D3.js zoom.wheelDelta()函数

D3.js的zoom.wheelDelta()函数用于将 wheel delta函数设置为指定函数并返回缩放行为。

句法：

zoom.wheelDelta([delta])

参数：此函数接受如上所述和下文所述的单个参数。

• delta：此参数用于将车轮增量函数设置为指定函数。

返回值：此函数返回缩放行为。

下面的程序说明了D3.js中的zoom.wheelDelta()函数

示例 1：

HTML

 
 
 
    
     
     
    
        
    
        svg text {  
            fill: green;  
            font: 20px sans-serif;  
            text-anchor: center;  
        }  
            
        rect {
          pointer-events: all;
        }
    
       
 
      
 
    
         
            Geeksforgeeks 
         
        
        D3.js | zoom.wheelDelta() Function
            
        
            
        
            var width = 400;
            var height = 200;
                
            var svg = d3.select("svg")
              .attr("width",width)
              .attr("height",height);
                  
            // The scale used to display the axis.
            var scale = d3.scaleLinear()
              .range([10,width-20])
              .domain([0,100]);
                 
            var shadowScale = scale.copy();
                
            var axis = d3.axisBottom()
              .scale(scale);
                  
            var g = svg.append("g")
              .attr("transform","translate(0,50)")
              .call(axis);
                  
            // Standard zoom behavior:
            var zoom = d3.zoom()
              .scaleExtent([1,10])
              .translateExtent([[0, 0], [width, height]])
              .wheelDelta(myDelta)
              .on("zoom", zoomed);
                 
            // Call the Zoom.
            var rect = svg.append("rect")
              .attr("width",width)
              .attr("height",height)
              .attr("fill","none")
              .call(zoom);
                            
            function zoomed() {
              var t = d3.event.transform;
              scale.domain(t.rescaleX(shadowScale).domain());
              g.call(axis);
            }
            function myDelta() {
              return -d3.event.deltaY * 
             (d3.event.deltaMode ? 120 : 1) / 1500;
            }
         
    
   

输出：

示例 2：

HTML

 
 
 
    
      
    
    
         
    
        rect {
            fill: green;
            opacity: 0.5;
            stroke: black;
            stroke-width: 1px;
        }
             
        svg {
            border: 1px solid;
            font: 13px sans-serif;
        }
    
         
 
       
 
    
         
            Geeksforgeeks 
         
         
        D3.js | zoom.wheelDelta() Function
             
        
        
             
        
                var width = 400;
                var height=250;
                var size=30;
                 
                var svg = d3.select('#GFG')
                    .append('svg')
                    .attr('width', width)
                    .attr('height', height)
                       
                var g = svg.append('g')
                   
                var numrects = 100;
                var rects = [];
                for (var i = 0; i < numrects; i++)
                    rects.push({'x': 1 +
                         Math.floor(Math.random() * width),
                        'y': 1+Math.floor(Math.random() * height),
                        'h': 3+Math.floor(Math.random() * size),
                        'w': 3+Math.floor(Math.random() * size)
                    });
                 
                g.selectAll('rect')
                    .data(rects)
                    .enter()
                    .append('rect')
                    .attr('x', function(d) { return d.x; })
                    .attr('y', function(d) { return d.y; })
                    .attr('height', function(d) { return d.h; })
                    .attr('width', function(d) { return d.w; })
                    .classed('no-zoom', true)
                 
                var zoomed = d3.zoom()
                    .wheelDelta(myDelta)
                    .scaleExtent([1,10])
                    .on('zoom', function(d){ 
                        g.attr('transform', d3.event.transform); 
                    });
                 
                svg.call(zoomed);
                function myDelta() {
              return d3.event.deltaY / 10;
            }
        
    
 
     

输出：