ScrollBar: set valueIsAdjusting property to true while smooth scrolling animation is running (issue #50)

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

@@ -473,6 +473,8 @@ public class FlatScrollBarUI
 		if( animator != null )
 			animator.cancel();
 
+		scrollbar.setValueIsAdjusting( true );
+
 		// if invoked while animation is running, calculation of new value
 		// should start at the previous target value
 		if( targetValue != Integer.MIN_VALUE )
@@ -487,7 +489,8 @@ public class FlatScrollBarUI
 			scrollbar.setValue( oldValue );
 
 			setValueAnimated( newValue );
-		}
+		} else
+			scrollbar.setValueIsAdjusting( false );
 
 		inRunAndSetValueAnimated = false;
 	}
@@ -498,6 +501,8 @@ public class FlatScrollBarUI
 	private int delta;
 
 	public void setValueAnimated( int value ) {
+		scrollbar.setValueIsAdjusting( true );
+
 		// create animator
 		if( animator == null ) {
 			int duration = FlatUIUtils.getUIInt( "ScrollPane.smoothScrolling.duration", 200 );
@@ -510,9 +515,15 @@ public class FlatScrollBarUI
 					return;
 				}
 
+				// re-enable valueIsAdjusting if disabled while animation is running
+				// (e.g. in mouse released listener)
+				if( !scrollbar.getValueIsAdjusting() )
+					scrollbar.setValueIsAdjusting( true );
+
 				scrollbar.setValue( targetValue - delta + Math.round( delta * fraction ) );
 			}, () -> {
 				targetValue = Integer.MIN_VALUE;
+				scrollbar.setValueIsAdjusting( false );
 			});
 
 			animator.setResolution( resolution );

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatSmoothScrollingTest.java

@@ -0,0 +1,144 @@
+/*
+ * Copyright 2020 FormDev Software GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.formdev.flatlaf.testing;
+
+import java.awt.event.AdjustmentEvent;
+import java.awt.event.AdjustmentListener;
+import java.util.ArrayList;
+import java.util.Arrays;
+import javax.swing.*;
+import net.miginfocom.swing.*;
+
+/**
+ * @author Karl Tauber
+ */
+public class FlatSmoothScrollingTest
+	extends FlatTestPanel
+{
+	public static void main( String[] args ) {
+		SwingUtilities.invokeLater( () -> {
+			FlatTestFrame frame = FlatTestFrame.create( args, "FlatSmoothScrollingTest" );
+			UIManager.put( "ScrollBar.showButtons", true );
+			frame.showFrame( FlatSmoothScrollingTest::new );
+		} );
+	}
+
+	FlatSmoothScrollingTest() {
+		initComponents();
+
+		scrollPane1.getVerticalScrollBar().addAdjustmentListener( new AdjustmentHandler( "list vert" ) );
+		scrollPane1.getHorizontalScrollBar().addAdjustmentListener( new AdjustmentHandler( "list horz" ) );
+
+		ArrayList<String> items = new ArrayList<>();
+		for( char ch = '0'; ch < 'z'; ch++ ) {
+			char[] chars = new char[ch - '0' + 1];
+			Arrays.fill( chars, ch );
+			items.add( new String( chars ) );
+		}
+
+		list1.setModel( new AbstractListModel<String>() {
+			@Override
+			public int getSize() {
+				return items.size();
+			}
+
+			@Override
+			public String getElementAt( int index ) {
+				return items.get( index );
+			}
+		} );
+	}
+
+	private void smoothScrollingChanged() {
+		UIManager.put( "ScrollPane.smoothScrolling", smoothScrollingCheckBox.isSelected() );
+	}
+
+	private void initComponents() {
+		// JFormDesigner - Component initialization - DO NOT MODIFY  //GEN-BEGIN:initComponents
+		smoothScrollingCheckBox = new JCheckBox();
+		listLabel = new JLabel();
+		scrollPane1 = new JScrollPane();
+		list1 = new JList<>();
+
+		//======== this ========
+		setLayout(new MigLayout(
+			"ltr,insets dialog,hidemode 3",
+			// columns
+			"[]" +
+			"[200]",
+			// rows
+			"[]" +
+			"[::200,grow,fill]"));
+
+		//---- smoothScrollingCheckBox ----
+		smoothScrollingCheckBox.setText("Smooth scrolling");
+		smoothScrollingCheckBox.setSelected(true);
+		smoothScrollingCheckBox.addActionListener(e -> smoothScrollingChanged());
+		add(smoothScrollingCheckBox, "cell 0 0 2 1,alignx left,growx 0");
+
+		//---- listLabel ----
+		listLabel.setText("JList:");
+		add(listLabel, "cell 0 1,aligny top,growy 0");
+
+		//======== scrollPane1 ========
+		{
+			scrollPane1.setViewportView(list1);
+		}
+		add(scrollPane1, "cell 1 1,growx");
+		// JFormDesigner - End of component initialization  //GEN-END:initComponents
+	}
+
+	// JFormDesigner - Variables declaration - DO NOT MODIFY  //GEN-BEGIN:variables
+	private JCheckBox smoothScrollingCheckBox;
+	private JLabel listLabel;
+	private JScrollPane scrollPane1;
+	private JList<String> list1;
+	// JFormDesigner - End of variables declaration  //GEN-END:variables
+
+	//---- class AdjustmentHandler --------------------------------------------
+
+	private static class AdjustmentHandler
+		implements AdjustmentListener
+	{
+		private final String name;
+		private int count;
+
+		AdjustmentHandler( String name ) {
+			this.name = name;
+		}
+
+		@Override
+		public void adjustmentValueChanged( AdjustmentEvent e ) {
+			System.out.printf( "%s (%d):  %s  %3d  %b%n",
+				name, ++count,
+				adjustmentType2Str( e.getAdjustmentType() ),
+				e.getValue(),
+				e.getValueIsAdjusting() );
+		}
+
+		private String adjustmentType2Str( int adjustmentType ) {
+			switch( adjustmentType ) {
+				case AdjustmentEvent.UNIT_INCREMENT:  return "UNIT_INCREMENT";
+				case AdjustmentEvent.UNIT_DECREMENT:  return "UNIT_DECREMENT";
+				case AdjustmentEvent.BLOCK_INCREMENT: return "BLOCK_INCREMENT";
+				case AdjustmentEvent.BLOCK_DECREMENT: return "BLOCK_DECREMENT";
+				case AdjustmentEvent.TRACK:           return "TRACK";
+				default:                              return "unknown type";
+			}
+		}
+	}
+}

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatSmoothScrollingTest.jfd

@@ -0,0 +1,43 @@
+JFDML JFormDesigner: "7.0.2.0.298" Java: "14" encoding: "UTF-8"
+
+new FormModel {
+	contentType: "form/swing"
+	root: new FormRoot {
+		add( new FormContainer( "com.formdev.flatlaf.testing.FlatTestPanel", new FormLayoutManager( class net.miginfocom.swing.MigLayout ) {
+			"$layoutConstraints": "ltr,insets dialog,hidemode 3"
+			"$columnConstraints": "[][200]"
+			"$rowConstraints": "[][::200,grow,fill]"
+		} ) {
+			name: "this"
+			add( new FormComponent( "javax.swing.JCheckBox" ) {
+				name: "smoothScrollingCheckBox"
+				"text": "Smooth scrolling"
+				"selected": true
+				addEvent( new FormEvent( "java.awt.event.ActionListener", "actionPerformed", "smoothScrollingChanged", false ) )
+			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+				"value": "cell 0 0 2 1,alignx left,growx 0"
+			} )
+			add( new FormComponent( "javax.swing.JLabel" ) {
+				name: "listLabel"
+				"text": "JList:"
+			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+				"value": "cell 0 1,aligny top,growy 0"
+			} )
+			add( new FormContainer( "javax.swing.JScrollPane", new FormLayoutManager( class javax.swing.JScrollPane ) ) {
+				name: "scrollPane1"
+				add( new FormComponent( "javax.swing.JList" ) {
+					name: "list1"
+					auxiliary() {
+						"JavaCodeGenerator.typeParameters": "String"
+						"JavaCodeGenerator.variableLocal": false
+					}
+				} )
+			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+				"value": "cell 1 1,growx"
+			} )
+		}, new FormLayoutConstraints( null ) {
+			"location": new java.awt.Point( 0, 0 )
+			"size": new java.awt.Dimension( 790, 715 )
+		} )
+	}
+}