How to automatically scroll stage by edge drag?

If you’re looking to enhance your Konva.js application’s user experience, implementing an auto-scroll feature is a great way to go. This functionality is especially useful in interactive UIs where users need to drag items or navigate large canvases. By enabling the scroll to automatically move when a user drags an item to the bottom or right edge of the viewport, you create a smoother and more intuitive interaction.

Instructions: Start dragging of any shape. Drag it near corder of the stage. Stage will start scrolling.

Scroll By Edge Drag Demoview raw

<!DOCTYPE html>
<html>
  <head>
    <script src="https://unpkg.com/[email protected]/konva.min.js"></script>
    <meta charset="utf-8" />
    <title>Konva Canvas Scrolling Drag Demo</title>
    <style>
      body {
        margin: 0;
        padding: 0;
        overflow: hidden;
        background-color: #f0f0f0;
      }
    </style>
  </head>

  <body>
    <div id="container"></div>
    <script>
      var width = window.innerWidth;
      var height = window.innerHeight;

      var stage = new Konva.Stage({
        container: 'container',
        width: width,
        height: height,
      });

      var layer = new Konva.Layer();
      stage.add(layer);

      var NUMBER = 100;

      function generateNode() {
        return new Konva.Circle({
          x: width * (Math.random() * 2 - 1),
          y: height * (Math.random() * 2 - 1),
          radius: 40,
          fill: 'red',
          stroke: 'black',
          draggable: true,
        });
      }

      for (var i = 0; i < NUMBER; i++) {
        layer.add(generateNode());
      }

      let scrollInterval = null;

      stage.on('dragstart', (e) => {
        const duration = 1000 / 60;
        scrollInterval = setInterval(() => {
          const pos = stage.getPointerPosition();
          const offset = 100;
          const isNearLeft = pos.x < offset;
          if (isNearLeft) {
            stage.x(stage.x() + 2);
            e.target.x(e.target.x() - 2);
          }
          const isNearRight = pos.x > stage.width() - offset;
          if (isNearRight) {
            stage.x(stage.x() - 2);
            e.target.x(e.target.x() + 2);
          }
          const isNearTop = pos.y < offset;
          if (isNearTop) {
            stage.y(stage.y() + 2);
            e.target.y(e.target.y() - 2);
          }
          const isNearBottom = pos.y > stage.height() - offset;
          if (isNearBottom) {
            stage.y(stage.y() - 2);
            e.target.y(e.target.y() + 2);
          }
        }, duration);
      });
      stage.on('dragend', () => {
        clearInterval(scrollInterval);
      });
    </script>
  </body>
</html>

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