Limit the tooltip size of calculation trails to 50 lines

If the trail contains too many items, it becomes very slow and anyway
can only show part of the calculation. One could think of more
meaningful ways to condense the display, but this change just cuts
of the display after 50 lines.

Issue: #3225

name.abuchen.portfolio.ui/src/name/abuchen/portfolio/ui/util/MoneyTrailDataSource.java

@@ -3,6 +3,7 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Optional;
 
 import org.eclipse.jface.layout.GridDataFactory;
 import org.eclipse.jface.layout.GridLayoutFactory;
@@ -40,17 +41,40 @@ public Composite createPlainComposite(Composite parent)
         heading.setText(trail.getLabel());
         GridDataFactory.fillDefaults().span(depth + 3, 1).applyTo(heading);
 
-        addRow(composite, trail.getRecord(), depth - 1, depth);
+        // if the trail contains too many items, it becomes very slow and anyway
+        // can only show part of the calculation. With this variable, we limit
+        // the number of rows to be created and rendered
+        int[] rowsToCreate = new int[] { 50 };
+
+        addRow(rowsToCreate, composite, trail.getRecord(), depth - 1, depth);
+
+        if (rowsToCreate[0] < 0)
+        {
+            Label info = new Label(composite, SWT.NONE);
+            info.setBackground(composite.getBackground());
+            info.setText("..."); //$NON-NLS-1$
+            GridDataFactory.fillDefaults().span(depth + 3, 1).applyTo(info);
+        }
 
         return composite;
     }
 
-    private Label addRow(Composite composite, TrailRecord trail, int level, int depth)
+    private Optional<Label> addRow(int[] rowsToCreate, Composite composite, TrailRecord trail, int level, int depth)
     {
         List<Label> inputs = new ArrayList<>();
 
         for (TrailRecord child : trail.getInputs())
-            inputs.add(addRow(composite, child, level - 1, depth));
+            addRow(rowsToCreate, composite, child, level - 1, depth).ifPresent(inputs::add);
+
+        if (rowsToCreate[0] <= 0)
+        {
+            // in order to show a message that rows are missing, we need to know
+            // that trail did not just accidentally fit into the limit
+            rowsToCreate[0] = -10;
+            return Optional.empty();
+        }
+
+        rowsToCreate[0]--;
 
         Label date = new Label(composite, SWT.NONE);
         date.setBackground(composite.getBackground());
@@ -85,7 +109,7 @@ private Label addRow(Composite composite, TrailRecord trail, int level, int dept
             }
         }
 
-        return answer;
+        return Optional.of(answer);
     }
 
     private void highlight(List<Label> outputs, List<Label> inputs)