--- a/flys-client/ChangeLog	Thu Oct 13 12:30:08 2011 +0000
+++ b/flys-client/ChangeLog	Thu Oct 13 12:34:46 2011 +0000
@@ -1,3 +1,15 @@
+2011-10-13	Felix Wolfsteller	<felix.wolfsteller@intevation.de>
+
+	In W-Diff selection GUI, track which items have been removed from the
+	listgrid, remove corresponding artifacts from collection if they are
+	not needed anymore using the new RemoveArtifactService.
+
+	* src/main/java/de/intevation/flys/client/client/ui/DatacageTwinPanel.java:
+	  Track removed items from ListGrid until clicking on "proceed". Then,
+	  check whether artifacts removed from the list are still needed to
+	  calculate other difference (which are still in the ListGrid), remove
+	  them otherwise.
+
 2011-10-13	Felix Wolfsteller	<felix.wolfsteller@intevation.de>
 
 	Added helper in use of new RemoveArtifactService.

--- a/flys-client/src/main/java/de/intevation/flys/client/client/ui/DatacageTwinPanel.java	Thu Oct 13 12:30:08 2011 +0000
+++ b/flys-client/src/main/java/de/intevation/flys/client/client/ui/DatacageTwinPanel.java	Thu Oct 13 12:34:46 2011 +0000
@@ -8,16 +8,20 @@
 import com.google.gwt.core.client.GWT;
 import com.google.gwt.user.client.rpc.AsyncCallback;
 
+import com.smartgwt.client.data.Record;
+import com.smartgwt.client.types.ListGridFieldType;
 import com.smartgwt.client.widgets.Canvas;
-import com.smartgwt.client.widgets.Label;
 import com.smartgwt.client.widgets.layout.HLayout;
 import com.smartgwt.client.widgets.layout.VLayout;
 import com.smartgwt.client.widgets.grid.ListGrid;
 import com.smartgwt.client.widgets.grid.ListGridField;
 import com.smartgwt.client.widgets.grid.ListGridRecord;
 import com.smartgwt.client.widgets.events.ClickEvent;
+import com.smartgwt.client.widgets.grid.events.RecordClickEvent;
+import com.smartgwt.client.widgets.grid.events.RecordClickHandler;
 
 import de.intevation.flys.client.shared.model.Artifact;
+import de.intevation.flys.client.shared.model.Collection;
 import de.intevation.flys.client.shared.model.Data;
 import de.intevation.flys.client.shared.model.DataItem;
 import de.intevation.flys.client.shared.model.DefaultData;
@@ -28,13 +32,14 @@
 import de.intevation.flys.client.client.FLYSConstants;
 import de.intevation.flys.client.client.event.StepForwardEvent;
 import de.intevation.flys.client.shared.model.Recommendation;
-import de.intevation.flys.client.shared.model.ToLoad;
 import de.intevation.flys.client.shared.model.Recommendation.Facet;
 import de.intevation.flys.client.shared.model.Recommendation.Filter;
 
+import de.intevation.flys.client.client.Config;
 import de.intevation.flys.client.client.services.LoadArtifactService;
 import de.intevation.flys.client.client.services.LoadArtifactServiceAsync;
-import de.intevation.flys.client.client.Config;
+import de.intevation.flys.client.client.services.RemoveArtifactService;
+import de.intevation.flys.client.client.services.RemoveArtifactServiceAsync;
 
 // TODO Probably better to branch off AbstractUIProvider.
 // TODO Merge with other datacage-widget impls.
@@ -51,11 +56,23 @@
 
     protected User user;
 
+    /** ListGrid that displays user-selected pairs to build differences with. */
     protected ListGrid differencesList;
 
+    /*
+     * List to track previously selected but now removed pairs. (Needed to
+     * be able to identify artifacts that can be removed from the collection.
+     */
+    protected List<RecommendationPairRecord> removedPairs =
+        new ArrayList<RecommendationPairRecord>();
+
+    /** Service handle to clone and add artifacts to collection. */
     LoadArtifactServiceAsync loadArtifactService = GWT.create(
             de.intevation.flys.client.client.services.LoadArtifactService.class);
 
+    /** Service to remove artifacts from collection. */
+    RemoveArtifactServiceAsync removeArtifactService = GWT.create(
+            de.intevation.flys.client.client.services.RemoveArtifactService.class);
 
     public DatacageTwinPanel(User user) {
         super();
@@ -170,6 +187,7 @@
 
     /**
      * Validates the selection.
+     * @return List of internationalized errror messages (if any).
      */
     @Override
     public List<String> validate() {
@@ -197,22 +215,50 @@
         differencesList = new ListGrid();
 
         differencesList.setCanEdit(false);
-        differencesList.setCanRemoveRecords(true);
         differencesList.setCanSort(false);
         differencesList.setHeight(150);
         differencesList.setShowAllRecords(true);
 
         ListGridField nameField    = new ListGridField("first",  "Minuend");
         ListGridField capitalField = new ListGridField("second", "Subtrahend");
+        // Track removed rows, therefore more or less reimplement
+        // setCanRecomeRecords.
+        final ListGridField removeField  =
+            new ListGridField("_removeRecord", "Remove Record"){{
+                setType(ListGridFieldType.ICON);
+                setIcon("[SKIN]/actions/remove.png");
+                setCanEdit(false);
+                setCanFilter(false);
+                setCanSort(false);
+                setCanGroupBy(false);
+                setCanFreeze(false);
+                setWidth(25);
+        }};
+
         differencesList.setFields(new ListGridField[] {nameField,
-           capitalField});
-
+           capitalField, removeField});
+        
+        differencesList.addRecordClickHandler(new RecordClickHandler() {
+                public void onRecordClick(final RecordClickEvent event) {
+                    // Just handle remove-clicks
+                    if(!event.getField().getName().equals(removeField.getName())) {
+                        return;
+                    }    
+                    trackRemoved(event.getRecord());
+                    event.getViewer().removeData(event.getRecord());
+                }
+            });
         layout.addMember(differencesList);
 
         return layout;
     }
 
 
+    public void trackRemoved(Record r) {
+        RecommendationPairRecord pr = (RecommendationPairRecord) r;
+        this.removedPairs.add(pr);
+    }
+
     /**
      * Validates data, does nothing if invalid, otherwise clones new selected
      * waterlevels and add them to collection, forward the artifact.
@@ -230,10 +276,6 @@
         Config config = Config.getInstance();
         ListGridRecord[] records = differencesList.getRecords();
 
-        // TODO Problem when same facet participates in two diffs.
-        //
-        // Resolve whether "new" ones were already cloned.
-
         List<Recommendation> ar  = new ArrayList<Recommendation>();
         List<Recommendation> all = new ArrayList<Recommendation>();
         for (ListGridRecord record : records) {
@@ -252,6 +294,51 @@
 
         final Recommendation[] toClone = ar.toArray(new Recommendation[ar.size()]);
         final Recommendation[] toUse   = all.toArray(new Recommendation[all.size()]);
+
+        // Find out whether "old" artifacts have to be removed.
+        List<String> artifactIdsToRemove = new ArrayList<String>();
+        for (RecommendationPairRecord rp: this.removedPairs) {
+            Recommendation first  = rp.getFirst();
+            Recommendation second = rp.getSecond();
+
+            for (Recommendation recommendation: toUse) {
+                if (first != null && first.getIDs().equals(recommendation.getIDs())) {
+                    first = null;
+                }
+                if (second != null && second.getIDs().equals(recommendation.getIDs())) {
+                    second = null;
+                }
+
+                if (first == null && second == null) {
+                    break;
+                }
+            }
+            if (first != null) {
+                artifactIdsToRemove.add(first.getIDs());
+            }
+            if (second != null) {
+                artifactIdsToRemove.add(second.getIDs());
+            }
+        }
+
+        // Remove old artifacts, if any. Do this asychronously without much
+        // feedback.
+        for(final String uuid: artifactIdsToRemove) {
+            removeArtifactService.remove(this.collection,
+                uuid,
+                config.getServerUrl(),
+                config.getLocale(),
+                new AsyncCallback<Collection>() {
+                    public void onFailure(Throwable caught) {
+                        GWT.log("RemoveArtifact (" + uuid + ") failed.");
+                    }
+                    public void onSuccess(Collection collection) {
+                        GWT.log("RemoveArtifact succeeded");
+                    }
+                });
+        }
+
+        // Clone new ones, go forward.
         loadArtifactService.loadMany(
               this.collection,
               toClone,
@@ -273,6 +360,9 @@
     }
 
 
+    /**
+     * Create Data and DataItem from selection.
+     */
     protected Data[] getData(
             Recommendation[] newRecommendations,
             Artifact[] newArtifacts,