react-native/Libraries/Components/MaskedView/MaskedViewIOS.ios.js

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule MaskedViewIOS
 * @flow
 */

const PropTypes = require('prop-types');
const React = require('React');
const StyleSheet = require('StyleSheet');
const View = require('View');
const ViewPropTypes = require('ViewPropTypes');
const requireNativeComponent = require('requireNativeComponent');

import type { ViewProps } from 'ViewPropTypes';

type Props = ViewProps & {
  children: any,
  /**
   * Should be a React element to be rendered and applied as the
   * mask for the child element.
   */
  maskElement: React.Element<any>,
};

/**
 * Renders the child view with a mask specified in the `maskElement` prop.
 *
 * ```
 * import React from 'react';
 * import { MaskedView, Text, View } from 'react-native';
 *
 * class MyMaskedView extends React.Component {
 *   render() {
 *     return (
 *       <MaskedView
 *         style={{ flex: 1 }}
 *         maskElement={
 *           <View style={styles.maskContainerStyle}>
 *             <Text style={styles.maskTextStyle}>
 *               Basic Mask
 *             </Text>
 *           </View>
 *         }
 *       >
 *         <View style={{ flex: 1, backgroundColor: 'blue' }} />
 *       </MaskedView>
 *     );
 *   }
 * }
 * ```
 *
 * The above example will render a view with a blue background that fills its
 * parent, and then mask that view with text that says "Basic Mask".
 *
 * The alpha channel of the view rendered by the `maskElement` prop determines how
 * much of the view's content and background shows through. Fully or partially
 * opaque pixels allow the underlying content to show through but fully
 * transparent pixels block that content.
 *
 */
class MaskedViewIOS extends React.Component<Props> {
  static propTypes = {
    ...ViewPropTypes,
    maskElement: PropTypes.element.isRequired,
  };

  _hasWarnedInvalidRenderMask = false;

  render() {
    const { maskElement, children, ...otherViewProps } = this.props;

    if (!React.isValidElement(maskElement)) {
      if (!this._hasWarnedInvalidRenderMask) {
        console.warn(
          'MaskedView: Invalid `maskElement` prop was passed to MaskedView. ' +
            'Expected a React Element. No mask will render.'
        );
        this._hasWarnedInvalidRenderMask = true;
      }
      return <View {...otherViewProps}>{children}</View>;
    }

    return (
      <RCTMaskedView {...otherViewProps}>
        <View pointerEvents="none" style={StyleSheet.absoluteFill}>
          {maskElement}
        </View>
        {children}
      </RCTMaskedView>
    );
  }
}

const RCTMaskedView = requireNativeComponent('RCTMaskedView', {
  name: 'RCTMaskedView',
  displayName: 'RCTMaskedView',
  propTypes: {
    ...ViewPropTypes,
  },
});

module.exports = MaskedViewIOS;