fix ClassCastException during drag-and-drop caused by transient tab state

CHANGELOG.md

@@ -44,6 +44,7 @@ Note that this project **does not** adhere to [Semantic Versioning](https://semv
 
 - We added a fallback for the "Convert to biblatex" cleanup when it failed to populate the `date` field if `year` contained a full date in ISO format (e.g., `2011-11-11`). [#11868](https://github.com/JabRef/jabref/issues/11868)
 - We fixed an issue where directory check for relative path was not handled properly under library properties. [#13017](https://github.com/JabRef/jabref/issues/13017)
+- We fixed an exception on tab dragging. [#12921](https://github.com/JabRef/jabref/issues/12921)
 - We fixed an issue where the option for which method to use when parsing plaintext citations was unavailable in the 'Create New Entry' tool. [#8808](https://github.com/JabRef/jabref/issues/8808)
 - We fixed an issue where the "Make/Sync bibliography" button in the OpenOffice/LibreOffice sidebar was not enabled when a jstyle was selected. [#13055](https://github.com/JabRef/jabref/pull/13055)
 - We fixed an issue where CSL bibliography title properties would be saved even if the "Modify bibliography title" dialog was closed without pressing the "OK" button. [#13074](https://github.com/JabRef/jabref/pull/13074)

jabgui/src/main/java/org/jabref/gui/frame/JabRefFrame.java

@@ -15,7 +15,6 @@
 import javafx.beans.value.ObservableValue;
 import javafx.collections.ListChangeListener;
 import javafx.collections.ObservableList;
-import javafx.collections.transformation.FilteredList;
 import javafx.event.Event;
 import javafx.geometry.Orientation;
 import javafx.scene.control.ContextMenu;
@@ -374,13 +373,7 @@ private void initKeyBindings() {
     }
 
     private void initBindings() {
-        // Bind global state
-        FilteredList<Tab> filteredTabs = new FilteredList<>(tabbedPane.getTabs());
-        filteredTabs.setPredicate(LibraryTab.class::isInstance);
-
-        // This variable cannot be inlined, since otherwise the list created by EasyBind is being garbage collected
-        openDatabaseList = EasyBind.map(filteredTabs, tab -> ((LibraryTab) tab).getBibDatabaseContext());
-        EasyBind.bindContent(stateManager.getOpenDatabases(), openDatabaseList);
+        BindingsHelper.bindContentFiltered(tabbedPane.getTabs(), stateManager.getOpenDatabases(), LibraryTab.class::isInstance);
 
         // the binding for stateManager.activeDatabaseProperty() is at org.jabref.gui.LibraryTab.onDatabaseLoadingSucceed
 

jabgui/src/main/java/org/jabref/gui/util/BindingsHelper.java

@@ -4,6 +4,7 @@
 import java.util.Map;
 import java.util.function.Consumer;
 import java.util.function.Function;
+import java.util.function.Predicate;
 
 import javafx.beans.binding.BooleanBinding;
 import javafx.beans.binding.ObjectBinding;
@@ -19,6 +20,10 @@
 import javafx.collections.ObservableMap;
 import javafx.css.PseudoClass;
 import javafx.scene.Node;
+import javafx.scene.control.Tab;
+
+import org.jabref.gui.LibraryTab;
+import org.jabref.model.database.BibDatabaseContext;
 
 import com.tobiasdiez.easybind.EasyBind;
 import com.tobiasdiez.easybind.PreboundBinding;
@@ -189,6 +194,63 @@ public static <T> Subscription subscribeFuture(ObservableValue<T> observable, Co
         return () -> observable.removeListener(listener);
     }
 
+    public static void bindContentFiltered(ObservableList<Tab> source, ObservableList<BibDatabaseContext> target, Predicate<Tab> filter) {
+        // FIXME: See https://github.com/JabRef/jabref-koppor/pull/713 - workaround in place until issue is resolved.
+        // Original code used FilteredList and EasyBind to filter and map tabs directly:
+        // FilteredList<Tab> filteredTabs = new FilteredList<>(tabbedPane.getTabs());
+        // filteredTabs.setPredicate(LibraryTab.class::isInstance);
+        // openDatabaseList = EasyBind.map(filteredTabs, tab -> ((LibraryTab) tab).getBibDatabaseContext());
+        // EasyBind.bindContent(stateManager.getOpenDatabases(), openDatabaseList);
+        // Once JabRef#713 is fixed, remove this comment and the bindContentFiltered() method, and restore the original code
+
+        Function<Tab, BibDatabaseContext> tabToContext = tab -> ((LibraryTab) tab).getBibDatabaseContext();
+        // Initial sync
+        target.setAll(source.stream()
+                            .filter(filter)
+                            .map(tabToContext)
+                            .toList());
+
+        source.addListener((ListChangeListener<Tab>) change -> {
+            while (change.next()) {
+                if (change.wasPermutated()) {
+                    // We need a fresh copy as permutation is much harder to mirror
+                    List<BibDatabaseContext> reordered = source.stream()
+                                                               .filter(filter)
+                                                               .map(tabToContext)
+                                                               .toList();
+                    target.setAll(reordered);
+                }
+
+                if (change.wasRemoved()) {
+                    for (Tab removed : change.getRemoved()) {
+                        if (filter.test(removed)) {
+                            target.remove(tabToContext.apply(removed));
+                        }
+                    }
+                }
+
+                if (change.wasAdded()) {
+                    int sourceIndex = change.getFrom();
+                    int targetIndex = 0;
+
+                    // We need to add at the correct place - therefore, we need to find out the correct position
+                    for (int i = 0; i < sourceIndex; i++) {
+                        Tab tab = source.get(i);
+                        if (filter.test(tab)) {
+                            targetIndex++;
+                        }
+                    }
+
+                    for (Tab added : change.getAddedSubList()) {
+                        if (filter.test(added)) {
+                            target.add(targetIndex++, tabToContext.apply(added));
+                        }
+                    }
+                }
+            }
+        });
+    }
+
     private static class BidirectionalBinding<A, B> {
 
         private final ObservableValue<A> propertyA;