Add more context information to criteriaScript in GridDropTargetConnector (#11321)

* Add more context information to criteriaScript in GridDropTargetConnector

When using drag and drop in Grids and TreeGrids a criteriaScript can be specified.
However, this criteriaScript only gets an event as input parameter.
It would be helpful if the criteriaScript would get more information:
- the DropLocation
- the targetElement which is used as a base for the DropLocation

This change provides a protected method in DropTargetExtensionConnector
which decides, if the drop is allowed by the criteriaScript.
This method is overriden in GridDropTargetConnector to
provide the both parameters dropLocation and targetElement.

* add Test UI for criteriaScript with targetElement and dropLocation

* add some description for the Test UI

1 files changed, 86 insertions, 0 deletions

diff --git a/uitest/src/main/java/com/vaadin/tests/components/grid/GridDropCriteriaScript.java b/uitest/src/main/java/com/vaadin/tests/components/grid/GridDropCriteriaScript.java
new file mode 100644
index 0000000000..3d036a3d3b
--- /dev/null
+++ b/uitest/src/main/java/com/vaadin/tests/components/grid/GridDropCriteriaScript.java
@@ -0,0 +1,86 @@
+package com.vaadin.tests.components.grid;
+
+import com.vaadin.annotations.Theme;
+import com.vaadin.annotations.Widgetset;
+import com.vaadin.server.VaadinRequest;
+import com.vaadin.shared.ui.ContentMode;
+import com.vaadin.shared.ui.grid.DropLocation;
+import com.vaadin.shared.ui.grid.DropMode;
+import com.vaadin.tests.components.AbstractTestUI;
+import com.vaadin.ui.Grid;
+import com.vaadin.ui.Label;
+import com.vaadin.ui.components.grid.GridDragSource;
+import com.vaadin.ui.components.grid.GridDropTarget;
+
+import java.util.ArrayList;
+import java.util.List;
+
+@Theme("valo")
+@Widgetset("com.vaadin.DefaultWidgetSet")
+public class GridDropCriteriaScript extends AbstractTestUI {
+
+    class GridItem {
+        public final String caption;
+        public final DropLocation dropLocation;
+
+        public GridItem(String caption, DropLocation dropLocation) {
+            this.caption = caption;
+            this.dropLocation = dropLocation;
+        }
+
+        public String getCaption() {
+            return caption;
+        }
+
+        public DropLocation getDropLocation() {
+            return dropLocation;
+        }
+    }
+
+    @Override
+    protected void setup(VaadinRequest request) {
+        getUI().setMobileHtml5DndEnabled(true);
+
+        final Label label = new Label("<h1>Test for existance of targetElement "
+                + "and dropLocation in criteriaScript</h1>"
+                + "<p>Drag one of the grid items.</p>"
+                + "<p>While dragging, hints in form of lines show "
+                + "where the item is allowed to be dropped.</p>"
+                + "<p>Test passed:" + "<ul>"
+                + "<li>ABOVE: Only a line above the item is displayed while dragging over the item</li>"
+                + "<li>BELOW: Only a line below the item is displayed while dragging over the item</li>"
+                + "<li>ON_TOP: Only a border around the item is displayed while dragging over the item</li>"
+                + "</ul>" + "</p>" + "<p>Test failed:" + "<ul>"
+                + "<li>otherwise</li>" + "</ul>" + "</p>", ContentMode.HTML);
+
+        final Grid<GridItem> grid = new Grid<>();
+        grid.addColumn(GridItem::getCaption);
+        grid.setStyleGenerator(
+                gridItem -> "dropLocation-" + gridItem.getDropLocation());
+
+        new GridDragSource<>(grid);
+
+        final GridDropTarget<GridItem> dropTarget = new GridDropTarget<>(grid,
+                DropMode.ON_TOP_OR_BETWEEN);
+        dropTarget.setDropCriteriaScript(
+                "return targetElement.classList.contains('dropLocation-' + dropLocation);");
+
+        grid.setItems(createItems());
+
+        addComponents(label, grid);
+    }
+
+    private List<GridItem> createItems() {
+        final ArrayList<GridItem> list = new ArrayList<>();
+        for (int i = 0; i < 10; i++) {
+            for (DropLocation dropLocation : new DropLocation[] {
+                    DropLocation.ON_TOP, DropLocation.ABOVE,
+                    DropLocation.BELOW }) {
+                list.add(new GridItem(i + ": " + dropLocation.name(),
+                        dropLocation));
+            }
+        }
+        return list;
+    }
+
+}