Shared database synchronized by FocusChangedEvent (#6771)

* Added FocusChangedEvent, fired in BibEntry when setFocusedField is called. Focus is changed in EntryEditor.
CoarseChangeFilter with no special function -> does not work with shared databases.

* Uncomment FieldChangedEvent listener.

* Removed FocusChangedEvent.java due to improper dependencies.
Introduced DelayTaskThrottler on CoarseChangeFilter.

* Delete FocusChangedEvent.java

* Update EntryEditor.java

* Update CoarseChangeFilter.java

* Update CoarseChangeFilter.java

* Update CoarseChangeFilter.java

Co-authored-by: m-mauersberger <nOch.1.G@t!>
Co-authored-by: Tobias Diez <tobiasdiez@gmx.de>

src/main/java/org/jabref/model/database/event/CoarseChangeFilter.java

@@ -1,5 +1,8 @@
 package org.jabref.model.database.event;
 
+import java.util.Optional;
+
+import org.jabref.logic.util.DelayTaskThrottler;
 import org.jabref.model.database.BibDatabaseContext;
 import org.jabref.model.entry.event.FieldChangedEvent;
 import org.jabref.model.entry.field.Field;
@@ -12,30 +15,56 @@
  */
 public class CoarseChangeFilter {
 
-    private final EventBus eventBus = new EventBus();
-    private Field lastFieldChanged;
     private final BibDatabaseContext context;
+    private final EventBus eventBus = new EventBus();
+    private final DelayTaskThrottler delayPost;
+
+    private Optional<Field> lastFieldChanged;
+    private int totalDelta;
 
     public CoarseChangeFilter(BibDatabaseContext bibDatabaseContext) {
         // Listen for change events
         bibDatabaseContext.getDatabase().registerListener(this);
         bibDatabaseContext.getMetaData().registerListener(this);
         this.context = bibDatabaseContext;
+        // Delay event post by 5 seconds
+        this.delayPost = new DelayTaskThrottler(5000);
+        this.lastFieldChanged = Optional.empty();
+        this.totalDelta = 0;
     }
 
     @Subscribe
     public synchronized void listen(@SuppressWarnings("unused") BibDatabaseContextChangedEvent event) {
-        if (!(event instanceof FieldChangedEvent)) {
+        Runnable eventPost = () -> {
+            // Reset total change delta
+            totalDelta = 0;
+            // Post event
             eventBus.post(event);
+        };
+
+        if (!(event instanceof FieldChangedEvent)) {
+            eventPost.run();
         } else {
             // Only relay event if the field changes are more than one character or a new field is edited
             FieldChangedEvent fieldChange = (FieldChangedEvent) event;
-            boolean isEditOnNewField = lastFieldChanged == null || !lastFieldChanged.equals(fieldChange.getField());
+            // Sum up change delta
+            totalDelta += fieldChange.getDelta();
+
+            // If editing is started
+            boolean isNewEdit = lastFieldChanged.isEmpty();
+            // If other field is edited
+            boolean isEditOnOtherField = !lastFieldChanged.get().equals(fieldChange.getField());
+            // Only deltas of 1 registered by fieldChange, major change means editing much content
+            boolean isMajorChange = totalDelta >= 100;
 
-            if (fieldChange.getDelta() > 1 || isEditOnNewField) {
-                lastFieldChanged = fieldChange.getField();
-                eventBus.post(event);
+            if ((isEditOnOtherField && !isNewEdit) || isMajorChange) {
+                // Submit old changes immediately
+                eventPost.run();
+            } else {
+                delayPost.schedule(eventPost);
             }
+            // Set new last field
+            lastFieldChanged = Optional.of(fieldChange.getField());
         }
     }