Deprecate and avoid unload event handler

user/src/com/google/gwt/user/client/Window.java

@@ -506,6 +506,7 @@ public HandlerManager getHandlers() {
   // Package protected for testing.
   static WindowHandlers handlers;
   private static boolean closeHandlersInitialized;
+  private static boolean beforeCloseHandlersInitialized;
   private static boolean scrollHandlersInitialized;
   private static boolean resizeHandlersInitialized;
   private static int lastResizeWidth;
@@ -518,7 +519,10 @@ public HandlerManager getHandlers() {
    *
    * @param handler the handler
    * @return returns the handler registration
+   * @deprecated This method requires the use of the {@code unload} browser event, which is
+   * deprecated in all browsers.
    */
+  @Deprecated
   public static HandlerRegistration addCloseHandler(CloseHandler<Window> handler) {
     maybeInitializeCloseHandlers();
     return addHandler(CloseEvent.getType(), handler);
@@ -531,7 +535,6 @@ public static HandlerRegistration addCloseHandler(CloseHandler<Window> handler)
    * @return returns the handler registration
    */
   public static HandlerRegistration addResizeHandler(ResizeHandler handler) {
-    maybeInitializeCloseHandlers();
     maybeInitializeResizeHandlers();
     return addHandler(ResizeEvent.getType(), handler);
   }
@@ -556,7 +559,7 @@ public static void addWindowCloseListener(WindowCloseListener listener) {
    */
   public static HandlerRegistration addWindowClosingHandler(
       ClosingHandler handler) {
-    maybeInitializeCloseHandlers();
+    maybeInitializeBeforeCloseHandlers();
     return addHandler(Window.ClosingEvent.getType(), handler);
   }
 
@@ -579,7 +582,6 @@ public static void addWindowResizeListener(WindowResizeListener listener) {
    */
   public static HandlerRegistration addWindowScrollHandler(
       Window.ScrollHandler handler) {
-    maybeInitializeCloseHandlers();
     maybeInitializeScrollHandlers();
     return addHandler(Window.ScrollEvent.getType(), handler);
   }
@@ -910,13 +912,21 @@ private static WindowHandlers getHandlers() {
     return handlers;
   }
 
+  @Deprecated
   private static void maybeInitializeCloseHandlers() {
     if (GWT.isClient() && !closeHandlersInitialized) {
-      impl.initWindowCloseHandler();
+      impl.initWindowUnloadHandler();
       closeHandlersInitialized = true;
     }
   }
 
+  private static void maybeInitializeBeforeCloseHandlers() {
+    if (GWT.isClient() && !beforeCloseHandlersInitialized) {
+      impl.initWindowBeforeUnloadHandler();
+      beforeCloseHandlersInitialized = true;
+    }
+  }
+
   private static void maybeInitializeResizeHandlers() {
     if (GWT.isClient() && !resizeHandlersInitialized) {
       impl.initWindowResizeHandler();

user/src/com/google/gwt/user/client/impl/WindowImpl.java

@@ -29,11 +29,30 @@ public native String getHash() /*-{
   public native String getQueryString() /*-{
     return $wnd.location.search;
   }-*/;
-
-  public native void initWindowCloseHandler() /*-{
+
+  @Deprecated
+  public void initWindowCloseHandler() {
+    initWindowUnloadHandler();
+    initWindowBeforeUnloadHandler();
+  }
+
+  @Deprecated
+  public native void initWindowUnloadHandler() /*-{
+    var oldOnUnload = $wnd.onunload;
+
+    $wnd.onunload = $entry(function(evt) {
+      try {
+        @com.google.gwt.user.client.Window::onClosed()();
+      } finally {
+        oldOnUnload && oldOnUnload(evt);
+        $wnd.onunload = null;
+      }
+    });
+  }-*/;
+
+  public native void initWindowBeforeUnloadHandler() /*-{
     var oldOnBeforeUnload = $wnd.onbeforeunload;
-    var oldOnUnload =  $wnd.onunload;
-
+
     // Old mozilla doesn't like $entry's explicit return statement and
     // will always pop up a confirmation dialog.  This is worked around by
     // just wrapping the call to onClosing(), which still has the semantics
@@ -55,18 +74,6 @@ public native void initWindowCloseHandler() /*-{
       }
       // returns undefined.
     };
-
-    $wnd.onunload = $entry(function(evt) {
-      try {
-        @com.google.gwt.user.client.Window::onClosed()();
-      } finally {
-        oldOnUnload && oldOnUnload(evt);
-        $wnd.onresize = null;
-        $wnd.onscroll = null;
-        $wnd.onbeforeunload = null;
-        $wnd.onunload = null;
-      }
-    });
   }-*/;
 
   public native void initWindowResizeHandler() /*-{

user/src/com/google/gwt/user/client/ui/Anchor.java

@@ -73,7 +73,7 @@ public class Anchor extends FocusWidget implements HasHorizontalAlignment,
    * 
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    * 
    * @param element the element to be wrapped
    */

user/src/com/google/gwt/user/client/ui/Button.java

@@ -47,7 +47,7 @@ public class Button extends ButtonBase {
    * 
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    * 
    * @param element the element to be wrapped
    */

user/src/com/google/gwt/user/client/ui/FileUpload.java

@@ -54,7 +54,7 @@ public class FileUpload extends FocusWidget implements HasName, HasChangeHandler
    * 
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    * 
    * @param element the element to be wrapped
    */

user/src/com/google/gwt/user/client/ui/FormPanel.java

@@ -253,7 +253,7 @@ interface IFrameTemplate extends SafeHtmlTemplates {
    *
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    *
    * <p>
    * The specified form element's target attribute will not be set, and the
@@ -280,7 +280,7 @@ public static FormPanel wrap(Element element) {
    *
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    *
    * <p>
    * If the createIFrame parameter is set to <code>true</code>, then the wrapped

user/src/com/google/gwt/user/client/ui/Frame.java

@@ -52,7 +52,7 @@ public class Frame extends Widget implements HasLoadHandlers {
    * 
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    * 
    * @param element the element to be wrapped
    */

user/src/com/google/gwt/user/client/ui/HTML.java

@@ -61,7 +61,7 @@ public class HTML extends Label
    *
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    *
    * @param element the element to be wrapped
    */

user/src/com/google/gwt/user/client/ui/HTMLPanel.java

@@ -50,7 +50,7 @@ public static String createUniqueId() {
    *
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    *
    * @param element the element to be wrapped
    */

user/src/com/google/gwt/user/client/ui/Hidden.java

@@ -34,7 +34,7 @@ public class Hidden extends Widget implements HasName, TakesValue<String>, IsEdi
    * 
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    * 
    * @param element the element to be wrapped
    */

user/src/com/google/gwt/user/client/ui/Image.java

@@ -484,7 +484,7 @@ public static void prefetch(SafeUri url) {
    * 
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    * 
    * @param element the element to be wrapped
    */

user/src/com/google/gwt/user/client/ui/InlineHTML.java

@@ -55,7 +55,7 @@ public class InlineHTML extends HTML {
    *
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    *
    * @param element the element to be wrapped
    */

user/src/com/google/gwt/user/client/ui/InlineLabel.java

@@ -46,7 +46,7 @@ public class InlineLabel extends Label {
    *
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    *
    * @param element the element to be wrapped
    */

user/src/com/google/gwt/user/client/ui/Label.java

@@ -115,7 +115,7 @@ public class Label extends LabelBase<String> implements HasDirectionalText,
    *
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    *
    * @param element the element to be wrapped
    */

user/src/com/google/gwt/user/client/ui/ListBox.java

@@ -99,7 +99,7 @@ public class ListBox extends FocusWidget implements SourcesChangeEvents,
    * 
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    * 
    * @param element the element to be wrapped
    * @return list box

user/src/com/google/gwt/user/client/ui/PasswordTextBox.java

@@ -46,7 +46,7 @@ public class PasswordTextBox extends TextBox {
    * 
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    * 
    * @param element the element to be wrapped
    */

user/src/com/google/gwt/user/client/ui/ResetButton.java

@@ -38,7 +38,7 @@ public class ResetButton extends Button {
    * 
    * This element must already be attached to the document. If the element is
    * removed from the document, you must call
-   * {@link RootPanel#detachNow(Widget)}.
+   * {@link Widget#removeFromParent()}.
    * 
    * @param element the element to be wrapped
    */

user/src/com/google/gwt/user/client/ui/RootPanel.java

@@ -18,13 +18,10 @@
 import com.google.gwt.dom.client.BodyElement;
 import com.google.gwt.dom.client.Document;
 import com.google.gwt.dom.client.Element;
-import com.google.gwt.event.logical.shared.CloseEvent;
-import com.google.gwt.event.logical.shared.CloseHandler;
 import com.google.gwt.i18n.client.BidiUtils;
 import com.google.gwt.i18n.client.HasDirection;
 import com.google.gwt.i18n.client.LocaleInfo;
 import com.google.gwt.user.client.Event;
-import com.google.gwt.user.client.Window;
 
 import java.util.HashMap;
 import java.util.HashSet;
@@ -92,11 +89,13 @@ public void execute(Widget w) {
    * This method may only be called per widget, and only for widgets that were
    * originally passed to {@link #detachOnWindowClose(Widget)}.
    * </p>
-   * 
+   *
    * @param widget the widget that no longer needs to be cleaned up when the
    *          page closes
    * @see #detachOnWindowClose(Widget)
+   * @deprecated Instead, use {@link Widget#removeFromParent()}.
    */
+  @Deprecated
   public static void detachNow(Widget widget) {
     assert widgetsToDetach.contains(widget) : "detachNow() called on a widget "
         + "not currently in the detach list";
@@ -111,25 +110,30 @@ public static void detachNow(Widget widget) {
   /**
    * Adds a widget to the detach list. This is the list of widgets to be
    * detached when the page unloads.
-   * 
+   *
    * <p>
    * This method must be called for all widgets that have no parent widgets.
    * These are most commonly {@link RootPanel RootPanels}, but can also be any
    * widget used to wrap an existing element on the page. Failing to do this may
    * cause these widgets to leak memory. This method is called automatically by
    * widgets' wrap methods (e.g.
-   * {@link Button#wrap(com.google.gwt.dom.client.Element)}).
+   * {@link Button#wrap(Element)}).
    * </p>
-   * 
+   *
    * <p>
    * This method may <em>not</em> be called on any widget whose element is
    * contained in another widget. This is to ensure that the DOM and Widget
    * hierarchies cannot get into an inconsistent state.
    * </p>
-   * 
+   *
    * @param widget the widget to be cleaned up when the page closes
    * @see #detachNow(Widget)
+   * @deprecated While originally introduced to combat memory leaks in old browsers, this is no
+   * longer necessary, and the unload event used by this method is being removed from browsers.
+   * Additionally, it is unreliable as a means to ensure calls to {@link Widget#onUnload()}. See
+   * <a href="https://github.com/gwtproject/gwt/issues/9908">Issue 9908</a> for more information.
    */
+  @Deprecated
   public static void detachOnWindowClose(Widget widget) {
     assert !widgetsToDetach.contains(widget) : "detachOnUnload() called twice "
         + "for the same widget";
@@ -188,8 +192,6 @@ public static RootPanel get(String id) {
     // on the first RootPanel.get(String) or RootPanel.get()
     // call.
     if (rootPanels.size() == 0) {
-      hookWindowClosing();
-
       // If we're in a RTL locale, set the RTL directionality
       // on the entire document.
       if (LocaleInfo.getCurrentLocale().isRTL()) {
@@ -223,16 +225,37 @@ public static native com.google.gwt.user.client.Element getBodyElement() /*-{
 
   /**
    * Determines whether the given widget is in the detach list.
-   * 
+   * <p>
+   * Note that modern browsers do not have the memory leaks that originally required use of this
+   * feature - it is retained only to support application-specific detach events.
+   * </p>
+   *
    * @param widget the widget to be checked
    * @return <code>true</code> if the widget is in the detach list
+   * @deprecated Use of the detach list requires the unload event, which is planned to be removed
+   * in future browser updates. See notice on {@link #detachOnWindowClose(Widget)} and
+   * <a href="https://github.com/gwtproject/gwt/issues/9908">Issue 9908</a> for more information.
    */
+  @Deprecated
   public static boolean isInDetachList(Widget widget) {
     return widgetsToDetach.contains(widget);
   }
 
-  // Package-protected for use by unit tests. Do not call this method directly.
-  static void detachWidgets() {
+  /**
+   * Detaches all widgets that were set to be detached on window close by a call to
+   * {@link #detachOnWindowClose}. Formerly was package-protected, now can be called by projects
+   * that required the old behavior and are willing to set up their own onclose handler on the
+   * window.
+   * <p>
+   * Note that modern browsers do not have the memory leaks that originally required use of this
+   * feature - it is retained only to support application-specific detach events.
+   * </p>
+   *
+   * @deprecated See notice on {@link #detachOnWindowClose(Widget)} and
+   * <a href="https://github.com/gwtproject/gwt/issues/9908">Issue 9908</a> for more information.
+   */
+  @Deprecated
+  public static void detachWidgets() {
     // When the window is closing, detach all widgets that need to be
     // cleaned up. This will cause all of their event listeners
     // to be unhooked, which will avoid potential memory leaks.
@@ -258,15 +281,6 @@ private static native Element getRootElement() /*-{
     return $doc;
   }-*/;
 
-  private static void hookWindowClosing() {
-    // Catch the window closing event.
-    Window.addCloseHandler(new CloseHandler<Window>() {
-      public void onClose(CloseEvent<Window> closeEvent) {
-        detachWidgets();
-      }
-    });
-  }
-
   /*
    * Checks to see whether the given element has any parent element that
    * belongs to a widget. This is not terribly efficient, and is thus only used