[add] initial ScrollView

Supports the following props: `children`, `contentContainerStyle`,
`horizontal`, `onScroll`, `scrollEnabled`, `scrollEventThrottle`, and
`style`.

Fix #6

docs/components/ScrollView.md

@@ -1,6 +1,7 @@
 # ScrollView
 
-TODO
+Scrollable `View` for use with bounded height, either by setting the height of
+the view directly (discouraged) or by bounding the height of ancestor views.
 
 ## Props
 
@@ -11,27 +12,29 @@ Child content.
 **contentContainerStyle**: style
 
 These styles will be applied to the scroll view content container which wraps
-all of the child views. Example:
+all of the child views.
 
 **horizontal**: bool = false
 
-When true, the scroll view's children are arranged horizontally in a row instead of vertically in a column. Default: `false`.
+When true, the scroll view's children are arranged horizontally in a row
+instead of vertically in a column.
 
 **onScroll**: function
 
-Fires at most once per frame during scrolling. The frequency of the events can be contolled using the `scrollEventThrottle` prop.
+Fires at most once per frame during scrolling. The frequency of the events can
+be contolled using the `scrollEventThrottle` prop.
 
-**scrollEnabled**: bool
+**scrollEnabled**: bool = true
 
-When false, the content does not scroll. Default: `true`.
+When false, the content does not scroll.
 
-**scrollEventThrottle**: number
+**scrollEventThrottle**: number = 0
 
 This controls how often the scroll event will be fired while scrolling (in
 events per seconds). A higher number yields better accuracy for code that is
-tracking the scroll position, but can lead to scroll performance problems.
-Default: `0` (the scroll event will be sent only once each time the view is
-scrolled.)
+tracking the scroll position, but can lead to scroll performance problems. The
+default value is `0`, which means the scroll event will be sent only once each
+time the view is scrolled.
 
 **style**: style
 
@@ -40,20 +43,42 @@ scrolled.)
 ## Examples
 
 ```js
-import React, { ScrollView } from 'react-native-web'
+import React, { ScrollView, StyleSheet } from 'react-native-web'
 
-const { Component, PropTypes } = React;
+import Item from './Item'
 
-class Example extends Component {
-  static propTypes = {
+export default class App extends React.Component {
+  constructor(props, context) {
+    super(props, context)
+    this.state = {
+      items: Array.from({ length: 20 }).map((_, i) => ({ id: i }))
+    }
   }
 
-  static defaultProps = {
+  onScroll(e) {
+    console.log(e)
   }
 
   render() {
     return (
+      <ScrollView
+        children={this.state.items.map((item) => <Item {...item} />)}
+        contentContainerStyle={styles.container}
+        horizontal
+        onScroll={(e) => this.onScroll(e)}
+        scrollEventThrottle={60}
+        style={styles.root}
+      />
     )
   }
 }
+
+const styles = StyleSheet.create({
+  root: {
+    borderWidth: '1px'
+  },
+  container: {
+    padding: '10px'
+  }
+})
 ```

examples/components/App.js

@@ -1,7 +1,7 @@
 import GridView from './GridView'
 import Heading from './Heading'
 import MediaQueryWidget from './MediaQueryWidget'
-import React, { Image, StyleSheet, Text, TextInput, Touchable, View } from '../../src'
+import React, { Image, StyleSheet, ScrollView, Text, TextInput, Touchable, View } from '../../src'
 
 export default class App extends React.Component {
   static propTypes = {
@@ -9,6 +9,13 @@ export default class App extends React.Component {
     style: View.propTypes.style
   }
 
+  constructor(...args) {
+    super(...args)
+    this.state = {
+      scrollEnabled: true
+    }
+  }
+
   render() {
     const { mediaQuery } = this.props
     const rootStyles = {
@@ -152,6 +159,52 @@ export default class App extends React.Component {
             )
           })}
         </GridView>
+
+        <Heading size='large'>ScrollView</Heading>
+        <label>
+          <input
+            checked={this.state.scrollEnabled}
+            onChange={() => this.setState({
+              scrollEnabled: !this.state.scrollEnabled
+            })}
+            type='checkbox'
+          /> Enable scroll
+        </label>
+
+        <Heading>Default layout</Heading>
+        <View style={styles.scrollViewContainer}>
+          <ScrollView
+            contentContainerStyle={styles.scrollViewContentContainerStyle}
+            onScroll={e => console.log('ScrollView.onScroll', e)}
+            scrollEnabled={this.state.scrollEnabled}
+            scrollEventThrottle={1} // 1 event per second
+            style={styles.scrollViewStyle}
+          >
+            {Array.from({ length: 50 }).map((item, i) => (
+              <View key={i} style={styles.box}>
+                <Text>{i}</Text>
+              </View>
+            ))}
+          </ScrollView>
+        </View>
+
+        <Heading>Horizontal layout</Heading>
+        <View style={styles.scrollViewContainer}>
+          <ScrollView
+            contentContainerStyle={styles.scrollViewContentContainerStyle}
+            horizontal
+            onScroll={e => console.log('ScrollView.onScroll', e)}
+            scrollEnabled={this.state.scrollEnabled}
+            scrollEventThrottle={1} // 1 event per second
+            style={styles.scrollViewStyle}
+          >
+            {Array.from({ length: 50 }).map((item, i) => (
+              <View key={i} style={{...styles.box, ...styles.horizontalBox}}>
+                <Text>{i}</Text>
+              </View>
+            ))}
+          </ScrollView>
+        </View>
       </View>
     )
   }
@@ -179,6 +232,9 @@ const styles = StyleSheet.create({
     justifyContent: 'center',
     borderWidth: '1px'
   },
+  horizontalBox: {
+    width: '50px'
+  },
   boxFull: {
     width: '100%'
   },
@@ -194,5 +250,14 @@ const styles = StyleSheet.create({
     borderWidth: 1,
     height: '200px',
     justifyContent: 'center'
+  },
+  scrollViewContainer: {
+    height: '200px'
+  },
+  scrollViewStyle: {
+    borderWidth: '1px'
+  },
+  scrollViewContentContainerStyle: {
+    padding: '10px'
   }
 })

package.json

@@ -17,6 +17,7 @@
   },
   "dependencies": {
     "inline-style-prefixer": "^0.3.3",
+    "lodash.debounce": "^3.1.1",
     "react-tappable": "^0.7.1",
     "react-textarea-autosize": "^3.0.0"
   },

src/components/ScrollView/ScrollViewStylePropTypes.js

@@ -0,0 +1,4 @@
+import View from '../View'
+export default {
+  ...(View.stylePropTypes)
+}

src/components/ScrollView/__tests__/index-test.js

@@ -1 +1,11 @@
 /* eslint-env mocha */
+
+import * as utils from '../../../modules/specHelpers'
+
+import ScrollView from '../'
+
+suite('components/ScrollView', () => {
+  test('prop "style"', () => {
+    utils.assertProps.style(ScrollView)
+  })
+})

src/components/ScrollView/index.js

@@ -1,18 +1,138 @@
+import { pickProps } from '../../modules/filterObjectProps'
+import debounce from 'lodash.debounce'
 import React, { PropTypes } from 'react'
+import ScrollViewStylePropTypes from './ScrollViewStylePropTypes'
+import StyleSheet from '../../modules/StyleSheet'
 import View from '../View'
 
+const scrollViewStyleKeys = Object.keys(ScrollViewStylePropTypes)
+
+const styles = StyleSheet.create({
+  initial: {
+    flexGrow: 1,
+    flexShrink: 1,
+    overflow: 'scroll'
+  },
+  initialContentContainer: {
+    flexGrow: 1,
+    flexShrink: 1
+  },
+  row: {
+    flexDirection: 'row'
+  }
+})
+
 class ScrollView extends React.Component {
   static propTypes = {
-    children: PropTypes.any
+    children: PropTypes.any,
+    contentContainerStyle: PropTypes.shape(ScrollViewStylePropTypes),
+    horizontal: PropTypes.bool,
+    onScroll: PropTypes.func,
+    scrollEnabled: PropTypes.bool,
+    scrollEventThrottle: PropTypes.number,
+    style: PropTypes.shape(ScrollViewStylePropTypes)
   }
 
   static defaultProps = {
-    className: ''
+    contentContainerStyle: styles.initialContentContainer,
+    horizontal: false,
+    scrollEnabled: true,
+    scrollEventThrottle: 0,
+    style: styles.initial
+  }
+
+  constructor(...args) {
+    super(...args)
+    this._debouncedOnScrollEnd = debounce(this._onScrollEnd, 100)
+    this.state = {
+      isScrolling: false
+    }
+  }
+
+  _onScroll(e) {
+    const { scrollEventThrottle } = this.props
+    const { isScrolling, scrollLastTick } = this.state
+
+    // A scroll happened, so the scroll bumps the debounce.
+    this._debouncedOnScrollEnd(e)
+
+    if (isScrolling) {
+      // Scroll last tick may have changed, check if we need to notify
+      if (this._shouldEmitScrollEvent(scrollLastTick, scrollEventThrottle)) {
+        this._onScrollTick(e)
+      }
+    } else {
+      // Weren't scrolling, so we must have just started
+      this._onScrollStart(e)
+    }
+  }
+
+  _onScrollStart() {
+    this.setState({
+      isScrolling: true,
+      scrollLastTick: Date.now()
+    })
+  }
+
+  _onScrollTick(e) {
+    const { onScroll } = this.props
+    this.setState({
+      scrollLastTick: Date.now()
+    })
+    if (onScroll) onScroll(e)
+  }
+
+  _onScrollEnd(e) {
+    const { onScroll } = this.props
+    this.setState({
+      isScrolling: false
+    })
+    if (onScroll) onScroll(e)
+  }
+
+  _shouldEmitScrollEvent(lastTick, eventThrottle) {
+    const timeSinceLastTick = Date.now() - lastTick
+    return (eventThrottle > 0 && timeSinceLastTick >= (1000 / eventThrottle))
+  }
+
+  _maybePreventScroll(e) {
+    const { scrollEnabled } = this.props
+    if (!scrollEnabled) e.preventDefault()
   }
 
   render() {
+    const {
+      children,
+      contentContainerStyle,
+      horizontal,
+      style
+    } = this.props
+
+    const resolvedStyle = pickProps(style, scrollViewStyleKeys)
+    const resolvedContentContainerStyle = pickProps(contentContainerStyle, scrollViewStyleKeys)
+
     return (
-      <View {...this.props} />
+      <View
+        _className='ScrollView'
+        onScroll={(e) => this._onScroll(e)}
+        onTouchMove={(e) => this._maybePreventScroll(e)}
+        onWheel={(e) => this._maybePreventScroll(e)}
+        style={{
+          ...styles.initial,
+          ...resolvedStyle
+        }}
+      >
+        {children ? (
+          <View
+            children={children}
+            style={{
+              ...styles.initialContentContainer,
+              ...resolvedContentContainerStyle,
+              ...(horizontal && styles.row)
+            }}
+          />
+        ) : null}
+      </View>
     )
   }
 }