Fix table.setCurrentPageFirstItemIndex(n) to load only needed rows (#14135)

Change-Id: I0186ce32f915b39a012bb653e501b0cad72a9f32

client/src/com/vaadin/client/ui/VScrollTable.java

@@ -196,6 +196,8 @@ public class VScrollTable extends FlowPanel implements HasWidgets,
     /** For internal use only. May be removed or replaced in the future. */
     public boolean immediate;
 
+    private boolean updatedReqRows = true;
+
     private boolean nullSelectionAllowed = true;
 
     private SelectMode selectMode = SelectMode.NONE;
@@ -2393,10 +2395,32 @@ public class VScrollTable extends FlowPanel implements HasWidgets,
                 // if client connection is busy, don't bother loading it more
                 VConsole.log("Postponed rowfetch");
                 schedule(250);
+            } else if (!updatedReqRows && allRenderedRowsAreNew()) {
+
+                /*
+                 * If all rows are new, there might have been a server-side call
+                 * to Table.setCurrentPageFirstItemIndex(int) In this case,
+                 * scrolling event takes way too late, and all the rows from
+                 * previous viewport to this one were requested.
+                 * 
+                 * This should prevent requesting unneeded rows by updating
+                 * reqFirstRow and reqRows before needing them. See (#14135)
+                 */
+
+                setReqFirstRow((firstRowInViewPort - (int) (pageLength * cache_rate)));
+                int last = firstRowInViewPort + (int) (cache_rate * pageLength)
+                        + pageLength - 1;
+                if (last >= totalRows) {
+                    last = totalRows - 1;
+                }
+                setReqRows(last - getReqFirstRow() + 1);
+                updatedReqRows = true;
+                schedule(250);
             } else {
 
                 int firstRendered = scrollBody.getFirstRendered();
                 int lastRendered = scrollBody.getLastRendered();
+
                 if (lastRendered > totalRows) {
                     lastRendered = totalRows - 1;
                 }
@@ -6267,6 +6291,7 @@ public class VScrollTable extends FlowPanel implements HasWidgets,
             public Widget getWidgetForPaintable() {
                 return this;
             }
+
         }
 
         protected class VScrollTableGeneratedRow extends VScrollTableRow {
@@ -6998,8 +7023,7 @@ public class VScrollTable extends FlowPanel implements HasWidgets,
             return;
         }
 
-        if (firstRowInViewPort - pageLength * cache_rate > lastRendered
-                || firstRowInViewPort + pageLength + pageLength * cache_rate < firstRendered) {
+        if (allRenderedRowsAreNew()) {
             // need a totally new set of rows
             rowRequestHandler
                     .setReqFirstRow((firstRowInViewPort - (int) (pageLength * cache_rate)));
@@ -7010,6 +7034,7 @@ public class VScrollTable extends FlowPanel implements HasWidgets,
             }
             rowRequestHandler.setReqRows(last
                     - rowRequestHandler.getReqFirstRow() + 1);
+            updatedReqRows = false;
             rowRequestHandler.deferRowFetch();
             return;
         }
@@ -7032,6 +7057,14 @@ public class VScrollTable extends FlowPanel implements HasWidgets,
         }
     }
 
+    private boolean allRenderedRowsAreNew() {
+        int firstRowInViewPort = calcFirstRowInViewPort();
+        int firstRendered = scrollBody.getFirstRendered();
+        int lastRendered = scrollBody.getLastRendered();
+        return (firstRowInViewPort - pageLength * cache_rate > lastRendered || firstRowInViewPort
+                + pageLength + pageLength * cache_rate < firstRendered);
+    }
+
     protected int calcFirstRowInViewPort() {
         return (int) Math.ceil(scrollTop / scrollBody.getRowHeight());
     }

uitest/src/com/vaadin/tests/components/table/SetPageFirstItemLoadsNeededRowsOnly.java

@@ -0,0 +1,109 @@
+/*
+ * Copyright 2000-2014 Vaadin Ltd.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.tests.components.table;
+
+import java.io.Serializable;
+import java.util.List;
+
+import com.vaadin.data.util.BeanContainer;
+import com.vaadin.server.VaadinRequest;
+import com.vaadin.tests.components.AbstractTestUI;
+import com.vaadin.ui.Label;
+import com.vaadin.ui.Table;
+import com.vaadin.ui.VerticalLayout;
+
+/**
+ * 
+ * @author Vaadin Ltd
+ */
+
+@SuppressWarnings("serial")
+public class SetPageFirstItemLoadsNeededRowsOnly extends AbstractTestUI {
+
+    /*
+     * (non-Javadoc)
+     * 
+     * @see com.vaadin.tests.components.AbstractTestUI#setup(com.vaadin.server.
+     * VaadinRequest)
+     */
+    @Override
+    protected void setup(VaadinRequest request) {
+        final VerticalLayout layout = new VerticalLayout();
+        addComponent(layout);
+
+        final Label label = new Label("");
+        addComponent(label);
+
+        BeanContainer<String, Bean> beans = new BeanContainer<String, Bean>(
+                Bean.class) {
+            @Override
+            public List<String> getItemIds(int startIndex, int numberOfIds) {
+                label.setValue("rows requested: " + numberOfIds);
+                return super.getItemIds(startIndex, numberOfIds);
+            }
+        };
+
+        beans.setBeanIdProperty("i");
+        for (int i = 0; i < 2000; i++) {
+            beans.addBean(new Bean(i));
+        }
+
+        final Table table = new Table("Beans", beans);
+        table.setVisibleColumns(new Object[] { "i" });
+        layout.addComponent(table);
+
+        table.setCurrentPageFirstItemIndex(table.size() - 1);
+    }
+
+    /*
+     * (non-Javadoc)
+     * 
+     * @see com.vaadin.tests.components.AbstractTestUI#getTestDescription()
+     */
+    @Override
+    protected String getTestDescription() {
+        return "Only cached rows and rows in viewport should be rendered after "
+                + "calling table.setCurrentPageFirstItemIndex(n) - as opposed to all rows "
+                + "between the previous position and new position";
+    }
+
+    /*
+     * (non-Javadoc)
+     * 
+     * @see com.vaadin.tests.components.AbstractTestUI#getTicketNumber()
+     */
+    @Override
+    protected Integer getTicketNumber() {
+        return 14135;
+    }
+
+    public class Bean implements Serializable {
+
+        private Integer i;
+
+        public Bean(Integer i) {
+            this.i = i;
+        }
+
+        public Integer getI() {
+            return i;
+        }
+
+        public void setI(Integer i) {
+            this.i = i;
+        }
+    }
+}

uitest/src/com/vaadin/tests/components/table/SetPageFirstItemLoadsNeededRowsOnlyTest.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2000-2014 Vaadin Ltd.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.tests.components.table;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+import com.vaadin.testbench.elements.LabelElement;
+import com.vaadin.tests.tb3.MultiBrowserTest;
+
+/**
+ * 
+ * @author Vaadin Ltd
+ */
+public class SetPageFirstItemLoadsNeededRowsOnlyTest extends MultiBrowserTest {
+
+    /*
+     * expectedRowsRequested is related to VScrollTable's cache_rate and
+     * pageLength. See for instance VScrollTable.ensureCacheFilled().
+     * 
+     * This also takes into account if the visible rows are at the very start or
+     * end of the table, if the user scrolled or the
+     * Table.setCurrentPageFirstItemIndex(int) method was used.
+     * 
+     * This value should not change if cache_rate and pageLength are not changed
+     * as well, and if this test remains constant: the table is scrolled to the
+     * very end (done in the actual UI: SetPageFirstItemLoadsNeededRowsOnly).
+     */
+    private int expectedRowsRequested = 45;
+
+    @Test
+    public void verifyLoadedRows() throws InterruptedException {
+
+        openTestURL();
+
+        // wait for events to be processed in UI after loading page
+        sleep(2000);
+
+        String labelValue = $(LabelElement.class).get(1).getText();
+        String expectedLabelValue = "rows requested: " + expectedRowsRequested;
+        String errorMessage = "Too many rows were requested";
+        assertEquals(errorMessage, expectedLabelValue, labelValue);
+    }
+}