Touch Backend for react-dnd
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rubenv and longlho Fix examples (#106)
Examples are currently broken due to a changed export in DragDropContext.
Latest commit faacba3 Aug 7, 2018

README.md

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react-dnd-touch-backend

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Touch Backend for react-dnd

Usage

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

import { default as TouchBackend } from 'react-dnd-touch-backend';
import { DragDropContext } from 'react-dnd';

var YourApp = React.createClass(
  /* ... */

);

module.exports = 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

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 }] }));

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 i && npm 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.