org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/ApplicationActiveListener.java

   1 /*******************************************************************************
   2  * Copyright (c) 2021 Thomas Wolf <thomas.wolf@paranor.ch> and others.
   3  *
   4  * All rights reserved. This program and the accompanying materials
   5  * are made available under the terms of the Eclipse Public License 2.0
   6  * which accompanies this distribution, and is available at
   7  * https://www.eclipse.org/legal/epl-2.0/
   8  *
   9  * SPDX-License-Identifier: EPL-2.0
  10  *
  11  * Contributors:
  12  *    Thomas Wolf - factored out of Activator
  13  *******************************************************************************/
  14 package org.eclipse.egit.ui.internal;
  15
  16 import org.eclipse.e4.core.services.events.IEventBroker;
  17 import org.eclipse.e4.ui.workbench.UIEvents;
  18 import org.eclipse.swt.SWTException;
  19 import org.eclipse.swt.widgets.Display;
  20 import org.eclipse.ui.IWindowListener;
  21 import org.eclipse.ui.IWorkbenchWindow;
  22 import org.eclipse.ui.PlatformUI;
  23 import org.osgi.service.component.annotations.Component;
  24 import org.osgi.service.component.annotations.Deactivate;
  25 import org.osgi.service.event.Event;
  26 import org.osgi.service.event.EventConstants;
  27 import org.osgi.service.event.EventHandler;
  28
  29 /**
  30  * Determines whether any shell of the application is active and fires an event
  31  * when the value changes.
  32  */
  33 @Component(property = {
  34                 EventConstants.EVENT_TOPIC + '='
  35                                 + UIEvents.UILifeCycle.APP_STARTUP_COMPLETE,
  36                 EventConstants.EVENT_TOPIC + '='
  37                                 + UIEvents.UILifeCycle.APP_SHUTDOWN_STARTED })
  38 public class ApplicationActiveListener implements EventHandler {
  39
  40         /**
  41          * Event topic for the events posted by this component.
  42          */
  43         public static final String TOPIC_APPLICATION_ACTIVE = "org/eclipse/egit/ui/APPLICATION_ACTIVE"; //$NON-NLS-1$
  44
  45         private volatile WindowTracker listener;
  46
  47         @Override
  48         public void handleEvent(Event event) {
  49                 String topic = event.getTopic();
  50                 if (topic == null) {
  51                         return;
  52                 }
  53                 switch (topic) {
  54                 case UIEvents.UILifeCycle.APP_STARTUP_COMPLETE:
  55                         if (listener == null) {
  56                                 listener = new WindowTracker();
  57                                 listener.update();
  58                                 PlatformUI.getWorkbench().addWindowListener(listener);
  59                         }
  60                         break;
  61                 case UIEvents.UILifeCycle.APP_SHUTDOWN_STARTED:
  62                         shutDown();
  63                         break;
  64                 default:
  65                         break;
  66                 }
  67         }
  68
  69         @Deactivate
  70         void shutDown() {
  71                 if (listener != null) {
  72                         PlatformUI.getWorkbench().removeWindowListener(listener);
  73                         listener = null;
  74                 }
  75         }
  76
  77         private static class WindowTracker implements IWindowListener {
  78
  79                 private boolean isActive;
  80
  81                 void update() {
  82                         if (PlatformUI.isWorkbenchRunning()) {
  83                                 Display display = PlatformUI.getWorkbench().getDisplay();
  84                                 if (display != null && !display.isDisposed()) {
  85                                         try {
  86                                                 display.asyncExec(() -> {
  87                                                         boolean wasActive = isActive;
  88                                                         isActive = !display.isDisposed()
  89                                                                         && display.getActiveShell() != null;
  90                                                         if (wasActive != isActive) {
  91                                                                 notify(isActive);
  92                                                         }
  93                                                 });
  94                                         } catch (SWTException e) {
  95                                                 // Silently ignore -- display was disposed already
  96                                         }
  97                                 }
  98                         }
  99                 }
 100
 101                 private void notify(boolean active) {
 102                         if (PlatformUI.isWorkbenchRunning()) {
 103                                 IEventBroker broker = PlatformUI.getWorkbench()
 104                                                 .getService(IEventBroker.class);
 105                                 if (broker != null) {
 106                                         broker.post(TOPIC_APPLICATION_ACTIVE,
 107                                                         Boolean.valueOf(active));
 108                                 }
 109                         }
 110                 }
 111
 112                 @Override
 113                 public void windowActivated(IWorkbenchWindow window) {
 114                         update();
 115                 }
 116
 117                 @Override
 118                 public void windowDeactivated(IWorkbenchWindow window) {
 119                         update();
 120                 }
 121
 122                 @Override
 123                 public void windowClosed(IWorkbenchWindow window) {
 124                         update();
 125                 }
 126
 127                 @Override
 128                 public void windowOpened(IWorkbenchWindow window) {
 129                         update();
 130                 }
 131         }
 132 }