The purpose of this method is to convert a color name into a
numeric value, and thence into a
# - - - N a m e P i c k e r . _ _ s e t B y N a m e def __setByName ( self, colorName ): """Convert a color name to RGB values as a Color instance. [ colorName is a string -> if colorName is defined in either Tkinter or our color pick list -> call self.__callback and pass it that color as a Color instance else -> pop up a Dialog window complaining about the undefined color name ] """
In theory, a properly installed X Window system will have a file
rgb.txt that lists all the standard
color names. In theory, any application should be able to use a
color name from that file, and the window system will recognize
it. In practice, the presence of that file is not guaranteed,
and even if does exist, we have no assurance that the set of
color names accepted by the window system is the same as the
contents of the file.
In case the
rgb.txt file is missing, this
program contains a data structure which represents the contents
of one version of that file.
However, there is another source for translating color names to
RGB values. Every Tkinter widget has a method named
.winfo_rgb() which takes a color name and returns a
each value is in the range [0,
So, our liberal policy will be to try the latter technique
first. If that fails, we can still use the list that appears in
the pick list to convert names to RGB values. That way, if the
two sources differ, we implement the union of their values.
There is a discussion of the
Dialog pop-up in
Section 12.4, “
MenuBar.__helpTyping()”. See also
Section 14.3, “
PickList.lookupName(): Convert a color name
to a color value”.
#-- 1 -- # [ if (Tkinter recognizes (colorName) as a color) or # (colorName) is defined in self.__pickList) -> # rgb := that color as a tuple (r, g, b) of values # in [0,MAX_PARAM] # else -> # pop up a Dialog complaining about the undefined # color name # return ] try: rgb = self.winfo_rgb ( colorName ) except: rgb = self.__pickList.lookupName ( colorName ) if not rgb: Dialog ( self, title="Message", bitmap="info", default=0, strings=("Dismiss",), text=("Color '%s' is undefined." % colorName) ) return
All that remains is to convert
rgb to a
Color and call the callback.
#-- 2 -- # [ if self.__callback is not None -> # call self.__callback with a Color made from rgb # else -> I ] if self.__callback is not None: self.__callback ( Color ( *rgb ) )