javascript - 获取裁剪线可见区域长度 d3

Question

我正在尝试使用 ClipPath 剪裁带圆圈的线，并通过拖动成功完成。这是我的工作代码；

function clipData(svg, cx, cy) {

    var clip = svg.append("defs")
        .append("clipPath") // define a clip path
        .attr("id", "clip") // give the clipPath an ID
        .append("circle") // shape it as an ellipse
        .attr("id", "my-circle")
        .attr("cx", 100) // position the x-centre
        .attr("cy", 80) // position the y-centre
        .attr("r", 80) // set the x radius
        .attr("fill", "yellow")

    svg.append("circle") // shape it as an ellipse
        .attr("cx", 100) // position the x-centre
        .attr("cy", 80) // position the y-centre
        .attr("r", 80) // set the x radius
        .attr("fill", "red")


    var g = svg.append("g")
        .datum({
            x: 0,
            y: 0
        })
        .attr("id", "child")
        //.attr("transform", function(d) { return 'translate(' + d.x + ' '+ d.y + ')'; })

        .call(d3.drag()
            .on("start", function(d) {
                d3.select(this).raise().classed("active", true);

            })
            .on("drag", function(d) {
                d3.select(this).attr("transform", "translate(" + (d3.event.x) + "," + (d3.event.y) + ")");
                d3.select("#svgGreen").selectAll("*").remove();
                clipData(svg, d3.event.x + cx, d3.event.y + cy);

            })
            .on("end", function(d) {
                d3.select(this).classed("active", false);
            }));


    g.append("line")
        .attr("clip-path", "url(#clip)")
        .attr("x1", cx)
        .attr("y1", cy)
        .attr("x2", cx + 100)
        .attr("y2", cy + 100)
        .style("stroke", "purple")
        .style("stroke-width", 12)

}

var svg = d3.select("#svgGreen");
var cx = 100,
    cy = 80,
    x = 0,
    y = 0;

clipData(svg, cx, cy);

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.5.0/d3.min.js"></script>
<svg xmlns="http://www.w3.org/2000/svg" version="1.1"  className="clip-path" id="svgGreen">
</svg>

现在我试图在剪裁后获取 线的可见部分的长度。但是当我尝试从线的 x-y 点获取它时，我总是得到与剪裁前相同的长度，

Is there any way that I can get only visible Line length after clipping??

Answer 1

根据 MDN

A clipping path is conceptually equivalent to a custom viewport for the referencing element. Thus, it affects the rendering of an element, but not the element's inherent geometry: the bounding box of a clipped element (meaning, an element which references a element via a clip-path property, or a child of the referencing element) must remain the same as if it were not clipped.

因此无论是否裁剪，此元素的大小始终保持不变。我认为您应该考虑使用另一种方法来满足您的需求。