Properly dispose font in FontRegistry upon display disposal

bundles/org.eclipse.jface/META-INF/MANIFEST.MF

@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: %pluginName
 Bundle-SymbolicName: org.eclipse.jface;singleton:=true
-Bundle-Version: 3.35.100.qualifier
+Bundle-Version: 3.35.200.qualifier
 Bundle-Vendor: %providerName
 Bundle-Localization: plugin
 Export-Package: org.eclipse.jface,

bundles/org.eclipse.jface/src/org/eclipse/jface/resource/FontRegistry.java

@@ -25,6 +25,7 @@
 import java.util.MissingResourceException;
 import java.util.ResourceBundle;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 import org.eclipse.core.runtime.Assert;
 import org.eclipse.jface.util.Policy;
@@ -207,7 +208,7 @@ void addAllocatedFontsToStale(Font defaultFont) {
 	 */
 	protected Runnable displayRunnable = this::clearCaches;
 
-	private boolean displayDisposeHooked;
+	private final Set<Display> displayDisposeHooked = ConcurrentHashMap.newKeySet();
 
 	private final boolean cleanOnDisplayDisposal;
 
@@ -492,7 +493,7 @@ private FontRecord createFont(String symbolicName, FontData[] fonts) {
 		if (display == null) {
 			return null;
 		}
-		if (cleanOnDisplayDisposal && !displayDisposeHooked) {
+		if (cleanOnDisplayDisposal && !displayDisposeHooked.contains(display)) {
 			hookDisplayDispose(display);
 		}
 
@@ -718,7 +719,7 @@ protected void clearCaches() {
 		stringToFontRecord.clear();
 		staleFonts.clear();
 
-		displayDisposeHooked = false;
+		displayDisposeHooked.remove(Display.getCurrent());
 	}
 
 	/**
@@ -736,7 +737,7 @@ private void disposeFonts(Iterator<Font> iterator) {
 	 * Hook a dispose listener on the SWT display.
 	 */
 	private void hookDisplayDispose(Display display) {
-		displayDisposeHooked = true;
+		displayDisposeHooked.add(display);
 		display.disposeExec(displayRunnable);
 	}
 

tests/org.eclipse.jface.tests/META-INF/MANIFEST.MF

@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: %Bundle-Name
 Bundle-SymbolicName: org.eclipse.jface.tests
-Bundle-Version: 1.4.700.qualifier
+Bundle-Version: 1.4.800.qualifier
 Automatic-Module-Name: org.eclipse.jface.tests
 Bundle-RequiredExecutionEnvironment: JavaSE-17
 Require-Bundle: org.junit;bundle-version="4.12.0",

tests/org.eclipse.jface.tests/src/org/eclipse/jface/tests/resources/FontRegistryTest.java

@@ -14,8 +14,20 @@
 package org.eclipse.jface.tests.resources;
 
 import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assume.assumeTrue;
 
+import java.time.Duration;
+import java.time.Instant;
+import java.util.concurrent.atomic.AtomicReference;
+
+import org.eclipse.core.runtime.Platform.OS;
+import org.eclipse.jface.resource.FontRegistry;
 import org.eclipse.jface.resource.JFaceResources;
+import org.eclipse.swt.graphics.Device;
 import org.eclipse.swt.graphics.Font;
 import org.eclipse.swt.graphics.FontData;
 import org.eclipse.swt.widgets.Display;
@@ -41,4 +53,48 @@ public void testBug544026() {
 		assertArrayEquals(fontData, JFaceResources.getDefaultFont().getFontData());
 	}
 
+	@Test
+	public void multipleDisplayDispose() {
+		assumeTrue("multiple Display instance only allowed on Windows", OS.isWindows());
+
+		FontRegistry fontRegistry = new FontRegistry();
+		Display secondDisplay = initializeDisplayInSeparateThread();
+		Font fontOnSecondDisplay = secondDisplay.syncCall(fontRegistry::defaultFont);
+
+		Font fontOnThisDisplayBeforeSecondDisplayDispose = fontRegistry.defaultFont();
+		Device displayOfFontOnSecondDisplay = fontOnSecondDisplay.getDevice();
+		// font registry returns same font for every display
+		assertEquals(secondDisplay, displayOfFontOnSecondDisplay);
+		assertEquals(fontOnThisDisplayBeforeSecondDisplayDispose, fontOnSecondDisplay);
+
+		// after disposing font's display, registry should reinitialize the font
+		secondDisplay.syncExec(secondDisplay::dispose);
+		assertTrue(fontOnSecondDisplay.isDisposed());
+		Font fontOnThisDisplayAfterSecondDisplayDispose = fontRegistry.defaultFont();
+		assertNotEquals(fontOnThisDisplayAfterSecondDisplayDispose, fontOnSecondDisplay);
+	}
+
+	private static Display initializeDisplayInSeparateThread() {
+		AtomicReference<Display> displayReference = new AtomicReference<>();
+		new Thread(() -> {
+			Display display = new Display();
+			displayReference.set(display);
+			while (!display.isDisposed()) {
+				if (!display.readAndDispatch()) {
+					display.sleep();
+				}
+			}
+		}, "async display creation").start();
+		waitForDisplayInstantiation(displayReference);
+		return displayReference.get();
+	}
+
+	private static void waitForDisplayInstantiation(AtomicReference<Display> displayReference) {
+		Instant maximumEndTime = Instant.now().plus(Duration.ofSeconds(10));
+		while (displayReference.get() == null) {
+			assertFalse("display was not instantiated in time", Instant.now().isAfter(maximumEndTime));
+			Thread.yield();
+		}
+	}
+
 }