Wraping text for the Raphsel js library

# *** first steps with coffescript and Raphael ***

window.onload = ->
    paper = new Raphael document.getElementById('canvas_container'), '100%', '100%'

    # help-functions =======================>

    # computing of the char widths for a given font-family and fontsize
    computeCharWidthMap = (fontFamily, fontSize) ->
        # ascii bonds
        ascii_lower_bound = 32
        ascii_upper_bound = 126

        # object for storing
        #charWidthMap = {}
        # using objects as (hash)maps ugly! ugly !ugly!
        charWidthMap = new Object();

        for asciiChar in [ascii_lower_bound..ascii_upper_bound]
            letter = String.fromCharCode(asciiChar)
            drawnLetter = paper.text(-1000, -1000, letter).attr('font-family': fontFamily, 'font-size': fontSize)
            charWidthMap[letter] = drawnLetter.getBBox().width
            #console.log 'letter: ' + letter, drawnLetter.getBBox().width

        return charWidthMap

    # wrap given text (string) and return the wrapped string and its size
    wrapTextToGivenWidth = (originalText, wrappingWidth, charWidthMap) ->

        # remove all whitespaces at beginning
        # todo

        # check if the text not empty after the previous step
        # todo
        # if so -> throw exception or return empty string ?

        textWidth = 0 # replace with the max(prefix-length ... textwidth)
        textHeight = globalFontSize
        # indexing variables
        lastSpaceCharIndex = 0
        prefixLenghtsArray = []
        # indexing variable for the line breaks
        lineBreakIndexes = []

        for char, index in originalText.split ''
            # check index to avoid indexOutOfBounds ...
            if index < 1
                prefixLenghtsArray.push charWidthMap[char]
            # compute the prefix lenght to the current index
            else prefixLenghtsArray.push charWidthMap[char] + prefixLenghtsArray[index-1] + 1 # add one pixel for the kerning

            # note appearence of a space-character
            if (char == ' ')
                lastSpaceCharIndex = index

            # test if the maximum allowed text width reached
            if (prefixLenghtsArray[index] > wrappingWidth)
                # case : space characters before the curent index present and not already present in the indexing array
                if lastSpaceCharIndex > 0 && lastSpaceCharIndex not in lineBreakIndexes
                    # index of the line break is after the last space character
                    lineBreakIndexes.push(lastSpaceCharIndex + 1)
                    # increase the text height because of the new linebrek
                    textHeight += globalFontSize
                    # now correct the prefix lengths from the position behind the last space character
                    for position in [lastSpaceCharIndex + 1 .. index]
                        prefixLenghtsArray[position] = prefixLenghtsArray[position] - prefixLenghtsArray[lastSpaceCharIndex]
                else
                    # no space characters before the current index -> the line break on the current index
                    lineBreakIndexes.push(index)
                    # correct the current prefix length
                    prefixLenghtsArray[index] = charWidthMap[char]
                    # increase the text height because of the new linebrek
                    textHeight += globalFontSize
            else
                # compare the length prefix (should save computing against maxElement(array))
                textWidth = Math.max(textWidth, prefixLenghtsArray[index])

            #console.log 'preffix Array nr. ' + index, prefixLenghtsArray, 'linebreak indexes nr. ' + index, lineBreakIndexes

        # inserting the line breaks
        for position in lineBreakIndexes
            #originalText = originalText.substr(0, position) + '\n' + originalText.substr(position)
            originalText = [originalText.slice(0, position), '\n', originalText.slice(position)].join('') # slightly faster than the previous one

        # explicit return statement
        return (
            wrappedText: originalText
            width: textWidth
            height: textHeight
        )

    # =========================================================

    globalFontFamily = 'Helvetica'
    globalFontSize = 16
    globalCharWidthMap = computeCharWidthMap(globalFontFamily, globalFontSize)

    testText = wrapTextToGivenWidth('Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.', 300, globalCharWidthMap)
    #console.log 'char width map:', globalCharWidthMap, 'wrapped text:' , testText

    drawTestText = paper.text(100, 200, testText.wrappedText).attr('font-family': globalFontFamily, 'font-size': globalFontSize, 'text-anchor': 'start')
    text2Bbox = drawTestText.getBBox()
    paper.text(600, 100, 'boundig-box size :\n' + 'width: ' + text2Bbox.width + ' height: ' + text2Bbox.height).attr('font-family': globalFontFamily, 'font-size': globalFontSize)
    paper.text(600, 200, 'computed size :\n' + 'width: ' + testText.width + ' height: ' + testText.height).attr('font-family': globalFontFamily, 'font-size': globalFontSize)