feat(SimpleViewSlider): add keepPrecedingViewsMounted prop

Author: jedwards1211

README.md

@@ -180,3 +180,10 @@ ReactDOM.render(
   document.getElementById('root')
 )
 ```
+
+### Additional props
+
+##### `keepPrecedingViewsMounted: boolean` (default: `false`)
+
+If `true`, `SimpleViewSlider` will keep views preceding the active view mounted, but not views following the active view.
+(As mentioned above, the order is determined by the `children`'s `key`s.)

src/index.js

@@ -318,7 +318,9 @@ export default class ViewSlider extends React.Component<Props, State> {
 
     const finalViewportStyle = {
       position: 'relative',
-      transform: `translateX(${activeView * spacing * (rtl ? 100 : -100)}%)`,
+      transform: `translateX(calc(${activeView *
+        spacing *
+        (rtl ? 100 : -100)}% + 0px))`,
       whiteSpace: 'nowrap',
       minHeight: '100%',
       direction: rtl ? 'rtl' : 'ltr',

src/simple.js

@@ -9,6 +9,7 @@ import type { Props as ViewSliderProps, ViewProps } from './index'
 export type Props = {
   children?: any,
   keepViewsMounted?: ?boolean,
+  keepPrecedingViewsMounted?: ?boolean,
   animateHeight?: ?boolean,
   transitionDuration?: ?number,
   transitionTimingFunction?: ?string,
@@ -48,10 +49,7 @@ export function createSimpleViewSlider(
       const activeView = parseInt(child.key)
       const views = []
       views[activeView] = child
-      this.state = {
-        views,
-        activeView,
-      }
+      this.state = { views, activeView }
     }
 
     componentDidUpdate(prevProps: Props) {
@@ -60,10 +58,14 @@ export function createSimpleViewSlider(
         const activeView = parseInt(child.key)
         const views = [...this.state.views]
         views[activeView] = child
-        this.setState({
-          views,
-          activeView,
-        })
+        if (!this.props.keepViewsMounted) {
+          views.length = Math.min(views.length, activeView + 1)
+        }
+        this.setState({ views, activeView })
+      } else if (prevProps.keepViewsMounted && !this.props.keepViewsMounted) {
+        const views = [...this.state.views]
+        views.length = Math.min(views.length, this.state.activeView + 1)
+        this.setState({ views })
       }
     }
 
@@ -75,12 +77,15 @@ export function createSimpleViewSlider(
         // Flow's React.ComponentType + defaultProps is foobar...
         spacing,
         rtl,
+        keepViewsMounted,
+        keepPrecedingViewsMounted,
         ...props
       } = this.props
       const { activeView, views } = this.state
       return (
         <ViewSlider
           {...props}
+          keepViewsMounted={keepViewsMounted || keepPrecedingViewsMounted}
           spacing={(spacing: any)}
           rtl={(rtl: any)}
           renderView={this.renderView}

test/index.js

@@ -157,6 +157,104 @@ describe('SimpleViewSlider', () => {
     clock.tick(1000)
     expect(comp.text()).to.equal('Child 1')
 
+    comp.unmount()
+  })
+  it('keepViewsMounted works', () => {
+    const comp = mount(
+      <SimpleViewSlider keepViewsMounted>
+        <div key={0}>Child 0</div>
+      </SimpleViewSlider>
+    )
+
+    expect(comp.text()).to.equal('Child 0')
+
+    comp.setProps({
+      children: <div key={1}>Child 1</div>,
+    })
+
+    clock.tick(1000)
+    expect(comp.update().text()).to.equal('Child 0Child 1')
+
+    comp.setProps({
+      children: <div key={2}>Child 2</div>,
+    })
+
+    clock.tick(1000)
+    expect(comp.update().text()).to.equal('Child 0Child 1Child 2')
+
+    comp.setProps({
+      children: <div key={1}>Child a</div>,
+    })
+
+    clock.tick(1000)
+    expect(comp.update().text()).to.equal('Child 0Child aChild 2')
+
+    comp.unmount()
+  })
+  it('keepPrecedingViewsMounted works', () => {
+    const comp = mount(
+      <SimpleViewSlider keepPrecedingViewsMounted>
+        <div key={0}>Child 0</div>
+      </SimpleViewSlider>
+    )
+
+    expect(comp.text()).to.equal('Child 0')
+
+    comp.setProps({
+      children: <div key={1}>Child 1</div>,
+    })
+
+    clock.tick(1000)
+    expect(comp.update().text()).to.equal('Child 0Child 1')
+
+    comp.setProps({
+      children: <div key={2}>Child 2</div>,
+    })
+
+    clock.tick(1000)
+    expect(comp.update().text()).to.equal('Child 0Child 1Child 2')
+
+    comp.setProps({
+      children: <div key={1}>Child a</div>,
+    })
+
+    clock.tick(1000)
+    expect(comp.update().text()).to.equal('Child 0Child a')
+
+    comp.unmount()
+  })
+  it('changing keepPrecedingViewsMounted works', () => {
+    const comp = mount(
+      <SimpleViewSlider keepViewsMounted>
+        <div key={0}>Child 0</div>
+      </SimpleViewSlider>
+    )
+
+    expect(comp.text()).to.equal('Child 0')
+
+    comp.setProps({
+      children: <div key={1}>Child 1</div>,
+    })
+
+    clock.tick(1000)
+    expect(comp.update().text()).to.equal('Child 0Child 1')
+
+    comp.setProps({
+      children: <div key={2}>Child 2</div>,
+    })
+
+    clock.tick(1000)
+    expect(comp.update().text()).to.equal('Child 0Child 1Child 2')
+
+    comp.setProps({
+      keepViewsMounted: false,
+      keepPrecedingViewsMounted: true,
+      children: <div key={1}>Child a</div>,
+    })
+
+    clock.tick(1000)
+    expect(comp.update().text()).to.equal('Child 0Child a')
+
     comp.unmount()
   })
 })