Destroy unused handles od resources

This Contribution destroys those handles for the resources which were
created for zoom levels which no monitor has anymore. The process is
triggered on a DPI_CHANGED event.

contributes to #62 and #127

Author: amartya4256

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

@@ -693,6 +693,9 @@ public boolean loadFont (String path) {
 }
 
 void new_Object (Object object) {
+	if (!tracking) {
+		return;
+	}
 	synchronized (trackingLock) {
 		for (int i=0; i<objects.length; i++) {
 			if (objects [i] == null) {

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/graphics/Resource.java

@@ -13,6 +13,7 @@
  *******************************************************************************/
 package org.eclipse.swt.graphics;
 
+import java.util.*;
 import java.util.function.*;
 
 import org.eclipse.swt.*;
@@ -123,6 +124,19 @@ public Resource() {
 void destroy() {
 }
 
+/**
+ * This method is supposed to be overridden by those resources which contain
+ * multiple handles for different zoom levels. The method destroys handles of
+ * the resource for all the zoom levels expect for the those passed in the
+ * argument.
+ *
+ * @param zoomLevels The zoom levels for which the handles are supposed to be
+ *                   retained.
+ */
+void destroyHandlesExcept(Set<Integer> zoomLevels) {
+
+}
+
 /**
  * Disposes of the operating system resources associated with
  * this resource. Applications must dispose of all resources
@@ -158,7 +172,7 @@ void ignoreNonDisposed() {
 }
 
 void init() {
-	if (device.tracking) device.new_Object(this);
+	device.new_Object(this);
 }
 
 void initNonDisposeTracking() {

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

@@ -911,6 +911,9 @@ long logProc (long log_domain, long log_level, long message, long user_data) {
 }
 
 void new_Object (Object object) {
+	if (!tracking) {
+		return;
+	}
 	synchronized (trackingLock) {
 		for (int i=0; i<objects.length; i++) {
 			if (objects [i] == null) {

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

@@ -14,10 +14,13 @@
 package org.eclipse.swt.graphics;
 
 
+import java.util.*;
+
 import org.eclipse.swt.*;
 import org.eclipse.swt.internal.*;
 import org.eclipse.swt.internal.gdip.*;
 import org.eclipse.swt.internal.win32.*;
+import org.eclipse.swt.widgets.*;
 
 /**
  * This class is the abstract superclass of all device objects,
@@ -117,6 +120,7 @@ public Device(DeviceData data) {
 			debug = data.debug;
 			tracking = data.tracking;
 		}
+		initializeObjects();
 		if (tracking) {
 			startTracking();
 		}
@@ -148,26 +152,25 @@ public void setTracking(boolean tracking) {
 	if (tracking == this.tracking) {
 		return;
 	}
-	this.tracking = tracking;
+	initializeObjects();
 	if (tracking) {
 		startTracking();
 	} else {
 		stopTracking();
 	}
 }
 
-private void startTracking() {
-	errors = new Error [128];
+private void initializeObjects() {
 	objects = new Object [128];
 	trackingLock = new Object ();
 }
 
+private void startTracking() {
+	errors = new Error [128];
+}
+
 private void stopTracking() {
-	synchronized (trackingLock) {
-		objects = null;
-		errors = null;
-		trackingLock = null;
-	}
+	errors = null;
 }
 
 
@@ -336,13 +339,13 @@ public void dispose () {
 
 			destroy ();
 			disposed = true;
-			if (tracking) {
-				synchronized (trackingLock) {
-					printErrors ();
-					objects = null;
+			synchronized (trackingLock) {
+				printErrors ();
+				objects = null;
+				if (tracking) {
 					errors = null;
-					trackingLock = null;
 				}
+				trackingLock = null;
 			}
 		}
 	}
@@ -353,7 +356,9 @@ void dispose_Object (Object object) {
 		for (int i=0; i<objects.length; i++) {
 			if (objects [i] == object) {
 				objects [i] = null;
-				errors [i] = null;
+				if(tracking) {
+					errors [i] = null;
+				}
 				return;
 			}
 		}
@@ -436,26 +441,27 @@ public DeviceData getDeviceData () {
 	DeviceData data = new DeviceData ();
 	data.debug = debug;
 	data.tracking = tracking;
-	if (tracking) {
-		synchronized (trackingLock) {
-			int count = 0, length = objects.length;
-			for (int i=0; i<length; i++) {
-				if (objects [i] != null) count++;
-			}
-			int index = 0;
-			data.objects = new Object [count];
+	synchronized (trackingLock) {
+		int count = 0, length = objects.length;
+		for (int i=0; i<length; i++) {
+			if (objects [i] != null) count++;
+		}
+		int index = 0;
+		data.objects = new Object [count];
+		if (tracking) {
 			data.errors = new Error [count];
-			for (int i=0; i<length; i++) {
-				if (objects [i] != null) {
-					data.objects [index] = objects [i];
+		} else {
+			data.errors = new Error [0];
+		}
+		for (int i=0; i<length; i++) {
+			if (objects [i] != null) {
+				data.objects [index] = objects [i];
+				if (tracking) {
 					data.errors [index] = errors [i];
-					index++;
 				}
+				index++;
 			}
 		}
-	} else {
-		data.objects = new Object [0];
-		data.errors = new Error [0];
 	}
 	return data;
 }
@@ -820,26 +826,30 @@ void new_Object (Object object) {
 		for (int i=0; i<objects.length; i++) {
 			if (objects [i] == null) {
 				objects [i] = object;
-				errors [i] = new Error ();
+				if (tracking) {
+					errors [i] = new Error ();
+				}
 				return;
 			}
 		}
 		Object [] newObjects = new Object [objects.length + 128];
 		System.arraycopy (objects, 0, newObjects, 0, objects.length);
 		newObjects [objects.length] = object;
 		objects = newObjects;
-		Error [] newErrors = new Error [errors.length + 128];
-		System.arraycopy (errors, 0, newErrors, 0, errors.length);
-		newErrors [errors.length] = new Error ();
-		errors = newErrors;
+		if (tracking) {
+			Error [] newErrors = new Error [errors.length + 128];
+			System.arraycopy (errors, 0, newErrors, 0, errors.length);
+			newErrors [errors.length] = new Error ();
+			errors = newErrors;
+		}
 	}
 }
 
 void printErrors () {
 	if (!DEBUG) return;
 	if (tracking) {
 		synchronized (trackingLock) {
-			if (objects == null || errors == null) return;
+			if (objects == null && errors == null) return;
 			int objectCount = 0;
 			int colors = 0, cursors = 0, fonts = 0, gcs = 0, images = 0;
 			int paths = 0, patterns = 0, regions = 0, textLayouts = 0, transforms = 0;
@@ -874,8 +884,10 @@ void printErrors () {
 					string = string.substring (0, string.length () - 2);
 					System.err.println (string);
 				}
-				for (Error error : errors) {
-					if (error != null) error.printStackTrace (System.err);
+				if(tracking) {
+					for (Error error : errors) {
+						if (error != null) error.printStackTrace (System.err);
+					}
 				}
 			}
 		}
@@ -947,4 +959,22 @@ public void setWarnings (boolean warnings) {
 protected int getDeviceZoom () {
 	return DPIUtil.mapDPIToZoom ( _getDPIx ());
 }
+
+/**
+ * Destroys the handles of all the resources in the resource tracker by
+ * identifying the zoom levels which is not valid for any monitor
+ *
+ * @noreference This method is not intended to be referenced by clients.
+ */
+public static void win32_destroyUnusedHandles(Display display) {
+	Set<Integer> availableZoomLevels = new HashSet<>();
+	for (Monitor monitor : display.getMonitors()) {
+	    availableZoomLevels.add(DPIUtil.getZoomForAutoscaleProperty(monitor.getZoom()));
+	}
+	for (Object object: ((Device) display).objects) {
+		if (object instanceof Resource resource) {
+			resource.destroyHandlesExcept(availableZoomLevels);
+		}
+	}
+}
 }

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

@@ -1186,16 +1186,31 @@ void destroy () {
 
 private void destroyHandle () {
 	for (Long handle : zoomLevelToHandle.values()) {
-		if (type == SWT.ICON) {
-			OS.DestroyIcon (handle);
-		} else {
-			OS.DeleteObject (handle);
-		}
+		destroyHandle(handle);
 	}
 	zoomLevelToHandle.clear();
 	handle = 0;
 }
 
+@Override
+void destroyHandlesExcept(Set<Integer> zoomLevels) {
+	zoomLevelToHandle.entrySet().removeIf(entry -> {
+		if (!zoomLevels.contains(entry.getKey()) && entry.getKey() != DPIUtil.getZoomForAutoscaleProperty(initialNativeZoom)) {
+			destroyHandle(entry.getValue());
+            return true;
+        }
+        return false;
+	});
+}
+
+private void destroyHandle(long handle) {
+	if (type == SWT.ICON) {
+		OS.DestroyIcon (handle);
+	} else {
+		OS.DeleteObject (handle);
+	}
+}
+
 /**
  * Compares the argument to the receiver, and returns true
  * if they represent the <em>same</em> object using a class

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

@@ -438,6 +438,17 @@ void destroy() {
 	zoomLevelToHandle.clear();
 }
 
+@Override
+void destroyHandlesExcept(Set<Integer> zoomLevels) {
+	zoomLevelToHandle.entrySet().removeIf(entry -> {
+		if (!zoomLevels.contains(entry.getKey()) && entry.getKey() != initialZoom) {
+			Gdip.GraphicsPath_delete(entry.getValue());
+            return true;
+        }
+        return false;
+	});
+}
+
 /**
  * Replaces the first four elements in the parameter with values that
  * describe the smallest rectangle that will completely contain the

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

@@ -260,21 +260,7 @@ void setImageHandle(Image image, int zoom) {
 @Override
 void destroy() {
 	for (long handle: zoomLevelToHandle.values()) {
-		int type = Gdip.Brush_GetType(handle);
-		switch (type) {
-			case Gdip.BrushTypeSolidColor:
-				Gdip.SolidBrush_delete(handle);
-				break;
-			case Gdip.BrushTypeHatchFill:
-				Gdip.HatchBrush_delete(handle);
-				break;
-			case Gdip.BrushTypeLinearGradient:
-				Gdip.LinearGradientBrush_delete(handle);
-				break;
-			case Gdip.BrushTypeTextureFill:
-				Gdip.TextureBrush_delete(handle);
-				break;
-		}
+		destroyHandle(handle);
 	}
 	zoomLevelToHandle.clear();
 	if (bitmapDestructor != null) {
@@ -283,6 +269,35 @@ void destroy() {
 	}
 }
 
+@Override
+void destroyHandlesExcept(Set<Integer> zoomLevels) {
+	zoomLevelToHandle.entrySet().removeIf(entry -> {
+		if (!zoomLevels.contains(entry.getKey()) && entry.getKey() != initialZoom) {
+			destroyHandle(entry.getValue());
+            return true;
+        }
+        return false;
+	});
+}
+
+private void destroyHandle(long handle) {
+	int type = Gdip.Brush_GetType(handle);
+	switch (type) {
+		case Gdip.BrushTypeSolidColor:
+			Gdip.SolidBrush_delete(handle);
+			break;
+		case Gdip.BrushTypeHatchFill:
+			Gdip.HatchBrush_delete(handle);
+			break;
+		case Gdip.BrushTypeLinearGradient:
+			Gdip.LinearGradientBrush_delete(handle);
+			break;
+		case Gdip.BrushTypeTextureFill:
+			Gdip.TextureBrush_delete(handle);
+			break;
+	}
+}
+
 /**
  * Returns <code>true</code> if the Pattern has been disposed,
  * and <code>false</code> otherwise.

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

@@ -227,6 +227,17 @@ void destroy () {
 	operations.clear();
 }
 
+@Override
+void destroyHandlesExcept(Set<Integer> zoomLevels) {
+	zoomToHandle.entrySet().removeIf(entry -> {
+		if (!zoomLevels.contains(entry.getKey()) && entry.getKey() != initialZoom) {
+			OS.DeleteObject(entry.getValue());
+            return true;
+        }
+        return false;
+	});
+}
+
 /**
  * Compares the argument to the receiver, and returns true
  * if they represent the <em>same</em> object using a class