Updated row and spacer handling for Escalator (#11438)

Updated row and spacer handling for Escalator.

Main changes:
- Spacers are only maintained and checked for rows that have DOM
representation, and not at all if there is no details generator. This
gives notable performance improvements to some particularly large Grids
- Escalator no longer tries to trim away any rows that don't fit within
the viewport just because a details row gets opened in Grid. This leads
to some increase in simultaneous DOM elements, but simplifies the logic
considerably. For example opening or closing details rows doesn't
require checking the overall content validity beyond the details row
itself anymore, but some repositioning at most. There are also no longer
any orphaned spacers without corresponding DOM rows.
- Spacers are better integrated into the overall position calculations.
- Some public methods that are no longer used by Escalator or have
changed functionality or order of operations. Any extending classes that
tap into row, spacer, or scroll position handling are likely to need
reworking after this update.
- Auto-detecting row height is delayed until Escalator is both attached
and displayed.

3 files changed, 102 insertions, 8 deletions

diff --git a/uitest/src/main/java/com/vaadin/tests/components/treegrid/TreeGridBigDetailsManager.java b/uitest/src/main/java/com/vaadin/tests/components/treegrid/TreeGridBigDetailsManager.java
index 5699ee4372..8fb9a358e4 100644
--- a/uitest/src/main/java/com/vaadin/tests/components/treegrid/TreeGridBigDetailsManager.java
+++ b/uitest/src/main/java/com/vaadin/tests/components/treegrid/TreeGridBigDetailsManager.java
@@ -48,7 +48,7 @@ public class TreeGridBigDetailsManager extends AbstractTestUI {
         treeGrid.setSizeFull();
         treeGrid.addColumn(String::toString).setCaption("String")
                 .setId("string");
-        treeGrid.addColumn((i) -> "--").setCaption("Nothing");
+        treeGrid.addColumn((i) -> items.indexOf(i)).setCaption("Index");
         treeGrid.setHierarchyColumn("string");
         treeGrid.setDetailsGenerator(
                 row -> new Label("details for " + row.toString()));
@@ -77,21 +77,54 @@ public class TreeGridBigDetailsManager extends AbstractTestUI {
             treeGrid.collapse(items);
         });
         collapseAll.setId("collapseAll");
+        @SuppressWarnings("deprecation")
         Button scrollTo55 = new Button("Scroll to 55",
                 event -> treeGrid.scrollTo(55));
         scrollTo55.setId("scrollTo55");
         scrollTo55.setVisible(false);
+        Button scrollTo3055 = new Button("Scroll to 3055",
+                event -> treeGrid.scrollTo(3055));
+        scrollTo3055.setId("scrollTo3055");
+        scrollTo3055.setVisible(false);
+        Button scrollToEnd = new Button("Scroll to end",
+                event -> treeGrid.scrollToEnd());
+        scrollToEnd.setId("scrollToEnd");
+        scrollToEnd.setVisible(false);
+        Button scrollToStart = new Button("Scroll to start",
+                event -> treeGrid.scrollToStart());
+        scrollToStart.setId("scrollToStart");
+        scrollToStart.setVisible(false);
+
+        Button toggle15 = new Button("Toggle 15",
+                event -> treeGrid.setDetailsVisible(items.get(15),
+                        !treeGrid.isDetailsVisible(items.get(15))));
+        toggle15.setId("toggle15");
+        toggle15.setVisible(false);
+
+        Button toggle3000 = new Button("Toggle 3000",
+                event -> treeGrid.setDetailsVisible(items.get(3000),
+                        !treeGrid.isDetailsVisible(items.get(3000))));
+        toggle3000.setId("toggle3000");
+        toggle3000.setVisible(false);
+
         Button addGrid = new Button("Add grid", event -> {
             addComponent(treeGrid);
             getLayout().setExpandRatio(treeGrid, 2);
             scrollTo55.setVisible(true);
+            scrollTo3055.setVisible(true);
+            scrollToEnd.setVisible(true);
+            scrollToStart.setVisible(true);
+            toggle15.setVisible(true);
+            toggle3000.setVisible(true);
         });
         addGrid.setId("addGrid");
 
         addComponents(
                 new HorizontalLayout(showDetails, hideDetails, expandAll,
                         collapseAll),
-                new HorizontalLayout(addGrid, scrollTo55));
+                new HorizontalLayout(scrollTo55, scrollTo3055, scrollToEnd,
+                        scrollToStart),
+                new HorizontalLayout(addGrid, toggle15, toggle3000));
 
         getLayout().getParent().setHeight("100%");
         getLayout().setHeight("100%");
diff --git a/uitest/src/main/java/com/vaadin/tests/widgetset/client/grid/EscalatorBasicClientFeaturesWidget.java b/uitest/src/main/java/com/vaadin/tests/widgetset/client/grid/EscalatorBasicClientFeaturesWidget.java
index 2d7dd5cc37..941f1ce928 100644
--- a/uitest/src/main/java/com/vaadin/tests/widgetset/client/grid/EscalatorBasicClientFeaturesWidget.java
+++ b/uitest/src/main/java/com/vaadin/tests/widgetset/client/grid/EscalatorBasicClientFeaturesWidget.java
@@ -1,9 +1,12 @@
 package com.vaadin.tests.widgetset.client.grid;
 
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 import com.google.gwt.core.client.Duration;
+import com.google.gwt.core.client.Scheduler;
 import com.google.gwt.core.client.Scheduler.ScheduledCommand;
 import com.google.gwt.dom.client.TableCellElement;
 import com.google.gwt.user.client.DOM;
@@ -16,6 +19,8 @@ import com.vaadin.client.widget.escalator.RowContainer;
 import com.vaadin.client.widget.escalator.RowContainer.BodyRowContainer;
 import com.vaadin.client.widget.escalator.Spacer;
 import com.vaadin.client.widget.escalator.SpacerUpdater;
+import com.vaadin.client.widget.escalator.events.SpacerIndexChangedEvent;
+import com.vaadin.client.widget.escalator.events.SpacerIndexChangedHandler;
 import com.vaadin.client.widgets.Escalator;
 import com.vaadin.shared.ui.grid.ScrollDestination;
 import com.vaadin.tests.widgetset.client.v7.grid.PureGWTTestApplication;
@@ -156,6 +161,7 @@ public class EscalatorBasicClientFeaturesWidget
         private int rowCounter = 0;
         private final List<Integer> columns = new ArrayList<>();
         private final List<Integer> rows = new ArrayList<>();
+        private final Map<Integer, Integer> spacers = new HashMap<>();
 
         @SuppressWarnings("boxing")
         public void insertRows(final int offset, final int amount) {
@@ -247,6 +253,11 @@ public class EscalatorBasicClientFeaturesWidget
                             cell.setColSpan(2);
                         }
                     }
+                    if (spacers.containsKey(cell.getRow()) && !escalator
+                            .getBody().spacerExists(cell.getRow())) {
+                        escalator.getBody().setSpacer(cell.getRow(),
+                                spacers.get(cell.getRow()));
+                    }
                 }
 
                 @Override
@@ -262,7 +273,12 @@ public class EscalatorBasicClientFeaturesWidget
         public void removeRows(final int offset, final int amount) {
             for (int i = 0; i < amount; i++) {
                 rows.remove(offset);
+                if (spacers.containsKey(offset + i)) {
+                    spacers.remove(offset + i);
+                }
             }
+            // the following spacers get their indexes updated through
+            // SpacerIndexChangedHandler
         }
 
         public void removeColumns(final int offset, final int amount) {
@@ -313,6 +329,21 @@ public class EscalatorBasicClientFeaturesWidget
         createFrozenMenu();
         createColspanMenu();
         createSpacerMenu();
+
+        escalator.addHandler(new SpacerIndexChangedHandler() {
+            @Override
+            public void onSpacerIndexChanged(SpacerIndexChangedEvent event) {
+                // remove spacer from old index and move to new index
+                Integer height = data.spacers.remove(event.getOldIndex());
+                if (height != null) {
+                    data.spacers.put(event.getNewIndex(), height);
+                } else {
+                    // no height, make sure the new index doesn't
+                    // point to anything else either
+                    data.spacers.remove(event.getNewIndex());
+                }
+            }
+        }, SpacerIndexChangedEvent.TYPE);
     }
 
     private void createFrozenMenu() {
@@ -558,11 +589,24 @@ public class EscalatorBasicClientFeaturesWidget
                     @Override
                     public void init(Spacer spacer) {
                         spacer.getElement().appendChild(DOM.createInputText());
+                        updateRowPositions(spacer);
                     }
 
                     @Override
                     public void destroy(Spacer spacer) {
                         spacer.getElement().removeAllChildren();
+                        updateRowPositions(spacer);
+                    }
+
+                    private void updateRowPositions(Spacer spacer) {
+                        if (spacer.getRow() < escalator.getBody()
+                                .getRowCount()) {
+                            Scheduler.get().scheduleFinally(() -> {
+                                escalator.getBody().updateRowPositions(
+                                        spacer.getRow(),
+                                        escalator.getBody().getRowCount());
+                            });
+                        }
                     }
                 }), menupath);
 
@@ -575,12 +619,18 @@ public class EscalatorBasicClientFeaturesWidget
     private void createSpacersMenuForRow(final int rowIndex,
             String[] menupath) {
         menupath = new String[] { menupath[0], menupath[1], "Row " + rowIndex };
-        addMenuCommand("Set 100px",
-                () -> escalator.getBody().setSpacer(rowIndex, 100), menupath);
-        addMenuCommand("Set 50px",
-                () -> escalator.getBody().setSpacer(rowIndex, 50), menupath);
-        addMenuCommand("Remove",
-                () -> escalator.getBody().setSpacer(rowIndex, -1), menupath);
+        addMenuCommand("Set 100px", () -> {
+            escalator.getBody().setSpacer(rowIndex, 100);
+            data.spacers.put(rowIndex, 100);
+        }, menupath);
+        addMenuCommand("Set 50px", () -> {
+            escalator.getBody().setSpacer(rowIndex, 50);
+            data.spacers.put(rowIndex, 50);
+        }, menupath);
+        addMenuCommand("Remove", () -> {
+            escalator.getBody().setSpacer(rowIndex, -1);
+            data.spacers.remove(rowIndex);
+        }, menupath);
         addMenuCommand("Scroll here (ANY, 0)", () -> escalator
                 .scrollToSpacer(rowIndex, ScrollDestination.ANY, 0), menupath);
         addMenuCommand("Scroll here row+spacer below (ANY, 0)", () -> escalator
@@ -596,6 +646,9 @@ public class EscalatorBasicClientFeaturesWidget
         } else {
             container.insertRows(offset, number);
         }
+        if (container.getRowCount() > offset + number) {
+            container.refreshRows(offset + number, container.getRowCount());
+        }
     }
 
     private void removeRows(final RowContainer container, int offset,
@@ -606,6 +659,9 @@ public class EscalatorBasicClientFeaturesWidget
         } else {
             container.removeRows(offset, number);
         }
+        if (container.getRowCount() > offset) {
+            container.refreshRows(offset, container.getRowCount());
+        }
     }
 
     private void insertColumns(final int offset, final int number) {
diff --git a/uitest/src/main/java/com/vaadin/tests/widgetset/client/grid/EscalatorProxy.java b/uitest/src/main/java/com/vaadin/tests/widgetset/client/grid/EscalatorProxy.java
index fe6f7ab94b..5d5148109b 100644
--- a/uitest/src/main/java/com/vaadin/tests/widgetset/client/grid/EscalatorProxy.java
+++ b/uitest/src/main/java/com/vaadin/tests/widgetset/client/grid/EscalatorProxy.java
@@ -125,6 +125,11 @@ public class EscalatorProxy extends Escalator {
             throw new UnsupportedOperationException(
                     "setNewRowCallback is not supported");
         }
+
+        @Override
+        public void updateRowPositions(int index, int numberOfRows) {
+            rowContainer.updateRowPositions(index, numberOfRows);
+        }
     }
 
     private class RowContainerProxy implements RowContainer {