Support RTL in HorizontalScrollSpec

Summary: as title. check layout direction and scroll to right if RTL Reviewed By: muraziz Differential Revision: D6845558 fbshipit-source-id: fb7284d138f17f805b3cfce5f05bcc5e3565e00b
chowjee · Jan 30, 2018 · 5b9286e · 5b9286e
1 parent b944bea
commit 5b9286e
Showing 1 changed file with 26 additions and 14 deletions.
diff --git a/litho-widget/src/main/java/com/facebook/litho/widget/HorizontalScrollSpec.java b/litho-widget/src/main/java/com/facebook/litho/widget/HorizontalScrollSpec.java
@@ -43,6 +43,7 @@
 import com.facebook.litho.annotations.PropDefault;
 import com.facebook.litho.annotations.ResType;
 import com.facebook.litho.annotations.State;
+import com.facebook.yoga.YogaDirection;
 
 /**
  * A component that wraps another component and allow it to be horizontally scrollable. It's
@@ -53,6 +54,8 @@
 @MountSpec
 class HorizontalScrollSpec {
 
+  private static final int LAST_SCROLL_POSITION_UNSET = -1;
+
   @PropDefault static final boolean scrollbarEnabled = true;
 
   private static final SynchronizedPool<Size> sSizePool =
@@ -137,7 +140,8 @@ static void onBoundsDefined(
       @FromMeasure Integer measuredComponentWidth,
       @FromMeasure Integer measuredComponentHeight,
       Output<Integer> componentWidth,
-      Output<Integer> componentHeight) {
+      Output<Integer> componentHeight,
+      Output<YogaDirection> layoutDirection) {
 
     // If onMeasure() has been called, this means the content component already
     // has a defined size, no need to calculate it again.
@@ -163,6 +167,8 @@ static void onBoundsDefined(
       componentWidth.set(measuredWidth);
       componentHeight.set(measuredHeight);
     }
+
+    layoutDirection.set(layout.getResolvedLayoutDirection());
   }
 
   @OnCreateMountContent
@@ -172,13 +178,14 @@ static HorizontalScrollLithoView onCreateMountContent(ComponentContext c) {
 
   @OnMount
   static void onMount(
-      ComponentContext context,
+      final ComponentContext context,
       final HorizontalScrollLithoView horizontalScrollLithoView,
       @Prop(optional = true, resType = ResType.BOOL) boolean scrollbarEnabled,
-      @State final ScrollPosition lastScrollPosition,
+      @State(canUpdateLazily = true) final int lastScrollPosition,
       @FromPrepare ComponentTree contentComponent,
       @FromBoundsDefined int componentWidth,
-      @FromBoundsDefined int componentHeight) {
+      @FromBoundsDefined int componentHeight,
+      @FromBoundsDefined final YogaDirection layoutDirection) {
 
     horizontalScrollLithoView.setHorizontalScrollBarEnabled(scrollbarEnabled);
     horizontalScrollLithoView.mount(contentComponent, componentWidth, componentHeight);
@@ -188,15 +195,26 @@ static void onMount(
           @Override
           public boolean onPreDraw() {
             horizontalScrollLithoView.getViewTreeObserver().removeOnPreDrawListener(this);
-            horizontalScrollLithoView.setScrollX(lastScrollPosition.x);
+
+            if (lastScrollPosition == LAST_SCROLL_POSITION_UNSET) {
+              if (layoutDirection == YogaDirection.RTL) {
+                horizontalScrollLithoView.fullScroll(HorizontalScrollView.FOCUS_RIGHT);
+              }
+              HorizontalScroll.lazyUpdateLastScrollPosition(
+                  context, horizontalScrollLithoView.getScrollX());
+            } else {
+              horizontalScrollLithoView.setScrollX(lastScrollPosition);
+            }
+
             return true;
           }
         });
     viewTreeObserver.addOnScrollChangedListener(
         new ViewTreeObserver.OnScrollChangedListener() {
           @Override
           public void onScrollChanged() {
-            lastScrollPosition.x = horizontalScrollLithoView.getScrollX();
+            HorizontalScroll.lazyUpdateLastScrollPosition(
+                context, horizontalScrollLithoView.getScrollX());
           }
         });
   }
@@ -209,10 +227,8 @@ static void onUnmount(
   }
 
   @OnCreateInitialState
-  static void onCreateInitialState(
-      ComponentContext c,
-      StateValue<ScrollPosition> lastScrollPosition) {
-    lastScrollPosition.set(new ScrollPosition());
+  static void onCreateInitialState(ComponentContext c, StateValue<Integer> lastScrollPosition) {
+    lastScrollPosition.set(LAST_SCROLL_POSITION_UNSET);
   }
 
   static class HorizontalScrollLithoView extends HorizontalScrollView {
@@ -269,8 +285,4 @@ private static Size acquireSize() {
   private static void releaseSize(Size size) {
     sSizePool.release(size);
   }
-
-  static class ScrollPosition {
-    int x = 0;
-  }
 }