ScrollPane: use smooth scrolling when rotating the mouse wheel (issue #50)

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatScrollBarUI.java

@@ -28,8 +28,6 @@ import java.beans.PropertyChangeListener;
 import java.lang.invoke.MethodHandles;
 import java.util.Map;
 import java.util.Objects;
-import javax.swing.BoundedRangeModel;
-import javax.swing.DefaultBoundedRangeModel;
 import javax.swing.InputMap;
 import javax.swing.JButton;
 import javax.swing.JComponent;
@@ -37,7 +35,6 @@ import javax.swing.JScrollBar;
 import javax.swing.JScrollPane;
 import javax.swing.SwingUtilities;
 import javax.swing.UIManager;
-import javax.swing.event.ChangeListener;
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.basic.BasicScrollBarUI;
 import com.formdev.flatlaf.FlatClientProperties;
@@ -450,7 +447,11 @@ public class FlatScrollBarUI
 		} );
 	}
 
-	protected void runAndSetValueAnimated( Runnable r ) {
+	/**
+	 * Runs the given runnable, which should modify the scroll bar value,
+	 * and then animate scroll bar value from old value to new value.
+	 */
+	public void runAndSetValueAnimated( Runnable r ) {
 		if( !isSmoothScrollingEnabled() ) {
 			r.run();
 			return;
@@ -459,9 +460,6 @@ public class FlatScrollBarUI
 		if( animator != null )
 			animator.cancel();
 
-		int[] newValue = new int[1];
-
-		runWithoutValueChangeEvents( scrollbar, () -> {
 		// if invoked while animation is running, calculation of new value
 		// should start at the previous target value
 		if( targetValue != Integer.MIN_VALUE )
@@ -471,18 +469,17 @@ public class FlatScrollBarUI
 
 		r.run();
 
-			newValue[0] = scrollbar.getValue();
+		int newValue = scrollbar.getValue();
 		scrollbar.setValue( oldValue );
-		} );
 
-		setValueAnimated( newValue[0] );
+		setValueAnimated( newValue );
 	}
 
 	private Animator animator;
 	private int targetValue = Integer.MIN_VALUE;
 	private int delta;
 
-	protected void setValueAnimated( int value ) {
+	public void setValueAnimated( int value ) {
 		// create animator
 		if( animator == null ) {
 			int duration = FlatUIUtils.getUIInt( "ScrollPane.smoothScrolling.duration", 200 );
@@ -527,29 +524,6 @@ public class FlatScrollBarUI
 		return UIManager.getBoolean( "ScrollPane.smoothScrolling" );
 	}
 
-	protected static void runWithoutValueChangeEvents( JScrollBar scrollBar, Runnable r ) {
-		BoundedRangeModel model = scrollBar.getModel();
-		if( !(model instanceof DefaultBoundedRangeModel) ) {
-			r.run();
-			return;
-		}
-
-		DefaultBoundedRangeModel m = (DefaultBoundedRangeModel) model;
-
-		// remove all listeners
-		ChangeListener[] changeListeners = m.getChangeListeners();
-		for( ChangeListener l : changeListeners )
-			m.removeChangeListener( l );
-
-		try {
-			r.run();
-		} finally {
-			// add all listeners
-			for( ChangeListener l : changeListeners )
-				m.addChangeListener( l );
-		}
-	}
-
 	//---- class ScrollBarHoverListener ---------------------------------------
 
 	// using static field to disabling hover for other scroll bars

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatScrollPaneUI.java

@@ -135,12 +135,25 @@ public class FlatScrollPaneUI
 		MouseWheelListener superListener = super.createMouseWheelListener();
 		return e -> {
 			if( isSmoothScrollingEnabled() &&
-				scrollpane.isWheelScrollingEnabled() &&
+				scrollpane.isWheelScrollingEnabled() )
-				e.getScrollType() == MouseWheelEvent.WHEEL_UNIT_SCROLL &&
+			{
+				if( e.getScrollType() == MouseWheelEvent.WHEEL_UNIT_SCROLL &&
 					e.getPreciseWheelRotation() != 0 &&
 					e.getPreciseWheelRotation() != e.getWheelRotation() )
 				{
-				mouseWheelMovedSmooth( e );
+					// precise scrolling
+					mouseWheelMovedPrecise( e );
+				} else {
+					// smooth scrolling
+					JScrollBar scrollBar = findScrollBarToScroll( e );
+					if( scrollBar != null && scrollBar.getUI() instanceof FlatScrollBarUI ) {
+						FlatScrollBarUI ui = (FlatScrollBarUI) scrollBar.getUI();
+						ui.runAndSetValueAnimated( () -> {
+							superListener.mouseWheelMoved( e );
+						} );
+					} else
+						superListener.mouseWheelMoved( e );
+				}
 			} else
 				superListener.mouseWheelMoved( e );
 		};
@@ -157,19 +170,16 @@ public class FlatScrollPaneUI
 		return UIManager.getBoolean( "ScrollPane.smoothScrolling" );
 	}
 
-	private void mouseWheelMovedSmooth( MouseWheelEvent e ) {
+	private void mouseWheelMovedPrecise( MouseWheelEvent e ) {
 		// return if there is no viewport
 		JViewport viewport = scrollpane.getViewport();
 		if( viewport == null )
 			return;
 
 		// find scrollbar to scroll
-		JScrollBar scrollbar = scrollpane.getVerticalScrollBar();
+		JScrollBar scrollbar = findScrollBarToScroll( e );
-		if( scrollbar == null || !scrollbar.isVisible() || e.isShiftDown() ) {
+		if( scrollbar == null )
-			scrollbar = scrollpane.getHorizontalScrollBar();
-			if( scrollbar == null || !scrollbar.isVisible() )
 			return;
-		}
 
 		// consume event
 		e.consume();
@@ -262,6 +272,16 @@ public class FlatScrollPaneUI
 */
 	}
 
+	private JScrollBar findScrollBarToScroll( MouseWheelEvent e ) {
+		JScrollBar scrollBar = scrollpane.getVerticalScrollBar();
+		if( scrollBar == null || !scrollBar.isVisible() || e.isShiftDown() ) {
+			scrollBar = scrollpane.getHorizontalScrollBar();
+			if( scrollBar == null || !scrollBar.isVisible() )
+				return null;
+		}
+		return scrollBar;
+	}
+
 	@Override
 	protected PropertyChangeListener createPropertyChangeListener() {
 		PropertyChangeListener superListener = super.createPropertyChangeListener();