From 38a6eec0db85a5204e85a9a92b4dee2db9641671 Mon Sep 17 00:00:00 2001
From: Mengjue Wang <mengjuew@fb.com>
Date: Mon, 11 Jul 2016 20:43:57 -0700
Subject: [PATCH] Provide RTL support for new Navigator -- Make RTL works in
 NUX

Summary: Provide RTL support in NavigationPager

Reviewed By: fkgozali

Differential Revision: D3536850

fbshipit-source-id: 29890a125dc5e001b4c10208cd53bfeca0d9b5c3
---
 .../NavigationPagerPanResponder.js              | 17 +++++++++++++----
 .../NavigationPagerStyleInterpolator.js         |  9 +++++++--
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/Libraries/CustomComponents/NavigationExperimental/NavigationPagerPanResponder.js b/Libraries/CustomComponents/NavigationExperimental/NavigationPagerPanResponder.js
index e7c085098..6bd5410b1 100644
--- a/Libraries/CustomComponents/NavigationExperimental/NavigationPagerPanResponder.js
+++ b/Libraries/CustomComponents/NavigationExperimental/NavigationPagerPanResponder.js
@@ -15,6 +15,7 @@
 const Animated = require('Animated');
 const NavigationAbstractPanResponder = require('NavigationAbstractPanResponder');
 const NavigationCardStackPanResponder = require('NavigationCardStackPanResponder');
+const I18nManager = require('I18nManager');
 
 const clamp = require('clamp');
 
@@ -133,6 +134,9 @@ class NavigationPagerPanResponder extends NavigationAbstractPanResponder {
     const distance = isVertical ?
       layout.height.__getValue() :
       layout.width.__getValue();
+    const currentValue = I18nManager.isRTL && axis === 'dx' ?
+      this._startValue + (gesture[axis] / distance) :
+      this._startValue - (gesture[axis] / distance);
 
     const prevIndex = Math.max(
       0,
@@ -146,7 +150,7 @@ class NavigationPagerPanResponder extends NavigationAbstractPanResponder {
 
     const value = clamp(
       prevIndex,
-      this._startValue - (gesture[axis] / distance),
+      currentValue,
       nextIndex,
     );
 
@@ -171,14 +175,19 @@ class NavigationPagerPanResponder extends NavigationAbstractPanResponder {
     const axis = isVertical ? 'dy' : 'dx';
     const velocityAxis = isVertical ? 'vy' : 'vx';
     const index = navigationState.index;
-    const distance = gesture[axis];
+    const distance = I18nManager.isRTL && axis === 'dx' ?
+      -gesture[axis] :
+      gesture[axis];
+    const moveSpeed = I18nManager.isRTL && velocityAxis === 'vx' ?
+      -gesture[velocityAxis] :
+      gesture[velocityAxis];
 
     position.stopAnimation((value: number) => {
       this._reset();
       if (
         distance > DISTANCE_THRESHOLD  ||
         value <= index - POSITION_THRESHOLD ||
-        gesture[velocityAxis] > VELOCITY_THRESHOLD
+        moveSpeed > VELOCITY_THRESHOLD
       ) {
         onNavigateBack && onNavigateBack();
         return;
@@ -187,7 +196,7 @@ class NavigationPagerPanResponder extends NavigationAbstractPanResponder {
       if (
         distance < -DISTANCE_THRESHOLD ||
         value >= index  + POSITION_THRESHOLD ||
-        gesture[velocityAxis] < -VELOCITY_THRESHOLD
+        moveSpeed < -VELOCITY_THRESHOLD
       ) {
         onNavigateForward && onNavigateForward();
       }
diff --git a/Libraries/CustomComponents/NavigationExperimental/NavigationPagerStyleInterpolator.js b/Libraries/CustomComponents/NavigationExperimental/NavigationPagerStyleInterpolator.js
index 87a211b1a..950aa5eb1 100644
--- a/Libraries/CustomComponents/NavigationExperimental/NavigationPagerStyleInterpolator.js
+++ b/Libraries/CustomComponents/NavigationExperimental/NavigationPagerStyleInterpolator.js
@@ -32,6 +32,8 @@
  */
 'use strict';
 
+const I18nManager = require('I18nManager');
+
 import type  {
   NavigationSceneRendererProps,
 } from 'NavigationTypeDefinition';
@@ -87,11 +89,14 @@ function forHorizontal(props: NavigationSceneRendererProps): Object {
 
   const index = scene.index;
   const inputRange = [index - 1, index, index + 1];
-
   const width = layout.initWidth;
+  const outputRange = I18nManager.isRTL ?
+    ([-width, 0, width]: Array<number>) :
+    ([width, 0, -width]: Array<number>);
+
   const translateX = position.interpolate({
     inputRange,
-    outputRange: ([width, 0, -width]: Array<number>),
+    outputRange,
   });
 
   return {