 
                 # 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 && 


    ###*
     * This function is called only if in Chrome, because the insertion of a caracter
     * by the browser may 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 


        # 6- position selection
        rg = document.createRange()
        rg.setStart(bp1.cont, bp1.offset)
        rg.setEnd(  bp2.cont, bp2.offset)
        if @isFirefox
            sel = this.currentSel.sel
        else
            sel = document.getSelection()
        sel.removeAllRanges()
        sel.addRange(rg)

        
        return true
