Deprecate DefaultSWTFontRegistry and switch to ScalingSWTFontRegistry

    1)Always use ScalingSWTFontRegistry
    2)Rename DefaultSWTFontRegistry -> LegacySWTFontRegistry as this is not default anymore
    3)Add a system property to use LegacySWTFontRegistry without monitor specific scaling active
    4)Deprecate the LegacySWTFontRegistry(DefaultSWTFontRegistry)
    5)additionally the change also makes sure all fonts are cached when they are created, this is necessary to make
    sure the systemfonts would also be cached when they are created
    (this change is to fix  Test_org_eclipse_swt_graphics_GC.test_setFontLorg_eclipse_swt_graphics_Font which was broken with ScalingSwtFontRegistry)

Author: arunjose696

bundles/org.eclipse.swt/Eclipse SWT Tests/win32/org/eclipse/swt/internal/DefaultSWTFontRegistryTests.java renamed to bundles/org.eclipse.swt/Eclipse SWT Tests/win32/org/eclipse/swt/internal/LegacySWTFontRegistryTests.java

@@ -23,15 +23,15 @@
 import org.junit.jupiter.api.extension.*;
 
 @ExtendWith(PlatformSpecificExecutionExtension.class)
-class DefaultSWTFontRegistryTests {
+class LegacySWTFontRegistryTests {
 	private static String TEST_FONT = "Helvetica";
 	private Display display;
 	private SWTFontRegistry fontRegistry;
 
 	@BeforeEach
 	public void setUp() {
 		this.display = Display.getDefault();
-		this.fontRegistry = new DefaultSWTFontRegistry(display);
+		this.fontRegistry = new LegacySWTFontRegistry(display);
 	}
 
 	@AfterEach

bundles/org.eclipse.swt/Eclipse SWT Tests/win32/org/eclipse/swt/widgets/ControlWin32Tests.java

@@ -44,15 +44,41 @@ public void testScaleFontCorrectlyInAutoScaleSzenario() {
 	}
 
 	@Test
-	public void testDoNotScaleFontCorrectlyInNoAutoScaleSzenario() {
+	public void testScaleFontCorrectlyInNoAutoScaleSzenario() {
 		DPIUtil.setMonitorSpecificScaling(false);
 		Display display = Display.getDefault();
 
-		assertFalse("Autoscale property is not set to false", display.isRescalingAtRuntime());
+		assertFalse("Autoscale property is not set to true", display.isRescalingAtRuntime());
 		int scalingFactor = 2;
 		FontComparison fontComparison = updateFont(scalingFactor);
-		assertEquals("Font height in pixels is different when setting the same font again",
-				fontComparison.originalFontHeight, fontComparison.currentFontHeight);
+		assertEquals("Font height in pixels is not adjusted according to the scale factor",
+				fontComparison.originalFontHeight * scalingFactor, fontComparison.currentFontHeight);
+	}
+
+	@Test
+	public void testDoNotScaleFontCorrectlyInNoAutoScaleSzenarioWithLegacyFontRegistry() {
+		DPIUtil.setMonitorSpecificScaling(false);
+		String originalValue = System.getProperty("swt.fontRegistry");
+		System.setProperty("swt.fontRegistry", "LEGACY");
+		try {
+			Display display = Display.getDefault();
+
+			assertFalse("Autoscale property is not set to false", display.isRescalingAtRuntime());
+			int scalingFactor = 2;
+			FontComparison fontComparison = updateFont(scalingFactor);
+			assertEquals("Font height in pixels is different when setting the same font again",
+					fontComparison.originalFontHeight, fontComparison.currentFontHeight);
+
+
+		}
+		finally {
+			if (originalValue != null) {
+		        System.setProperty("swt.fontRegistry", originalValue);
+		    } else {
+		        System.clearProperty("swt.fontRegistry");
+		    }
+		}
+
 	}
 
 	@Test

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/internal/DefaultSWTFontRegistry.java renamed to bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/internal/LegacySWTFontRegistry.java

@@ -19,19 +19,25 @@
 import org.eclipse.swt.internal.win32.*;
 
 /**
- * This class is used in the win32 implementation only to support
- * unscaled fonts in multiple DPI zoom levels.
+ * <p>
+ * Formerly {@code DefaultSWTFontRegistry}, this class is deprecated. Use {@code ScalingSWTFontRegistry} instead.
+ * To temporarily fall back to legacy font behavior ({@code LegacySWTFontRegistry})
+ * (e.g., if issues arise in existing RCP products), set the system property: {@code
+ * -Dswt.fontRegistry=LEGACY
+ * }
+ * </p>
  *
  * As this class is only intended to be used internally via {@code SWTFontProvider},
  * it should neither be instantiated nor referenced in a client application.
  * The behavior can change any time in a future release.
  */
-final class DefaultSWTFontRegistry implements SWTFontRegistry {
+@Deprecated(forRemoval= true, since= "2025-09")
+final class LegacySWTFontRegistry implements SWTFontRegistry {
 	private static FontData KEY_SYSTEM_FONTS = new FontData();
 	private Map<FontData, Font> fontsMap = new HashMap<>();
 	private Device device;
 
-	DefaultSWTFontRegistry(Device device) {
+	LegacySWTFontRegistry(Device device) {
 		this.device = device;
 	}
 

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/internal/SWTFontProvider.java

@@ -105,10 +105,32 @@ public static void disposeFontRegistry(Device device) {
 		}
 	}
 
+	private static enum FontRegistryType {
+		LEGACY, SCALING;
+
+		public static FontRegistryType fromString(String s) {
+			if (s == null) {
+				return SCALING;
+			}
+			for (FontRegistryType type : values()) {
+				if (type.name().equalsIgnoreCase(s)) {
+					return type;
+				}
+			}
+			return SCALING; // fallback to default if invalid
+		}
+	}
+
+	private static final String SWT_FONT_REGISTRY = "swt.fontRegistry";
+
 	private static SWTFontRegistry newFontRegistry(Device device) {
-		if (device instanceof Display display && display.isRescalingAtRuntime()) {
-			return new ScalingSWTFontRegistry(device);
+		String registryProp = System.getProperty(SWT_FONT_REGISTRY);
+		FontRegistryType fontRegistryValue = FontRegistryType.fromString(registryProp);
+		if (fontRegistryValue == FontRegistryType.LEGACY && device instanceof Display display
+				&& !display.isRescalingAtRuntime()) {
+			return new LegacySWTFontRegistry(device);
 		}
-		return new DefaultSWTFontRegistry(device);
+		return new ScalingSWTFontRegistry(device);
+
 	}
 }

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/internal/ScalingSWTFontRegistry.java

@@ -44,7 +44,9 @@ private Font getScaledFont(int zoom) {
 
 		private Font createAndCacheFont(int zoom) {
 			Font newFont = createFont(zoom);
-			customFontHandlesKeyMap.put(Font.win32_getHandle(newFont), this);
+			FontData clonedFontData = new FontData(newFont.getFontData()[0].toString());
+			fontsKeyMap.put(clonedFontData, this);
+			fontHandlesKeyMap.put(Font.win32_getHandle(newFont), this);
 			scaledFonts.put(zoom, newFont);
 			return newFont;
 		}
@@ -108,8 +110,8 @@ protected void dispose() {
 	}
 
 	private ScaledFontContainer systemFontContainer;
-	private Map<FontData, ScaledFontContainer> customFontsKeyMap = new HashMap<>();
-	private Map<Long, ScaledFontContainer> customFontHandlesKeyMap = new HashMap<>();
+	private Map<FontData, ScaledFontContainer> fontsKeyMap = new HashMap<>();
+	private Map<Long, ScaledFontContainer> fontHandlesKeyMap = new HashMap<>();
 	private Device device;
 
 	ScalingSWTFontRegistry(Device device) {
@@ -125,27 +127,27 @@ public Font getSystemFont(int zoom) {
 	@Override
 	public Font getFont(FontData fontData, int zoom) {
 		ScaledFontContainer container;
-		if (customFontsKeyMap.containsKey(fontData)) {
-			container = customFontsKeyMap.get(fontData);
+		if (fontsKeyMap.containsKey(fontData)) {
+			container = fontsKeyMap.get(fontData);
 		} else {
 			FontData clonedFontData = new FontData(fontData.toString());
 			container = new ScaledCustomFontContainer(clonedFontData);
-			customFontsKeyMap.put(clonedFontData, container);
+			fontsKeyMap.put(clonedFontData, container);
 		}
 		return container.getScaledFont(zoom);
 	}
 
 	@Override
 	public Font getFont(long fontHandle, int zoom) {
-		if (customFontHandlesKeyMap.containsKey(fontHandle)) {
-			return customFontHandlesKeyMap.get(fontHandle).getScaledFont(zoom);
+		if (fontHandlesKeyMap.containsKey(fontHandle)) {
+			return fontHandlesKeyMap.get(fontHandle).getScaledFont(zoom);
 		}
 		return Font.win32_new(device, fontHandle, zoom);
 	}
 
 	@Override
 	public void dispose() {
-		customFontsKeyMap.values().forEach(ScaledFontContainer::dispose);
-		customFontsKeyMap.clear();
+		fontsKeyMap.values().forEach(ScaledFontContainer::dispose);
+		fontsKeyMap.clear();
 	}
 }