 
                 # if chrome => listen to keyup to correct the insertion of the
                 # first caracter of an empty line
+                @isFirefox = `'MozBoxSizing' in document.documentElement.style`
                 @isSafari = Object.prototype.toString.call(window.HTMLElement)
                 @isSafari = @isSafari.indexOf('Constructor') > 0
                 @isChrome = !@isSafari && 


        # 6- position selection
        rg = document.createRange()
        rg.setStart(breakPoints[0].cont,breakPoints[0].offset)
        rg.setEnd(breakPoints[1].cont,breakPoints[1].offset)
        @currentSel.sel.removeAllRanges()
        @currentSel.sel.addRange(rg)

        
        return true


    ###*
     * This function is called only if in Chrome, because the insertion of a caracter
     * by the browser may be out of a span. 
     * This is du to a bug in Chrome : you can create a range with its start 
     * break point in an empty span. But if you add this range to the selection,
     * then this latter will not respect your range and its start break point 
