.set('- no custom themes -')
            else:
                self.opt_menu_theme_custom.SetMenu(item_list, item_list[0])
        else:  # User theme selected.
            item_list = idleConf.GetSectionList('user', 'highlight')
            item_list.sort()
            self.opt_menu_theme_custom.SetMenu(item_list, current_option)
            item_list = idleConf.GetSectionList('default', 'highlight')
            item_list.sort()
            self.opt_menu_theme_builtin.SetMenu(item_list, item_list[0])
        self.set_theme_type()
        # Load theme element option menu.
        theme_names = list(self.theme_elements.keys())
        theme_names.sort(key=lambda x: self.theme_elements[x][1])
        self.opt_menu_highlight_target.SetMenu(theme_names, theme_names[0])
        self.paint_theme_sample()
        self.set_highlight_target()

    def var_changed_builtin_theme(self, *params):
        """Process new builtin theme selection.

        Add the changed theme's name to the changed_items and recreate
        the sample with the values from the selected theme.
        """
        old_themes = ('IDLE Classic', 'IDLE New')
        value = self.builtin_theme.get()
        if value not in old_themes:
            if idleConf.GetOption('main', 'Theme', 'name') not in old_themes:
                changes.add_option('main', 'Theme', 'name', old_themes[0])
            changes.add_option('main', 'Theme', 'name2', value)
            self.new_custom_theme.config(text='New theme, see Help',
                                         fg='#500000')
        else:
            changes.add_option('main', 'Theme', 'name', value)
            changes.add_option('main', 'Theme', 'name2', '')
            self.new_custom_theme.config(text='', fg='black')
        self.paint_theme_sample()

    def var_changed_custom_theme(self, *params):
        """Process new custom theme selection.

        If a new custom theme is selected, add the name to the
        changed_items and apply the theme to the sample.
        """
        value = self.custom_theme.get()
        if value != '- no custom themes -':
            changes.add_option('main', 'Theme', 'name', value)
            self.paint_theme_sample()

    def var_changed_is_builtin_theme(self, *params):
        """Process toggle between builtin and custom theme.

        Update the default toggle value and apply the newly
        selected theme type.
        """
        value = self.is_builtin_theme.get()
        changes.add_option('main', 'Theme', 'default', value)
        if value:
            self.var_changed_builtin_theme()
        else:
            self.var_changed_custom_theme()

    def var_changed_color(self, *params):
        "Process change to color choice."
        self.on_new_color_set()

    def var_changed_highlight_target(self, *params):
        "Process selection of new target tag for highlighting."
        self.set_highlight_target()

    def set_theme_type(self):
        """Set available screen options based on builtin or custom theme.

        Attributes accessed:
            is_builtin_theme

        Attributes updated:
            opt_menu_theme_builtin
            opt_menu_theme_custom
            button_delete_custom_theme
            radio_theme_custom

        Called from:
            handler for radio_theme_builtin and radio_theme_custom
            delete_custom_theme
            create_new_theme
            load_theme_cfg
        """
        if self.is_builtin_theme.get():
            self.opt_menu_theme_builtin['state'] = NORMAL
            self.opt_menu_theme_custom['state'] = DISABLED
            self.button_delete_custom_theme['state'] = DISABLED
        else:
            self.opt_menu_theme_builtin['state'] = DISABLED
            self.radio_theme_custom['state'] = NORMAL
            self.opt_menu_theme_custom['state'] = NORMAL
            self.button_delete_custom_theme['state'] = NORMAL

    def get_color(self):
        """Handle button to select a new color for the target tag.

        If a new color is selected while using a builtin theme, a
        name must be supplied to create a custom theme.

        Attributes accessed:
            highlight_target
            frame_color_set
            is_builtin_theme

        Attributes updated:
            color

        Methods:
            get_new_theme_name
            create_new_theme
        """
        target = self.highlight_target.get()
        prev_color = self.frame_color_set.cget('bg')
        rgbTuplet, color_string = tkColorChooser.askcolor(
                parent=self, title='Pick new color for : '+target,
                initialcolor=prev_color)
        if color_string and (color_string != prev_color):
            # User didn't cancel and they chose a new color.
            if self.is_builtin_theme.get():  # Current theme is a built-in.
                message = ('Your changes will be saved as a new Custom Theme. '
                           'Enter a name for your new Custom Theme below.')
                new_theme = self.get_new_theme_name(message)
                if not new_theme:  # User cancelled custom theme creation.
                    return
                else:  # Create new custom theme based on previously active theme.
                    self.create_new_theme(new_theme)
                    self.color.set(color_string)
            else:  # Current theme is user defined.
                self.color.set(color_string)

    def on_new_color_set(self):
        "Display sample of new color selection on the dialog."
        new_color=self.color.get()
        self.frame_color_set.config(bg=new_color)  # Set sample.
        plane ='foreground' if self.fg_bg_toggle.get() else 'background'
        sample_element = self.theme_elements[self.highlight_target.get()][0]
        self.highlight_sample.tag_config(sample_element, **{plane:new_color})
        theme = self.custom_theme.get()
        theme_element = sample_element + '-' + plane
        changes.add_option('highlight', theme, theme_element, new_color)

    def get_new_theme_name(self, message):
        "Return name of new theme from query popup."
        used_names = (idleConf.GetSectionList('user', 'highlight') +
                idleConf.GetSectionList('default', 'highlight'))
        new_theme = SectionName(
                self, 'New Custom Theme', message, used_names).result
        return new_theme

    def save_as_new_theme(self):
        """Prompt for new theme name and create the theme.

        Methods:
            get_new_theme_name
            create_new_theme
        """
        new_theme_name = self.get_new_theme_name('New Theme Name:')
        if new_theme_name:
            self.create_new_theme(new_theme_name)

    def create_new_theme(self, new_theme_name):
        """Create a new custom theme with the given name.

        Create the new theme based on the previously active theme
        with the current changes applied.  Once it is saved, then
        activate the new theme.

        Attributes accessed:
            builtin_theme
            custom_theme

        Attributes updated:
            opt_menu_theme_custom
            is_builtin_theme

        Method:
            save_new_theme
            set_theme_type
        """
        if self.is_builtin_theme.get():
            theme_type = 'default'
            theme_name = self.builtin_theme.get()
        else:
            theme_type = 'user'
            theme_name = self.custom_theme.get()
        new_theme = idleConf.GetThemeDict(theme_type, theme_name)
        # Apply any of the old theme's unsaved changes to the new theme.
        if theme_name in changes['highlight']:
            theme_changes = changes['highlight'][theme_name]
            for element in theme_changes:
                new_theme[element] = theme_changes[element]
        # Save the new theme.
        self.save_new_theme(new_theme_name, new_theme)
        # Change GUI over to the new theme.
        custom_theme_list = idleConf.GetSectionList('user', 'highlight')
        custom_theme_list.sort()
        self.opt_menu_theme_custom.SetMenu(custom_theme_list, new_theme_name)
        self.is_builtin_theme.set(0)
        self.set_theme_type()

    def set_highlight_target(self):
        """Set fg/bg toggle and color based on highlight tag target.

        Instance variables accessed:
            highlight_target

        Attributes updated:
            radio_fg
            radio_bg
            fg_bg_toggle

        Methods:
            set_color_sample

        Called from:
            var_changed_highlight_target
            load_theme_cfg
        """
        if self.highlight_target.get() == 'Cursor':  # bg not possible
            self.radio_fg['state'] = DISABLED
            self.radio_bg['state'] = DISABLED
            self.fg_bg_toggle.set(1)
        else:  # Both fg and bg can be set.
            self.radio_fg['state'] = NORMAL
            self.radio_bg['state'] = NORMAL
            self.fg_bg_toggle.set(1)
        self.set_color_sample()

    def set_color_sample_binding(self, *args):
        """Change color sample based on foreground/background toggle.

        Methods:
            set_color_sample
        """
        self.set_color_sample()

    def set_color_sample(self):
        """Set the color of the frame background to reflect the selected target.

        Instance variables accessed:
            theme_elements
            highlight_target
            fg_bg_toggle
            highlight_sample

        Attributes updated:
            frame_color_set
        """
        # Set the color sample area.
        tag = self.theme_elements[self.highlight_target.get()][0]
        plane = 'foreground' if self.fg_bg_toggle.get() else 'background'
        color = self.highlight_sample.tag_cget(tag, plane)
        self.frame_color_set.config(bg=color)

    def paint_theme_sample(self):
        """Apply the theme colors to each element tag in the sample text.

        Instance attributes accessed:
            theme_elements
            is_builtin_theme
            builtin_theme
            custom_theme

        Attributes updated:
            highlight_sample: Set the tag elements to the theme.

        Methods:
            set_color_sample

        Called from:
            var_changed_builtin_theme
            var_changed_custom_theme
            load_theme_cfg
        """
        if self.is_builtin_theme.get():  # Default theme
            theme = self.builtin_theme.get()
        else:  # User theme
            theme = self.custom_theme.get()
        for element_title in self.theme_elements:
            element = self.theme_elements[element_title][0]
            colors = idleConf.GetHighlight(theme, element)
            if element == 'cursor':  # Cursor sample needs special painting.
                colors['background'] = idleConf.GetHighlight(
                        theme, 'normal', fgBg='bg')
            # Handle any unsaved changes to this theme.
            if theme in changes['highlight']:
                theme_dict = changes['highlight'][theme]
                if element + '-foreground' in theme_dict:
                    colors['foreground'] = theme_dict[element + '-foreground']
                if element + '-background' in theme_dict:
                    colors['background'] = theme_dict[element + '-background']
            self.highlight_sample.tag_config(element, **colors)
        self.set_color_sample()

    def save_new_theme(self, theme_name, theme):
        """Save a newly created theme to idleConf.

        theme_name - string, the name of the new theme
        theme - dictionary containing the new theme
        """
        if not idleConf.userCfg['highlight'].has_section(theme_name):
            idleConf.userCfg['highlight'].add_section(theme_name)
        for element in theme:
            value = theme[element]
            idleConf.userCfg['highlight'].SetOption(theme_name, element, value)

    def delete_custom_theme(self):
        """Handle event to delete custom theme.

        The current theme is deactivated and the default theme is
        activated.  The custom theme is permanently removed from
        the config file.

        Attributes accessed:
            custom_theme

        Attributes updated:
            radio_theme_custom
            opt_menu_theme_custom
            is_builtin_theme
            builtin_theme

        Methods:
            deactivate_current_config
            save_all_changed_extensions
            activate_config_changes
            set_theme_type
        """
        theme_name = self.custom_theme.get()
        delmsg = 'Are you sure you wish to delete the theme %r ?'
        if not tkMessageBox.askyesno(
                'Delete Theme',  delmsg % theme_name, parent=self):
            return
        self.deactivate_current_config()
        # Remove theme from changes, config, and file.
        changes.delete_section('highlight', theme_name)
        # Reload user theme list.
        item_list = idleConf.GetSectionList('user', 'highlight')
        item_list.sort()
        if not item_list:
            self.radio_theme_custom['state'] = DISABLED
            self.opt_menu_theme_custom.SetMenu(item_list, '- no custom themes -')
        else:
            self.opt_menu_theme_custom.SetMenu(item_list, item_list[0])
        # Revert to default theme.
        self.is_builtin_theme.set(idleConf.defaultCfg['main'].Get('Theme', 'default'))
        self.builtin_theme.set(idleConf.defaultCfg['main'].Get('Theme', 'name'))
        # User can't back out of these changes, they must be applied now.
        changes.save_all()
        self.save_all_changed_extensions()
        self.activate_config_changes()
        self.set_theme_type()


    def create_page_keys(self):
        """Return frame of widgets for Keys tab.

        Tk Variables:
            builtin_keys: Menu variable for built-in keybindings.
            custom_keys: Menu variable for custom keybindings.
            are_keys_builtin: Selector for built-in or custom keybindings.
            keybinding: Action/key bindings.

        Methods:
            load_key_config: Set table.
            load_keys_list: Reload active set.
            keybinding_selected: Bound to list_bindings button release.
            get_new_keys: Command for button_new_keys.
            get_new_keys_name: Call popup.
            create_new_key_set: Combine active keyset and changes.
            set_keys_type: Command for are_keys_builtin.
            delete_custom_keys: Command for button_delete_custom_keys.
            save_as_new_key_set: Command for button_save_custom_keys.
            save_new_key_set: Save to idleConf.userCfg['keys'] (is function).
            deactivate_current_config: Remove keys bindings in editors.

        Widget Structure:  (*) widgets bound to self
            frame
                frame_custom: LabelFrame
                    frame_target: Frame
                        target_title: Label
                        scroll_target_y: Scrollbar
                        scroll_target_x: Scrollbar
                        (*)list_bindings: ListBox
                        (*)button_new_keys: Button
                frame_key_sets: LabelFrame
                    frames[0]: Frame
                        (*)radio_keys_builtin: Radiobutton - are_keys_builtin
                        (*)radio_keys_custom: Radiobutton - are_keys_builtin
                        (*)opt_menu_keys_builtin: DynOptionMenu - builtin_keys
                        (*)opt_menu_keys_custom: DynOptionMenu - custom_keys
                        (*)new_custom_keys: Label
                    frames[1]: Frame
                        (*)button_delete_custom_keys: Button
                        button_save_custom_keys: Button
        """
        parent = self.parent
        self.builtin_keys = tracers.add(
                StringVar(parent), self.var_changed_builtin_keys)
        self.custom_keys = tracers.add(
                StringVar(parent), self.var_changed_custom_keys)
        self.are_keys_builtin = tracers.add(
                BooleanVar(parent), self.var_changed_are_keys_builtin)
        self.keybinding = tracers.add(
                StringVar(parent), self.var_changed_keybinding)

        # Widget creation:
        # body and section frames.
        frame = Frame(self.note)
        frame_custom = LabelFrame(
                frame, borderwidth=2, relief=GROOVE,
                text=' Custom Key Bindings ')
        frame_key_sets = LabelFrame(
                frame, borderwidth=2, relief=GROOVE, text=' Key Set ')
        #frame_custom
        frame_target = Frame(frame_custom)
        target_title = Label(frame_target, text='Action - Key(s)')
        scroll_target_y = Scrollbar(frame_target)
        scroll_target_x = Scrollbar(frame_target, orient=HORIZONTAL)
        self.list_bindings = Listbox(
                frame_target, takefocus=FALSE, exportselection=FALSE)
        self.list_bindings.bind('<ButtonRelease-1>', self.keybinding_selected)
        scroll_target_y.config(command=self.list_bindings.yview)
        scroll_target_x.config(command=self.list_bindings.xview)
        self.list_bindings.config(yscrollcommand=scroll_target_y.set)
        self.list_bindings.config(xscrollcommand=scroll_target_x.set)
        self.button_new_keys = Button(
                frame_custom, text='Get New Keys for Selection',
                command=self.get_new_keys, state=DISABLED)
        #frame_key_sets
        frames = [Frame(frame_key_sets, padx=2, pady=2, borderwidth=0)
                  for i in range(2)]
        self.radio_keys_builtin = Radiobutton(
                frames[0], variable=self.are_keys_builtin, value=1,
                command=self.set_keys_type, text='Use a Built-in Key Set')
        self.radio_keys_custom = Radiobutton(
                frames[0], variable=self.are_keys_builtin,  value=0,
                command=self.set_keys_type, text='Use a Custom Key Set')
        self.opt_menu_keys_builtin = DynOptionMenu(
                frames[0], self.builtin_keys, None, command=None)
        self.opt_menu_keys_custom = DynOptionMenu(
                frames[0], self.custom_keys, None, command=None)
        self.button_delete_custom_keys = Button(
                frames[1], text='Delete Custom Key Set',
                command=self.delete_custom_keys)
        button_save_custom_keys = Button(
                frames[1], text='Save as New Custom Key Set',
                command=self.save_as_new_key_set)
        self.new_custom_keys = Label(frames[0], bd=2)

        ##widget packing
        #body
        frame_custom.pack(side=BOTTOM, padx=5, pady=5, expand=TRUE, fill=BOTH)
        frame_key_sets.pack(side=BOTTOM, padx=5, pady=5, fill=BOTH)
        #frame_custom
        self.button_new_keys.pack(side=BOTTOM, fill=X, padx=5, pady=5)
        frame_target.pack(side=LEFT, padx=5, pady=5, expand=TRUE, fill=BOTH)
        #frame target
        frame_target.columnconfigure(0, weight=1)
        frame_target.rowconfigure(1, weight=1)
        target_title.grid(row=0, column=0, columnspan=2, sticky=W)
        self.list_bindings.grid(row=1, column=0, sticky=NSEW)
        scroll_target_y.grid(row=1, column=1, sticky=NS)
        scroll_target_x.grid(row=2, column=0, sticky=EW)
        #frame_key_sets
        self.radio_keys_builtin.grid(row=0, column=0, sticky=W+NS)
        self.radio_keys_custom.grid(row=1, column=0, sticky=W+NS)
        self.opt_menu_keys_builtin.grid(row=0, column=1, sticky=NSEW)
        self.opt_menu_keys_custom.grid(row=1, column=1, sticky=NSEW)
        self.new_custom_keys.grid(row=0, column=2, sticky=NSEW, padx=5, pady=5)
        self.button_delete_custom_keys.pack(side=LEFT, fill=X, expand=True, padx=2)
        button_save_custom_keys.pack(side=LEFT, fill=X, expand=True, padx=2)
        frames[0].pack(side=TOP, fill=BOTH, expand=True)
        frames[1].pack(side=TOP, fill=X, expand=True, pady=2)
        return frame

    def load_key_cfg(self):
        "Load current configuration settings for the keybinding options."
        # Set current keys type radiobutton.
        self.are_keys_builtin.set(idleConf.GetOption(
                'main', 'Keys', 'default', type='bool', default=1))
        # Set current keys.
        current_option = idleConf.CurrentKeys()
        # Load available keyset option menus.
        if self.are_keys_builtin.get():  # Default theme selected.
            item_list = idleConf.GetSectionList('default', 'keys')
            item_list.sort()
            self.opt_menu_keys_builtin.SetMenu(item_list, current_option)
            item_list = idleConf.GetSectionList('user', 'keys')
            item_list.sort()
            if not item_list:
                self.radio_keys_custom['state'] = DISABLED
                self.custom_keys.set('- no custom keys -')
            else:
                self.opt_menu_keys_custom.SetMenu(item_list, item_list[0])
        else:  # User key set selected.
            item_list = idleConf.GetSectionList('user', 'keys')
            item_list.sort()
            self.opt_menu_keys_custom.SetMenu(item_list, current_option)
            item_list = idleConf.GetSectionList('default', 'keys')
            item_list.sort()
            self.opt_menu_keys_builtin.SetMenu(item_list, idleConf.default_keys())
        self.set_keys_type()
        # Load keyset element list.
        keyset_name = idleConf.CurrentKeys()
        self.load_keys_list(keyset_name)

    def var_changed_builtin_keys(self, *params):
        "Process selection of builtin key set."
        old_keys = (
            'IDLE Classic Windows',
            'IDLE Classic Unix',
            'IDLE Classic Mac',
            'IDLE Classic OSX',
        )
        value = self.builtin_keys.get()
        if value not in old_keys:
            if idleConf.GetOption('main', 'Keys', 'name') not in old_keys:
                changes.add_option('main', 'Keys', 'name', old_keys[0])
            changes.add_option('main', 'Keys', 'name2', value)
            self.new_custom_keys.config(text='New key set, see Help',
                                        fg='#500000')
        else:
            changes.add_option('main', 'Keys', 'name', value)
            changes.add_option('main', 'Keys', 'name2', '')
            self.new_custom_keys.config(text='', fg='black')
        self.load_keys_list(value)

    def var_changed_custom_keys(self, *params):
        "Process selection of custom key set."
        value = self.custom_keys.get()
        if value != '- no custom keys -':
            changes.add_option('main', 'Keys', 'name', value)
            self.load_keys_list(value)

    def var_changed_are_keys_builtin(self, *params):
        "Process toggle between builtin key set and custom key set."
        value = self.are_keys_builtin.get()
        changes.add_option('main', 'Keys', 'default', value)
        if value:
            self.var_changed_builtin_keys()
        else:
            self.var_changed_custom_keys()

    def var_changed_keybinding(self, *params):
        "Store change to a keybinding."
        value = self.keybinding.get()
        key_set = self.custom_keys.get()
        event = self.list_bindings.get(ANCHOR).split()[0]
        if idleConf.IsCoreBinding(event):
            changes.add_option('keys', key_set, event, value)
        else:  # Event is an extension binding.
            ext_name = idleConf.GetExtnNameForEvent(event)
            ext_keybind_section = ext_name + '_cfgBindings'
            changes.add_option('extensions', ext_keybind_section, event, value)

    def set_keys_type(self):
        "Set available screen options based on builtin or custom key set."
        if self.are_keys_builtin.get():
            self.opt_menu_keys_builtin['state'] = NORMAL
            self.opt_menu_keys_custom['state'] = DISABLED
            self.button_delete_custom_keys['state'] = DISABLED
        else:
            self.opt_menu_keys_builtin['state'] = DISABLED
            self.radio_keys_custom['state'] = NORMAL
            self.opt_menu_keys_custom['state'] = NORMAL
            self.button_delete_custom_keys['state'] = NORMAL

    def get_new_keys(self):
        """Handle event to change key binding for selected line.

        A selection of a key/binding in the list of current
        bindings pops up a dialog to enter a new binding.  If
        the current key set is builtin and a binding has
        changed, then a name for a custom key set needs to be
        entered for the change to be applied.
        """
        list_index = self.list_bindings.index(ANCHOR)
        binding = self.list_bindings.get(list_index)
        bind_name = binding.split()[0]
        if self.are_keys_builtin.get():
            current_key_set_name = self.builtin_keys.get()
        else:
            current_key_set_name = self.custom_keys.get()
        current_bindings = idleConf.GetCurrentKeySet()
        if current_key_set_name in changes['keys']:  # unsaved changes
            key_set_changes = changes['keys'][current_key_set_name]
            for event in key_set_changes:
                current_bindings[event] = key_set_changes[event].split()
        current_key_sequences = list(current_bindings.values())
        new_keys = GetKeysDialog(self, 'Get New Keys', bind_name,
                current_key_sequences).result
        if new_keys:
            if self.are_keys_builtin.get():  # Current key set is a built-in.
                message = ('Your changes will be saved as a new Custom Key Set.'
                           ' Enter a name for your new Custom Key Set below.')
                new_keyset = self.get_new_keys_name(message)
                if not new_keyset:  # User cancelled custom key set creation.
                    self.list_bindings.select_set(list_index)
                    self.list_bindings.select_anchor(list_index)
                    return
                else:  # Create new custom key set based on previously active key set.
                    self.create_new_key_set(new_keyset)
            self.list_bindings.delete(list_index)
            self.list_bindings.insert(list_index, bind_name+' - '+new_keys)
            self.list_bindings.select_set(list_index)
            self.list_bindings.select_anchor(list_index)
            self.keybinding.set(new_keys)
        else:
            self.list_bindings.select_set(list_index)
            self.list_bindings.select_anchor(list_index)

    def get_new_keys_name(self, message):
        "Return new key set name from query popup."
        used_names = (idleConf.GetSectionList('user', 'keys') +
                idleConf.GetSectionList('default', 'keys'))
        new_keyset = SectionName(
                self, 'New Custom Key Set', message, used_names).result
        return new_keyset

    def save_as_new_key_set(self):
        "Prompt for name of new key set and save changes using that name."
        new_keys_name = self.get_new_keys_name('New Key Set Name:')
        if new_keys_name:
            self.create_new_key_set(new_keys_name)

    def keybinding_selected(self, event):
        "Activate button to assign new keys to selected action."
        self.button_new_keys['state'] = NORMAL

    def create_new_key_set(self, new_key_set_name):
        """Create a new custom key set with the given name.

        Create the new key set based on the previously active set
        with the current changes applied.  Once it is saved, then
        activate the new key set.
        """
        if self.are_keys_builtin.get():
            prev_key_set_name = self.builtin_keys.get()
        else:
            prev_key_set_name = self.custom_keys.get()
        prev_keys = idleConf.GetCoreKeys(prev_key_set_name)
        new_keys = {}
        for event in prev_keys:  # Add key set to changed items.
            event_name = event[2:-2]  # Trim off the angle brackets.
            binding = ' '.join(prev_keys[event])
            new_keys[event_name] = binding
        # Handle any unsaved changes to prev key set.
        if prev_key_set_name in changes['keys']:
            key_set_changes = changes['keys'][prev_key_set_name]
            for event in key_set_changes:
                new_keys[event] = key_set_changes[event]
        # Save the new key set.
        self.save_new_key_set(new_key_set_name, new_keys)
        # Change GUI over to the new key set.
        custom_key_list = idleConf.GetSectionList('user', 'keys')
        custom_key_list.sort()
        self.opt_menu_keys_custom.SetMenu(custom_key_list, new_key_set_name)
        self.are_keys_builtin.set(0)
        self.set_keys_type()

    def load_keys_list(self, keyset_name):
        """Reload the list of action/key binding pairs for the active key set.

        An action/key binding can be selected to change the key binding.
        """
        reselect = 0
        if self.list_bindings.curselection():
            reselect = 1
            list_index = self.list_bindings.index(ANCHOR)
        keyset = idleConf.GetKeySet(keyset_name)
        bind_names = list(keyset.keys())
        bind_names.sort()
        self.list_bindings.delete(0, END)
        for bind_name in bind_names:
            key = ' '.join(keyset[bind_name])
            bind_name = bind_name[2:-2]  # Trim off the angle brackets.
            if keyset_name in changes['keys']:
                # Handle any unsaved changes to this key set.
                if bind_name in changes['keys'][keyset_name]:
                    key = changes['keys'][keyset_name][bind_name]
            self.list_bindings.insert(END, bind_name+' - '+key)
        if reselect:
            self.list_bindings.see(list_index)
            self.list_bindings.select_set(list_index)
            self.list_bindings.select_anchor(list_index)

    def save_new_key_set(self, keyset_name, keyset):
        """Save a newly created core key set.

        keyset_name - string, the name of the new key set
        keyset - dictionary containing the new key set
        """
        if not idleConf.userCfg['keys'].has_section(keyset_name):
            idleConf.userCfg['keys'].add_section(keyset_name)
        for event in keyset:
            value = keyset[event]
            idleConf.userCfg['keys'].SetOption(keyset_name, event, value)

    def delete_custom_keys(self):
        """Handle event to delete a custom key set.

        Applying the delete deactivates the current configuration and
        reverts to the default.  The custom key set is permanently
        deleted from the config file.
        """
        keyset_name=self.custom_keys.get()
        delmsg = 'Are you sure you wish to delete the key set %r ?'
        if not tkMessageBox.askyesno(
                'Delete Key Set',  delmsg % keyset_name, parent=self):
            return
        self.deactivate_current_config()
        # Remove key set from changes, config, and file.
        changes.delete_section('keys', keyset_name)
        # Reload user key set list.
        item_list = idleConf.GetSectionList('user', 'keys')
        item_list.sort()
        if not item_list:
            self.radio_keys_custom['state'] = DISABLED
            self.opt_menu_keys_custom.SetMenu(item_list, '- no custom keys -')
        else:
            self.opt_menu_keys_custom.SetMenu(item_list, item_list[0])
        # Revert to default key set.
        self.are_keys_builtin.set(idleConf.defaultCfg['main']
                                .Get('Keys', 'default'))
        self.builtin_keys.set(idleConf.defaultCfg['main'].Get('Keys', 'name')
                             or idleConf.default_keys())
        # User can't back out of these changes, they must be applied now.
        changes.save_all()
        self.save_all_changed_extensions()
        self.activate_config_changes()
        self.set_keys_type()

    def deactivate_current_config(self):
        """Remove current key bindings.

        Iterate over window instances defined in parent and remove
        the keybindings.
        """
        # Before a config is saved, some cleanup of current
        # config must be done - remove the previous keybindings.
        win_instances = self.parent.instance_dict.keys()
        for instance in win_instances:
            instance.RemoveKeybindings()

    def activate_config_changes(self):
        """Apply configuration changes to current windows.

        Dynamically update the current parent window instances
        with some of the configuration changes.
        """
        win_instances = self.parent.instance_dict.keys()
        for instance in win_instances:
            instance.ResetColorizer()
            instance.ResetFont()
            instance.set_notabs_indentwidth()
            instance.ApplyKeybindings()
            instance.reset_help_menu_entries()


    def create_page_general(self):
        """Return frame of widgets for General tab.

        Enable users to provisionally change general options. Function
        load_general_cfg intializes tk variables and helplist using
        idleConf.  Radiobuttons startup_shell_on and startup_editor_on
        set var startup_edit. Radiobuttons save_ask_on and save_auto_on
        set var autosave. Entry boxes win_width_int and win_height_int
        set var win_width and win_height.  Setting var_name invokes the
        default callback that adds option to changes.

        Helplist: load_general_cfg loads list user_helplist with
        name, position pairs and copies names to listbox helplist.
        Clicking a name invokes help_source selected. Clicking
        button_helplist_name invokes helplist_item_name, which also
        changes user_helplist.  These functions all call
        set_add_delete_state. All but load call update_help_changes to
        rewrite changes['main']['HelpFiles'].

        Widget Structure:  (*) widgets bound to self
            frame
                frame_run: LabelFrame
                    startup_title: Label
                    (*)startup_editor_on: Radiobutton - startup_edit
                    (*)startup_shell_on: Radiobutton - startup_edit
                frame_save: LabelFrame
                    run_save_title: Label
                    (*)save_ask_on: Radiobutton - autosave
                    (*)save_auto_on: Radiobutton - autosave
                frame_win_size: LabelFrame
                    win_size_title: Label
                    win_width_title: Label
                    (*)win_width_int: Entry - win_width
                    win_height_title: Label
                    (*)win_height_int: Entry - win_height
                frame_help: LabelFrame
                    frame_helplist: Frame
                        frame_helplist_buttons: Frame
                            (*)button_helplist_edit
                            (*)button_helplist_add
                            (*)button_helplist_remove
                        (*)helplist: ListBox
                        scroll_helplist: Scrollbar
        """
        parent = self.parent
        self.startup_edit = tracers.add(
                IntVar(parent), ('main', 'General', 'editor-on-startup'))
        self.autosave = tracers.add(
                IntVar(parent), ('main', 'General', 'autosave'))
        self.win_width = tracers.add(
                StringVar(parent), ('main', 'EditorWindow', 'width'))
        self.win_height = tracers.add(
                StringVar(parent), ('main', 'EditorWindow', 'height'))

        # Create widgets:
        # body and section frames.
        frame = Frame(self.note)
        frame_run = LabelFrame(frame, borderwidth=2, relief=GROOVE,
                              text=' Startup Preferences ')
        frame_save = LabelFrame(frame, borderwidth=2, relief=GROOVE,
                               text=' autosave Preferences ')
        frame_win_size = Frame(frame, borderwidth=2, relief=GROOVE)
        frame_help = LabelFrame(frame, borderwidth=2, relief=GROOVE,
                               text=' Additional Help Sources ')
        # frame_run.
        startup_title = Label(frame_run, text='At Startup')
        self.startup_editor_on = Radiobutton(
                frame_run, variable=self.startup_edit, value=1,
                text="Open Edit Window")
        self.startup_shell_on = Radiobutton(
                frame_run, variable=self.startup_edit, value=0,
                text='Open Shell Window')
        # frame_save.
        run_save_title = Label(frame_save, text='At Start of Run (F5)  ')
        self.save_ask_on = Radiobutton(
                frame_save, variable=self.autosave, value=0,
                text="Prompt to Save")
        self.save_auto_on = Radiobutton(
                frame_save, variable=self.autosave, value=1,
                text='No Prompt')
        # frame_win_size.
        win_size_title = Label(
                frame_win_size, text='Initial Window Size  (in characters)')
        win_width_title = Label(frame_win_size, text='Width')
        self.win_width_int = Entry(
                frame_win_size, textvariable=self.win_width, width=3)
        win_height_title = Label(frame_win_size, text='Height')
        self.win_height_int = Entry(
                frame_win_size, textvariable=self.win_height, width=3)
        # frame_help.
        frame_helplist = Frame(frame_help)
        frame_helplist_buttons = Frame(frame_helplist)
        self.helplist = Listbox(
                frame_helplist, height=5, takefocus=True,
                exportselection=FALSE)
        scroll_helplist = Scrollbar(frame_helplist)
        scroll_helplist['command'] = self.helplist.yview
        self.helplist['yscrollcommand'] = scroll_helplist.set
        self.helplist.bind('<ButtonRelease-1>', self.help_source_selected)
        self.button_helplist_edit = Button(
                frame_helplist_buttons, text='Edit', state=DISABLED,
                width=8, command=self.helplist_item_edit)
        self.button_helplist_add = Button(
                frame_helplist_buttons, text='Add',
                width=8, command=self.helplist_item_add)
        self.button_helplist_remove = Button(
                frame_helplist_buttons, text='Remove', state=DISABLED,
                width=8, command=self.helplist_item_remove)

        # Pack widgets:
        # body.
        frame_run.pack(side=TOP, padx=5, pady=5, fill=X)
        frame_save.pack(side=TOP, padx=5, pady=5, fill=X)
        frame_win_size.pack(side=TOP, padx=5, pady=5, fill=X)
        frame_help.pack(side=TOP, padx=5, pady=5, expand=TRUE, fill=BOTH)
        # frame_run.
        startup_title.pack(side=LEFT, anchor=W, padx=5, pady=5)
        self.startup_shell_on.pack(side=RIGHT, anchor=W, padx=5, pady=5)
        self.startup_editor_on.pack(side=RIGHT, anchor=W, padx=5, pady=5)
        # frame_save.
        run_save_title.pack(side=LEFT, anchor=W, padx=5, pady=5)
        self.save_auto_on.pack(side=RIGHT, anchor=W, padx=5, pady=5)
        self.save_ask_on.pack(side=RIGHT, anchor=W, padx=5, pady=5)
        # frame_win_size.
        win_size_title.pack(side=LEFT, anchor=W, padx=5, pady=5)
        self.win_height_int.pack(side=RIGHT, anchor=E, padx=10, pady=5)
        win_height_title.pack(side=RIGHT, anchor=E, pady=5)
        self.win_width_int.pack(side=RIGHT, anchor=E, padx=10, pady=5)
        win_width_title.pack(side=RIGHT, anchor=E, pady=5)
        # frame_help.
        frame_helplist_buttons.pack(side=RIGHT, padx=5, pady=5, fill=Y)
        frame_helplist.pack(side=TOP, padx=5, pady=5, expand=TRUE, fill=BOTH)
        scroll_helplist.pack(side=RIGHT, anchor=W, fill=Y)
        self.helplist.pack(side=LEFT, anchor=E, expand=TRUE, fill=BOTH)
        self.button_helplist_edit.pack(side=TOP, anchor=W, pady=5)
        self.button_helplist_add.pack(side=TOP, anchor=W)
        self.button_helplist_remove.pack(side=TOP, anchor=W, pady=5)

        return frame

    def load_general_cfg(self):
        "Load current configuration settings for the general options."
        # Set startup state.
        self.startup_edit.set(idleConf.GetOption(
                'main', 'General', 'editor-on-startup', default=0, type='bool'))
        # Set autosave state.
        self.autosave.set(idleConf.GetOption(
                'main', 'General', 'autosave', default=0, type='bool'))
        # Set initial window size.
        self.win_width.set(idleConf.GetOption(
                'main', 'EditorWindow', 'width', type='int'))
        self.win_height.set(idleConf.GetOption(
                'main', 'EditorWindow', 'height', type='int'))
        # Set additional help sources.
        self.user_helplist = idleConf.GetAllExtraHelpSourcesList()
        self.helplist.delete(0, 'end')
        for help_item in self.user_helplist:
            self.helplist.insert(END, help_item[0])
        self.set_add_delete_state()

    def var_changed_startup_edit(self, *params):
        "Store change to toggle for starting IDLE in the editor or shell."
        value = self.startup_edit.get()
        changes.add_option('main', 'General', 'editor-on-startup', value)

    def var_changed_autosave(self, *params):
        "Store change to autosave."
        value = self.autosave.get()
        changes.add_option('main', 'General', 'autosave', value)

    def var_changed_win_width(self, *params):
        "Store change to window width."
        value = self.win_width.get()
        changes.add_option('main', 'EditorWindow', 'width', value)

    def var_changed_win_height(self, *params):
        "Store change to window height."
        value = self.win_height.get()
        changes.add_option('main', 'EditorWindow', 'height', value)

    def help_source_selected(self, event):
        "Handle event for selecting additional help."
        self.set_add_delete_state()

    def set_add_delete_state(self):
        "Toggle the state for the help list buttons based on list entries."
        if self.helplist.size() < 1:  # No entries in list.
            self.button_helplist_edit['state'] = DISABLED
            self.button_helplist_remove['state'] = DISABLED
        else:  # Some entries.
            if self.helplist.curselection():  # There currently is a selection.
                self.button_helplist_edit['state'] = NORMAL
                self.button_helplist_remove['state'] = NORMAL
            else:  # There currently is not a selection.
                self.button_helplist_edit['state'] = DISABLED
                self.button_helplist_remove['state'] = DISABLED

    def helplist_item_add(self):
        """Handle add button for the help list.

        Query for name and location of new help sources and add
        them to the list.
        """
        help_source = HelpSource(self, 'New Help Source').result
        if help_source:
            self.user_helplist.append(help_source)
            self.helplist.insert(END, help_source[0])
            self.update_help_changes()

    def helplist_item_edit(self):
        """Handle edit button for the help list.

        Query with existing help source information and update
        config if the values are changed.
        """
        item_index = self.helplist.index(ANCHOR)
        help_source = self.user_helplist[item_index]
        new_help_source = HelpSource(
                self, 'Edit Help Source',
                menuitem=help_source[0],
                filepath=help_source[1],
                ).result
        if new_help_source and new_help_source != help_source:
            self.user_helplist[item_index] = new_help_source
            self.helplist.delete(item_index)
            self.helplist.insert(item_index, new_help_source[0])
            self.update_help_changes()
            self.set_add_delete_state()  # Selected will be un-selected

    def helplist_item_remove(self):
        """Handle remove button for the help list.

        Delete the help list item from config.
        """
        item_index = self.helplist.index(ANCHOR)
        del(self.user_helplist[item_index])
        self.helplist.delete(item_index)
        self.update_help_changes()
        self.set_add_delete_state()

    def update_help_changes(self):
        "Clear and rebuild the HelpFiles section in changes"
        changes['main']['HelpFiles'] = {}
        for num in range(1, len(self.user_helplist) + 1):
            changes.add_option(
                    'main', 'HelpFiles', str(num),
                    ';'.join(self.user_helplist[num-1][:2]))


    def create_page_extensions(self):
        """Part of the config dialog used for configuring IDLE extensions.

        This code is generic - it works for any and all IDLE extensions.

        IDLE extensions save their configuration options using idleConf.
        This code reads the current configuration using idleConf, supplies a
        GUI interface to change the configuration values, and saves the
        changes using idleConf.

        Not all changes take effect immediately - some may require restarting IDLE.
        This depends on each extension's implementation.

        All values are treated as text, and it is up to the user to supply
        reasonable values. The only exception to this are the 'enable*' options,
        which are boolean, and can be toggled with a True/False button.

        Methods:
            load_extentions:
            extension_selected: Handle selection from list.
            create_extension_frame: Hold widgets for one extension.
            set_extension_value: Set in userCfg['extensions'].
            save_all_changed_extensions: Call extension page Save().
        """
        parent = self.parent
        frame = Frame(self.note)
        self.ext_defaultCfg = idleConf.defaultCfg['extensions']
        self.ext_userCfg = idleConf.userCfg['extensions']
        self.is_int = self.register(is_int)
        self.load_extensions()
        # Create widgets - a listbox shows all available extensions, with the
        # controls for the extension selected in the listbox to the right.
        self.extension_names = StringVar(self)
        frame.rowconfigure(0, weight=1)
        frame.columnconfigure(2, weight=1)
        self.extension_list = Listbox(frame, listvariable=self.extension_names,
                                      selectmode='browse')
        self.extension_list.bind('<<ListboxSelect>>', self.extension_selected)
        scroll = Scrollbar(frame, command=self.extension_list.yview)
        self.extension_list.yscrollcommand=scroll.set
        self.details_frame = LabelFrame(frame, width=250, height=250)
        self.extension_list.grid(column=0, row=0, sticky='nws')
        scroll.grid(column=1, row=0, sticky='ns')
        self.details_frame.grid(column=2, row=0, sticky='nsew', padx=[10, 0])
        frame.configure(padx=10, pady=10)
        self.config_frame = {}
        self.current_extension = None

        self.outerframe = self                      # TEMPORARY
        self.tabbed_page_set = self.extension_list  # TEMPORARY

        # Create the frame holding controls for each extension.
        ext_names = ''
        for ext_name in sorted(self.extensions):
            self.create_extension_frame(ext_name)
            ext_names = ext_names + '{' + ext_name + '} '
        self.extension_names.set(ext_names)
        self.extension_list.selection_set(0)
        self.extension_selected(None)

        return frame

    def load_extensions(self):
        "Fill self.extensions with data from the default and user configs."
        self.extensions = {}
        for ext_name in idleConf.GetExtensions(active_only=False):
            self.extensions[ext_name] = []

        for ext_name in self.extensions:
            opt_list = sorted(self.ext_defaultCfg.GetOptionList(ext_name))

            # Bring 'enable' options to the beginning of the list.
            enables = [opt_name for opt_name in opt_list
                       if opt_name.startswith('enable')]
            for opt_name in enables:
                opt_list.remove(opt_name)
            opt_list = enables + opt_list

            for opt_name in opt_list:
                def_str = self.ext_defaultCfg.Get(
                        ext_name, opt_name, raw=True)
                try:
                    def_obj = {'True':True, 'False':False}[def_str]
                    opt_type = 'bool'
                except KeyError:
                    try:
                        def_obj = int(def_str)
                        opt_type = 'int'
                    except ValueError:
                        def_obj = def_str
                        opt_type = None
                try:
                    value = self.ext_userCfg.Get(
                            ext_name, opt_name, type=opt_type, raw=True,
                            default=def_obj)
                except ValueError:  # Need this until .Get fixed.
                    value = def_obj  # Bad values overwritten by entry.
                var = StringVar(self)
                var.set(str(value))

                self.extensions[ext_name].append({'name': opt_name,
                                                  'type': opt_type,
                                                  'default': def_str,
                                                  'value': value,
                                                  'var': var,
                                                 })

    def extension_selected(self, event):
        "Handle selection of an extension from the list."
        newsel = self.extension_list.curselection()
        if newsel:
            newsel = self.extension_list.get(newsel)
        if newsel is None or newsel != self.current_extension:
            if self.current_extension:
                self.details_frame.config(text='')
                self.config_frame[self.current_extension].grid_forget()
                self.current_extension = None
        if newsel:
            self.details_frame.config(text=newsel)
            self.config_frame[newsel].grid(column=0, row=0, sticky='nsew')
            self.current_extension = newsel

    def create_extension_frame(self, ext_name):
        """Create a frame holding the widgets to configure one extension"""
        f = VerticalScrolledFrame(self.details_frame, height=250, width=250)
        self.config_frame[ext_name] = f
        entry_area = f.interior
        # Create an entry for each configuration option.
        for row, opt in enumerate(self.extensions[ext_name]):
            # Create a row with a label and entry/checkbutton.
            label = Label(entry_area, text=opt['name'])
            label.grid(row=row, column=0, sticky=NW)
            var = opt['var']
            if opt['type'] == 'bool':
                Checkbutton(entry_area, textvariable=var, variable=var,
                            onvalue='True', offvalue='False',
                            indicatoron=FALSE, selectcolor='', width=8
                            ).grid(row=row, column=1, sticky=W, padx=7)
            elif opt['type'] == 'int':
                Entry(entry_area, textvariable=var, validate='key',
                      validatecommand=(self.is_int, '%P')
                      ).grid(row=row, column=1, sticky=NSEW, padx=7)

            else:
                Entry(entry_area, textvariable=var
                      ).grid(row=row, column=1, sticky=NSEW, padx=7)
        return

    def set_extension_value(self, section, opt):
        """Return True if the configuration was added or changed.

        If the value is the same as the default, then remove it
        from user config file.
        """
        name = opt['name']
        default = opt['default']
        value = opt['var'].get().strip() or default
        opt['var'].set(value)
        # if self.defaultCfg.has_section(section):
        # Currently, always true; if not, indent to return.
        if (value == default):
            return self.ext_userCfg.RemoveOption(section, name)
        # Set the option.
        return self.ext_userCfg.SetOption(section, name, value)

    def save_all_changed_extensions(self):
        """Save configuration changes to the user config file.

        Attributes accessed:
            extensions

        Methods:
            set_extension_value
        """
        has_changes = False
        for ext_name in self.extensions:
            options = self.extensions[ext_name]
            for opt in options:
                if self.set_extension_value(ext_name, opt):
                    has_changes = True
        if has_changes:
            self.ext_userCfg.Save()


class FontPage(Frame):

    def __init__(self, parent, highpage):
        super().__init__(parent)
        self.parent = parent
        self.highlight_sample = highpage.highlight_sample
        self.create_page_font_tab()
        self.load_font_cfg()
        self.load_tab_cfg()

    def create_page_font_tab(self):
        """Return frame of widgets for Font/Tabs tab.

        Fonts: Enable users to provisionally change font face, size, or
        boldness and to see the consequence of proposed choices.  Each
        action set 3 options in changes structuree and changes the
        corresponding aspect of the font sample on this page and
        highlight sample on highlight page.

        Function load_font_cfg initializes font vars and widgets from
        idleConf entries and tk.

        Fontlist: mouse button 1 click or up or down key invoke
        on_fontlist_select(), which sets var font_name.

        Sizelist: clicking the menubutton opens the dropdown menu. A
        mouse button 1 click or return key sets var font_size.

        Bold_toggle: clicking the box toggles var font_bold.

        Changing any of the font vars invokes var_changed_font, which
        adds all 3 font options to changes and calls set_samples.
        Set_samples applies a new font constructed from the font vars to
        font_sample and to highlight_sample on the hightlight page.

        Tabs: Enable users to change spaces entered for indent tabs.
        Changing indent_scale value with the mouse sets Var space_num,
        which invokes the default callback to add an entry to
        changes.  Load_tab_cfg initializes space_num to default.

        Widget Structure:  (*) widgets bound to self
            frame (of tab_pages)
                frame_font: LabelFrame
                    frame_font_name: Frame
                        font_name_title: Label
                        (*)fontlist: ListBox - font_name
                        scroll_font: Scrollbar
                    frame_font_param: Frame
                        font_size_title: Label
                        (*)sizelist: DynOptionMenu - font_size
                        (*)bold_toggle: Checkbutton - font_bold
                    frame_font_sample: Frame
                        (*)font_sample: Label
                frame_indent: LabelFrame
                        indent_title: Label
                        (*)indent_scale: Scale - space_num
        """
        parent = self.parent
        self.font_name = tracers.add(StringVar(parent), self.var_changed_font)
        self.font_size = tracers.add(StringVar(parent), self.var_changed_font)
        self.font_bold = tracers.add(BooleanVar(parent), self.var_changed_font)
        self.space_num = tracers.add(IntVar(self), ('main', 'Indent', 'num-spaces'))

        # Create widgets:
        # body and body section frames.
        frame = self
        frame_font = LabelFrame(
                frame, borderwidth=2, relief=GROOVE, text=' Base Editor Font ')
        frame_indent = LabelFrame(
                frame, borderwidth=2, relief=GROOVE, text=' Indentation Width ')
        # frame_font.
        frame_font_name = Frame(frame_font)
        frame_font_param = Frame(frame_font)
        font_name_title = Label(
                frame_font_name, justify=LEFT, text='Font Face :')
        self.fontlist = Listbox(frame_font_name, height=5,
                                takefocus=True, exportselection=FALSE)
        self.fontlist.bind('<ButtonRelease-1>', self.on_fontlist_select)
        self.fontlist.bind('<KeyRelease-Up>', self.on_fontlist_select)
        self.fontlist.bind('<KeyRelease-Down>', self.on_fontlist_select)
        scroll_font = Scrollbar(frame_font_name)
        scroll_font.config(command=self.fontlist.yview)
        self.fontlist.config(yscrollcommand=scroll_font.set)
        font_size_title = Label(frame_font_param, text='Size :')
        self.sizelist = DynOptionMenu(frame_font_param, self.font_size, None)
        self.bold_toggle = Checkbutton(
                frame_font_param, variable=self.font_bold,
                onvalue=1, offvalue=0, text='Bold')
        frame_font_sample = Frame(frame_font, relief=SOLID, borderwidth=1)
        temp_font = tkFont.Font(parent, ('courier', 10, 'normal'))
        self.font_sample = Label(
                frame_font_sample, justify=LEFT, font=temp_font,
                text='AaBbCcDdEe\nFfGgHhIiJj\n1234567890\n#:+=(){}[]')
        # frame_indent.
        indent_title = Label(
                frame_indent, justify=LEFT,
                text='Python Standard: 4 Spaces!')
        self.indent_scale = Scale(
                frame_indent, variable=self.space_num,
                orient='horizontal', tickinterval=2, from_=2, to=16)

        # Pack widgets:
        # body.
        frame_font.pack(side=LEFT, padx=5, pady=5, expand=TRUE, fill=BOTH)
        frame_indent.pack(side=LEFT, padx=5, pady=5, fill=Y)
        # frame_font.
        frame_font_name.pack(side=TOP, padx=5, pady=5, fill=X)
        frame_font_param.pack(side=TOP, padx=5, pady=5, fill=X)
        font_name_title.pack(side=TOP, anchor=W)
        self.fontlist.pack(side=LEFT, expand=TRUE, fill=X)
        scroll_font.pack(side=LEFT, fill=Y)
        font_size_title.pack(side=LEFT, anchor=W)
        self.sizelist.pack(side=LEFT, anchor=W)
        self.bold_toggle.pack(side=LEFT, anchor=W, padx=20)
        frame_font_sample.pack(side=TOP, padx=5, pady=5, expand=TRUE, fill=BOTH)
        self.font_sample.pack(expand=TRUE, fill=BOTH)
        # frame_indent.
        frame_indent.pack(side=TOP, fill=X)
        indent_title.pack(side=TOP, anchor=W, padx=5)
        self.indent_scale.pack(side=TOP, padx=5, fill=X)

        return frame

    def load_font_cfg(self):
        """Load current configuration settings for the font options.

        Retrieve current font with idleConf.GetFont and font families
        from tk. Setup fontlist and set font_name.  Setup sizelist,
        which sets font_size.  Set font_bold.  Call set_samples.
        """
        configured_font = idleConf.GetFont(self, 'main', 'EditorWindow')
        font_name = configured_font[0].lower()
        font_size = configured_font[1]
        font_bold  = configured_font[2]=='bold'

        # Set editor font selection list and font_name.
        fonts = list(tkFont.families(self))
        fonts.sort()
        for font in fonts:
            self.fontlist.insert(END, font)
        self.font_name.set(font_name)
        lc_fonts = [s.lower() for s in fonts]
        try:
            current_font_index = lc_fonts.index(font_name)
            self.fontlist.see(current_font_index)
            self.fontlist.select_set(current_font_index)
            self.fontlist.select_anchor(current_font_index)
            self.fontlist.activate(current_font_index)
        except ValueError:
            pass
        # Set font size dropdown.
        self.sizelist.SetMenu(('7', '8', '9', '10', '11', '12', '13', '14',
                               '16', '18', '20', '22', '25', '29', '34', '40'),
                              font_size)
        # Set font weight.
        self.font_bold.set(font_bold)
        self.set_samples()

    def var_changed_font(self, *params):
        """Store changes to font attributes.

        When one font attribute changes, save them all, as they are
        not independent from each other. In particular, when we are
        overriding the default font, we need to write out everything.
        """
        value = self.font_name.get()
        changes.add_option('main', 'EditorWindow', 'font', value)
        value = self.font_size.get()
        changes.add_option('main', 'EditorWindow', 'font-size', value)
        value = self.font_bold.get()
        changes.add_option('main', 'EditorWindow', 'font-bold', value)
        self.set_samples()

    def on_fontlist_select(self, event):
        """Handle selecting a font from the list.

        Event can result from either mouse click or Up or Down key.
        Set font_name and example displays to selection.
        """
        font = self.fontlist.get(
                ACTIVE if event.type.name == 'KeyRelease' else ANCHOR)
        self.font_name.set(font.lower())

    def set_samples(self, event=None):
        """Update update both screen samples with the font settings.

        Called on font initialization and change events.
        Accesses font_name, font_size, and font_bold Variables.
        Updates font_sample and hightlight page highlight_sample.
        """
        font_name = self.font_name.get()
        font_weight = tkFont.BOLD if self.font_bold.get() else tkFont.NORMAL
        new_font = (font_name, self.font_size.get(), font_weight)
        self.font_sample['font'] = new_font
        self.highlight_sample['font'] = new_font

    def load_tab_cfg(self):
        """Load current configuration settings for the tab options.

        Attributes updated:
            space_num: Set to value from idleConf.
        """
        # Set indent sizes.
        space_num = idleConf.GetOption(
            'main', 'Indent', 'num-spaces', default=4, type='int')
        self.space_num.set(space_num)

    def var_changed_space_num(self, *params):
        "Store change to indentation size."
        value = self.space_num.get()
        changes.add_option('main', 'Indent', 'num-spaces', value)


class VarTrace:
    """Maintain Tk variables trace state."""

    def __init__(self):
        """Store Tk variables and callbacks.

        untraced: List of tuples (var, callback)
            that do not have the callback attached
            to the Tk var.
        traced: List of tuples (var, callback) where
            that callback has been attached to the var.
        """
        self.untraced = []
        self.traced = []

    def clear(self):
        "Clear lists (for tests)."
        self.untraced.clear()
        self.traced.clear()

    def add(self, var, callback):
        """Add (var, callback) tuple to untraced list.

        Args:
            var: Tk variable instance.
            callback: Either function name to be used as a callback
                or a tuple with IdleConf config-type, section, and
                option names used in the default callback.

        Return:
            Tk variable instance.
        """
        if isinstance(callback, tuple):
            callback = self.make_callback(var, callback)
        self.untraced.append((var, callback))
        return var

    @staticmethod
    def make_callback(var, config):
        "Return default callback function to add values to changes instance."
        def default_callback(*params):
            "Add config values to changes instance."
            changes.add_option(*config, var.get())
        return default_callback

    def attach(self):
        "Attach callback to all vars that are not traced."
        while self.untraced:
            var, callback = self.untraced.pop()
            var.trace_add('write', callback)
            self.traced.append((var, callback))

    def detach(self):
        "Remove callback from traced vars."
        while self.traced:
            var, callback = self.traced.pop()
            var.trace_remove('write', var.trace_info()[0][1])
            self.untraced.append((var, callback))


tracers = VarTrace()

help_common = '''\
When you click either the Apply or Ok buttons, settings in this
dialog that are different from IDLE's default are saved in
a .idlerc directory in your home directory. Except as noted,
these changes apply to all versions of IDLE installed on this
machine. Some do not take affect until IDLE is restarted.
[Cancel] only cancels changes made since the last save.
'''
help_pages = {
    'Highlighting': '''
Highlighting:
The IDLE Dark color theme is new in October 2015.  It can only
be used with older IDLE releases if it is saved as a custom
theme, with a different name.
''',
    'Keys': '''
Keys:
The IDLE Modern Unix key set is new in June 2016.  It can only
be used with older IDLE releases if it is saved as a custom
key set, with a different name.
''',
    'Extensions': '''
Extensions:

Autocomplete: Popupwait is milleseconds to wait after key char, without
cursor movement, before popping up completion box.  Key char is '.' after
identifier or a '/' (or '\\' on Windows) within a string.

FormatParagraph: Max-width is max chars in lines after re-formatting.
Use with paragraphs in both strings and comment blocks.

ParenMatch: Style indicates what is highlighted when closer is entered:
'opener' - opener '({[' corresponding to closer; 'parens' - both chars;
'expression' (default) - also everything in between.  Flash-delay is how
long to highlight if cursor is not moved (0 means forever).
'''
}


def is_int(s):
    "Return 's is blank or represents an int'"
    if not s:
        return True
    try:
        int(s)
        return True
    except ValueError:
        return False


class VerticalScrolledFrame(Frame):
    """A pure Tkinter vertically scrollable frame.

    * Use the 'interior' attribute to place widgets inside the scrollable frame
    * Construct and pack/place/grid normally
    * This frame only allows vertical scrolling
    """
    def __init__(self, parent, *args, **kw):
        Frame.__init__(self, parent, *args, **kw)

        # Create a canvas object and a vertical scrollbar for scrolling it.
        vscrollbar = Scrollbar(self, orient=VERTICAL)
        vscrollbar.pack(fill=Y, side=RIGHT, expand=FALSE)
        canvas = Canvas(self, bd=0, highlightthickness=0,
                        yscrollcommand=vscrollbar.set, width=240)
        canvas.pack(side=LEFT, fill=BOTH, expand=TRUE)
        vscrollbar.config(command=canvas.yview)

        # Reset the view.
        canvas.xview_moveto(0)
        canvas.yview_moveto(0)

        # Create a frame inside the canvas which will be scrolled with it.
        self.interior = interior = Frame(canvas)
        interior_id = canvas.create_window(0, 0, window=interior, anchor=NW)

        # Track changes to the canvas and frame width and sync them,
        # also updating the scrollbar.
        def _configure_interior(event):
            # Update the scrollbars to match the size of the inner frame.
            size = (interior.winfo_reqwidth(), interior.winfo_reqheight())
            canvas.config(scrollregion="0 0 %s %s" % size)
        interior.bind('<Configure>', _configure_interior)

        def _configure_canvas(event):
            if interior.winfo_reqwidth() != canvas.winfo_width():
                # Update the inner frame's width to fill the canvas.
                canvas.itemconfigure(interior_id, width=canvas.winfo_width())
        canvas.bind('<Configure>', _configure_canvas)

        return


if __name__ == '__main__':
    import unittest
    unittest.main('idlelib.idle_test.test_configdialog',
                  verbosity=2, exit=False)
    from idlelib.idle_test.htest import run
    run(ConfigDialog)