From dd9b0bbfbc24ba413b4594f08840fb3582e40b09 Mon Sep 17 00:00:00 2001
From: Denis Konoplev <denis.konoplev@jetbrains.com>
Date: Fri, 31 Jan 2020 09:45:40 +0300
Subject: [PATCH] IDEA-231689: Fix touch scroll on tap

GitOrigin-RevId: 06bd63245f6f3414ef8e44834e965e10d8ffcd59
---
 .../src/com/intellij/ui/components/JBScrollPane.java          | 2 +-
 .../src/com/intellij/util/ui/MouseWheelSmoothScroll.java      | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/platform/platform-api/src/com/intellij/ui/components/JBScrollPane.java b/platform/platform-api/src/com/intellij/ui/components/JBScrollPane.java
index b97da86534e5..a745f91250c1 100644
--- a/platform/platform-api/src/com/intellij/ui/components/JBScrollPane.java
+++ b/platform/platform-api/src/com/intellij/ui/components/JBScrollPane.java
@@ -201,7 +201,7 @@ public class JBScrollPane extends JScrollPane {
         boolean isAdjustedDeltaZero = bar instanceof JBScrollBar && ((JBScrollBar)bar).getDeltaAdjusted(event) == 0.0;
 
         if (isWheelScrollEnabled && isBarVisible && !isAdjustedDeltaZero) {
-          if (UISettings.getShadowInstance().getAnimatedScrolling()) {
+          if (UISettings.getShadowInstance().getAnimatedScrolling() || TouchScrollUtil.isTouchScroll(event)) {
             if (mySmoothScroll == null) {
               mySmoothScroll = MouseWheelSmoothScroll.create(() -> {
                 return ScrollSettings.isEligibleFor(pane);
diff --git a/platform/platform-api/src/com/intellij/util/ui/MouseWheelSmoothScroll.java b/platform/platform-api/src/com/intellij/util/ui/MouseWheelSmoothScroll.java
index 9973d2a8bc18..5c7339534ba1 100644
--- a/platform/platform-api/src/com/intellij/util/ui/MouseWheelSmoothScroll.java
+++ b/platform/platform-api/src/com/intellij/util/ui/MouseWheelSmoothScroll.java
@@ -154,6 +154,9 @@ public class MouseWheelSmoothScroll {
   }
 
   private static int getRoundedAtLeastToOne(double value) {
+    if (value == 0.0) {
+      return 0;
+    }
     if (abs(value) < 1) {
       return value > 0 ? 1 : -1;
     }
@@ -248,6 +251,7 @@ public class MouseWheelSmoothScroll {
 
     public void registerBegin() {
       beginTime = System.currentTimeMillis();
+      lastDelta = 0;
     }
 
     public void registerUpdate(int delta) {