fix for PROBPLUGIN-121

de.prob.ui/plugin.xml

@@ -508,12 +508,6 @@
                         value="enabled">
                   </equals>
                </with>
-               <with
-                     variable="de.prob.core.history.backward_service">
-                  <equals
-                        value="enabled">
-                  </equals>
-               </with>
             </and>
          </enabledWhen>
       </handler>
@@ -529,12 +523,6 @@
                   <equals
                         value="enabled">
                   </equals>
-               </with>
-                              <with
-                     variable="de.prob.core.history.forward_service">
-                  <equals
-                        value="enabled">
-                  </equals>
                </with>
             </and>
          </enabledWhen>
@@ -1267,17 +1255,6 @@
                priorityLevel="workbench">
          </variable>
       </sourceProvider>
-      <sourceProvider
-            provider="de.prob.ui.services.HistoryActiveProvider">
-         <variable
-               name="de.prob.core.history.forward_service"
-               priorityLevel="workbench">
-         </variable>
-         <variable
-               name="de.prob.core.history.backward_service"
-               priorityLevel="workbench">
-         </variable>
-      </sourceProvider>
       <sourceProvider
             provider="de.prob.ui.ltl.CounterExampleLoadedProvider">
          <variable

de.prob.ui/src/de/prob/ui/StateBasedViewPart.java

@@ -132,11 +132,7 @@ public abstract class StateBasedViewPart extends ViewPart implements
 		};
 		Display.getDefault().asyncExec(runnable);
 
-		ISourceProviderService service = (ISourceProviderService) getSite()
-				.getService(ISourceProviderService.class);
-		HistoryActiveProvider sourceProvider = (HistoryActiveProvider) service
-				.getSourceProvider(HistoryActiveProvider.FORWARD_SERVICE);
-		sourceProvider.historyChange();
+
 
 	}
 

de.prob.ui/src/de/prob/ui/operationview/HistoryBackHandler.java

@@ -18,12 +18,11 @@ public class HistoryBackHandler extends AbstractHandler implements IHandler {
 		Logger.assertProB("history != null", history != null);
 		int pos = history.getCurrentPosition() - 1;
 		try {
-			pos = Integer
-					.parseInt(event.getParameter("de.prob.ui.history.pos"));
+			pos = Integer.parseInt(event.getParameter("de.prob.ui.history.pos"));
 		} catch (NumberFormatException e) {
 			// one step back
 		}
-		Logger.assertProB("pos >= 0", pos >= 0);
+		if (pos >= 0)
 			try {
 				history.gotoPos(pos);
 			} catch (ProBException e) {

de.prob.ui/src/de/prob/ui/operationview/HistoryForwardHandler.java

@@ -17,12 +17,11 @@ public class HistoryForwardHandler extends AbstractHandler implements IHandler {
 		Logger.assertProB("history != null", history != null);
 		int pos = history.getCurrentPosition() + 1;
 		try {
-			pos = Integer
-					.parseInt(event.getParameter("de.prob.ui.history.pos"));
+			pos = Integer.parseInt(event.getParameter("de.prob.ui.history.pos"));
 		} catch (NumberFormatException e) {
 			// one step back
 		}
-		Logger.assertProB("pos < last position", pos < history.size());
+		if (pos < history.size())
 			try {
 				history.gotoPos(pos);
 			} catch (ProBException e) {