Created
March 4, 2016 09:22
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Detect modifier keys from underlying (or global) drag events
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import pick from 'lodash/pick'; | |
import bindAll from 'lodash/bindAll'; | |
import React from 'react'; | |
import ReactDOM from 'react-dom'; | |
const MODIFIER_KEYS = ['ctrlKey', 'shiftKey', 'altKey', 'metaKey']; | |
/** | |
* Detects drag modifier keys on drag events that originated | |
* from the wrapped component | |
* | |
* @param {boolean} options.listenForAllDragEvents | |
* if true it will detect modifier keys for all drag events, and not | |
* just the ones originating from the wrapped component | |
*/ | |
export default function detectDragModifierKeys(options = {}) { | |
return function(Component) { | |
return class DetectDragModifierKeys extends React.Component { | |
constructor(props) { | |
super(props); | |
bindAll(this, 'onDrag', 'onDragStart', 'onDragEnd'); | |
this._isDragOrigin = false; | |
this.state = { | |
dragModifierKeys: MODIFIER_KEYS.reduce((mem, key) => { | |
mem[key] = false; | |
return mem; | |
}, {}) | |
}; | |
} | |
componentDidMount(event) { | |
window.addEventListener('dragstart', this.onDragStart); | |
window.addEventListener('dragend', this.onDragStart); | |
// The 'drag' event doesn't detect modifier keys in FF for some reason. | |
// Therefore we listen for dragover on the window instead, which roughly | |
// gives the same result | |
window.addEventListener('dragover', this.onDrag); | |
} | |
componentWillUnmount(event) { | |
window.removeEventListener('dragstart', this.onDragStart); | |
window.removeEventListener('dragend', this.onDragEnd); | |
window.removeEventListener('dragover', this.onDrag); | |
} | |
onDragStart(event) { | |
// Determine whether or not the the drag event | |
// originated from inside the wrapped component | |
this._isDragOrigin = ReactDOM.findDOMNode(this._wrapped).contains(event.target); | |
} | |
onDragEnd(event) { | |
this._isDragOrigin = false; | |
} | |
onDrag(event) { | |
if (this._isDragOrigin || options.listenForAllDragEvents) { | |
const {dragModifierKeys} = this.state; | |
const hasChanged = Object.keys(dragModifierKeys).some(key => { | |
return dragModifierKeys[key] !== event[key]; | |
}); | |
if (hasChanged) { | |
this.setState({dragModifierKeys: pick(event, MODIFIER_KEYS)}); | |
} | |
} | |
} | |
render() { | |
return ( | |
<Component | |
ref={c => this._wrapped = c} | |
{...this.props} | |
{...this.state} | |
/> | |
); | |
} | |
}; | |
}; | |
} |
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