CODEWITHSUNDEEP
javascriptd3.jssvgtransform
interwebjill
interwebjill

Reputation: 950

Resetting drag with multiple elements

I have multiple svg groups (each containing a circle and text) which I am dragging via d3-drag from an initial position. I have a rectangular hit zone that I only want one of these draggable groups in at a time. So whenever two groups are in the hit zone, I would like the first group that was in the hit zone to fade away and reappear in its initial position.

I have tried doing this via a function which translates the group back to its initial position by finding the current position of the circle shape and translating like:

translate(${-current_x}, ${-current_y})

This does translate the group back to the (0,0) position, so I have to offset by its initial position. I do this by setting the initial x and y values of the circle shape as attributes in the circle element and incorporating these into the translation:

translate(${-current_x + initial_x}, ${-current_y + initial_y})

Here is a block of my attempt:

https://bl.ocks.org/interwebjill/fb9b0d648df769ed72aeb2755d3ff7d5

And here it is in snippet form:

    const circleRadius = 40;
    const variables = ['one', 'two', 'three', 'four'];
    const inZone = [];
    
    // DOM elements
    const svg = d3.select("body").append("svg")
      .attr("width", 960)
      .attr("height", 500)
    
    const dragDockGroup = svg.append('g')
      .attr('id', 'draggables-dock');
    
    const dock = dragDockGroup.selectAll('g')
      .data(variables)
      .enter().append("g")
      .attr("id", (d, i) => `dock-${variables[i]}`);

    dock.append("circle")
      .attr("cx", (d, i) => circleRadius * (2 * i + 1))
      .attr("cy", circleRadius)
      .attr("r", circleRadius)
      .style("stroke", "none")
      .style("fill", "palegoldenrod");

    dock.append("text")
      .attr("x", (d, i) => circleRadius * (2 * i + 1))
      .attr("y", circleRadius)
      .attr("text-anchor", "middle")
      .style("fill", "white")
      .text((d, i) => variables[i]);
    
    const draggablesGroup = svg.append('g')
    	.attr('id', 'draggables');
    
    const draggables = draggablesGroup.selectAll('g')
      .data(variables)
      .enter().append("g")
      .attr("id", (d, i) => variables[i])
      .call(d3.drag()
          .on("start", dragStarted)
          .on("drag", dragged)
          .on("end", dragEnded));

    draggables.append('circle')
      .attr("cx", (d, i) => circleRadius * (2 * i + 1))
      .attr("cy", circleRadius)
      .attr("initial_x", (d, i) => circleRadius * (2 * i + 1))
      .attr("initial_y", circleRadius)
      .attr("r", circleRadius)
      .style("stroke", "orange")
      .style("fill", "yellowgreen");

    draggables.append("text")
       .attr("x", (d, i) => circleRadius * (2 * i + 1))
       .attr("y", circleRadius)
       .attr("text-anchor", "middle")
       .style("fill", "white")
       .text((d, i) => variables[i]);
    
    svg.append('rect')
      .attr("x", 960/2)
      .attr("y", 0)
      .attr("width", 100)
      .attr("height", 500/2)
      .attr("fill-opacity", 0)
      .style("stroke", "#848276")
      .attr("id", "hitZone");
    
    // functions
    function dragStarted() {
      d3.select(this).raise().classed("active", true);
  	}

  	function dragged() {
      d3.select(this).select("text").attr("x", d3.event.x).attr("y", d3.event.y);
      d3.select(this).select("circle").attr("cx", d3.event.x).attr("cy", d3.event.y);
  	}

  function dragEnded() {
    d3.select(this).classed("active", false);
    d3.select(this).lower();
    let hit = d3.select(document.elementFromPoint(d3.event.sourceEvent.clientX, d3.event.sourceEvent.clientY)).attr("id");

    if (hit == "hitZone") {
      inZone.push(this.id);
      if (inZone.length > 1) {
        let resetVar = inZone.shift();
        resetCircle(resetVar);
      }
    }
    
    d3.select(this).raise();
  }

  function resetCircle(resetVar) {
    let current_x = d3.select(`#${resetVar}`)
      .select('circle')
      .attr('cx');

    let current_y = d3.select(`#${resetVar}`)
      .select('circle')
      .attr('cy');

    let initial_x = d3.select(`#${resetVar}`)
      .select('circle')
      .attr('initial_x');

    let initial_y = d3.select(`#${resetVar}`)
      .select('circle')
      .attr('initial_y');

    d3.select(`#${resetVar}`)
      .transition()
        .duration(2000)
        .style('opacity', 0)
      .transition()
        .duration(2000)
        .attr('transform', `translate(${-current_x}, ${-current_y})`)
      .transition()
        .duration(2000)
        .style('opacity', 1);
  }
 body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
 <script src="https://d3js.org/d3.v5.min.js"></script>

Here are the problems:

  1. While using translate(${-current_x}, ${-current_y}) works, when I try using translate(${-current_x + initial_x}, ${-current_y + initial_y}), the translation uses very large negative numbers (for example, translate(-52640, -4640)).

  2. While using translate(${-current_x}, ${-current_y}) works, when I try to drag this translated group again, the group immediately repeats the previous translate(${-current_x}, ${-current_y})

Upvotes: 2

Views: 149

Answers (1)

Andrew Reid
Andrew Reid

Reputation: 38201

Your code runs into difficulties because you are positioning both the g elements and the children text and circles.

Circles and text are originally positioned by x/y attributes:

draggables.append('circle')
  .attr("cx", (d, i) => circleRadius * (2 * i + 1))
  .attr("cy", circleRadius)

draggables.append("text")
   .attr("x", (d, i) => circleRadius * (2 * i + 1))
   .attr("y", circleRadius)

Drag events move the circles and text here:

d3.select(this).select("text").attr("x", d3.event.x).attr("y", d3.event.y);
d3.select(this).select("circle").attr("cx", d3.event.x).attr("cy", d3.event.y);

And then we reset the circles and text by trying to offset the parent g with a transform:

d3.select(`#${resetVar}`).attr('transform', `translate(${-current_x}, ${-current_y})`)

Where current_x and current_y are the current x,y values for the circles and text. We have also stored the initial x,y values for the text, but altogether, this becomes a more convoluted then necessary as we have two competing sets of positioning coordinates.

This can be simplified a fair amount. Instead of positioning both the text and the circles, simply apply a transform to the parent g holding both the circle and the text. Then when we drag we update the transform, and when we finish, we reset the transform.

Now we have no modification of x,y/cx,cy attributes and transforms for positioning the elements relative to one another. No offsets and the parent g's transform will always represent the position of the circle and the text.

Below I keep track of the original transform with the datum (not an element attribute) - normally I would use a property of the datum, but you have non-object data, so I just replace the datum with the original transform:

const circleRadius = 40;
const variables = ['one', 'two', 'three', 'four'];
const inZone = [];
    
// DOM elements
const svg = d3.select("body").append("svg")
  .attr("width", 960)
  .attr("height", 500)
    
const dragDockGroup = svg.append('g')
  .attr('id', 'draggables-dock');

// Immovable placemarkers:
const dock = dragDockGroup.selectAll('g')
  .data(variables)
  .enter().append("g")
  .attr("id", (d, i) => `dock-${variables[i]}`);

dock.append("circle")
  .attr("cx", (d, i) => circleRadius * (2 * i + 1))
  .attr("cy", circleRadius)
  .attr("r", circleRadius)
  .style("stroke", "none")
  .style("fill", "palegoldenrod");

dock.append("text")
  .attr("x", (d, i) => circleRadius * (2 * i + 1))
  .attr("y", circleRadius)
  .attr("text-anchor", "middle")
  .style("fill", "white")
  .text((d, i) => variables[i]);

// Dragables
const draggablesGroup = svg.append('g')
  .attr('id', 'draggables');
    
const draggables = draggablesGroup.selectAll('g')
  .data(variables)
  .enter()
  .append("g")
  .datum(function(d,i) {
     return "translate("+[circleRadius * (2 * i + 1),circleRadius]+")";
  })
  .attr("transform", (d,i) => d)
  .attr("id", (d, i) => variables[i])
  .call(d3.drag()
     .on("start", dragStarted)
     .on("drag", dragged)
     .on("end", dragEnded));

draggables.append('circle')
  .attr("r", circleRadius)
  .style("stroke", "orange")
  .style("fill", "yellowgreen");

draggables.append("text")
  .attr("text-anchor", "middle")
  .style("fill", "white")
  .text((d, i) => variables[i]);
    
svg.append('rect')
   .attr("x", 960/2)
   .attr("y", 0)
   .attr("width", 100)
   .attr("height", 500/2)
   .attr("fill-opacity", 0)
   .style("stroke", "#848276")
   .attr("id", "hitZone");
    
 // functions
function dragStarted() {
    d3.select(this).raise();
 }

function dragged() {
   d3.select(this).attr("transform","translate("+[d3.event.x,d3.event.y]+")")
}

function dragEnded() {
  d3.select(this).lower();
  let hit = d3.select(document.elementFromPoint(d3.event.sourceEvent.clientX, d3.event.sourceEvent.clientY)).attr("id");

  if (hit == "hitZone") {
    inZone.push(this.id);
    if (inZone.length > 1) {
    let resetVar = inZone.shift();
    resetCircle(resetVar);
   }
  }
    
  d3.select(this).raise();
}

function resetCircle(resetVar) {
  d3.select(`#${resetVar}`)
   .transition()
     .duration(500)
     .style('opacity', 0)
   .transition()
     .duration(500)
     .attr("transform", (d,i) => d)
   .transition()
     .duration(500)
     .style('opacity', 1);
}
 
body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
<script src="https://d3js.org/d3.v5.min.js"></script>

Upvotes: 3

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