Fix scrollTo for destination START and END and add regression testing. (#11707)

- Initial implementation erroneously assumed that
ScrollDestination.START would only be used for scrolling up and
ScrollDestination.END for scrolling down. That's obviously not what they
are for, otherwise everyone would be using ScrollDestination.ANY.
- Moved actual scrolling to within the helper method that originally
only calculated the new scroll position. Parent method became too long
otherwise.

Fixes #11706

2 files changed, 324 insertions, 0 deletions

diff --git a/uitest/src/main/java/com/vaadin/tests/components/grid/GridScrollDestination.java b/uitest/src/main/java/com/vaadin/tests/components/grid/GridScrollDestination.java
new file mode 100644
index 0000000000..f58ffa1fe7
--- /dev/null
+++ b/uitest/src/main/java/com/vaadin/tests/components/grid/GridScrollDestination.java
@@ -0,0 +1,33 @@
+package com.vaadin.tests.components.grid;
+
+import java.util.Arrays;
+import java.util.stream.IntStream;
+
+import com.vaadin.server.VaadinRequest;
+import com.vaadin.shared.ui.grid.ScrollDestination;
+import com.vaadin.tests.components.AbstractTestUI;
+import com.vaadin.ui.Button;
+import com.vaadin.ui.Grid;
+import com.vaadin.ui.NativeSelect;
+import com.vaadin.ui.TextField;
+
+public class GridScrollDestination extends AbstractTestUI {
+
+    @Override
+    protected void setup(VaadinRequest request) {
+        Grid<Integer> grid = new Grid<>();
+        grid.addColumn(Integer::intValue).setCaption("number");
+        grid.setItems(IntStream.range(0, 100).boxed());
+        TextField tf = new TextField("row index", "50");
+        NativeSelect<ScrollDestination> ns = new NativeSelect<>(
+                "scroll destination",
+                Arrays.asList(ScrollDestination.values()));
+        ns.setValue(ScrollDestination.ANY);
+        Button button = new Button("Scroll to above row index", (event) -> {
+            int rowIndex = Integer.parseInt(tf.getValue());
+            grid.scrollTo(rowIndex, ns.getValue());
+        });
+        addComponents(tf, ns, button, grid);
+    }
+
+}
diff --git a/uitest/src/test/java/com/vaadin/tests/components/grid/GridScrollDestinationTest.java b/uitest/src/test/java/com/vaadin/tests/components/grid/GridScrollDestinationTest.java
new file mode 100644
index 0000000000..67a831557d
--- /dev/null
+++ b/uitest/src/test/java/com/vaadin/tests/components/grid/GridScrollDestinationTest.java
@@ -0,0 +1,291 @@
+package com.vaadin.tests.components.grid;
+
+import static org.hamcrest.number.IsCloseTo.closeTo;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
+
+import java.util.List;
+
+import org.junit.Test;
+import org.openqa.selenium.WebElement;
+
+import com.vaadin.shared.ui.grid.ScrollDestination;
+import com.vaadin.testbench.By;
+import com.vaadin.testbench.TestBenchElement;
+import com.vaadin.testbench.elements.ButtonElement;
+import com.vaadin.testbench.elements.GridElement;
+import com.vaadin.testbench.elements.NativeSelectElement;
+import com.vaadin.tests.tb3.SingleBrowserTest;
+
+public class GridScrollDestinationTest extends SingleBrowserTest {
+
+    private ButtonElement button;
+    private GridElement grid;
+    private TestBenchElement header;
+    private TestBenchElement tableWrapper;
+
+    @Override
+    public void setup() throws Exception {
+        super.setup();
+        openTestURL();
+        button = $(ButtonElement.class).first();
+        grid = $(GridElement.class).first();
+        header = grid.getHeader();
+        tableWrapper = grid.getTableWrapper();
+    }
+
+    private void assertElementAtTop(WebElement row) {
+        assertThat((double) row.getLocation().getY(), closeTo(
+                header.getLocation().getY() + header.getSize().getHeight(),
+                1d));
+    }
+
+    private void assertElementAtBottom(WebElement row) {
+        assertThat(
+                (double) row.getLocation().getY() + row.getSize().getHeight(),
+                closeTo((double) tableWrapper.getLocation().getY()
+                        + tableWrapper.getSize().getHeight(), 1d));
+    }
+
+    private void assertElementAtMiddle(WebElement row) {
+        assertThat((double) row.getLocation()
+                .getY() + (row.getSize().getHeight() / 2), closeTo(
+                        (double) tableWrapper.getLocation().getY()
+                                + header.getSize().getHeight()
+                                + ((tableWrapper.getSize().getHeight()
+                                        - header.getSize().getHeight()) / 2),
+                        1d));
+    }
+
+    @Test
+    public void destinationAny() {
+        // ScrollDestination.ANY selected by default
+
+        // scroll down
+        button.click();
+
+        // expect the row at the bottom of the viewport
+        List<WebElement> rows = grid.getBody()
+                .findElements(By.className("v-grid-row"));
+        // last rendered row is a buffer row, inspect second to last
+        WebElement row = rows.get(rows.size() - 2);
+        assertEquals("50", row.getText());
+
+        assertElementAtBottom(row);
+
+        // scroll to end
+        grid.scrollToRow((int) grid.getRowCount() - 1);
+
+        // ensure row 50 is out of visual range, first two rows are out of view
+        // and getText can't find the contents so inspect the third row
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        row = rows.get(2);
+
+        assertGreater(row.getText() + " is not greater than 52",
+                Integer.valueOf(row.getText()), 52);
+
+        // scroll up
+        button.click();
+
+        // expect the row at the top of the viewport
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        // first rendered row is a buffer row, inspect second
+        row = rows.get(1);
+        assertEquals("50", row.getText());
+
+        assertElementAtTop(row);
+
+        // scroll up by a few rows
+        grid.scrollToRow(45);
+
+        // refresh row references
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        row = rows.get(6);
+        assertEquals("50", row.getText());
+
+        // scroll while already within viewport
+        button.click();
+
+        // expect no change since the row is still within viewport
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        row = rows.get(6);
+        assertEquals("50", row.getText());
+    }
+
+    @Test
+    public void destinationEnd() {
+        $(NativeSelectElement.class).first()
+                .selectByText(ScrollDestination.END.name());
+
+        // scroll down
+        button.click();
+
+        // expect the row at the bottom of the viewport
+        List<WebElement> rows = grid.getBody()
+                .findElements(By.className("v-grid-row"));
+        // last rendered row is a buffer row, inspect second to last
+        WebElement row = rows.get(rows.size() - 2);
+        assertEquals("50", row.getText());
+
+        assertElementAtBottom(row);
+
+        // scroll to end
+        grid.scrollToRow((int) grid.getRowCount() - 1);
+
+        // ensure row 50 is out of visual range, first two rows are out of view
+        // and getText can't find the contents so inspect the third row
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        row = rows.get(2);
+
+        assertGreater(row.getText() + " is not greater than 52",
+                Integer.valueOf(row.getText()), 52);
+
+        // scroll up
+        button.click();
+
+        // expect the row at the bottom of the viewport
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        // last rendered row is a buffer row, inspect second to last
+        row = rows.get(rows.size() - 2);
+        assertEquals("50", row.getText());
+
+        assertElementAtBottom(row);
+
+        // scroll down by a few rows
+        grid.scrollToRow(55);
+
+        // refresh row references
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        row = rows.get(rows.size() - 7);
+        assertEquals("50", row.getText());
+
+        // scroll while already within viewport
+        button.click();
+
+        // expect the row at the bottom of the viewport again
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        row = rows.get(rows.size() - 2);
+        assertEquals("50", row.getText());
+
+        assertElementAtBottom(row);
+    }
+
+    @Test
+    public void destinationStart() {
+        $(NativeSelectElement.class).first()
+                .selectByText(ScrollDestination.START.name());
+
+        // scroll down
+        button.click();
+
+        // expect the row at the top of the viewport
+        List<WebElement> rows = grid.getBody()
+                .findElements(By.className("v-grid-row"));
+        // first rendered row is a buffer row, inspect second
+        WebElement row = rows.get(1);
+        assertEquals("50", row.getText());
+
+        assertElementAtTop(row);
+
+        // scroll to end
+        grid.scrollToRow((int) grid.getRowCount() - 1);
+
+        // ensure row 50 is out of visual range, first two rows are out of view
+        // and getText can't find the contents so inspect the third row
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        row = rows.get(2);
+
+        assertGreater(row.getText() + " is not greater than 52",
+                Integer.valueOf(row.getText()), 52);
+
+        // scroll up
+        button.click();
+
+        // expect the row at the top of the viewport
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        // first rendered row is a buffer row, inspect second
+        row = rows.get(1);
+        assertEquals("50", row.getText());
+
+        assertElementAtTop(row);
+
+        // scroll up by a few rows
+        grid.scrollToRow(45);
+
+        // refresh row references
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        row = rows.get(6);
+        assertEquals("50", row.getText());
+
+        // scroll while already within viewport
+        button.click();
+
+        // expect the row at the top of the viewport again
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        row = rows.get(1);
+        assertEquals("50", row.getText());
+
+        assertElementAtTop(row);
+    }
+
+    @Test
+    public void destinationMiddle() {
+        NativeSelectElement destinationSelect = $(NativeSelectElement.class)
+                .first();
+        destinationSelect.selectByText(ScrollDestination.MIDDLE.name());
+
+        // scroll down
+        button.click();
+
+        // expect the row at the middle of the viewport
+        List<WebElement> rows = grid.getBody()
+                .findElements(By.className("v-grid-row"));
+        // inspect the middle row
+        WebElement row = rows.get(rows.size() / 2);
+        assertEquals("50", row.getText());
+
+        assertElementAtMiddle(row);
+
+        // scroll to end
+        grid.scrollToRow((int) grid.getRowCount() - 1);
+
+        // ensure row 50 is out of visual range, first two rows are out of view
+        // and getText can't find the contents so inspect the third row
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        row = rows.get(2);
+
+        assertGreater(row.getText() + " is not greater than 52",
+                Integer.valueOf(row.getText()), 52);
+
+        // scroll up
+        button.click();
+
+        // expect the row at the middle of the viewport
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        // first rendered row is a buffer row, inspect second
+        row = rows.get(rows.size() / 2);
+        assertEquals("50", row.getText());
+
+        assertElementAtMiddle(row);
+
+        // scroll down by a few rows
+        destinationSelect.selectByText(ScrollDestination.START.name());
+        button.click();
+
+        // refresh row references
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        row = rows.get(1);
+        assertEquals("50", row.getText());
+
+        // scroll while already within viewport
+        destinationSelect.selectByText(ScrollDestination.MIDDLE.name());
+        button.click();
+
+        // expect the row at the top of the viewport again
+        rows = grid.getBody().findElements(By.className("v-grid-row"));
+        row = rows.get(rows.size() / 2);
+        assertEquals("50", row.getText());
+
+        assertElementAtMiddle(row);
+    }
+}