From 58df074c19b546765be2b2f1f359c607a1ce048f Mon Sep 17 00:00:00 2001
From: Nikita Shanin <shaninnik@gmail.com>
Date: Fri, 3 Jan 2020 12:54:45 -0500
Subject: [PATCH] disable momentum scrolling for vertical ScrollView

---
 Libraries/Components/ScrollView/ScrollView.js            | 4 ++--
 React/Views/ScrollView/RCTScrollView.m                   | 2 ++
 .../com/facebook/react/views/scroll/ReactScrollView.java | 9 +++++++++
 .../react/views/scroll/ReactScrollViewManager.java       | 6 ++++++
 4 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/Libraries/Components/ScrollView/ScrollView.js b/Libraries/Components/ScrollView/ScrollView.js
index 59f5517a9d8b89..51305ff5ccef47 100644
--- a/Libraries/Components/ScrollView/ScrollView.js
+++ b/Libraries/Components/ScrollView/ScrollView.js
@@ -401,8 +401,8 @@ export type Props = $ReadOnly<{|
   /**
    * When true, the scroll view stops on the next index (in relation to scroll
    * position at release) regardless of how fast the gesture is. This can be
-   * used for horizontal pagination when the page is less than the width of
-   * the ScrollView. The default value is false.
+   * used for pagination when the page is less than the width of the
+   * horizontal ScrollView or the height of the vertical ScrollView. The default value is false.
    */
   disableIntervalMomentum?: ?boolean,
   /**
diff --git a/React/Views/ScrollView/RCTScrollView.m b/React/Views/ScrollView/RCTScrollView.m
index 4b4d46a50a1ae5..a307cfe69e788c 100644
--- a/React/Views/ScrollView/RCTScrollView.m
+++ b/React/Views/ScrollView/RCTScrollView.m
@@ -738,6 +738,8 @@ - (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoi
     if (isHorizontal) {
       // Use current scroll offset to determine the next index to snap to when momentum disabled
       targetContentOffsetAlongAxis = self.disableIntervalMomentum ? scrollView.contentOffset.x : targetContentOffset->x;
+    } else {
+      targetContentOffsetAlongAxis = self.disableIntervalMomentum ? scrollView.contentOffset.y : targetContentOffset->y;
     }
 
     // Offset based on desired alignment
diff --git a/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollView.java b/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollView.java
index 10e1e443c95267..48664a960ca12a 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollView.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollView.java
@@ -73,6 +73,7 @@ public class ReactScrollView extends ScrollView
   private @Nullable String mScrollPerfTag;
   private @Nullable Drawable mEndBackground;
   private int mEndFillColor = Color.TRANSPARENT;
+  private boolean mDisableIntervalMomentum = false;
   private int mSnapInterval = 0;
   private float mDecelerationRate = 0.985f;
   private @Nullable List<Integer> mSnapOffsets;
@@ -135,6 +136,10 @@ private OverScroller getOverScrollerFromParent() {
     return scroller;
   }
 
+  public void setDisableIntervalMomentum(boolean disableIntervalMomentum) {
+    mDisableIntervalMomentum = disableIntervalMomentum;
+  }
+
   public void setSendMomentumEvents(boolean sendMomentumEvents) {
     mSendMomentumEvents = sendMomentumEvents;
   }
@@ -609,6 +614,10 @@ private void flingAndSnap(int velocityY) {
 
     int maximumOffset = getMaxScrollY();
     int targetOffset = predictFinalScrollPosition(velocityY);
+    if (mDisableIntervalMomentum) {
+      targetOffset = getScrollY();
+    }
+
     int smallerOffset = 0;
     int largerOffset = maximumOffset;
     int firstOffset = 0;
diff --git a/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollViewManager.java b/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollViewManager.java
index d1bb2e4070cdde..0f435ad4aa612e 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollViewManager.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollViewManager.java
@@ -85,6 +85,12 @@ public void setDecelerationRate(ReactScrollView view, float decelerationRate) {
     view.setDecelerationRate(decelerationRate);
   }
 
+  @ReactProp(name = "disableIntervalMomentum")
+  public void setDisableIntervalMomentum(
+      ReactScrollView view, boolean disbaleIntervalMomentum) {
+    view.setDisableIntervalMomentum(disbaleIntervalMomentum);
+  }
+
   @ReactProp(name = "snapToInterval")
   public void setSnapToInterval(ReactScrollView view, float snapToInterval) {
     // snapToInterval needs to be exposed as a float because of the Javascript interface.