FlatSmoothScrollingTest:

- added slider to horizontally scale chart
- improved chart legend
- record stack for points in chart and show in tooltip on hover

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

@@ -48,7 +48,7 @@ public class FlatAnimatorTest
 
 		updateChartDelayedChanged();
 
-		lineChartPanel.setSecondWidth( 500 );
+		lineChartPanel.setOneSecondWidth( 500 );
 		mouseWheelTestPanel.lineChartPanel = lineChartPanel;
 	}
 
@@ -217,7 +217,7 @@ public class FlatAnimatorTest
 				value = startValue + Math.round( (targetValue - startValue) * fraction );
 				valueLabel.setText( String.valueOf( value ) );
 
-				lineChartPanel.addValue( value / (double) MAX_VALUE, Color.red );
+				lineChartPanel.addValue( value / (double) MAX_VALUE, false, Color.red, null );
 			}, () -> {
 				targetValue = -1;
 			} );
@@ -235,7 +235,7 @@ public class FlatAnimatorTest
 			// for unprecise wheels the rotation value is usually -1 or +1
 			// for precise wheels the rotation value is in range ca. -10 to +10,
 			// depending how fast the wheel is rotated
-			lineChartPanel.addValue( 0.5 + (preciseWheelRotation / 20.), true, Color.red );
+			lineChartPanel.addValue( 0.5 + (preciseWheelRotation / 20.), true, Color.red, null );
 
 			// increase/decrease target value if animation is in progress
 			int newValue = (int) ((targetValue < 0 ? value : targetValue) + (STEP * preciseWheelRotation));
@@ -252,7 +252,7 @@ public class FlatAnimatorTest
 				value = newValue;
 				valueLabel.setText( String.valueOf( value ) );
 
-				lineChartPanel.addValue( value / (double) MAX_VALUE, Color.red );
+				lineChartPanel.addValue( value / (double) MAX_VALUE, false, Color.red, null );
 				return;
 			}
 

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

@@ -24,11 +24,15 @@ import java.awt.Graphics;
 import java.awt.Graphics2D;
 import java.awt.Point;
 import java.awt.Rectangle;
+import java.awt.event.HierarchyEvent;
+import java.awt.event.MouseEvent;
+import java.text.MessageFormat;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.stream.Collectors;
 import javax.swing.*;
 import javax.swing.event.ChangeEvent;
@@ -37,6 +41,7 @@ import javax.swing.table.AbstractTableModel;
 import javax.swing.tree.*;
 import com.formdev.flatlaf.FlatLaf;
 import com.formdev.flatlaf.ui.FlatUIUtils;
+import com.formdev.flatlaf.util.ColorFunctions;
 import com.formdev.flatlaf.util.HSLColor;
 import com.formdev.flatlaf.util.HiDPIUtils;
 import com.formdev.flatlaf.util.UIScale;
@@ -59,8 +64,12 @@ public class FlatSmoothScrollingTest
 	FlatSmoothScrollingTest() {
 		initComponents();
 
+		oneSecondWidthChanged();
 		updateChartDelayedChanged();
 
+		ToolTipManager.sharedInstance().setInitialDelay( 0 );
+		ToolTipManager.sharedInstance().setDismissDelay( Integer.MAX_VALUE );
+
 		// allow enabling/disabling smooth scrolling with Alt+S without moving focus to checkbox
 		registerKeyboardAction(
 			e -> {
@@ -107,8 +116,17 @@ public class FlatSmoothScrollingTest
 		customScrollPane.getVerticalScrollBar().getModel().addChangeListener( new ScrollBarChangeHandler( customScrollPane, true, "custom vert", Color.pink ) );
 		customScrollPane.getHorizontalScrollBar().getModel().addChangeListener( new ScrollBarChangeHandler( customScrollPane, false, "custom horz", Color.pink.darker() ) );
 
+		// clear chart on startup
+		addHierarchyListener( e -> {
+			if( (e.getChangeFlags() & HierarchyEvent.SHOWING_CHANGED) != 0 && isShowing() )
+				EventQueue.invokeLater( this::clearChart );
+		});
+
 		ArrayList<String> items = new ArrayList<>();
 		for( char ch = '0'; ch < 'z'; ch++ ) {
+			if( (ch > '9' && ch < 'A') || (ch > 'Z' && ch < 'a') )
+				continue;
+
 			char[] chars = new char[ch - '0' + 1];
 			Arrays.fill( chars, ch );
 			items.add( new String( chars ) );
@@ -167,20 +185,47 @@ public class FlatSmoothScrollingTest
 		}
 
 		// text components
-		String text = items.stream().collect( Collectors.joining( "\n" ) );
-		textArea.setText( text );
+		String longText = items.stream().collect( Collectors.joining( " " ) ) + ' '
+			+ items.stream().limit( 20 ).collect( Collectors.joining( " " ) );
+		String text = items.stream().collect( Collectors.joining( "\n" ) ) + '\n';
+		textArea.setText( longText + '\n' + text );
 		textPane.setText( text );
 		editorPane.setText( text );
 
 		textArea.select( 0, 0 );
 		textPane.select( 0, 0 );
 		editorPane.select( 0, 0 );
+
+		EventQueue.invokeLater( () -> {
+			EventQueue.invokeLater( () -> {
+				list.requestFocusInWindow();
+			} );
+		} );
 	}
 
 	private void smoothScrollingChanged() {
 		UIManager.put( "ScrollPane.smoothScrolling", smoothScrollingCheckBox.isSelected() );
 	}
 
+	private void oneSecondWidthChanged() {
+		int oneSecondWidth = oneSecondWidthSlider.getValue();
+		int msPerLineX =
+			oneSecondWidth <= 2000 ? 100 :
+			oneSecondWidth <= 4000 ? 50 :
+			oneSecondWidth <= 8000 ? 25 :
+			10;
+
+		lineChartPanel.setOneSecondWidth( oneSecondWidth );
+		lineChartPanel.setMsPerLineX( msPerLineX );
+		lineChartPanel.revalidate();
+		lineChartPanel.repaint();
+
+		if( xLabelText == null )
+			xLabelText = xLabel.getText();
+		xLabel.setText( MessageFormat.format( xLabelText, msPerLineX ) );
+	}
+	private String xLabelText;
+
 	private void clearChart() {
 		lineChartPanel.clear();
 	}
@@ -243,7 +288,13 @@ public class FlatSmoothScrollingTest
 		panel3 = new JPanel();
 		chartScrollPane = new JScrollPane();
 		lineChartPanel = new FlatSmoothScrollingTest.LineChartPanel();
-		label1 = new JLabel();
+		panel4 = new JPanel();
+		xLabel = new JLabel();
+		JLabel rectsLabel = new JLabel();
+		JLabel yLabel = new JLabel();
+		JLabel dotsLabel = new JLabel();
+		JLabel oneSecondWidthLabel = new JLabel();
+		oneSecondWidthSlider = new JSlider();
 		updateChartDelayedCheckBox = new JCheckBox();
 		clearChartButton = new JButton();
 
@@ -407,7 +458,7 @@ public class FlatSmoothScrollingTest
 					// columns
 					"[grow,fill]",
 					// rows
-					"[300,grow,fill]"));
+					"[100:300,grow,fill]"));
 
 				//======== chartScrollPane ========
 				{
@@ -420,13 +471,50 @@ public class FlatSmoothScrollingTest
 		}
 		add(splitPane1, "cell 0 1");
 
-		//---- label1 ----
-		label1.setText("X: time (200ms per line) / Y: scroll bar value (10% per line)");
-		add(label1, "cell 0 2");
+		//======== panel4 ========
+		{
+			panel4.setLayout(new MigLayout(
+				"insets 0,hidemode 3,gapy 0",
+				// columns
+				"[fill]para" +
+				"[fill]",
+				// rows
+				"[]" +
+				"[]"));
+
+			//---- xLabel ----
+			xLabel.setText("X: time ({0}ms per line)");
+			panel4.add(xLabel, "cell 0 0");
+
+			//---- rectsLabel ----
+			rectsLabel.setText("Rectangles: scrollbar values (mouse hover shows stack)");
+			panel4.add(rectsLabel, "cell 1 0");
+
+			//---- yLabel ----
+			yLabel.setText("Y: scroll bar value (10% per line)");
+			panel4.add(yLabel, "cell 0 1");
+
+			//---- dotsLabel ----
+			dotsLabel.setText("Dots: disabled blitting mode in JViewport");
+			panel4.add(dotsLabel, "cell 1 1");
+		}
+		add(panel4, "cell 0 2");
+
+		//---- oneSecondWidthLabel ----
+		oneSecondWidthLabel.setText("Scale X:");
+		oneSecondWidthLabel.setDisplayedMnemonic('A');
+		oneSecondWidthLabel.setLabelFor(oneSecondWidthSlider);
+		add(oneSecondWidthLabel, "cell 0 2,alignx right,growx 0");
+
+		//---- oneSecondWidthSlider ----
+		oneSecondWidthSlider.setMinimum(1000);
+		oneSecondWidthSlider.setMaximum(10000);
+		oneSecondWidthSlider.addChangeListener(e -> oneSecondWidthChanged());
+		add(oneSecondWidthSlider, "cell 0 2,alignx right,growx 0,wmax 100");
 
 		//---- updateChartDelayedCheckBox ----
 		updateChartDelayedCheckBox.setText("Update chart delayed");
-		updateChartDelayedCheckBox.setMnemonic('U');
+		updateChartDelayedCheckBox.setMnemonic('P');
 		updateChartDelayedCheckBox.setSelected(true);
 		updateChartDelayedCheckBox.addActionListener(e -> updateChartDelayedChanged());
 		add(updateChartDelayedCheckBox, "cell 0 2,alignx right,growx 0");
@@ -471,7 +559,9 @@ public class FlatSmoothScrollingTest
 	private JPanel panel3;
 	private JScrollPane chartScrollPane;
 	private FlatSmoothScrollingTest.LineChartPanel lineChartPanel;
-	private JLabel label1;
+	private JPanel panel4;
+	private JLabel xLabel;
+	private JSlider oneSecondWidthSlider;
 	private JCheckBox updateChartDelayedCheckBox;
 	private JButton clearChartButton;
 	// JFormDesigner - End of variables declaration  //GEN-END:variables
@@ -490,7 +580,7 @@ public class FlatSmoothScrollingTest
 		ScrollBarChangeHandler( DebugScrollPane scrollPane, boolean vertical, String name, Color chartColor ) {
 			this.name = name;
 			this.chartColor = chartColor;
-			this.chartColor2 = chartColor.brighter();
+			this.chartColor2 = ColorFunctions.lighten( chartColor, 0.1f );
 
 			// add change listener to viewport that is invoked from JViewport.setViewPosition()
 			scrollPane.getViewport().addChangeListener( e -> {
@@ -498,8 +588,15 @@ public class FlatSmoothScrollingTest
 				if( vertical == scrollPane.lastScrollingWasVertical &&
 					scrollPane.getViewport().getScrollMode() != JViewport.BLIT_SCROLL_MODE )
 				{
-					JScrollBar sb = vertical ? scrollPane.getVerticalScrollBar() : scrollPane.getHorizontalScrollBar();
-					lineChartPanel.addValue( getChartValue( sb.getModel() ), true, chartColor );
+					// calculate value from view position because scrollbar value is not yet up-to-date
+					JViewport viewport = scrollPane.getViewport();
+					Point viewPosition = viewport.getViewPosition();
+					Dimension viewSize = viewport.getViewSize();
+					double value = vertical
+						? ((double) viewPosition.y) / (viewSize.height - viewport.getHeight())
+						: ((double) viewPosition.x) / (viewSize.width - viewport.getWidth());
+
+					lineChartPanel.addValue( value, true, chartColor, name );
 				}
 			} );
 		}
@@ -509,7 +606,7 @@ public class FlatSmoothScrollingTest
 			DefaultBoundedRangeModel m = (DefaultBoundedRangeModel) e.getSource();
 			boolean smoothScrolling = smoothScrollingCheckBox.isSelected();
 
-			lineChartPanel.addValue( getChartValue( m ), smoothScrolling ? chartColor : chartColor2 );
+			lineChartPanel.addValue( getChartValue( m ), false, smoothScrolling ? chartColor : chartColor2, name );
 
 			long t = System.nanoTime() / 1000000;
 
@@ -561,6 +658,20 @@ public class FlatSmoothScrollingTest
 
 					super.setViewPosition( p );
 				}
+
+				@Override
+				public void paint( Graphics g ) {
+					super.paint( g );
+
+					if( backingStoreImage != null ) {
+						System.out.println( "---------------------------------------------" );
+						System.out.println( "WARNING: backingStoreImage was used for painting" );
+						System.out.println( "View: " + getView() );
+						System.out.println( "Clip: " + g.getClipBounds() );
+						new Exception().printStackTrace( System.out );
+						System.out.println( "---------------------------------------------" );
+					}
+				}
 			};
 		}
 	}
@@ -572,25 +683,31 @@ public class FlatSmoothScrollingTest
 		implements Scrollable
 	{
 		private static final int NEW_SEQUENCE_TIME_LAG = 500;
-		private static final int NEW_SEQUENCE_GAP = 50;
+		private static final int NEW_SEQUENCE_GAP = 100;
+		private static final int HIT_OFFSET = 4;
 
-		private int secondWidth = 1000;
+		private int oneSecondWidth = 1000;
+		private int msPerLineX = 200;
 
 		private static class Data {
 			final double value;
 			final boolean dot;
 			final long time; // in milliseconds
+			final String name;
+			final Exception stack;
 
-			Data( double value, boolean dot, long time ) {
+			Data( double value, boolean dot, long time, String name, Exception stack ) {
 				this.value = value;
 				this.dot = dot;
 				this.time = time;
+				this.name = name;
+				this.stack = stack;
 			}
 
 			@Override
 			public String toString() {
 				// for debugging
-				return String.valueOf( value );
+				return "value=" + value + ", dot=" + dot + ", time=" + time + ", name=" + name;
 			}
 		}
 
@@ -599,20 +716,23 @@ public class FlatSmoothScrollingTest
 		private Color lastUsedChartColor;
 		private boolean updateDelayed;
 
+		private final List<Point> lastPoints = new ArrayList<>();
+		private final List<Data> lastDatas = new ArrayList<>();
+		private double lastSystemScaleFactor = 1;
+		private String lastToolTipPrinted;
+
 		LineChartPanel() {
 			int resolution = FlatUIUtils.getUIInt( "ScrollPane.smoothScrolling.resolution", 10 );
 
 			repaintTime = new Timer( resolution * 2, e -> repaintAndRevalidate() );
 			repaintTime.setRepeats( false );
+
+			ToolTipManager.sharedInstance().registerComponent( this );
 		}
 
-		void addValue( double value, Color chartColor ) {
-			addValue( value, false, chartColor );
-		}
-
-		void addValue( double value, boolean dot, Color chartColor ) {
+		void addValue( double value, boolean dot, Color chartColor, String name ) {
 			List<Data> chartData = color2dataMap.computeIfAbsent( chartColor, k -> new ArrayList<>() );
-			chartData.add( new Data( value, dot, System.nanoTime() / 1000000) );
+			chartData.add( new Data( value, dot, System.nanoTime() / 1000000, name, new Exception() ) );
 
 			lastUsedChartColor = chartColor;
 
@@ -635,8 +755,12 @@ public class FlatSmoothScrollingTest
 			this.updateDelayed = updateDelayed;
 		}
 
-		void setSecondWidth( int secondWidth ) {
-			this.secondWidth = secondWidth;
+		void setOneSecondWidth( int oneSecondWidth ) {
+			this.oneSecondWidth = oneSecondWidth;
+		}
+
+		void setMsPerLineX( int msPerLineX ) {
+			this.msPerLineX = msPerLineX;
 		}
 
 		private void repaintAndRevalidate() {
@@ -670,8 +794,9 @@ public class FlatSmoothScrollingTest
 		private void paintImpl( Graphics2D g, int x, int y, int width, int height, double scaleFactor ) {
 			FlatUIUtils.setRenderingHints( g );
 
-			int secondWidth = (int) (this.secondWidth * scaleFactor);
+			int oneSecondWidth = (int) (this.oneSecondWidth * scaleFactor);
 			int seqGapWidth = (int) (NEW_SEQUENCE_GAP * scaleFactor);
+			int hitOffset = (int) Math.round( UIScale.scale( HIT_OFFSET ) * scaleFactor );
 
 			Color lineColor = FlatUIUtils.getUIColor( "Component.borderColor", Color.lightGray );
 			Color lineColor2 = FlatLaf.isLafDark()
@@ -692,51 +817,51 @@ public class FlatSmoothScrollingTest
 			}
 
 			// paint vertical lines
-			int twoHundredMillisWidth = secondWidth / 5;
-			for( int i = twoHundredMillisWidth; i < width; i += twoHundredMillisWidth ) {
-				g.setColor( (i % secondWidth != 0) ? lineColor : lineColor2 );
-				g.drawLine( i, 0, i, height );
+			int perLineXWidth = Math.round( (oneSecondWidth / 1000f) * msPerLineX );
+			for( int i = 1, xv = perLineXWidth; xv < width; xv += perLineXWidth, i++ ) {
+				g.setColor( (i % 5 != 0) ? lineColor : lineColor2 );
+				g.drawLine( xv, 0, xv, height );
 			}
 
+			lastPoints.clear();
+			lastDatas.clear();
+			lastSystemScaleFactor = scaleFactor;
+
 			// paint lines
 			for( Map.Entry<Color, List<Data>> e : color2dataMap.entrySet() ) {
 				List<Data> chartData = e.getValue();
 				Color chartColor = e.getKey();
 				if( FlatLaf.isLafDark() )
 					chartColor = new HSLColor( chartColor ).adjustTone( 50 );
-				Color temporaryValueColor = new Color( (chartColor.getRGB() & 0xffffff) | 0x40000000, true );
+				Color temporaryValueColor = ColorFunctions.fade( chartColor, FlatLaf.isLafDark() ? 0.7f : 0.3f );
+				Color dataPointColor = ColorFunctions.fade( chartColor, FlatLaf.isLafDark() ? 0.6f : 0.2f );
 
+				// sequence start time and x coordinate
 				long seqTime = 0;
 				int seqX = 0;
+
+				// "previous" data point time, x/y coordinates and count
 				long ptime = 0;
 				int px = 0;
 				int py = 0;
 				int pcount = 0;
-				int s1 = UIScale.scale( 1 );
-				int s3 = UIScale.scale( 3 );
-
-				g.setColor( chartColor );
 
 				boolean first = true;
+				boolean isTemporaryValue = false;
+				int lastTemporaryValueIndex = -1;
+
 				int size = chartData.size();
 				for( int i = 0; i < size; i++ ) {
 					Data data = chartData.get( i );
-					int dy = (int) ((height - 1) * data.value);
 
-					if( data.dot ) {
-						int dotx = px;
-						if( i > 0 && data.time > ptime + NEW_SEQUENCE_TIME_LAG )
-							dotx += seqGapWidth;
-						g.fillRect( dotx - s1, dy - s1, s3, s3 );
-						continue;
-					}
+					boolean newSeq = (data.time > ptime + NEW_SEQUENCE_TIME_LAG);
+					ptime = data.time;
 
-					if( data.time > ptime + NEW_SEQUENCE_TIME_LAG ) {
+					if( newSeq ) {
+						// paint short horizontal line for previous sequence that has only one data point
 						if( !first && pcount == 0 ) {
-							g.drawLine( px, py, px + (int) (4 * scaleFactor), py );
-
-							// small vertical line to indicate data point
-							g.drawLine( px, py - s1, px, py + s1 );
+							g.setColor( chartColor );
+							g.drawLine( px, py, px + (int) Math.round( UIScale.scale( 8 ) * scaleFactor ), py );
 						}
 
 						// start new sequence
@@ -745,54 +870,69 @@ public class FlatSmoothScrollingTest
 						px = seqX;
 						pcount = 0;
 						first = false;
-					} else {
-						boolean isTemporaryValue = isTemporaryValue( chartData, i ) || isTemporaryValue( chartData, i - 1 );
-						if( isTemporaryValue )
-							g.setColor( temporaryValueColor );
+						isTemporaryValue = false;
+					}
+
+					// x/y coordinates of current data point
+					int dy = (int) ((height - 1) * data.value);
+					int dx = (int) (seqX + (((data.time - seqTime) / 1000.) * oneSecondWidth));
+
+					// paint rectangle to indicate data point
+					g.setColor( dataPointColor );
+					g.drawRect( dx - hitOffset, dy - hitOffset, hitOffset * 2, hitOffset * 2 );
+
+					// remember data point for tooltip
+					lastPoints.add( new Point( dx, dy ) );
+					lastDatas.add( data );
+
+					if( data.dot ) {
+						int s1 = (int) Math.round( UIScale.scale( 1 ) * scaleFactor );
+						int s3 = (int) Math.round( UIScale.scale( 3 ) * scaleFactor );
+						g.setColor( chartColor );
+						g.fillRect( dx - s1, dy - s1, s3, s3 );
+						continue;
+					}
+
+					if( !newSeq ) {
+						if( isTemporaryValue && i > lastTemporaryValueIndex )
+							isTemporaryValue = false;
+
+						g.setColor( isTemporaryValue ? temporaryValueColor : chartColor );
 
 						// line in sequence
-						int dx = (int) (seqX + (((data.time - seqTime) / 1000.) * secondWidth));
 						g.drawLine( px, py, dx, dy );
 
-						if( isTemporaryValue )
-							g.setColor( chartColor );
-
-						// small vertical lines to indicate data point
-						g.drawLine( px, py - s1, px, py + s1 );
-						g.drawLine( dx, dy - s1, dx, dy + s1 );
-
 						px = dx;
 						pcount++;
+
+						// check next data points for "temporary" value(s)
+						if( !isTemporaryValue ) {
+							// one or two values between two equal values are considered "temporary",
+							// which means that they are the target value for the following scroll animation
+							int stage = 0;
+							for( int j = i + 1; j < size && stage <= 2 && !isTemporaryValue; j++ ) {
+								Data nextData = chartData.get( j );
+								if( nextData.dot )
+									continue; // ignore dots
+
+								// check whether next data point is within 10 milliseconds
+								if( nextData.time > data.time + 10 )
+									break;
+
+								if( stage >= 1 && stage <= 2 && nextData.value == data.value ) {
+									isTemporaryValue = true;
+									lastTemporaryValueIndex = j;
+								}
+								stage++;
+							}
+						}
 					}
 
 					py = dy;
-					ptime = data.time;
 				}
 			}
 		}
 
-		/**
-		 * One or two values between two equal values are considered "temporary",
-		 * which means that they are the target value for the following scroll animation.
-		 */
-		private boolean isTemporaryValue( List<Data> chartData, int i ) {
-			if( i == 0 || i == chartData.size() - 1 )
-				return false;
-
-			Data dataBefore = chartData.get( i - 1 );
-			Data dataAfter = chartData.get( i + 1 );
-
-			if( dataBefore.dot || dataAfter.dot )
-				return false;
-
-			double valueBefore = dataBefore.value;
-			double valueAfter = dataAfter.value;
-
-			return valueBefore == valueAfter ||
-				(i < chartData.size() - 2 && valueBefore == chartData.get( i + 2 ).value) ||
-				(i > 1 && chartData.get( i - 2 ).value == valueAfter);
-		}
-
 		private int chartWidth() {
 			int width = 0;
 			for( List<Data> chartData : color2dataMap.values() )
@@ -817,7 +957,7 @@ public class FlatSmoothScrollingTest
 					px = seqX;
 				} else {
 					// line in sequence
-					int dx = (int) (seqX + (((data.time - seqTime) / 1000.) * secondWidth));
+					int dx = (int) (seqX + (((data.time - seqTime) / 1000.) * oneSecondWidth));
 					px = dx;
 				}
 
@@ -842,7 +982,7 @@ public class FlatSmoothScrollingTest
 
 		@Override
 		public int getScrollableUnitIncrement( Rectangle visibleRect, int orientation, int direction ) {
-			return secondWidth;
+			return oneSecondWidth;
 		}
 
 		@Override
@@ -861,6 +1001,98 @@ public class FlatSmoothScrollingTest
 		public boolean getScrollableTracksViewportHeight() {
 			return true;
 		}
+
+		@Override
+		public String getToolTipText( MouseEvent e ) {
+			int x = (int) Math.round( e.getX() * lastSystemScaleFactor );
+			int y = (int) Math.round( e.getY() * lastSystemScaleFactor );
+			int hitOffset = (int) Math.round( UIScale.scale( HIT_OFFSET ) * lastSystemScaleFactor );
+			StringBuilder buf = null;
+
+			int pointsCount = lastPoints.size();
+			for( int i = 0; i < pointsCount; i++ ) {
+				Point pt = lastPoints.get( i );
+
+				// check X/Y coordinates
+				if( x < pt.x - hitOffset || x > pt.x + hitOffset ||
+					y < pt.y - hitOffset || y > pt.y + hitOffset )
+				  continue;
+
+				if( buf == null ) {
+					buf = new StringBuilder( 5000 );
+					buf.append( "<html>" );
+				}
+
+				Data data = lastDatas.get( i );
+				buf.append( "<h2>" );
+				if( data.dot )
+					buf.append( "DOT: " );
+				buf.append( data.name ).append( ' ' ).append( data.value ).append( "</h2>" );
+
+				StackTraceElement[] stackTrace = data.stack.getStackTrace();
+				for( int j = 0; j < stackTrace.length; j++ ) {
+					StackTraceElement stackElement = stackTrace[j];
+					String className = stackElement.getClassName();
+					String methodName = stackElement.getMethodName();
+
+					// ignore methods from this class
+					if( className.startsWith( FlatSmoothScrollingTest.class.getName() ) )
+						continue;
+
+					int repeatCount = 0;
+					for( int k = j + 1; k < stackTrace.length; k++ ) {
+						if( !stackElement.equals( stackTrace[k] ) )
+							break;
+						repeatCount++;
+					}
+					j += repeatCount;
+
+					// append method
+					buf.append( className )
+						.append( ".<b>" )
+						.append( methodName )
+						.append( "</b> <span color=\"#888888\">" );
+					if( stackElement.getFileName() != null ) {
+						buf.append( '(' );
+						buf.append( stackElement.getFileName() );
+						if( stackElement.getLineNumber() >= 0 )
+							buf.append( ':' ).append( stackElement.getLineNumber() );
+						buf.append( ')' );
+					} else
+						buf.append( "(Unknown Source)" );
+					buf.append( "</span>" );
+					if( repeatCount > 0 )
+						buf.append( " <b>" ).append( repeatCount + 1 ).append( "x</b>" );
+					buf.append( "<br>" );
+
+					// break at some methods to make stack smaller
+					if( (className.startsWith( "java.awt.event.InvocationEvent" ) && methodName.equals( "dispatch" )) ||
+						(className.startsWith( "java.awt.Component" ) && methodName.equals( "processMouseWheelEvent" )) ||
+						(className.startsWith( "javax.swing.JComponent" ) && methodName.equals( "processKeyBinding" )) )
+					  break;
+				}
+				buf.append( "..." );
+			}
+
+			if( buf == null )
+				return null;
+
+			buf.append( "<html>" );
+			String toolTip = buf.toString();
+
+			// print to console
+			if( !Objects.equals( toolTip, lastToolTipPrinted ) ) {
+				lastToolTipPrinted = toolTip;
+
+				System.out.println( toolTip
+					.replace( "<br>", "\n" )
+					.replace( "<h2>", "\n---- " )
+					.replace( "</h2>", " ----\n" )
+					.replaceAll( "<[^>]+>", "" ) );
+			}
+
+			return buf.toString();
+		}
 	}
 
 	//---- class ColorIcon ----------------------------------------------------
@@ -892,6 +1124,5 @@ public class FlatSmoothScrollingTest
 		public int getIconHeight() {
 			return UIScale.scale( 12 );
 		}
-
 	}
 }

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

@@ -178,7 +178,7 @@ new FormModel {
 				add( new FormContainer( "javax.swing.JPanel", new FormLayoutManager( class net.miginfocom.swing.MigLayout ) {
 					"$layoutConstraints": "insets 3,hidemode 3"
 					"$columnConstraints": "[grow,fill]"
-					"$rowConstraints": "[300,grow,fill]"
+					"$rowConstraints": "[100:300,grow,fill]"
 				} ) {
 					name: "panel3"
 					add( new FormContainer( "javax.swing.JScrollPane", new FormLayoutManager( class javax.swing.JScrollPane ) ) {
@@ -196,16 +196,71 @@ new FormModel {
 			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
 				"value": "cell 0 1"
 			} )
-			add( new FormComponent( "javax.swing.JLabel" ) {
-				name: "label1"
-				"text": "X: time (200ms per line) / Y: scroll bar value (10% per line)"
+			add( new FormContainer( "javax.swing.JPanel", new FormLayoutManager( class net.miginfocom.swing.MigLayout ) {
+				"$layoutConstraints": "insets 0,hidemode 3,gapy 0"
+				"$columnConstraints": "[fill]para[fill]"
+				"$rowConstraints": "[][]"
+			} ) {
+				name: "panel4"
+				add( new FormComponent( "javax.swing.JLabel" ) {
+					name: "xLabel"
+					"text": "X: time ({0}ms per line)"
+				}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+					"value": "cell 0 0"
+				} )
+				add( new FormComponent( "javax.swing.JLabel" ) {
+					name: "rectsLabel"
+					"text": "Rectangles: scrollbar values (mouse hover shows stack)"
+					auxiliary() {
+						"JavaCodeGenerator.variableLocal": true
+					}
+				}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+					"value": "cell 1 0"
+				} )
+				add( new FormComponent( "javax.swing.JLabel" ) {
+					name: "yLabel"
+					"text": "Y: scroll bar value (10% per line)"
+					auxiliary() {
+						"JavaCodeGenerator.variableLocal": true
+					}
+				}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+					"value": "cell 0 1"
+				} )
+				add( new FormComponent( "javax.swing.JLabel" ) {
+					name: "dotsLabel"
+					"text": "Dots: disabled blitting mode in JViewport"
+					auxiliary() {
+						"JavaCodeGenerator.variableLocal": true
+					}
+				}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+					"value": "cell 1 1"
+				} )
 			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
 				"value": "cell 0 2"
 			} )
+			add( new FormComponent( "javax.swing.JLabel" ) {
+				name: "oneSecondWidthLabel"
+				"text": "Scale X:"
+				"displayedMnemonic": 65
+				"labelFor": new FormReference( "oneSecondWidthSlider" )
+				auxiliary() {
+					"JavaCodeGenerator.variableLocal": true
+				}
+			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+				"value": "cell 0 2,alignx right,growx 0"
+			} )
+			add( new FormComponent( "javax.swing.JSlider" ) {
+				name: "oneSecondWidthSlider"
+				"minimum": 1000
+				"maximum": 10000
+				addEvent( new FormEvent( "javax.swing.event.ChangeListener", "stateChanged", "oneSecondWidthChanged", false ) )
+			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+				"value": "cell 0 2,alignx right,growx 0,wmax 100"
+			} )
 			add( new FormComponent( "javax.swing.JCheckBox" ) {
 				name: "updateChartDelayedCheckBox"
 				"text": "Update chart delayed"
-				"mnemonic": 85
+				"mnemonic": 80
 				"selected": true
 				addEvent( new FormEvent( "java.awt.event.ActionListener", "actionPerformed", "updateChartDelayedChanged", false ) )
 			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {