Html - Position Element in the center of an SVG PATH element

MiguelFrias
October 4, 2023
118 views
0 votes
2 Answers

Im currently trying center and angular component element in the center of an svg path element. but i can not find the way to make this possible. the idea is getting something like this:

the line connecting the boxes is the svg path, and + button is the element i want to position in the middle no matter how long is the line between the two boxes.

currently this is how the HTML looks like.

connection.component.html

<div class="relative">
  <svg data-testid="connection" #svg>
    <path [ngClass]="{ 'source-connected': !!data.source, 'target-connected': !!data.target }" [attr.d]="path" /> ----> path element
  </svg>
  <exb-node-menu #menu></exb-node-menu> ----> need to position in the center
</div>

here you can find a simple working example of the issue sandbox, in the folder custom-connection you can find the svg with button i need to place in the center of the svg

Answers

I not sure if it’s possible to do this with path, but if you use lines it’s make things a lot simpler.

The midpoint of the line. The midpoint MM between two points A(x1,y1)A(x1,y1) and B(x2,y2)B(x2,y2) is given by:

here is an example svg.

here’s an example

let selectedElement = null;
  let offsetX, offsetY;

  document.getElementById('startCircle').addEventListener('mousedown', startDrag);
  document.getElementById('endCircle').addEventListener('mousedown', startDrag);
  document.getElementById('svgCanvas').addEventListener('mousemove', drag);
  document.getElementById('svgCanvas').addEventListener('mouseup', endDrag);
  document.getElementById('svgCanvas').addEventListener('mouseleave', endDrag);

  function startDrag(evt) {
    selectedElement = evt.target;
    offsetX = evt.clientX - parseFloat(selectedElement.getAttribute('cx'));
    offsetY = evt.clientY - parseFloat(selectedElement.getAttribute('cy'));
  }

  function drag(evt) {
    if (selectedElement) {
        let coord = getMousePosition(evt);
        selectedElement.setAttribute('cx', coord.x);
        selectedElement.setAttribute('cy', coord.y);
        
        if (selectedElement.id === 'startCircle') {
            document.getElementById('lineElement').setAttribute('x1', coord.x);
            document.getElementById('lineElement').setAttribute('y1', coord.y);
        } else if (selectedElement.id === 'endCircle') {
            document.getElementById('lineElement').setAttribute('x2', coord.x);
            document.getElementById('lineElement').setAttribute('y2', coord.y);
        }

        // Update the center circle's position
        let x1 = parseFloat(document.getElementById('lineElement').getAttribute('x1'));
        let y1 = parseFloat(document.getElementById('lineElement').getAttribute('y1'));
        let x2 = parseFloat(document.getElementById('lineElement').getAttribute('x2'));
        let y2 = parseFloat(document.getElementById('lineElement').getAttribute('y2'));

        let midX = (x1 + x2) / 2;
        let midY = (y1 + y2) / 2;

        document.getElementById('centerCircle').setAttribute('cx', midX);
        document.getElementById('centerCircle').setAttribute('cy', midY);
    }
}

  function endDrag(evt) {
    selectedElement = null;
  }

  function getMousePosition(evt) {
    let CTM = document.getElementById('svgCanvas').getScreenCTM();
    return {
      x: (evt.clientX - CTM.e + offsetX) / CTM.a,
      y: (evt.clientY - CTM.f + offsetY) / CTM.d
    };
  }

<div>
  <svg height="310" width="550" id="svgCanvas">
    <!-- Line -->
    <line id="lineElement" x1="5" y1="5" x2="200" y2="200" style="stroke:rgb(255,0,0);stroke-width:2" />
    
    <!-- Circle at the start of the line -->
    <circle id="startCircle" cx="5" cy="5" r="5" style="fill:rgb(255,0,0)" />
    
    <!-- Circle at the end of the line -->
    <circle id="endCircle" cx="200" cy="200" r="5" style="fill:rgb(255,0,0)" />
    
    <!-- Circle at the mid of the line -->
    <circle id="centerCircle" cx="102.5" cy="102.5" r="5" style="fill:rgb(0,255,0)" />
  </svg>
</div>

ckeck out this solution https://codepen.io/Arun-David/pen/xxmyEjR

I have this solution for u. You will have to adjust the button position because now it points to the top, left corner. I hope this helps u.

import {
  Component,
  ElementRef,
  Input,
  OnChanges,
  ViewChild
} from "@angular/core";
import { ClassicPreset } from "rete";

@Component({
  selector: "connection",
  template: `
    <div style="border:solid 1px red;">
      <svg #mySVG data-testid="connection" width="500" height="300">
        <defs>
          <path id="MyPath" [attr.d]="path" />
        </defs>
        <use xlink:href="#MyPath" fill="none" stroke="red" />

        <foreignObject xlink:href="#MyPath">
          <div style="border:1px green solid">I'm a div inside a SVG.</div>
        </foreignObject>
      </svg>
      <button
        [style.left.px]="cx"
        [style.top.px]="cy"
        style="position:absolute;"
      >
        Random button
      </button>
      <div></div>
    </div>
  `,
  styleUrls: ["./custom-connection.component.sass"]
})
export class CustomConnectionComponent implements OnChanges {
  @Input() data!: ClassicPreset.Connection<
    ClassicPreset.Node,
    ClassicPreset.Node
  >;

  public cx = 0;
  public cy = 0;

  @ViewChild("mySVG") mySVG!: ElementRef;

  _start: any;
  _end: any;

  @Input() set start(value: any) {
    this._start = value;
    this.ngOnChanges();
  }
  @Input() set end(value: any) {
    this._end = value;
    this.ngOnChanges();
  }
  @Input() path: string;

  ngOnChanges(): void {
    console.log("_start ", this._start);
    console.log("_end ", this._end);
    if (
      this._start === undefined ||
      this._start === null ||
      this._end === undefined ||
      this._end === null
    )
      return;

    let x = this._start.x - this._end.x;
    let y = this._start.y - this._end.y;
    this.cx =
      x < 0 ? Math.abs(x) / 2 + this._start.x : Math.abs(x) / 2 + this._end.x;
    this.cy =
      y < 0 ? Math.abs(y) / 2 + this._start.y : Math.abs(y) / 2 + this._end.y;
    console.log("go ", this.cx, " - ", this.cy);
  }
}

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Html – Position Element in the center of an SVG PATH element

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