From 3de489f693d51eb4f5ee4f20e5c2573ac6c89169 Mon Sep 17 00:00:00 2001
From: Karl Tauber <karl@jformdesigner.com>
Date: Fri, 9 Oct 2020 16:27:52 +0200
Subject: [PATCH] TabbedPane: - fixed jittery animated scrolling tabs - support
 disabling animated scrolling with "ScrollPane.smoothScrolling=false"

---
 .../com/formdev/flatlaf/ui/FlatTabbedPaneUI.java | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatTabbedPaneUI.java b/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatTabbedPaneUI.java
index 2911f304..5f408f53 100644
--- a/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatTabbedPaneUI.java
+++ b/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatTabbedPaneUI.java
@@ -100,6 +100,7 @@ import com.formdev.flatlaf.util.UIScale;
  * @uiDefault TabbedPane.showTabSeparators				boolean
  * @uiDefault TabbedPane.tabSeparatorsFullHeight		boolean
  * @uiDefault TabbedPane.hasFullBorder					boolean
+ * @uiDefault ScrollPane.smoothScrolling				boolean
  *
  * @author Karl Tauber
  */
@@ -577,6 +578,16 @@ public class FlatTabbedPaneUI
 		return tabPane.getTabLayoutPolicy() == JTabbedPane.SCROLL_TAB_LAYOUT;
 	}
 
+	protected boolean isSmoothScrollingEnabled() {
+		if( !Animator.useAnimation() )
+			return false;
+
+		// Note: Getting UI value "ScrollPane.smoothScrolling" here to allow
+		// applications to turn smooth scrolling on or off at any time
+		// (e.g. in application options dialog).
+		return UIManager.getBoolean( "ScrollPane.smoothScrolling" );
+	}
+
 	//---- class FlatScrollableTabButton --------------------------------------
 
 	protected class FlatScrollableTabButton
@@ -705,15 +716,14 @@ public class FlatTabbedPaneUI
 				return;
 
 			// do not use animation if disabled
-			if( !Animator.useAnimation() ) {
+			if( !isSmoothScrollingEnabled() ) {
 				tabViewport.setViewPosition( viewPosition );
 				setRolloverTab( lastMouseX, lastMouseY );
 				return;
 			}
 
 			// remember start and target view positions
-			if( startViewPosition == null )
-				startViewPosition = tabViewport.getViewPosition();
+			startViewPosition = tabViewport.getViewPosition();
 			targetViewPosition = viewPosition;
 
 			// create animator