Merge PR #1051: Zooming API

2025-12-06 05:50:53 +03:00 · 2025-11-25 12:30:09 +01:00
parent c8e2e78955 0fb4c811f6
commit 02636b260a
7 changed files with 793 additions and 39 deletions
--- a/flatlaf-core/src/main/java/com/formdev/flatlaf/FlatLaf.java
+++ b/flatlaf-core/src/main/java/com/formdev/flatlaf/FlatLaf.java
@@ -368,6 +368,22 @@ public abstract class FlatLaf
 					String.format( "a, address { color: #%06x; }", linkColor.getRGB() & 0xffffff ) );
 			}
 		};
+
+		// Initialize UIScale user scale factor immediately after FlatLaf was activated,
+		// which is necessary to ensure that UIScale.setZoomFactor(float)
+		// scales FlatLaf defaultDont correctly even if UIScale.scale() was not yet used.
+		// In other words: Without this, UIScale.setZoomFactor(float) would
+		// not work correctly if invoked between FlatLaf.setup() and crating UI.
+		PropertyChangeListener listener = new PropertyChangeListener() {
+			@Override
+			public void propertyChange( PropertyChangeEvent e ) {
+				if( "lookAndFeel".equals( e.getPropertyName() ) ) {
+					UIManager.removePropertyChangeListener( this );
+					UIScale.getUserScaleFactor();
+				}
+			}
+		};
+		UIManager.addPropertyChangeListener( listener );
 	}

 	@Override
@@ -707,11 +723,22 @@ public abstract class FlatLaf
 			uiFont = ((ActiveFont)defaultFont).derive( baseFont, fontSize -> {
 				return Math.round( fontSize * UIScale.computeFontScaleFactor( baseFont ) );
 			} );
-		}
+		} else if( defaultFont instanceof LazyValue )
+			uiFont = ActiveFont.toUIResource( (Font) ((LazyValue)defaultFont).createValue( defaults ) );

 		// increase font size if system property "flatlaf.uiScale" is set
 		uiFont = UIScale.applyCustomScaleFactor( uiFont );

+		// apply zoom factor to font size
+		float zoomFactor = UIScale.getZoomFactor();
+		if( zoomFactor != 1 ) {
+			// see also UIScale.setZoomFactor()
+			int unzoomedFontSize = uiFont.getSize();
+			defaults.put( "defaultFont.unzoomedSize", unzoomedFontSize );
+			int newFontSize = Math.max( Math.round( unzoomedFontSize * zoomFactor ), 1 );
+			uiFont = new FontUIResource( uiFont.deriveFont( (float) newFontSize ) );
+		}
+
 		// set default font
 		defaults.put( "defaultFont", uiFont );
 	}
@@ -1768,7 +1795,7 @@ public abstract class FlatLaf
 				return toUIResource( baseFont );
 		}

-		private FontUIResource toUIResource( Font font ) {
+		private static FontUIResource toUIResource( Font font ) {
 			// make sure that font is a UIResource for LaF switching
 			return (font instanceof FontUIResource)
 				? (FontUIResource) font
--- a/flatlaf-core/src/main/java/com/formdev/flatlaf/util/UIScale.java
+++ b/flatlaf-core/src/main/java/com/formdev/flatlaf/util/UIScale.java
@@ -27,7 +27,9 @@ import java.beans.PropertyChangeEvent;
 import java.beans.PropertyChangeListener;
 import java.beans.PropertyChangeSupport;
 import java.lang.reflect.Method;
+import java.util.Arrays;
 import javax.swing.LookAndFeel;
+import javax.swing.UIDefaults;
 import javax.swing.UIManager;
 import javax.swing.plaf.DimensionUIResource;
 import javax.swing.plaf.FontUIResource;
@@ -61,16 +63,28 @@ import com.formdev.flatlaf.FlatSystemProperties;
 * or if the default font is changed.
 * The user scale factor is computed based on the used font.
 * The JRE does not scale anything.
- * So we have to invoke {@link #scale(float)} where necessary.
+ * So we have to invoke {@link #scale(int)} where necessary.
 * There is only one user scale factor for all displays.
 * The user scale factor may change if the active LaF, "defaultFont" or "Label.font" has changed.
 * If system scaling mode is available the user scale factor is usually 1,
 * but may be larger on Linux or if the default font is changed.
 *
+ * <h2>Zooming</h2>
+ *
+ * Zooming allows appliations to easily zoom their UI, if FlatLaf is active Laf.
+ * This is done by changing user scale factor and default font.
+ * There are methods to increase, decrease and reset zoom factor.
+ * <p>
+ * Note: Only standard Swing components are zoomed.
+ *       Custom components need to use {@link #scale(int)} to zoom their UI.
+ *
 * @author Karl Tauber
 */
 public class UIScale
 {
+	/** @since 3.7 */ public static final String PROP_USER_SCALE_FACTOR = "userScaleFactor";
+	/** @since 3.7 */ public static final String PROP_ZOOM_FACTOR = "zoomFactor";
+
 	private static final boolean DEBUG = false;

 	private static PropertyChangeSupport changeSupport;
@@ -87,7 +101,7 @@ public class UIScale
 		changeSupport.removePropertyChangeListener( listener );
 	}

-	//---- system scaling (Java 9) --------------------------------------------
+	//---- system scaling (Java 9+) -------------------------------------------

 	private static Boolean jreHiDPI;

@@ -135,10 +149,13 @@ public class UIScale
 		return (isSystemScalingEnabled() && gc != null) ? gc.getDefaultTransform().getScaleX() : 1;
 	}

-	//---- user scaling (Java 8) ----------------------------------------------
+	//---- user scaling (Java 8 / zooming) ------------------------------------

+	private static float unzoomedScaleFactor = 1;
 	private static float scaleFactor = 1;
 	private static boolean initialized;
+	private static boolean listenerInitialized; // use extra flag for unit tests
+	private static boolean ignoreFontChange;

 	private static void initialize() {
 		if( initialized )
@@ -148,33 +165,43 @@ public class UIScale
 		if( !isUserScalingEnabled() )
 			return;

+		initializeListener();
+
+		updateScaleFactor( true );
+	}
+
+	private static void initializeListener() {
+		if( listenerInitialized )
+			return;
+		listenerInitialized = true;
+
 		// listener to update scale factor if LaF changed, "defaultFont" or "Label.font" changed
 		PropertyChangeListener listener = new PropertyChangeListener() {
 			@Override
 			public void propertyChange( PropertyChangeEvent e ) {
 				switch( e.getPropertyName() ) {
 					case "lookAndFeel":
-						// it is not necessary (and possible) to remove listener of old LaF defaults
+						// it is not possible (and necessary) to remove listener of old LaF defaults
+						// because it is not possible to access the UIDefault object of the old LaF
 						if( e.getNewValue() instanceof LookAndFeel )
 							UIManager.getLookAndFeelDefaults().addPropertyChangeListener( this );
-						updateScaleFactor();
+						updateScaleFactor( true );
 						break;

 					case "defaultFont":
 					case "Label.font":
-						updateScaleFactor();
+						if( !ignoreFontChange )
+							updateScaleFactor( false );
 						break;
 				}
 			}
 		};
-		UIManager.addPropertyChangeListener( listener );
 		UIManager.getDefaults().addPropertyChangeListener( listener );
 		UIManager.getLookAndFeelDefaults().addPropertyChangeListener( listener );
-
-		updateScaleFactor();
+		UIManager.addPropertyChangeListener( listener );
 	}

-	private static void updateScaleFactor() {
+	private static void updateScaleFactor( boolean lafChanged ) {
 		if( !isUserScalingEnabled() )
 			return;

@@ -185,17 +212,20 @@ public class UIScale
 			return;
 		}

-		// use font size to calculate scale factor (instead of DPI)
-		// because even if we are on a HiDPI display it is not sure
-		// that a larger font size is set by the current LaF
-		// (e.g. can avoid large icons with small text)
+		// get font that is used to calculate scale factor
 		Font font = null;
 		if( UIManager.getLookAndFeel() instanceof FlatLaf )
 			font = UIManager.getFont( "defaultFont" );
 		if( font == null )
 			font = UIManager.getFont( "Label.font" );

-		setUserScaleFactor( computeFontScaleFactor( font ), true );
+		float fontScaleFactor = computeFontScaleFactor( font );
+		if( lafChanged && UIManager.getLookAndFeel() instanceof FlatLaf ) {
+			// FlatLaf has applied zoom factor in FlatLaf.initDefaultFont() to defaultFont,
+			// so we need to take it into account to get correct user scale factor
+			fontScaleFactor /= zoomFactor;
+		}
+		setUserScaleFactor( fontScaleFactor, true );
 	}

 	/**
@@ -204,7 +234,7 @@ public class UIScale
 	 * @since 2
 	 */
 	public static float computeFontScaleFactor( Font font ) {
-		if( SystemInfo.isWindows ) {
+		if( SystemInfo.isWindows && !inUnitTests ) {
 			// Special handling for Windows to be compatible with OS scaling,
 			// which distinguish between "screen scaling" and "text scaling".
 			//  - Windows "screen scaling" scales everything (text, icon, gaps, etc.)
@@ -335,7 +365,7 @@ public class UIScale
 	}

 	/**
-	 * Returns the user scale factor.
+	 * Returns the user scale factor (including zoom factor).
 	 */
 	public static float getUserScaleFactor() {
 		initialize();
@@ -345,27 +375,49 @@ public class UIScale
 	/**
 	 * Sets the user scale factor.
 	 */
-	private static void setUserScaleFactor( float scaleFactor, boolean normalize ) {
-		if( normalize ) {
-			if( scaleFactor < 1f ) {
-				scaleFactor = FlatSystemProperties.getBoolean( FlatSystemProperties.UI_SCALE_ALLOW_SCALE_DOWN, false )
-					? Math.round( scaleFactor * 10f ) / 10f // round small scale factor to 1/10
-					: 1f;
-			} else if( scaleFactor > 1f ) // round scale factor to 1/4
-				scaleFactor = Math.round( scaleFactor * 4f ) / 4f;
-		}
+	private static void setUserScaleFactor( float unzoomedScaleFactor, boolean normalize ) {
+		if( normalize )
+			unzoomedScaleFactor = normalizeScaleFactor( unzoomedScaleFactor );

 		// minimum scale factor
-		scaleFactor = Math.max( scaleFactor, 0.1f );
+		unzoomedScaleFactor = Math.max( unzoomedScaleFactor, 0.1f );
+
+		if( unzoomedScaleFactor == UIScale.unzoomedScaleFactor )
+			return;
+
+		if( DEBUG )
+			System.out.println( "Unzoomed scale factor " + UIScale.unzoomedScaleFactor + " --> " + unzoomedScaleFactor );
+
+		UIScale.unzoomedScaleFactor = unzoomedScaleFactor;
+		setScaleFactor( unzoomedScaleFactor * zoomFactor );
+	}
+
+	private static void setScaleFactor( float scaleFactor ) {
+		// round scale factor to 1/100
+		scaleFactor = Math.round( scaleFactor * 100f ) / 100f;
+
+		if( scaleFactor == UIScale.scaleFactor )
+			return;

 		float oldScaleFactor = UIScale.scaleFactor;
 		UIScale.scaleFactor = scaleFactor;

 		if( DEBUG )
-			System.out.println( "HiDPI scale factor " + scaleFactor );
+			System.out.println( "Scale factor          " + oldScaleFactor + " --> " + scaleFactor + "   (unzoomed " + UIScale.unzoomedScaleFactor + ")" );

 		if( changeSupport != null )
-			changeSupport.firePropertyChange( "userScaleFactor", oldScaleFactor, scaleFactor );
+			changeSupport.firePropertyChange( PROP_USER_SCALE_FACTOR, oldScaleFactor, scaleFactor );
+	}
+
+	private static float normalizeScaleFactor( float scaleFactor ) {
+		if( scaleFactor < 1f ) {
+			return FlatSystemProperties.getBoolean( FlatSystemProperties.UI_SCALE_ALLOW_SCALE_DOWN, false )
+				? Math.round( scaleFactor * 10f ) / 10f // round small scale factor to 1/10
+				: 1f;
+		} else if( scaleFactor > 1f ) // round scale factor to 1/4
+			return Math.round( scaleFactor * 4f ) / 4f;
+		else
+			return scaleFactor;
 	}

 	/**
@@ -451,4 +503,185 @@ public class UIScale
 				? new InsetsUIResource( scale( insets.top ), scale( insets.left ), scale( insets.bottom ), scale( insets.right ) )
 				: new Insets          ( scale( insets.top ), scale( insets.left ), scale( insets.bottom ), scale( insets.right ) ));
 	}
+
+	//---- zoom ---------------------------------------------------------------
+
+	private static float zoomFactor = 1;
+	private static float[] supportedZoomFactors = { 1f, 1.1f, 1.25f, 1.5f, 1.75f, 2f };
+
+	/**
+	 * Returns the current zoom factor. Default is {@code 1}.
+	 *
+	 * @since 3.7
+	 */
+	public static float getZoomFactor() {
+		return zoomFactor;
+	}
+
+	/**
+	 * Sets the zoom factor.
+	 * Also updates user scale factor and default font (if FlatLaf is active Laf).
+	 * <p>
+	 * UI needs to be updated if zoom factor has changed. E.g.:
+	 * <pre>{@code
+	 * if( UIScale.setZoomFactor( newZoomFactor ) )
+	 *     FlatLaf.updateUI();
+	 * }</pre>
+	 *
+	 * @param zoomFactor new zoom factor
+	 * @return {@code true} if zoom factor has changed
+	 * @since 3.7
+	 */
+	public static boolean setZoomFactor( float zoomFactor ) {
+		// minimum zoom factor
+		zoomFactor = Math.max( zoomFactor, 0.1f );
+
+		if( UIScale.zoomFactor == zoomFactor )
+			return false;
+
+		float oldZoomFactor = UIScale.zoomFactor;
+		UIScale.zoomFactor = zoomFactor;
+
+		if( DEBUG )
+			System.out.println( "Zoom factor           " + oldZoomFactor + " --> " + zoomFactor );
+
+		setScaleFactor( UIScale.unzoomedScaleFactor * zoomFactor );
+
+		if( initialized && UIManager.getLookAndFeel() instanceof FlatLaf ) {
+			// see also FlatLaf.initDefaultFont()
+			UIDefaults defaults = UIManager.getLookAndFeelDefaults();
+			Font font = defaults.getFont( "defaultFont" );
+			int unzoomedSize = defaults.getInt( "defaultFont.unzoomedSize" );
+			if( unzoomedSize == 0 ) {
+				unzoomedSize = font.getSize();
+				defaults.put( "defaultFont.unzoomedSize", unzoomedSize );
+			}
+
+			// update "defaultFont"
+			ignoreFontChange = true;
+			try {
+				// get application default font before updating Laf default font
+				Font appFont = UIManager.getFont( "defaultFont" );
+
+				// update Laf default font
+				int newFontSize = Math.max( Math.round( unzoomedSize * zoomFactor ), 1 );
+				defaults.put( "defaultFont", new FontUIResource( font.deriveFont( (float) newFontSize ) ) );
+
+				if( DEBUG )
+					System.out.println( "Zoom Laf font         " + font.getSize() + " --> " + newFontSize + "   (unzoomed " + unzoomedSize + ")" );
+
+				// check whether application has changed default font
+				if( appFont != font ) {
+					// application has own default font --> also zoom it
+					int newAppFontSize = Math.max( Math.round( (appFont.getSize() / oldZoomFactor) * zoomFactor ), 1 );
+					UIManager.put( "defaultFont", appFont.deriveFont( (float) newAppFontSize ) );
+
+					if( DEBUG )
+						System.out.println( "Zoom app font         " + appFont.getSize() + " --> " + newAppFontSize );
+				}
+			} finally {
+				ignoreFontChange = false;
+			}
+		}
+
+		if( changeSupport != null )
+			changeSupport.firePropertyChange( PROP_ZOOM_FACTOR, oldZoomFactor, zoomFactor );
+
+		return true;
+	}
+
+	/**
+	 * Increases zoom factor using next greater factor in supported factors array.
+	 * <p>
+	 * UI needs to be updated if zoom factor has changed. E.g.:
+	 * <pre>{@code
+	 * if( UIScale.zoomIn() )
+	 *     FlatLaf.updateUI();
+	 * }</pre>
+	 *
+	 * @return {@code true} if zoom factor has changed
+	 * @see #getSupportedZoomFactors()
+	 * @since 3.7
+	 */
+	public static boolean zoomIn() {
+		int i = Arrays.binarySearch( supportedZoomFactors, zoomFactor );
+		int next = (i >= 0) ? i + 1 : -i - 1;
+		if( next >= supportedZoomFactors.length )
+			return false;
+
+		return setZoomFactor( supportedZoomFactors[next] );
+	}
+
+	/**
+	 * Decreases zoom factor using next smaller factor in supported factors array.
+	 * <p>
+	 * UI needs to be updated if zoom factor has changed. E.g.:
+	 * <pre>{@code
+	 * if( UIScale.zoomOut() )
+	 *     FlatLaf.updateUI();
+	 * }</pre>
+	 *
+	 * @return {@code true} if zoom factor has changed
+	 * @see #getSupportedZoomFactors()
+	 * @since 3.7
+	 */
+	public static boolean zoomOut() {
+		int i = Arrays.binarySearch( supportedZoomFactors, zoomFactor );
+		int prev = (i >= 0) ? i - 1 : -i - 2;
+		if( prev < 0 )
+			return false;
+
+		return setZoomFactor( supportedZoomFactors[prev] );
+	}
+
+	/**
+	 * Resets zoom factor to {@code 1}.
+	 * <p>
+	 * UI needs to be updated if zoom factor has changed. E.g.:
+	 * <pre>{@code
+	 * if( UIScale.zoomReset() )
+	 *     FlatLaf.updateUI();
+	 * }</pre>
+	 *
+	 * @return {@code true} if zoom factor has changed
+	 * @since 3.7
+	 */
+	public static boolean zoomReset() {
+		return setZoomFactor( 1 );
+	}
+
+	/**
+	 * Returns the supported zoom factors used for {@link #zoomIn()} and {@link #zoomOut()}.
+	 * <p>
+	 * Default is {@code [ 1f, 1.1f, 1.25f, 1.5f, 1.75f, 2f ]}.
+	 *
+	 * @since 3.7
+	 */
+	public static float[] getSupportedZoomFactors() {
+		return supportedZoomFactors.clone();
+	}
+
+	/**
+	 * Sets the supported zoom factors used for {@link #zoomIn()} and {@link #zoomOut()}.
+	 *
+	 * @since 3.7
+	 */
+	public static void setSupportedZoomFactors( float[] supportedZoomFactors ) {
+		UIScale.supportedZoomFactors = supportedZoomFactors.clone();
+		Arrays.sort( UIScale.supportedZoomFactors );
+
+		if( Arrays.binarySearch( UIScale.supportedZoomFactors, 1f ) < 0 )
+			throw new IllegalArgumentException( "supportedZoomFactors array must contain value 1f" );
+	}
+
+	//---- unit testing -------------------------------------------------------
+
+	static boolean inUnitTests;
+
+	static void tests_uninitialize() {
+		initialized = false;
+		unzoomedScaleFactor = 1;
+		scaleFactor = 1;
+		zoomFactor = 1;
+	}
 }
--- a/flatlaf-core/src/test/java/com/formdev/flatlaf/util/TestUIScale.java
+++ b/flatlaf-core/src/test/java/com/formdev/flatlaf/util/TestUIScale.java
@@ -0,0 +1,343 @@
+/*
+ * Copyright 2025 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.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import java.awt.Font;
+import java.util.Collections;
+import java.util.Map;
+import javax.swing.UIManager;
+import javax.swing.UnsupportedLookAndFeelException;
+import javax.swing.plaf.metal.MetalLookAndFeel;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import com.formdev.flatlaf.FlatDarkLaf;
+import com.formdev.flatlaf.FlatLaf;
+import com.formdev.flatlaf.FlatLightLaf;
+import com.formdev.flatlaf.FlatSystemProperties;
+
+/**
+ * @author Karl Tauber
+ */
+public class TestUIScale
+{
+	private static Map<String, String> FONT_EXTRA_DEFAULTS_1x = Collections.singletonMap(
+		"defaultFont", "{instance}java.awt.Font,Dialog,0,12" );
+	private static Map<String, String> FONT_EXTRA_DEFAULTS_1_5x = Collections.singletonMap(
+		"defaultFont", "{instance}java.awt.Font,Dialog,0,18" );
+
+	@BeforeAll
+	static void setup() {
+		UIScale.inUnitTests = true;
+
+		// disable platform specific fonts
+		System.setProperty( "flatlaf.uiScale.fontSizeDivider", "12" );
+		FlatLaf.setGlobalExtraDefaults( FONT_EXTRA_DEFAULTS_1x );
+	}
+
+	@AfterAll
+	static void cleanup() throws UnsupportedLookAndFeelException {
+		System.clearProperty( "flatlaf.uiScale.fontSizeDivider" );
+		FlatLaf.setGlobalExtraDefaults( null );
+
+		UIScale.inUnitTests = false;
+	}
+
+	@AfterEach
+	void afterEach() throws UnsupportedLookAndFeelException {
+		UIManager.setLookAndFeel( new MetalLookAndFeel() );
+		UIManager.put( "defaultFont", null );
+		UIManager.put( "Label.font", null );
+		FlatLaf.setGlobalExtraDefaults( FONT_EXTRA_DEFAULTS_1x );
+
+		UIScale.tests_uninitialize();
+	}
+
+	@Test
+	void testCustomScaleFactor() {
+		System.setProperty( FlatSystemProperties.UI_SCALE, "1.25x" );
+		assertScaleFactor( 1.25f );
+
+		System.setProperty( FlatSystemProperties.UI_SCALE, "2x" );
+		UIScale.tests_uninitialize();
+		assertScaleFactor( 2f );
+
+		System.clearProperty( FlatSystemProperties.UI_SCALE );
+	}
+
+	@Test
+	void testLabelFontScaling() {
+		assertInstanceOf( MetalLookAndFeel.class, UIManager.getLookAndFeel() );
+
+		testLabelFont(  8, 1f );
+		testLabelFont(  9, 1f );
+		testLabelFont( 10, 1f );
+		testLabelFont( 11, 1f );
+		testLabelFont( 12, 1f );
+		testLabelFont( 13, 1f );
+		testLabelFont( 14, 1.25f );
+		testLabelFont( 15, 1.25f );
+		testLabelFont( 16, 1.25f );
+		testLabelFont( 17, 1.5f );
+		testLabelFont( 18, 1.5f );
+		testLabelFont( 19, 1.5f );
+		testLabelFont( 20, 1.75f );
+		testLabelFont( 21, 1.75f );
+		testLabelFont( 22, 1.75f );
+		testLabelFont( 23, 2f );
+		testLabelFont( 24, 2f );
+		testLabelFont( 25, 2f );
+		testLabelFont( 26, 2.25f );
+	}
+
+	private void testLabelFont( int fontSize, float expectedScaleFactor ) {
+		UIManager.put( "Label.font", new Font( Font.DIALOG, Font.PLAIN, fontSize ) );
+		assertScaleFactor( expectedScaleFactor );
+	}
+
+	@Test
+	void testDefaultFontScaling() {
+		FlatLightLaf.setup();
+
+		testDefaultFont(  8, 1f );
+		testDefaultFont(  9, 1f );
+		testDefaultFont( 10, 1f );
+		testDefaultFont( 11, 1f );
+		testDefaultFont( 12, 1f );
+		testDefaultFont( 13, 1f );
+		testDefaultFont( 14, 1.25f );
+		testDefaultFont( 15, 1.25f );
+		testDefaultFont( 16, 1.25f );
+		testDefaultFont( 17, 1.5f );
+		testDefaultFont( 18, 1.5f );
+		testDefaultFont( 19, 1.5f );
+		testDefaultFont( 20, 1.75f );
+		testDefaultFont( 21, 1.75f );
+		testDefaultFont( 22, 1.75f );
+		testDefaultFont( 23, 2f );
+		testDefaultFont( 24, 2f );
+		testDefaultFont( 25, 2f );
+		testDefaultFont( 26, 2.25f );
+	}
+
+	private void testDefaultFont( int fontSize, float expectedScaleFactor ) {
+		UIManager.put( "defaultFont", new Font( Font.DIALOG, Font.PLAIN, fontSize ) );
+		assertScaleFactor( expectedScaleFactor );
+	}
+
+	@Test
+	void testInitialScaleFactorAndFontSizes() {
+		FlatLightLaf.setup();
+		assertScaleFactorAndFontSizes( 1f, 12, -1 );
+
+		FlatLaf.setGlobalExtraDefaults( FONT_EXTRA_DEFAULTS_1_5x );
+		FlatDarkLaf.setup();
+		assertScaleFactorAndFontSizes( 1.5f, 18, -1 );
+	}
+
+	@Test
+	void zoom_Metal() {
+		UIScale.setZoomFactor( 1.1f );
+		assertScaleFactor( 1.1f );
+
+		UIScale.setZoomFactor( 1.3f );
+		assertScaleFactor( 1.3f );
+
+		UIScale.setZoomFactor( 2.3f );
+		assertScaleFactor( 2.3f );
+	}
+
+	@Test
+	void zoom_1x() {
+		FlatLightLaf.setup();
+		testZoom( 0.7f,  0.7f,   8, -1 );
+		testZoom( 0.75f, 0.75f,  9, -1 );
+		testZoom( 0.8f,  0.8f,  10, -1 );
+		testZoom( 0.9f,  0.9f,  11, -1 );
+		testZoom( 1f,    1f,    12, -1 );
+		testZoom( 1.1f,  1.1f,  13, -1 );
+		testZoom( 1.2f,  1.2f,  14, -1 );
+		testZoom( 1.25f, 1.25f, 15, -1 );
+		testZoom( 1.3f,  1.3f,  16, -1 );
+		testZoom( 1.4f,  1.4f,  17, -1 );
+		testZoom( 1.5f,  1.5f,  18, -1 );
+		testZoom( 1.6f,  1.6f,  19, -1 );
+		testZoom( 1.7f,  1.7f,  20, -1 );
+		testZoom( 1.75f, 1.75f, 21, -1 );
+		testZoom( 1.8f,  1.8f,  22, -1 );
+		testZoom( 1.9f,  1.9f,  23, -1 );
+		testZoom( 2f,    2f,    24, -1 );
+		testZoom( 2.25f, 2.25f, 27, -1 );
+		testZoom( 2.5f,  2.5f,  30, -1 );
+		testZoom( 2.75f, 2.75f, 33, -1 );
+		testZoom( 3f,    3f,    36, -1 );
+		testZoom( 4f,    4f,    48, -1 );
+	}
+
+	@Test
+	void zoom_1_5x() {
+		FlatLaf.setGlobalExtraDefaults( FONT_EXTRA_DEFAULTS_1_5x );
+		FlatLightLaf.setup();
+
+		testZoom( 0.7f,  1.05f, 13, -1 );
+		testZoom( 0.75f, 1.13f, 14, -1 );
+		testZoom( 0.8f,  1.2f,  14, -1 );
+		testZoom( 0.9f,  1.35f, 16, -1 );
+		testZoom( 1f,    1.5f,  18, -1 );
+		testZoom( 1.1f,  1.65f, 20, -1 );
+		testZoom( 1.2f,  1.8f,  22, -1 );
+		testZoom( 1.25f, 1.88f, 23, -1 );
+		testZoom( 1.3f,  1.95f, 23, -1 );
+		testZoom( 1.4f,  2.1f,  25, -1 );
+		testZoom( 1.5f,  2.25f, 27, -1 );
+		testZoom( 1.6f,  2.4f,  29, -1 );
+		testZoom( 1.7f,  2.55f, 31, -1 );
+		testZoom( 1.75f, 2.63f, 32, -1 );
+		testZoom( 1.8f,  2.7f,  32, -1 );
+		testZoom( 1.9f,  2.85f, 34, -1 );
+		testZoom( 2f,    3f,    36, -1 );
+		testZoom( 2.25f, 3.38f, 41, -1 );
+		testZoom( 2.5f,  3.75f, 45, -1 );
+		testZoom( 2.75f, 4.13f, 50, -1 );
+		testZoom( 3f,    4.5f,  54, -1 );
+		testZoom( 4f,    6f,    72, -1 );
+	}
+
+	@Test
+	void zoomAppFont_1x() {
+		FlatLightLaf.setup();
+		UIManager.put( "defaultFont", new Font( Font.DIALOG, Font.PLAIN, 14 ) );
+
+		testZoom( 1f,    1.25f, 12, 14 );
+		testZoom( 1.1f,  1.38f, 13, 15 );
+		testZoom( 1.25f, 1.56f, 15, 17 );
+		testZoom( 1.5f,  1.88f, 18, 20 );
+		testZoom( 1.75f, 2.19f, 21, 23 );
+		testZoom( 2f,    2.5f,  24, 26 );
+		testZoom( 1f,    1.25f, 12, 13 );
+		testZoom( 2f,    2.5f,  24, 26 );
+	}
+
+	@Test
+	void zoomWithLafChange() {
+		FlatLightLaf.setup();
+		assertScaleFactorAndFontSizes( 1f, 12, -1 );
+		testZoom( 1.1f,  1.1f,  13, -1 );
+
+		FlatDarkLaf.setup();
+		assertScaleFactorAndFontSizes( 1.1f, 13, -1 );
+		testZoom( 1.2f,  1.2f,  14, -1 );
+
+		FlatLightLaf.setup();
+		assertScaleFactorAndFontSizes( 1.2f, 14, -1 );
+		testZoom( 1.3f,  1.3f,  16, -1 );
+
+		FlatLaf.setGlobalExtraDefaults( FONT_EXTRA_DEFAULTS_1_5x );
+		FlatDarkLaf.setup();
+		assertScaleFactorAndFontSizes( 1.95f, 23, -1 );
+		testZoom( 1.4f,  2.1f,  25, -1 );
+
+		FlatLightLaf.setup();
+		assertScaleFactorAndFontSizes( 2.1f, 25, -1 );
+		testZoom( 1.5f,  2.25f,  27, -1 );
+	}
+
+	@Test
+	void zoomWithDefaultFontChange() {
+		FlatLightLaf.setup();
+		assertScaleFactorAndFontSizes( 1f, 12, -1 );
+
+		float zoom1 = 1.4f;
+		testZoom( zoom1,  zoom1,  17, -1 );
+		testDefaultFont(  8, z( zoom1, 1f ) );
+		testDefaultFont(  9, z( zoom1, 1f ) );
+		testDefaultFont( 10, z( zoom1, 1f ) );
+		testDefaultFont( 11, z( zoom1, 1f ) );
+		testDefaultFont( 12, z( zoom1, 1f ) );
+		testDefaultFont( 13, z( zoom1, 1f ) );
+		testDefaultFont( 14, z( zoom1, 1.25f ) );
+		testDefaultFont( 15, z( zoom1, 1.25f ) );
+		testDefaultFont( 16, z( zoom1, 1.25f ) );
+		testDefaultFont( 17, z( zoom1, 1.5f ) );
+		testDefaultFont( 18, z( zoom1, 1.5f ) );
+		testDefaultFont( 19, z( zoom1, 1.5f ) );
+		testDefaultFont( 20, z( zoom1, 1.75f ) );
+		testDefaultFont( 21, z( zoom1, 1.75f ) );
+		testDefaultFont( 22, z( zoom1, 1.75f ) );
+		testDefaultFont( 23, z( zoom1, 2f ) );
+		testDefaultFont( 24, z( zoom1, 2f ) );
+		testDefaultFont( 25, z( zoom1, 2f ) );
+		testDefaultFont( 26, z( zoom1, 2.25f ) );
+
+		float zoom2 = 1.8f;
+		testZoom( zoom2,  4.05f,  22, 33 );
+		testDefaultFont(  8, z( zoom2, 1f ) );
+		testDefaultFont(  9, z( zoom2, 1f ) );
+		testDefaultFont( 10, z( zoom2, 1f ) );
+		testDefaultFont( 11, z( zoom2, 1f ) );
+		testDefaultFont( 12, z( zoom2, 1f ) );
+		testDefaultFont( 13, z( zoom2, 1f ) );
+		testDefaultFont( 14, z( zoom2, 1.25f ) );
+		testDefaultFont( 15, z( zoom2, 1.25f ) );
+		testDefaultFont( 16, z( zoom2, 1.25f ) );
+		testDefaultFont( 17, z( zoom2, 1.5f ) );
+		testDefaultFont( 18, z( zoom2, 1.5f ) );
+		testDefaultFont( 19, z( zoom2, 1.5f ) );
+		testDefaultFont( 20, z( zoom2, 1.75f ) );
+		testDefaultFont( 21, z( zoom2, 1.75f ) );
+		testDefaultFont( 22, z( zoom2, 1.75f ) );
+		testDefaultFont( 23, z( zoom2, 2f ) );
+		testDefaultFont( 24, z( zoom2, 2f ) );
+		testDefaultFont( 25, z( zoom2, 2f ) );
+		testDefaultFont( 26, z( zoom2, 2.25f ) );
+	}
+
+	private static float z( float zoom, float scale ) {
+		// round scale factor to 1/100
+		return Math.round( (zoom * scale) * 100f ) / 100f;
+	}
+
+	private static void testZoom( float zoomFactor, float expectedScaleFactor,
+		int expectedLafFontSize, int expectedAppFontSize )
+	{
+		UIScale.setZoomFactor( zoomFactor );
+		assertScaleFactorAndFontSizes( expectedScaleFactor, expectedLafFontSize, expectedAppFontSize );
+	}
+
+	private static void assertScaleFactorAndFontSizes( float expectedScaleFactor,
+		int expectedLafFontSize, int expectedAppFontSize )
+	{
+		assertScaleFactor( expectedScaleFactor );
+
+		Font lafFont = UIManager.getLookAndFeelDefaults().getFont( "defaultFont" );
+		Font appFont = UIManager.getFont( "defaultFont" );
+		assertEquals( expectedLafFontSize, lafFont.getSize() );
+		if( expectedAppFontSize > 0 ) {
+			assertNotEquals( lafFont, appFont );
+			assertEquals( expectedAppFontSize, appFont.getSize() );
+		} else
+			assertEquals( lafFont, appFont );
+	}
+
+	private static void assertScaleFactor( float expectedScaleFactor ) {
+		assertEquals( expectedScaleFactor, UIScale.getUserScaleFactor() );
+	}
+}