ie9 SVG - 绘制html文本的顶部

Question

我尝试使用鼠标事件动态绘制svg行覆盖现有html文本。它适用于Firefox，但与IE9崩溃。使用ie9绘制线条，但仅限于文档的未占用部分。当鼠标指针在html文本上移动时，当鼠标指针从一个箭头变为另一个时，你可以告诉ie9。以下是我的svg代码：

function SVG( docframe, objectType, color ){ this.svgID = "svg" + canvasCount++;

var height = parseFloat( docframe.style.height ) * 10;
var width = parseFloat( docframe.style.width ) * 10;
var svg = document.createElementNS( "http://www.w3.org/2000/svg", "svg" );
svg.setAttributeNS( "http://www.w3.org/2000/xmlns/", "xmlns:xlink",
                   SVG.xlinkns );
svg.color = color;
svg.setAttribute( 'width', width );
svg.setAttribute( 'height', height );
svg.setAttribute( "viewBox", "0 0 " + width + " " + height );
svg.style.width = width + "px";
svg.style.height = height + "px";
svg.setAttribute( 'id', this.svgID );
svg.style.overflow = 'visible';
svg.style.position = 'absolute';
svg.tabIndex = svg.style.zIndex = 10;
this.svg = svg;    

//append canvas to divf
docframe.appendChild( svg );

//Define Canvas functions
this.svg.onmousedown = function ( e )
{    
    var mouseX = 0;
    var mouseY = 0;
    coordinates.splice( 0, coordinates.length );    
    paint = true;

    //if IE
    if ( navigator.appName == "Microsoft Internet Explorer" )
    {
        mouseX = e.offsetX;
        mouseY = e.offsetY;
    }
    else
    {
        mouseX = ( e.layerX - dragOffsets.left );
        mouseY = ( e.layerY - dragOffsets.top );
    }        
    paint = true;
    addClick( mouseX, mouseY );
    redraw( this );       
}


this.svg.onmousemove = function ( e )
{
    if ( paint )
    {
        var mouseX = 0;
        var mouseY = 0;

        //if IE
        if ( navigator.appName == "Microsoft Internet Explorer" )
        {
            mouseX = e.offsetX;
            mouseY = e.offsetY;
        }
        else
        {
            mouseX = ( e.layerX - dragOffsets.left );
            mouseY = ( e.layerY - dragOffsets.top );
        }
        addClick( mouseX, mouseY);
        redraw( this );
    }        
}
this.svg.onmouseover = function ( e )
{
    if ( paint )
    {
        var mouseX = 0;
        var mouseY = 0;

        //if IE
        if ( navigator.appName == "Microsoft Internet Explorer" )
        {
            mouseX = e.offsetX;
            mouseY = e.offsetY;
        }
        else
        {
            mouseX = ( e.layerX - dragOffsets.left );
            mouseY = ( e.layerY - dragOffsets.top );
        }
        addClick( mouseX, mouseY);
        redraw( this );
    }
}
this.svg.onmouseup = function ( e )
{
    paint = false;
}
}

var paint;
var coordinates = new Array();

function MapPoints( x, y )
{
    this.x = x;
    this.y = y;
}

function addClick( x, y )
{
    if ( coordinates )
    {
        var mapPoints = new MapPoints( x, y );
        coordinates.push( mapPoints );
    }
}

function redraw( svg)
{
    if ( coordinates )
    {
        var coorlength = coordinates.length - 1;
        if ( coorlength >= 1 )
        {
            var obj = document.createElementNS( 'http://www.w3.org/2000/svg', 'line' );
            obj.setAttribute( 'x1', coordinates[coorlength - 1].x );
            obj.setAttribute( 'x2', coordinates[coorlength].x );
            obj.setAttribute( 'y1', coordinates[coorlength - 1].y );
            obj.setAttribute( 'y2', coordinates[coorlength].y );
            obj.setAttribute( 'stroke', svg.color );
            obj.setAttribute( 'stroke-width', 5 );

            svg.appendChild( obj );
        }
    }
}