BeforeInputEventPlugin.js

/**
 * Copyright (c) 2013-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import type {TopLevelTypes} from './BrowserEventConstants';

import {accumulateTwoPhaseDispatches} from 'events/EventPropagators';
import ExecutionEnvironment from 'fbjs/lib/ExecutionEnvironment';

import * as FallbackCompositionState from './FallbackCompositionState';
import SyntheticCompositionEvent from './SyntheticCompositionEvent';
import SyntheticInputEvent from './SyntheticInputEvent';

const END_KEYCODES = [9, 13, 27, 32]; // Tab, Return, Esc, Space
const START_KEYCODE = 229;

const canUseCompositionEvent =
  ExecutionEnvironment.canUseDOM && 'CompositionEvent' in window;

let documentMode = null;
if (ExecutionEnvironment.canUseDOM && 'documentMode' in document) {
  documentMode = document.documentMode;
}

// Webkit offers a very useful `textInput` event that can be used to
// directly represent `beforeInput`. The IE `textinput` event is not as
// useful, so we don't use it.
const canUseTextInputEvent =
  ExecutionEnvironment.canUseDOM && 'TextEvent' in window && !documentMode;

// In IE9+, we have access to composition events, but the data supplied
// by the native compositionend event may be incorrect. Japanese ideographic
// spaces, for instance (\u3000) are not recorded correctly.
const useFallbackCompositionData =
  ExecutionEnvironment.canUseDOM &&
  (!canUseCompositionEvent ||
    (documentMode && documentMode > 8 && documentMode <= 11));

const SPACEBAR_CODE = 32;
const SPACEBAR_CHAR = String.fromCharCode(SPACEBAR_CODE);

// Events and their corresponding property names.
const eventTypes = {
  beforeInput: {
    phasedRegistrationNames: {
      bubbled: 'onBeforeInput',
      captured: 'onBeforeInputCapture',
    },
    dependencies: [
      'topCompositionEnd',
      'topKeyPress',
      'topTextInput',
      'topPaste',
    ],
  },
  compositionEnd: {
    phasedRegistrationNames: {
      bubbled: 'onCompositionEnd',
      captured: 'onCompositionEndCapture',
    },
    dependencies: [
      'topBlur',
      'topCompositionEnd',
      'topKeyDown',
      'topKeyPress',
      'topKeyUp',
      'topMouseDown',
    ],
  },
  compositionStart: {
    phasedRegistrationNames: {
      bubbled: 'onCompositionStart',
      captured: 'onCompositionStartCapture',
    },
    dependencies: [
      'topBlur',
      'topCompositionStart',
      'topKeyDown',
      'topKeyPress',
      'topKeyUp',
      'topMouseDown',
    ],
  },
  compositionUpdate: {
    phasedRegistrationNames: {
      bubbled: 'onCompositionUpdate',
      captured: 'onCompositionUpdateCapture',
    },
    dependencies: [
      'topBlur',
      'topCompositionUpdate',
      'topKeyDown',
      'topKeyPress',
      'topKeyUp',
      'topMouseDown',
    ],
  },
};

// Track whether we've ever handled a keypress on the space key.
let hasSpaceKeypress = false;

/**
 * Return whether a native keypress event is assumed to be a command.
 * This is required because Firefox fires `keypress` events for key commands
 * (cut, copy, select-all, etc.) even though no character is inserted.
 */
function isKeypressCommand(nativeEvent) {
  return (
    (nativeEvent.ctrlKey || nativeEvent.altKey || nativeEvent.metaKey) &&
    // ctrlKey && altKey is equivalent to AltGr, and is not a command.
    !(nativeEvent.ctrlKey && nativeEvent.altKey)
  );
}

/**
 * Translate native top level events into event types.
 *
 * @param {string} topLevelType
 * @return {object}
 */
function getCompositionEventType(topLevelType) {
  switch (topLevelType) {
    case 'topCompositionStart':
      return eventTypes.compositionStart;
    case 'topCompositionEnd':
      return eventTypes.compositionEnd;
    case 'topCompositionUpdate':
      return eventTypes.compositionUpdate;
  }
}

/**
 * Does our fallback best-guess model think this event signifies that
 * composition has begun?
 *
 * @param {string} topLevelType
 * @param {object} nativeEvent
 * @return {boolean}
 */
function isFallbackCompositionStart(topLevelType, nativeEvent) {
  return topLevelType === 'topKeyDown' && nativeEvent.keyCode === START_KEYCODE;
}

/**
 * Does our fallback mode think that this event is the end of composition?
 *
 * @param {string} topLevelType
 * @param {object} nativeEvent
 * @return {boolean}
 */
function isFallbackCompositionEnd(topLevelType, nativeEvent) {
  switch (topLevelType) {
    case 'topKeyUp':
      // Command keys insert or clear IME input.
      return END_KEYCODES.indexOf(nativeEvent.keyCode) !== -1;
    case 'topKeyDown':
      // Expect IME keyCode on each keydown. If we get any other
      // code we must have exited earlier.
      return nativeEvent.keyCode !== START_KEYCODE;
    case 'topKeyPress':
    case 'topMouseDown':
    case 'topBlur':
      // Events are not possible without cancelling IME.
      return true;
    default:
      return false;
  }
}

/**
 * Google Input Tools provides composition data via a CustomEvent,
 * with the `data` property populated in the `detail` object. If this
 * is available on the event object, use it. If not, this is a plain
 * composition event and we have nothing special to extract.
 *
 * @param {object} nativeEvent
 * @return {?string}
 */
function getDataFromCustomEvent(nativeEvent) {
  const detail = nativeEvent.detail;
  if (typeof detail === 'object' && 'data' in detail) {
    return detail.data;
  }
  return null;
}

// Track the current IME composition status, if any.
let isComposing = false;

/**
 * @return {?object} A SyntheticCompositionEvent.
 */
function extractCompositionEvent(
  topLevelType,
  targetInst,
  nativeEvent,
  nativeEventTarget,
) {
  let eventType;
  let fallbackData;

  if (canUseCompositionEvent) {
    eventType = getCompositionEventType(topLevelType);
  } else if (!isComposing) {
    if (isFallbackCompositionStart(topLevelType, nativeEvent)) {
      eventType = eventTypes.compositionStart;
    }
  } else if (isFallbackCompositionEnd(topLevelType, nativeEvent)) {
    eventType = eventTypes.compositionEnd;
  }

  if (!eventType) {
    return null;
  }

  if (useFallbackCompositionData) {
    // The current composition is stored statically and must not be
    // overwritten while composition continues.
    if (!isComposing && eventType === eventTypes.compositionStart) {
      isComposing = FallbackCompositionState.initialize(nativeEventTarget);
    } else if (eventType === eventTypes.compositionEnd) {
      if (isComposing) {
        fallbackData = FallbackCompositionState.getData();
      }
    }
  }

  const event = SyntheticCompositionEvent.getPooled(
    eventType,
    targetInst,
    nativeEvent,
    nativeEventTarget,
  );

  if (fallbackData) {
    // Inject data generated from fallback path into the synthetic event.
    // This matches the property of native CompositionEventInterface.
    event.data = fallbackData;
  } else {
    const customData = getDataFromCustomEvent(nativeEvent);
    if (customData !== null) {
      event.data = customData;
    }
  }

  accumulateTwoPhaseDispatches(event);
  return event;
}

/**
 * @param {TopLevelTypes} topLevelType Record from `BrowserEventConstants`.
 * @param {object} nativeEvent Native browser event.
 * @return {?string} The string corresponding to this `beforeInput` event.
 */
function getNativeBeforeInputChars(topLevelType: TopLevelTypes, nativeEvent) {
  switch (topLevelType) {
    case 'topCompositionEnd':
      return getDataFromCustomEvent(nativeEvent);
    case 'topKeyPress':
      /**
       * If native `textInput` events are available, our goal is to make
       * use of them. However, there is a special case: the spacebar key.
       * In Webkit, preventing default on a spacebar `textInput` event
       * cancels character insertion, but it *also* causes the browser
       * to fall back to its default spacebar behavior of scrolling the
       * page.
       *
       * Tracking at:
       * https://code.google.com/p/chromium/issues/detail?id=355103
       *
       * To avoid this issue, use the keypress event as if no `textInput`
       * event is available.
       */
      const which = nativeEvent.which;
      if (which !== SPACEBAR_CODE) {
        return null;
      }

      hasSpaceKeypress = true;
      return SPACEBAR_CHAR;

    case 'topTextInput':
      // Record the characters to be added to the DOM.
      const chars = nativeEvent.data;

      // If it's a spacebar character, assume that we have already handled
      // it at the keypress level and bail immediately. Android Chrome
      // doesn't give us keycodes, so we need to blacklist it.
      if (chars === SPACEBAR_CHAR && hasSpaceKeypress) {
        return null;
      }

      return chars;

    default:
      // For other native event types, do nothing.
      return null;
  }
}

/**
 * For browsers that do not provide the `textInput` event, extract the
 * appropriate string to use for SyntheticInputEvent.
 *
 * @param {string} topLevelType Record from `BrowserEventConstants`.
 * @param {object} nativeEvent Native browser event.
 * @return {?string} The fallback string for this `beforeInput` event.
 */
function getFallbackBeforeInputChars(topLevelType: TopLevelTypes, nativeEvent) {
  // If we are currently composing (IME) and using a fallback to do so,
  // try to extract the composed characters from the fallback object.
  // If composition event is available, we extract a string only at
  // compositionevent, otherwise extract it at fallback events.
  if (isComposing) {
    if (
      topLevelType === 'topCompositionEnd' ||
      (!canUseCompositionEvent &&
        isFallbackCompositionEnd(topLevelType, nativeEvent))
    ) {
      const chars = FallbackCompositionState.getData();
      FallbackCompositionState.reset();
      isComposing = false;
      return chars;
    }
    return null;
  }

  switch (topLevelType) {
    case 'topPaste':
      // If a paste event occurs after a keypress, throw out the input
      // chars. Paste events should not lead to BeforeInput events.
      return null;
    case 'topKeyPress':
      /**
       * As of v27, Firefox may fire keypress events even when no character
       * will be inserted. A few possibilities:
       *
       * - `which` is `0`. Arrow keys, Esc key, etc.
       *
       * - `which` is the pressed key code, but no char is available.
       *   Ex: 'AltGr + d` in Polish. There is no modified character for
       *   this key combination and no character is inserted into the
       *   document, but FF fires the keypress for char code `100` anyway.
       *   No `input` event will occur.
       *
       * - `which` is the pressed key code, but a command combination is
       *   being used. Ex: `Cmd+C`. No character is inserted, and no
       *   `input` event will occur.
       */
      if (!isKeypressCommand(nativeEvent)) {
        // IE fires the `keypress` event when a user types an emoji via
        // Touch keyboard of Windows.  In such a case, the `char` property
        // holds an emoji character like `\uD83D\uDE0A`.  Because its length
        // is 2, the property `which` does not represent an emoji correctly.
        // In such a case, we directly return the `char` property instead of
        // using `which`.
        if (nativeEvent.char && nativeEvent.char.length > 1) {
          return nativeEvent.char;
        } else if (nativeEvent.which) {
          return String.fromCharCode(nativeEvent.which);
        }
      }
      return null;
    case 'topCompositionEnd':
      return useFallbackCompositionData ? null : nativeEvent.data;
    default:
      return null;
  }
}

/**
 * Extract a SyntheticInputEvent for `beforeInput`, based on either native
 * `textInput` or fallback behavior.
 *
 * @return {?object} A SyntheticInputEvent.
 */
function extractBeforeInputEvent(
  topLevelType,
  targetInst,
  nativeEvent,
  nativeEventTarget,
) {
  let chars;

  if (canUseTextInputEvent) {
    chars = getNativeBeforeInputChars(topLevelType, nativeEvent);
  } else {
    chars = getFallbackBeforeInputChars(topLevelType, nativeEvent);
  }

  // If no characters are being inserted, no BeforeInput event should
  // be fired.
  if (!chars) {
    return null;
  }

  const event = SyntheticInputEvent.getPooled(
    eventTypes.beforeInput,
    targetInst,
    nativeEvent,
    nativeEventTarget,
  );

  event.data = chars;
  accumulateTwoPhaseDispatches(event);
  return event;
}

/**
 * Create an `onBeforeInput` event to match
 * http://www.w3.org/TR/2013/WD-DOM-Level-3-Events-20131105/#events-inputevents.
 *
 * This event plugin is based on the native `textInput` event
 * available in Chrome, Safari, Opera, and IE. This event fires after
 * `onKeyPress` and `onCompositionEnd`, but before `onInput`.
 *
 * `beforeInput` is spec'd but not implemented in any browsers, and
 * the `input` event does not provide any useful information about what has
 * actually been added, contrary to the spec. Thus, `textInput` is the best
 * available event to identify the characters that have actually been inserted
 * into the target node.
 *
 * This plugin is also responsible for emitting `composition` events, thus
 * allowing us to share composition fallback code for both `beforeInput` and
 * `composition` event types.
 */
const BeforeInputEventPlugin = {
  eventTypes: eventTypes,

  extractEvents: function(
    topLevelType,
    targetInst,
    nativeEvent,
    nativeEventTarget,
  ) {
    const composition = extractCompositionEvent(
      topLevelType,
      targetInst,
      nativeEvent,
      nativeEventTarget,
    );

    const beforeInput = extractBeforeInputEvent(
      topLevelType,
      targetInst,
      nativeEvent,
      nativeEventTarget,
    );

    if (composition === null) {
      return beforeInput;
    }

    if (beforeInput === null) {
      return composition;
    }

    return [composition, beforeInput];
  },
};

export default BeforeInputEventPlugin;