react-dnd-touch-backend

Touch Backend for react-dnd

Instalation

npm:

 npm install react-dnd-touch-backend --save

yarn:

 yarn add react-dnd-touch-backend

Usage

Follow react-dnd docs to setup your app. Then swap out HTML5Backend for TouchBackend as such:

import React, { Component } from 'react';
import TouchBackend from 'react-dnd-touch-backend';
import { DragDropContext } from 'react-dnd';

class YourApp extends Component {
  /* ... */
}

export default DragDropContext(TouchBackend)(YourApp);

Options

You have the following options available to you, which you can pass in like so:

DragDropContext(TouchBackend(options))

Options include:

• enableTouchEvents
• enableMouseEvents
• enableKeyboardEvents
• delayTouchStart
• delayMouseStart
• touchSlop
• ignoreContextMenu
• scrollAngleRanges
• enableHoverOutsideTarget

Tips

Drag Preview

Since native Drag-n-Drop is not currently supported in touch devices. A custom DragPreview is required. Check out the example for a sample implementation.

We might try to build it directly in the Backend itself in the future to compensate for this limitation.

Mouse events support*

You can enable capturing mouse events by configuring your TouchBackend as follows:

DragDropContext(TouchBackend({ enableMouseEvents: true }));

NOTE: This is buggy due to the difference in touchstart/touchend event propagation compared to mousedown/mouseup/click. I highly recommend that you use react-dnd-html5-backend instead for a more performant native HTML5 drag capability.*

Other options

touchSlop

• Specifies the pixel distance moved before a drag is signaled.
• Default: 0

DragDropContext(TouchBackend({ touchSlop: 20 }));

ignoreContextMenu

• If true, prevents the contextmenu event from canceling a drag.
• Default: false

DragDropContext(TouchBackend({ ignoreContextMenu: true }));

scrollAngleRanges

• Specifies ranges of angles in degrees that drag events should be ignored. This is useful when you want to allow the user to scroll in a particular direction instead of dragging. Degrees move clockwise, 0/360 pointing to the left.
• Default: undefined

// allow vertical scrolling
DragDropContext(TouchBackend({ scrollAngleRanges: [{ start: 30, end: 150 }, { start: 210, end: 330 }] }));

// allow horizontal scrolling
DragDropContext(TouchBackend({ scrollAngleRanges: [{ start: 300 }, { end: 60 }, { start: 120, end: 240 }] }));

enableHoverOutsideTarget

• Continue dragging of currently dragged element when pointer leaves DropTarget area
• Default: undefined

DragDropContext(TouchBackend({ enableHoverOutsideTarget: true }));

getDropTargetElementsAtPoint

• Specify a custom function to find drop target elements at the given point. Useful for improving performance in environments (iOS Safari) where document.elementsFromPoint is not available.
• Default: undefined (use document.elementsFromPoint or inline elementsFromPoint "polyfill")

const hasNative = document && (document.elementsFromPoint || document.msElementsFromPoint);

function getDropTargetElementsAtPoint(x, y, availableDropTargets) {
  return dropTargets.filter(t => {
    const rect = t.getBoundingClientRect();
    return (x >= rect.left && x <= rect.right && 
            y <= rect.bottom && y >= rect.top);
  });
}

// use custom function only if elementsFromPoint is not supported 
DragDropContext(TouchBackend({
  getDropTargetElementsAtPoint: !hasNative && getDropTargetElementsAtPoint,
}))

Examples

The examples folder has a sample integration. In order to build it, run:

npm:

npm i && npm run dev

yarn:

yarn install && yarn run dev

Then navigate to localhost:7789 or (IP Address):7789 in your mobile browser to access the example. Code licensed under the MIT license. See LICENSE file for terms.