Fix Resource leak tracking issue on Windows

On Windows, SWT resources supporting multiple zoom levels are registered
via Device.registerResourceWithZoomSupport(), which retains strong
references to these resources. This prevents garbage collection and
breaks leak detection using Cleaner. Switching to use WeakReference to
allow proper GC behavior and enable the resource tracker to report
non-disposed resources correctly.

Fixes: #2335

Author: ShahzaibIbrahim

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/graphics/Device.java

@@ -14,6 +14,7 @@
 package org.eclipse.swt.graphics;
 
 
+import java.lang.ref.*;
 import java.util.*;
 import java.util.concurrent.*;
 
@@ -61,7 +62,7 @@ public abstract class Device implements Drawable {
 	String[] loadedFonts;
 
 	volatile boolean disposed;
-	private Set<Resource> resourcesWithZoomSupport  = ConcurrentHashMap.newKeySet();
+	private Set<WeakReference<Resource>> resourcesWithZoomSupport = ConcurrentHashMap.newKeySet();
 
 	/*
 	* TEMPORARY CODE. When a graphics object is
@@ -964,11 +965,11 @@ protected int getDeviceZoom () {
 }
 
 void registerResourceWithZoomSupport(Resource resource) {
-	resourcesWithZoomSupport.add(resource);
+	resourcesWithZoomSupport.add(new WeakReference<>(resource));
 }
 
 void deregisterResourceWithZoomSupport(Resource resource) {
-	resourcesWithZoomSupport.remove(resource);
+	resourcesWithZoomSupport.remove(new WeakReference<>(resource));
 }
 
 /**
@@ -982,7 +983,17 @@ public static void win32_destroyUnusedHandles(Display display) {
 	for (Monitor monitor : display.getMonitors()) {
 	    availableZoomLevels.add(DPIUtil.getZoomForAutoscaleProperty(monitor.getZoom()));
 	}
-	for (Resource resource: ((Device) display).resourcesWithZoomSupport) {
+	Set<WeakReference<Resource>> resources = ((Device) display).resourcesWithZoomSupport;
+	Iterator<WeakReference<Resource>> iterator = resources.iterator();
+
+	while (iterator.hasNext()) {
+		WeakReference<Resource> ref = iterator.next();
+		Resource resource = ref.get();
+		if (resource == null) {
+			// Clean up dead reference
+			iterator.remove();
+			continue;
+		}
 		resource.destroyHandlesExcept(availableZoomLevels);
 	}
 }