137 lines
4.4 KiB
JavaScript
137 lines
4.4 KiB
JavaScript
/**
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* Copyright (c) 2015-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*
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* @providesModule Dimensions
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* @flow
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*/
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'use strict';
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var DeviceInfo = require('DeviceInfo');
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var EventEmitter = require('EventEmitter');
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var Platform = require('Platform');
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var RCTDeviceEventEmitter = require('RCTDeviceEventEmitter');
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var invariant = require('fbjs/lib/invariant');
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var eventEmitter = new EventEmitter();
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var dimensionsInitialized = false;
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var dimensions = {};
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class Dimensions {
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/**
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* This should only be called from native code by sending the
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* didUpdateDimensions event.
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*
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* @param {object} dims Simple string-keyed object of dimensions to set
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*/
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static set(dims: {[key:string]: any}): void {
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// We calculate the window dimensions in JS so that we don't encounter loss of
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// precision in transferring the dimensions (which could be non-integers) over
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// the bridge.
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if (dims && dims.windowPhysicalPixels) {
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// parse/stringify => Clone hack
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dims = JSON.parse(JSON.stringify(dims));
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var windowPhysicalPixels = dims.windowPhysicalPixels;
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dims.window = {
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width: windowPhysicalPixels.width / windowPhysicalPixels.scale,
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height: windowPhysicalPixels.height / windowPhysicalPixels.scale,
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scale: windowPhysicalPixels.scale,
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fontScale: windowPhysicalPixels.fontScale,
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};
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if (Platform.OS === 'android') {
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// Screen and window dimensions are different on android
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var screenPhysicalPixels = dims.screenPhysicalPixels;
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dims.screen = {
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width: screenPhysicalPixels.width / screenPhysicalPixels.scale,
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height: screenPhysicalPixels.height / screenPhysicalPixels.scale,
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scale: screenPhysicalPixels.scale,
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fontScale: screenPhysicalPixels.fontScale,
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};
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// delete so no callers rely on this existing
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delete dims.screenPhysicalPixels;
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} else {
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dims.screen = dims.window;
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}
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// delete so no callers rely on this existing
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delete dims.windowPhysicalPixels;
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}
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Object.assign(dimensions, dims);
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if (dimensionsInitialized) {
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// Don't fire 'change' the first time the dimensions are set.
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eventEmitter.emit('change', {
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window: dimensions.window,
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screen: dimensions.screen
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});
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} else {
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dimensionsInitialized = true;
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}
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}
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/**
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* Initial dimensions are set before `runApplication` is called so they should
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* be available before any other require's are run, but may be updated later.
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*
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* Note: Although dimensions are available immediately, they may change (e.g
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* due to device rotation) so any rendering logic or styles that depend on
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* these constants should try to call this function on every render, rather
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* than caching the value (for example, using inline styles rather than
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* setting a value in a `StyleSheet`).
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*
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* Example: `var {height, width} = Dimensions.get('window');`
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*
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* @param {string} dim Name of dimension as defined when calling `set`.
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* @returns {Object?} Value for the dimension.
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*/
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static get(dim: string): Object {
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invariant(dimensions[dim], 'No dimension set for key ' + dim);
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return dimensions[dim];
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}
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/**
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* Add an event handler. Supported events:
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*
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* - `change`: Fires when a property within the `Dimensions` object changes. The argument
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* to the event handler is an object with `window` and `screen` properties whose values
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* are the same as the return values of `Dimensions.get('window')` and
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* `Dimensions.get('screen')`, respectively.
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*/
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static addEventListener(
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type: string,
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handler: Function
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) {
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invariant(
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type === 'change',
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'Trying to subscribe to unknown event: "%s"', type
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);
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eventEmitter.addListener(type, handler);
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}
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/**
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* Remove an event handler.
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*/
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static removeEventListener(
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type: string,
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handler: Function
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) {
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invariant(
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type === 'change',
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'Trying to remove listener for unknown event: "%s"', type
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);
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eventEmitter.removeListener(type, handler);
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}
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}
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Dimensions.set(DeviceInfo.Dimensions);
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RCTDeviceEventEmitter.addListener('didUpdateDimensions', function(update) {
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Dimensions.set(update);
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});
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module.exports = Dimensions;
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