var Checkfont = Class.create({
    checkedFonts: new Hash(),
    testString: 'mmmmmmmmmmlilg',
    testFontSize: '72px',
    standardFont: 'serif',
 
    initialize: function() {
        this.body = document.body;
        this.span = new Element('span').hide();
 
        this.body.insert(this.span);
        this.defaultDimensions = this._getFontDimensions(this.standardFont);
    },
 
    test: function(font) {
        font = font.toLowerCase();
 
        var alreadyChecked = this.checkedFonts.get(font);
        if (!Object.isUndefined(alreadyChecked)) {
            return alreadyChecked;
        }
 
        this.testDimensions = this._getFontDimensions(font);
 
        var test = true;
        if (font != this.standardFont) {
            test = (this.testDimensions.width != this.defaultDimensions.width
                || this.testDimensions.height != this.defaultDimensions.height);
        }
        this.checkedFonts.set(font, test);
        return test;
    },
 
    _getFontDimensions: function(font) {
        this.span.setStyle({
            fontFamily: font,
            fontSize: this.testFontSize
        }).update(this.testString);
        var fontDimensions = this.span.getDimensions();
        this.span.update();
        return fontDimensions;
    }
});