title: Design view of Eclipse windowbuilder pugin on Windows 8.1 x64 prompts "Unknown GUI toolkit"
body: <p>I was using Eclipse Kepler Release 1 x64, wiht Java 7 x64 on Windows 4 pro x64 and I had no problems with Eclipse WindowBuilder plugin. But since I upgraded to Windows 8.1 pro x64, WindowBuilder has stopped working. </p>
  
  <p>First the follwoing button is freezed and does not respond to user clicks.
  <img src="https://i.stack.imgur.com/lMPgF.png" alt="enter image description here"></p>
  
  <p>And if in project explorer I go to some java file that I have already created with WindowBuilder plugin in windows 7 x64, right click on it and choose: <em>Open with > WindowBuilder Editor</em>, source code opens fine, but when I switch to <em>Design</em> view, I get <code>Unknown GUI toolkit</code>.
  <img src="https://i.stack.imgur.com/wKU3I.png" alt="enter image description here"></p>
  
  <p>Stacktrace:</p>
  
  <pre><code>org.eclipse.wb.internal.core.utils.exception.DesignerException: 103 (Unknown GUI toolkit). guis.UsersAll
  at org.eclipse.wb.internal.core.parser.JavaInfoParser.prepareParseContext(JavaInfoParser.java:1195)
  at org.eclipse.wb.internal.core.parser.JavaInfoParser.parse(JavaInfoParser.java:242)
  at org.eclipse.wb.internal.core.parser.JavaInfoParser.access$9(JavaInfoParser.java:238)
  at org.eclipse.wb.internal.core.parser.JavaInfoParser$1.runObject(JavaInfoParser.java:153)
  at org.eclipse.wb.internal.core.parser.JavaInfoParser$1.runObject(JavaInfoParser.java:1)
  at org.eclipse.wb.internal.core.utils.execution.ExecutionUtils.runDesignTime(ExecutionUtils.java:159)
  at org.eclipse.wb.internal.core.parser.JavaInfoParser.parse(JavaInfoParser.java:151)
  at org.eclipse.wb.internal.core.editor.DesignPage.internal_refreshGEF(DesignPage.java:534)
  at org.eclipse.wb.internal.core.editor.DesignPage.access$9(DesignPage.java:522)
  at org.eclipse.wb.internal.core.editor.DesignPage$8$1.run(DesignPage.java:449)
  at org.eclipse.swt.widgets.Synchronizer.syncExec(Synchronizer.java:180)
  at org.eclipse.ui.internal.UISynchronizer.syncExec(UISynchronizer.java:150)
  at org.eclipse.swt.widgets.Display.syncExec(Display.java:4688)
  at org.eclipse.wb.internal.core.editor.DesignPage$8.run(DesignPage.java:446)
  at org.eclipse.jface.operation.ModalContext.runInCurrentThread(ModalContext.java:464)
  at org.eclipse.jface.operation.ModalContext.run(ModalContext.java:372)
  at org.eclipse.jface.dialogs.ProgressMonitorDialog.run(ProgressMonitorDialog.java:507)
  at org.eclipse.wb.internal.core.editor.DesignPage.internal_refreshGEF_withProgress(DesignPage.java:465)
  at org.eclipse.wb.internal.core.editor.DesignPage.internal_refreshGEF(DesignPage.java:415)
  at org.eclipse.wb.internal.core.editor.UndoManager.refreshDesignerEditor(UndoManager.java:381)
  at org.eclipse.wb.internal.core.editor.UndoManager.activate(UndoManager.java:90)
  at org.eclipse.wb.internal.core.editor.DesignPage.handleActiveState_True(DesignPage.java:263)
  at org.eclipse.wb.internal.core.editor.DesignPage.handleActiveState(DesignPage.java:241)
  at org.eclipse.wb.internal.core.editor.multi.DefaultMultiMode.showPage(DefaultMultiMode.java:125)
  at org.eclipse.wb.internal.core.editor.multi.DefaultMultiMode$1.widgetSelected(DefaultMultiMode.java:63)
  at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:248)
  at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
  at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1057)
  at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1081)
  at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1066)
  at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:778)
  at org.eclipse.swt.custom.CTabFolder.setSelection(CTabFolder.java:3080)
  at org.eclipse.swt.custom.CTabFolder.onMouse(CTabFolder.java:1772)
  at org.eclipse.swt.custom.CTabFolder$1.handleEvent(CTabFolder.java:279)
  at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
  at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1057)
  at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4170)
  at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3759)
  at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:1113)
  at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
  at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:997)
  at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:138)
  at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:610)
  at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
  at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:567)
  at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:150)
  at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:124)
  at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
  at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
  at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
  at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:354)
  at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:181)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
  at java.lang.reflect.Method.invoke(Unknown Source)
  at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:636)
  at org.eclipse.equinox.launcher.Main.basicRun(Main.java:591)
  at org.eclipse.equinox.launcher.Main.run(Main.java:1450)
  at org.eclipse.equinox.launcher.Main.main(Main.java:1426)
  </code></pre>
  
  <p>So can anyone tell me how to get WindowBuilder work on Eclipse on Windows 8.1 pro x64?</p>