Add API to add and obtain typed listeners to/from Widgets

Author: HannesWell

bundles/org.eclipse.swt/Eclipse SWT/cocoa/org/eclipse/swt/widgets/Widget.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2017 IBM Corporation and others.
+ * Copyright (c) 2000, 2024 IBM Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -13,6 +13,9 @@
  *******************************************************************************/
 package org.eclipse.swt.widgets;
 
+import java.util.*;
+import java.util.stream.*;
+
 import org.eclipse.swt.*;
 import org.eclipse.swt.events.*;
 import org.eclipse.swt.internal.*;
@@ -439,11 +442,11 @@ boolean resignFirstResponder (long id, long sel) {
 }
 
 /**
- * Adds the listener to the collection of listeners who will
+ * Adds the listener to the collection of {@link Listener listeners} who will
  * be notified when an event of the given type occurs. When the
  * event does occur in the widget, the listener is notified by
  * sending it the <code>handleEvent()</code> message. The event
- * type is one of the event constants defined in class <code>SWT</code>.
+ * type is one of the event constants defined in class {@link SWTError}.
  *
  * @param eventType the type of event to listen for
  * @param listener the listener which should be notified when the event occurs
@@ -456,8 +459,6 @@ boolean resignFirstResponder (long id, long sel) {
  *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
  * </ul>
  *
- * @see Listener
- * @see SWT
  * @see #getListeners(int)
  * @see #removeListener(int, Listener)
  * @see #notifyListeners
@@ -468,6 +469,43 @@ public void addListener (int eventType, Listener listener) {
 	_addListener (eventType, listener);
 }
 
+/**
+ * Adds the {@link EventListener typed listener} to the collection of listeners
+ * who will be notified when an event of the given types occurs.
+ * When the event does occur in the widget, the listener is notified
+ * by calling the type's handling methods.
+ * The event type is one of the event constants defined in class {@link SWT}
+ * and must correspond to the listeners type.
+ * If for example a {@link SelectionListener} is passed the {@code eventTypes}
+ * can be {@link SWT#Selection} or {@link SWT#DefaultSelection}.
+ *
+ * @param listener the listener which should be notified when the event occurs
+ * @param eventTypes the types of event to listen for
+ *
+ * @exception IllegalArgumentException <ul>
+ *    <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
+ * </ul>
+ * @exception SWTException <ul>
+ *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
+ *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
+ * </ul>
+ *
+ * @see #getTypedListeners(int, Class)
+ * @see #removeTypedListener(int, EventListener)
+ * @see #notifyListeners
+ * @since 3.126
+ */
+protected void addTypedListener (EventListener listener, int... eventTypes) {
+	checkWidget();
+	if (listener == null) {
+		SWT.error(SWT.ERROR_NULL_ARGUMENT);
+	}
+	TypedListener typedListener = new TypedListener(listener);
+	for (int eventType : eventTypes) {
+		_addListener(eventType, typedListener);
+	}
+}
+
 void _addListener (int eventType, Listener listener) {
 	if (eventTable == null) eventTable = new EventTable ();
 	eventTable.hook (eventType, listener);
@@ -948,9 +986,9 @@ boolean getDrawing () {
 }
 
 /**
- * Returns an array of listeners who will be notified when an event
+ * Returns an array of {@link Listener listeners} who will be notified when an event
  * of the given type occurs. The event type is one of the event constants
- * defined in class <code>SWT</code>.
+ * defined in class {@link SWT}.
  *
  * @param eventType the type of event to listen for
  * @return an array of listeners that will be notified when the event occurs
@@ -960,8 +998,6 @@ boolean getDrawing () {
  *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
  * </ul>
  *
- * @see Listener
- * @see SWT
  * @see #addListener(int, Listener)
  * @see #removeListener(int, Listener)
  * @see #notifyListeners
@@ -974,6 +1010,33 @@ public Listener[] getListeners (int eventType) {
 	return eventTable.getListeners(eventType);
 }
 
+/**
+ * Returns the typed listeners who will be notified when an event of the given type occurs.
+ * The event type is one of the event constants defined in class {@link SWT}
+ * and the specified listener-type must correspond to that event.
+ * If for example the {@code eventType} is {@link SWT#Selection},
+ * the listeners type should be {@link SelectionListener}.
+ *
+ * @param eventType the type of event to listen for
+ * @return a stream of typed listeners that will be notified when the event occurs
+ *
+ * @exception SWTException <ul>
+ *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
+ *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
+ * </ul>
+ *
+ * @see #addTypedListener(EventListener, int...)
+ * @see #removeTypedListener(int, EventListener)
+ * @see #notifyListeners
+ *
+ * @since 3.126
+ */
+public <L extends EventListener> Stream<L> getTypedListeners (int eventType, Class<L> listenerType) {
+	return Arrays.stream(getListeners(eventType)) //
+			.filter(TypedListener.class::isInstance).map(l -> ((TypedListener) l).eventListener)
+			.filter(listenerType::isInstance).map(listenerType::cast);
+}
+
 String getName () {
 	String string = getClass ().getName ();
 	int index = string.lastIndexOf ('.');
@@ -1463,11 +1526,42 @@ public void removeListener (int eventType, Listener listener) {
  * @noreference This method is not intended to be referenced by clients.
  * @nooverride This method is not intended to be re-implemented or extended by clients.
  */
-protected void removeListener (int eventType, SWTEventListener handler) {
+protected void removeListener (int eventType, SWTEventListener listener) {
+	removeTypedListener(eventType, listener);
+}
+
+/**
+ * Removes the listener from the collection of listeners who will
+ * be notified when an event of the given type occurs.
+ * <p>
+ * <b>IMPORTANT:</b> This method is <em>not</em> part of the SWT
+ * public API. It is marked public only so that it can be shared
+ * within the packages provided by SWT. It should never be
+ * referenced from application code.
+ * </p>
+ *
+ * @param eventType the type of event to listen for
+ * @param listener the listener which should no longer be notified
+ *
+ * @exception IllegalArgumentException <ul>
+ *    <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
+ * </ul>
+ * @exception SWTException <ul>
+ *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
+ *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
+ * </ul>
+ *
+ * @see Listener
+ * @see #addListener
+ *
+ * @noreference This method is not intended to be referenced by clients.
+ * @nooverride This method is not intended to be re-implemented or extended by clients.
+ */
+protected void removeTypedListener (int eventType, EventListener listener) {
 	checkWidget();
-	if (handler == null) error (SWT.ERROR_NULL_ARGUMENT);
+	if (listener == null) error (SWT.ERROR_NULL_ARGUMENT);
 	if (eventTable == null) return;
-	eventTable.unhook (eventType, handler);
+	eventTable.unhook (eventType, listener);
 }
 
 /**

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/widgets/EventTable.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2011 IBM Corporation and others.
+ * Copyright (c) 2000, 2024 IBM Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -14,6 +14,8 @@
 package org.eclipse.swt.widgets;
 
 
+import java.util.*;
+
 import org.eclipse.swt.*;
 import org.eclipse.swt.internal.*;
 
@@ -145,12 +147,12 @@ public void unhook (int eventType, Listener listener) {
 	}
 }
 
-public void unhook (int eventType, SWTEventListener listener) {
+public void unhook (int eventType, EventListener listener) {
 	if (types == null) return;
 	for (int i=0; i<types.length; i++) {
 		if (types [i] == eventType) {
 			if (listeners [i] instanceof TypedListener typedListener) {
-				if (typedListener.getEventListener () == listener) {
+				if (typedListener.eventListener == listener) {
 					remove (i);
 					return;
 				}

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/widgets/TypedListener.java

@@ -14,9 +14,11 @@
 package org.eclipse.swt.widgets;
 
 
-import org.eclipse.swt.internal.SWTEventListener;
+import java.util.*;
+
 import org.eclipse.swt.*;
 import org.eclipse.swt.events.*;
+import org.eclipse.swt.internal.*;
 
 /**
  * Instances of this class are <em>internal SWT implementation</em>
@@ -40,7 +42,7 @@ public class TypedListener implements Listener {
 	/**
 	 * The receiver's event listener
 	 */
-	protected SWTEventListener eventListener;
+	protected EventListener eventListener;
 
 /**
  * Constructs a new instance of this class for the given event listener.
@@ -59,6 +61,10 @@ public TypedListener (SWTEventListener listener) {
 	eventListener = listener;
 }
 
+TypedListener (EventListener listener) {
+	eventListener = listener;
+}
+
 /**
  * Returns the receiver's event listener.
  * <p>
@@ -73,7 +79,11 @@ public TypedListener (SWTEventListener listener) {
  * @noreference This method is not intended to be referenced by clients.
  */
 public SWTEventListener getEventListener () {
-	return eventListener;
+	// At the moment all typed listeners implement SWTEventListener but that interface is intended to be removed in the future and then they will only implement EventListener.
+	// This method should not be called for typed listeners listeners that only implement EventListener.
+	// This is only relevant for custom typed listeners that implement EventListener directly before SWTEventListener is eventually removed.
+	// But then the new Widget.getTypedListener() method can be used.
+	return (SWTEventListener) eventListener;
 }
 
 /**