Demo: add info label shows the current system/user scale factor and the java version

flatlaf-core/src/main/java/com/formdev/flatlaf/util/UIScale.java

@@ -19,6 +19,7 @@ package com.formdev.flatlaf.util;
 import java.awt.Dimension;
 import java.awt.Font;
 import java.awt.Graphics2D;
+import java.awt.GraphicsConfiguration;
 import java.awt.GraphicsEnvironment;
 import java.awt.Insets;
 import java.beans.PropertyChangeEvent;
@@ -42,6 +43,7 @@ import javax.swing.plaf.UIResource;
  * So the JRE does the scaling itself.
  * E.g. when you draw a 10px line, a 15px line is drawn on screen.
  * The scale factor may be different for each connected display.
+ * The scale factor may change for a window when moving the window from one display to another one.
  *
  * 2) user scaling mode
  *
@@ -51,6 +53,7 @@ import javax.swing.plaf.UIResource;
  * The JRE does not scale anything.
  * So we have to invoke {@link #scale(float)} where necessary.
  * There is only one user scale factor for all displays.
+ * The user scale factor may change if the active LaF or "Label.font" has changed.
  *
  * @author Karl Tauber
  */
@@ -89,6 +92,14 @@ public class UIScale
 		return jreHiDPI;
 	}
 
+	public static double getSystemScaleFactor( Graphics2D g ) {
+		return isJreHiDPIEnabled() ? g.getDeviceConfiguration().getDefaultTransform().getScaleX() : 1;
+	}
+
+	public static double getSystemScaleFactor( GraphicsConfiguration gc ) {
+		return isJreHiDPIEnabled() ? gc.getDefaultTransform().getScaleX() : 1;
+	}
+
 	//---- user scaling (Java 8) ----------------------------------------------
 
 	private static float scaleFactor = 1;

flatlaf-demo/src/main/java/com/formdev/flatlaf/demo/ControlBar.java

@@ -25,6 +25,7 @@ import javax.swing.plaf.metal.MetalLookAndFeel;
 import javax.swing.plaf.nimbus.NimbusLookAndFeel;
 import com.formdev.flatlaf.*;
 import com.formdev.flatlaf.util.SystemInfo;
+import com.formdev.flatlaf.util.UIScale;
 import net.miginfocom.swing.*;
 
 /**
@@ -102,11 +103,26 @@ class ControlBar
 		frame.addWindowListener( new WindowAdapter() {
 			@Override
 			public void windowOpened( WindowEvent e ) {
+				updateInfoLabel();
 				closeButton.requestFocusInWindow();
 			}
+			@Override
+			public void windowActivated( WindowEvent e ) {
+				updateInfoLabel();
+			}
 		} );
 	}
 
+	private void updateInfoLabel() {
+		double systemScaleFactor = UIScale.getSystemScaleFactor( getGraphicsConfiguration() );
+		float userScaleFactor = UIScale.getUserScaleFactor();
+		infoLabel.setText( "(Java " + System.getProperty( "java.version" )
+			+ (systemScaleFactor != 1 ? (";  system scale factor " + systemScaleFactor) : "")
+			+ (userScaleFactor != 1 ? (";  user scale factor " + userScaleFactor) : "")
+			+ (systemScaleFactor == 1 && userScaleFactor == 1 ? "; no scaling" : "")
+			+ ")" );
+	}
+
 	private void registerSwitchToLookAndFeel( int keyCode, String lafClassName ) {
 		((JComponent)frame.getContentPane()).registerKeyboardAction(
 			e -> {
@@ -138,6 +154,9 @@ class ControlBar
 				// change look and feel
 				UIManager.setLookAndFeel( newLaf.className );
 
+				// update info label because user scale factor may change
+				updateInfoLabel();
+
 				// update all components
 				SwingUtilities.updateComponentTreeUI( frame );
 
@@ -209,6 +228,7 @@ class ControlBar
 		lookAndFeelComboBox = new JComboBox<>();
 		rightToLeftCheckBox = new JCheckBox();
 		enabledCheckBox = new JCheckBox();
+		infoLabel = new JLabel();
 		closeButton = new JButton();
 
 		//======== this ========
@@ -242,6 +262,10 @@ class ControlBar
 		enabledCheckBox.addActionListener(e -> enabledChanged());
 		add(enabledCheckBox, "cell 2 1");
 
+		//---- infoLabel ----
+		infoLabel.setText("text");
+		add(infoLabel, "cell 3 1,alignx center,growx 0");
+
 		//---- closeButton ----
 		closeButton.setText("Close");
 		closeButton.addActionListener(e -> closePerformed());
@@ -254,6 +278,7 @@ class ControlBar
 	private JComboBox<LafInfo> lookAndFeelComboBox;
 	private JCheckBox rightToLeftCheckBox;
 	private JCheckBox enabledCheckBox;
+	private JLabel infoLabel;
 	private JButton closeButton;
 	// JFormDesigner - End of variables declaration  //GEN-END:variables
 

flatlaf-demo/src/main/java/com/formdev/flatlaf/demo/ControlBar.jfd

@@ -41,6 +41,12 @@ new FormModel {
 			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
 				"value": "cell 2 1"
 			} )
+			add( new FormComponent( "javax.swing.JLabel" ) {
+				name: "infoLabel"
+				"text": "text"
+			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+				"value": "cell 3 1,alignx center,growx 0"
+			} )
 			add( new FormComponent( "javax.swing.JButton" ) {
 				name: "closeButton"
 				"text": "Close"

flatlaf-demo/src/main/java/com/formdev/flatlaf/demo/FlatLafDemo.java

@@ -55,7 +55,6 @@ public class FlatLafDemo
 
 		// create frame
 		DemoFrame frame = new DemoFrame();
-		frame.setTitle( frame.getTitle() + " (Java " + System.getProperty( "java.version" ) + ")" );
 
 		// show frame
 		frame.pack();