HTML5 Canvas Mobile Scrolling and Native Events with Konva

By default Konva will prevent default behaviour of all pointer interactions with a stage. That will prevent unexpected scrolling of a page when you are trying to drag&drop a shape on a mobile device.

But in some cases you may want to keep default behaviour of browser events. In that case you may set preventDefault property of a shape to false.

Instructions: if you are on mobile device try to scroll a page by each rectangle. Green - should prevent default behaviour (no page scrolling). Red - will keep default behaviour (scrolling should work).

Vanilla

import Konva from 'konva';

const stage = new Konva.Stage({
  container: 'container',
  width: window.innerWidth,
  height: window.innerHeight,
});

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

// green rectangle - will prevent scrolling
const greenRect = new Konva.Rect({
  x: 50,
  y: 50,
  width: 100,
  height: 600,
  fill: 'green',
  stroke: 'black',
  strokeWidth: 4,
});
layer.add(greenRect);

// red rectangle - will NOT prevent scrolling
const redRect = new Konva.Rect({
  x: 200,
  y: 50,
  width: 100,
  height: 600,
  fill: 'red',
  stroke: 'black',
  strokeWidth: 4,
  preventDefault: false,
});
layer.add(redRect);

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React

import { Stage, Layer, Rect } from 'react-konva';

const App = () => {
  return (
    <Stage width={window.innerWidth} height={window.innerHeight}>
      <Layer>
        <Rect
          x={50}
          y={50}
          width={100}
          height={600}
          fill="green"
          stroke="black"
          strokeWidth={4}
        />
        <Rect
          x={200}
          y={50}
          width={100}
          height={600}
          fill="red"
          stroke="black"
          strokeWidth={4}
          preventDefault={false}
        />
      </Layer>
    </Stage>
  );
};

export default App;

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Vue

<template>
  <v-stage :config="stageSize">
    <v-layer>
      <v-rect :config="greenRectConfig" />
      <v-rect :config="redRectConfig" />
    </v-layer>
  </v-stage>
</template>

<script setup>
const stageSize = {
  width: window.innerWidth,
  height: window.innerHeight
};

const greenRectConfig = {
  x: 50,
  y: 50,
  width: 100,
  height: 600,
  fill: 'green',
  stroke: 'black',
  strokeWidth: 4
};

const redRectConfig = {
  x: 200,
  y: 50,
  width: 100,
  height: 600,
  fill: 'red',
  stroke: 'black',
  strokeWidth: 4,
  preventDefault: false
};
</script>

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