[add] useWindowDimensions hook

Add the 'useWindowDimensions' hook from React Native

Close #1487

packages/babel-plugin-react-native-web/src/moduleMap.js

@@ -64,5 +64,6 @@ module.exports = {
   findNodeHandle: true,
   processColor: true,
   render: true,
-  unmountComponentAtNode: true
+  unmountComponentAtNode: true,
+  useWindowDimensions: true
 };

packages/react-native-web/src/exports/DeviceInfo/index.js

@@ -7,12 +7,14 @@
  * @flow
  */
 
+import type { DisplayMetrics } from '../Dimensions';
+
 import { canUseDOM } from 'fbjs/lib/ExecutionEnvironment';
 import Dimensions from '../Dimensions';
 
 const DeviceInfo = {
   Dimensions: {
-    get windowPhysicalPixels() {
+    get windowPhysicalPixels(): DisplayMetrics {
       const { width, height, fontScale, scale } = Dimensions.get('window');
       return {
         width: width * scale,
@@ -21,7 +23,7 @@ const DeviceInfo = {
         fontScale
       };
     },
-    get screenPhysicalPixels() {
+    get screenPhysicalPixels(): DisplayMetrics {
       const { width, height, fontScale, scale } = Dimensions.get('screen');
       return {
         width: width * scale,

packages/react-native-web/src/exports/Dimensions/index.js

@@ -12,15 +12,31 @@ import { canUseDOM } from 'fbjs/lib/ExecutionEnvironment';
 import debounce from 'debounce';
 import invariant from 'fbjs/lib/invariant';
 
+export type DisplayMetrics = {|
+  fontScale: number,
+  height: number,
+  scale: number,
+  width: number
+|};
+
+type DimensionsValue = {|
+  window?: DisplayMetrics,
+  screen?: DisplayMetrics
+|};
+
+type DimensionKey = 'window' | 'screen';
+
+type DimensionEventListenerType = 'change';
+
 const win = canUseDOM
   ? window
   : {
       devicePixelRatio: undefined,
-      innerHeight: undefined,
-      innerWidth: undefined,
+      innerHeight: (undefined: any),
+      innerWidth: (undefined: any),
       screen: {
-        height: undefined,
-        width: undefined
+        height: (undefined: any),
+        width: (undefined: any)
       }
     };
 
@@ -28,12 +44,12 @@ const dimensions = {};
 const listeners = {};
 
 export default class Dimensions {
-  static get(dimension: string): Object {
+  static get(dimension: DimensionKey): DisplayMetrics {
     invariant(dimensions[dimension], `No dimension set for key ${dimension}`);
     return dimensions[dimension];
   }
 
-  static set(initialDimensions: ?{ [key: string]: any }): void {
+  static set(initialDimensions: ?DimensionsValue): void {
     if (initialDimensions) {
       if (canUseDOM) {
         invariant(false, 'Dimensions cannot be set in the browser');
@@ -64,12 +80,18 @@ export default class Dimensions {
     }
   }
 
-  static addEventListener(type: string, handler: Function): void {
+  static addEventListener(
+    type: DimensionEventListenerType,
+    handler: DimensionsValue => void
+  ): void {
     listeners[type] = listeners[type] || [];
     listeners[type].push(handler);
   }
 
-  static removeEventListener(type: string, handler: Function): void {
+  static removeEventListener(
+    type: DimensionEventListenerType,
+    handler: DimensionsValue => void
+  ): void {
     if (Array.isArray(listeners[type])) {
       listeners[type] = listeners[type].filter(_handler => _handler !== handler);
     }

packages/react-native-web/src/exports/useWindowDimensions/index.js

@@ -0,0 +1,35 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+'use strict';
+
+import type { DisplayMetrics } from '../Dimensions';
+
+import Dimensions from '../Dimensions';
+import { useEffect, useState } from 'react';
+
+export default function useWindowDimensions(): DisplayMetrics {
+  const [dims, setDims] = useState(() => Dimensions.get('window'));
+  useEffect(() => {
+    function handleChange({ window }) {
+      // $FlowFixMe
+      setDims(window);
+    }
+    Dimensions.addEventListener('change', handleChange);
+    // We might have missed an update between calling `get` in render and
+    // `addEventListener` in this handler, so we set it here. If there was
+    // no change, React will filter out this update as a no-op.
+    setDims(Dimensions.get('window'));
+    return () => {
+      Dimensions.removeEventListener('change', handleChange);
+    };
+  }, []);
+  return dims;
+}

packages/react-native-web/src/index.js

@@ -73,6 +73,9 @@ import TVEventHandler from './exports/TVEventHandler';
 // plugins
 import DeviceEventEmitter from './exports/DeviceEventEmitter';
 
+// hooks
+import useWindowDimensions from './exports/useWindowDimensions';
+
 export {
   // top-level API
   createElement as unstable_createElement,
@@ -145,5 +148,7 @@ export {
   TimePickerAndroid,
   TVEventHandler,
   // plugins
-  DeviceEventEmitter
+  DeviceEventEmitter,
+  // hooks
+  useWindowDimensions
 };