Add documentation on GridDragger (#10328)

This pathc also switches GridDragger to by default not allow drops on rows when the
grid has been sorted.

2 files changed, 38 insertions, 0 deletions

diff --git a/server/src/test/java/com/vaadin/tests/server/component/grid/GridDraggerOneGridTest.java b/server/src/test/java/com/vaadin/tests/server/component/grid/GridDraggerOneGridTest.java
index 6d24020e45..24e72566f4 100644
--- a/server/src/test/java/com/vaadin/tests/server/component/grid/GridDraggerOneGridTest.java
+++ b/server/src/test/java/com/vaadin/tests/server/component/grid/GridDraggerOneGridTest.java
@@ -45,6 +45,7 @@ public class GridDraggerOneGridTest {
     @Before
     public void setupListCase() {
         source = new Grid<>();
+        source.addColumn(s -> s).setId("1");
         dragger = new TestGridDragger(source);
     }
 
@@ -203,4 +204,23 @@ public class GridDraggerOneGridTest {
         verifyDataProvider("1", "0", "2", "4", "3");
     }
 
+    @Test
+    public void dropOnSortedGrid_byDefault_dropsToTheEnd() {
+        Assert.assertFalse(
+                "Default drops on sorted grid rows should not be allowed",
+                dragger.getGridDropTarget().isDropAllowedOnSortedGridRows());
+
+        source.setItems("0", "1", "2", "3", "4");
+
+        drop("3", DropLocation.BELOW, "1");
+
+        verifyDataProvider("0", "2", "3", "1", "4");
+
+        source.sort("1");
+
+        drop(null, DropLocation.EMPTY, "0");
+
+        verifyDataProvider("2", "3", "1", "4", "0");
+    }
+
 }
diff --git a/server/src/test/java/com/vaadin/tests/server/component/grid/GridDraggerTwoGridsTest.java b/server/src/test/java/com/vaadin/tests/server/component/grid/GridDraggerTwoGridsTest.java
index 0711b711df..c73641097d 100644
--- a/server/src/test/java/com/vaadin/tests/server/component/grid/GridDraggerTwoGridsTest.java
+++ b/server/src/test/java/com/vaadin/tests/server/component/grid/GridDraggerTwoGridsTest.java
@@ -47,6 +47,7 @@ public class GridDraggerTwoGridsTest {
     public void setupListCase() {
         source = new Grid<>();
         target = new Grid<>();
+        target.addColumn(s -> s).setId("1");
         dragger = new TestGridDragger(source, target);
 
         target.setItems(); // setup to use list data provider
@@ -249,4 +250,21 @@ public class GridDraggerTwoGridsTest {
         Assert.assertEquals("given drop index to target updater is wrong", 2,
                 updaterTrigger.get());
     }
+
+    @Test
+    public void dropOnSortedGrid_byDefault_dropsToTheEnd() {
+        Assert.assertFalse(
+                "Default drops on sorted grid rows should not be allowed",
+                dragger.getGridDropTarget().isDropAllowedOnSortedGridRows());
+
+        source.setItems("0", "1", "2");
+        target.setItems("4", "5");
+
+        target.sort("1");
+
+        drop(null, DropLocation.EMPTY, "0");
+
+        verifySourceDataProvider("1", "2");
+        verifyTargetDataProvider("4", "5", "0");
+    }
 }