micahstubbs/.block

## .block
license: MIT
border: no

## README.md

      
    Raw
  

              README.md
            
          
    a Canvas example that shows how to drag multiple shapes inside of another shape.  notice that the red circles can be dragged independently. notice that the black rectangle can also be dragged, keeping it's red-circle children in the same relative positions.
you could also think about this problem as "how to create a hierarchy of draggable shapes?". the short answer is: do it in the dragSubject() function
d3-drag docs on drag subjects
a fork of Multiple Shape Drag SVG
an iteration on this very helpful stackoverflow answer
this collection of d3-drag experiments also exist in github repo form at micahstubbs/d3-drag-experiments

  
## index.html
<!DOCTYPE html>
<html>
  <head>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.10.2/d3.min.js"></script>
    <meta charset="utf-8">
    <title>d3-drag-experiments</title>
  </head>
  <body>
    <script src="vis.js"></script>
  </body>
</html>

## preview.png

      
    Raw
  

              preview.png
            
          
## preview.xcf

      
    Raw
  

              preview.xcf
            
          
            View raw
        
    
## thumbnail.png

      
    Raw
  

              thumbnail.png
            
          
## vis.js
/* prettier-ignore */
d3.select('body')
  .append('canvas')
  .attr('width', 960)
  .attr('height', 500);

const canvas = d3.select('canvas');
const context = canvas.node().getContext('2d');
const width = canvas.property('width');
const height = canvas.property('height');

const circles = [{ x: 50, y: 60, radius: 10 }, { x: 100, y: 80, radius: 10 }];
const rects = [{ x: 10, y: 10, x2: 210, y2: 210 }];

render();

canvas.call(
  d3
    .drag()
    .subject(dragSubject)
    .on('start', dragStarted)
    .on('drag', dragged)
    .on('end', dragEnded)
    .on('start.render drag.render end.render', render)
);

function render() {
  context.clearRect(0, 0, width, height);
  // draw the black rectangle
  rects.forEach(rect => {
    context.fillStyle = 'black';
    context.clearRect(0, 0, width, height);
    context.fillRect(rect.x, rect.y, rect.x2, rect.y2);

    // draw the red circles
    circles.forEach(circle => {
      context.beginPath();
      context.moveTo(circle.x + rect.x + circle.radius, circle.y + rect.y);
      context.arc(
        circle.x + rect.x,
        circle.y + rect.y,
        circle.radius,
        0,
        2 * Math.PI
      );
      context.fillStyle = 'red';
      context.fill();
    });
  });
}

function dragSubject() {
  let i;
  const n = circles.length;
  let dx;
  let dy;
  let d2;
  const radius = 10;
  let s2 = radius * radius * 4; // Double the radius
  let circle;
  let subject;

  for (i = 0; i < n; i += 1) {
    circle = circles[i];
    console.log('circle from dragSubject', circle);
    dx = d3.event.x - circle.x - rects[0].x;
    dy = d3.event.y - circle.y - rects[0].y;
    d2 = dx * dx + dy * dy;

    console.log('dx', dx);
    console.log('dy', dy);
    console.log('d2', d2);
    console.log('s2', s2);

    if (d2 < s2) {
      subject = circle;
      s2 = d2;
    } else if (typeof subject === 'undefined') {
      rect = rects[0];
      subject = rect;
    }
  }
  return subject;
}

function dragStarted() {
  // circles.splice(circles.indexOf(d3.event.subject), 1);
  // circles.push(d3.event.subject);
  d3.event.subject.active = true;
}

function dragged() {
  d3.event.subject.x = d3.event.x;
  d3.event.subject.y = d3.event.y;
}

function dragEnded() {
  d3.event.subject.active = false;
}

// const group = container.append('g');

// const rect = group
//   .append('rect')
//   .attr('width', w)
//   .attr('height', h)
//   .attr('x', 10)
//   .attr('yx', 10);

// const circle1 = group
//   .append('circle')
//   .attr('cx', 50)
//   .attr('cy', 50)
//   .attr('r', 10)
//   .style('fill', 'red');

// const circle2 = group
//   .append('circle')
//   .attr('cx', 100)
//   .attr('cy', 70)
//   .attr('r', 10)
//   .style('fill', 'red');

// circle1.call(drag);
// circle2.call(drag);
// group.call(drag);
	<!DOCTYPE html>
	<html>
	<head>
	<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.10.2/d3.min.js"></script>
	<meta charset="utf-8">
	<title>d3-drag-experiments</title>
	</head>
	<body>
	<script src="vis.js"></script>
	</body>
	</html>
	/* prettier-ignore */
	d3.select('body')
	.append('canvas')
	.attr('width', 960)
	.attr('height', 500);

	const canvas = d3.select('canvas');
	const context = canvas.node().getContext('2d');
	const width = canvas.property('width');
	const height = canvas.property('height');

	const circles = [{ x: 50, y: 60, radius: 10 }, { x: 100, y: 80, radius: 10 }];
	const rects = [{ x: 10, y: 10, x2: 210, y2: 210 }];

	render();

	canvas.call(
	d3
	.drag()
	.subject(dragSubject)
	.on('start', dragStarted)
	.on('drag', dragged)
	.on('end', dragEnded)
	.on('start.render drag.render end.render', render)
	);

	function render() {
	context.clearRect(0, 0, width, height);
	// draw the black rectangle
	rects.forEach(rect => {
	context.fillStyle = 'black';
	context.clearRect(0, 0, width, height);
	context.fillRect(rect.x, rect.y, rect.x2, rect.y2);

	// draw the red circles
	circles.forEach(circle => {
	context.beginPath();
	context.moveTo(circle.x + rect.x + circle.radius, circle.y + rect.y);
	context.arc(
	circle.x + rect.x,
	circle.y + rect.y,
	circle.radius,
	0,
	2 * Math.PI
	);
	context.fillStyle = 'red';
	context.fill();
	});
	});
	}

	function dragSubject() {
	let i;
	const n = circles.length;
	let dx;
	let dy;
	let d2;
	const radius = 10;
	let s2 = radius * radius * 4; // Double the radius
	let circle;
	let subject;

	for (i = 0; i < n; i += 1) {
	circle = circles[i];
	console.log('circle from dragSubject', circle);
	dx = d3.event.x - circle.x - rects[0].x;
	dy = d3.event.y - circle.y - rects[0].y;
	d2 = dx * dx + dy * dy;

	console.log('dx', dx);
	console.log('dy', dy);
	console.log('d2', d2);
	console.log('s2', s2);

	if (d2 < s2) {
	subject = circle;
	s2 = d2;
	} else if (typeof subject === 'undefined') {
	rect = rects[0];
	subject = rect;
	}
	}
	return subject;
	}

	function dragStarted() {
	// circles.splice(circles.indexOf(d3.event.subject), 1);
	// circles.push(d3.event.subject);
	d3.event.subject.active = true;
	}

	function dragged() {
	d3.event.subject.x = d3.event.x;
	d3.event.subject.y = d3.event.y;
	}

	function dragEnded() {
	d3.event.subject.active = false;
	}

	// const group = container.append('g');

	// const rect = group
	// .append('rect')
	// .attr('width', w)
	// .attr('height', h)
	// .attr('x', 10)
	// .attr('yx', 10);

	// const circle1 = group
	// .append('circle')
	// .attr('cx', 50)
	// .attr('cy', 50)
	// .attr('r', 10)
	// .style('fill', 'red');

	// const circle2 = group
	// .append('circle')
	// .attr('cx', 100)
	// .attr('cy', 70)
	// .attr('r', 10)
	// .style('fill', 'red');

	// circle1.call(drag);
	// circle2.call(drag);
	// group.call(drag);