huey: Internal maintenance specification

This class is a compound widget that has two functions:

Here is the class interface:

# - - - - -   c l a s s   C o l o r R e a d o u t

class ColorReadout(Frame):
    """Displays text and background colors, and switches between them.

      Exports:
        ColorReadout ( parent, bg, fg, callback=None ):
          [ (parent is a Frame) and
            (bg is a background color as a Color) and
            (fg is a foreground color as a Color) and
            (callback is a function or None) ->
              parent  :=  parent with a new ColorReadout widget
                  added but not gridded, initially displaying
                  the background color, which will call
                  callback() whenever the user changes
                  between text to bg color ]

The next two methods return the current text and background colors, respectively; see Section 16.4, “ColorReadout.textColor(): Return the current text color” and Section 16.5, “ColorReadout.bgColor(): Return the current background color”.

        .textColor():
          [ return self's current text color as a Color instance ]
        .bgColor:
          [ return self's current background color as a Color instance ]

The .set() method changes the currently displayed color; see Section 16.2, “ColorReadout.set(): Change the displayed color”.

        .set ( color ):
          [ if self is currently displaying the text color ->
              self's text color  :=  color
            else ->
              self's background color  :=  color
            In any case ->
              call self.__callback(color) ]

To determine whether the user has selected text or background color, call this method; see Section 16.1, “ColorReadout.isText(): Which color are we displaying?”.

        .isText():
          [ if self is currently displaying the text color ->
              return True
            else -> return False ]

Here is the layout of the internal widgets, and the internal attributes that control them.

      Contained widgets:
        .__rgbLabel:      [ text label '#RRGGBB' ]
        .__textColorName:
          [ an Entry widget displaying self.__textColorVar ]
        .__bgColorName:
          [ an Entry widget displaying self.__bgColorVar ]
        .__textRadio:   [ a Radiobutton selecting text color ]
        .__bgRadio:     [ a Radiobutton selecting background color ]

      Grid plan:
           0              1
          +--------------+-------------------+
        0 |              | .__rgbLabel       |
          +--------------+-------------------+
        1 | .__bgRadio   | .__bgColorName    |
          +--------------+-------------------+
        2 | .__textRadio | .__textColorName  |
          +--------------+-------------------+

      State/Internals:
        .__callback:     [ as passed to constructor, read-only ]
        .__isTextVar:
          [ an IntVar that is 1 if displaying text color,
            0 if displaying background color ]
        .__bgColor:
          [ self's current background color as a Color instance ]
        .__bgColorVar:
          [ a StringVar displaying self.__bgColor as #RRGGBB ]
        .__textColor:
          [ self's current text color as a Color instance ]
        .__textColorVar:
          [ a StringVar displaying self.__textColor as #RRGGBB ]
    """