Avoid overlapping of elements

java/src/main/java/io/process/analytics/tools/bpmn/generator/algo/ShapeLayouter.java

@@ -21,14 +21,24 @@ public Grid layout(SortedDiagram diagram) {
         Grid grid = new Grid();
         for (Shape shape : diagram.getShapes()) {
             Position positionOfCurrentShape = positionShape(diagram, grid, shape);
-            grid.add(positionOfCurrentShape);
+            putOnGrid(grid, positionOfCurrentShape);
             log.debug("Adding {}:\n{}", shape::getName, () -> toAscii(grid));
             addRowsWhenShapeIsASplit(diagram, grid, shape, positionOfCurrentShape);
         }
         compactGrid(grid);
         return grid;
     }
 
+    private void putOnGrid(Grid grid, Position positionOfCurrentShape) {
+        if (grid.isFilled(positionOfCurrentShape)) {
+            //never overlap an element
+            grid.addRowAfter(positionOfCurrentShape.getY());
+            grid.add(positionOfCurrentShape.toBuilder().y(positionOfCurrentShape.getY() + 1).build());
+        } else {
+            grid.add(positionOfCurrentShape);
+        }
+    }
+
     private void addRowsWhenShapeIsASplit(SortedDiagram diagram, Grid grid, Shape shape, Position positionOfCurrentShape) {
         List<Edge> outgoingEdges = diagram.getOutgoingEdges(shape.getId());
         if (outgoingEdges.size() > 1) {

java/src/main/java/io/process/analytics/tools/bpmn/generator/model/Grid.java

@@ -108,4 +108,8 @@ public void removeEmptyRow(int y) {
             positions.add(cellToMove.toBuilder().y(cellToMove.getY() - 1).build());
         }
     }
+
+    public boolean isFilled(Position position) {
+        return positions.stream().anyMatch(p -> p.getX() == position.getX() && p.getY() == position.getY());
+    }
 }

java/src/test/java/io/process/analytics/tools/bpmn/generator/algo/ShapeLayouterTest.java

@@ -306,4 +306,40 @@ public void should_compact_grid_in_order_to_remove_extra_space() {
                 position(end, 4, 1))));
     }
 
+
+    @Test
+    public void should_not_overlap_joins() {
+        //+---------------------+
+        //|step1                |
+        //|step2  step4         |
+        //|              end    |
+        //|       step5         |
+        //|step3                |
+        //+---------------------+
+        SortedDiagram diagram = SortedDiagram.builder()
+                .shape(step1)
+                .shape(step2)
+                .shape(step3)
+                .shape(step4)
+                .shape(step5)
+                .shape(end)
+                .edge(edge(step1, step4))
+                .edge(edge(step2, step5))
+                .edge(edge(step3, step4))
+                .edge(edge(step4, end))
+                .edge(edge(step5, end))
+                .build();
+
+
+        Grid grid = shapeLayouter.layout(diagram);
+
+        assertThat(toAscii(grid)).isEqualTo(toAscii(Grid.of(
+                position(step1, 0, 0),
+                position(step2, 0, 1),
+                position(step3, 0, 4),
+                position(step4, 1, 1),
+                position(step5, 1, 3),
+                position(end, 2, 2))));
+    }
+
 }