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The purpose of this function is to assist in building an XHTML element that may have class attributes attached that come from multiple sources. It accepts a variable number of arguments, each of which specifies zero or more CSS class names in the form described in Section 14.2, “class-dict”.

For example, et.CLASS('a', 'b') would return the dictionary {'class': 'a b'}. The manifest constants defined in Section 13.4, “CSS constants”, which have names starting with “CSS_”, specify CSS classes in this way.

The purpose of the combineCss() function, then, is to produce a class-dict dictionary that combines class names from multiple sources. The function takes a variable number of arguments, each of which can be either None or a class-dict. If none of the arguments specify any class names, it returns an empty dictionary, otherwise it returns a class-dict that includes all the specified class names.

# - - -   c o m b i n e C s s

def combineCss(*cssList):
    '''Build a class-dict from multiple class-dicts.

      [ cssList is a list whose members are either class-dicts
        or None ->
          if cssList is empty or contains only None elements ->
            return a new, empty dictionary
          else ->
            return a class-dict representing all the class names
            named in cssList ]
    '''
    #-- 1
    nameList = []

    #-- 2
    # [ nameList  +:=  classes named in cssList ]
    for d in cssList:
        #-- 2 body
        # [ if d is None ->
        #     I
        #   else ->
        #     nameList  +:=  classes named in d ]
        if d is not None:
            nameList += d['class'].split()

    #-- 3
    if len(nameList) == 0:
        return {}
    else:
        return {'class': ' '.join(nameList)}