Maintain Grid scroll position on detach and reattach (#16220)

Change-Id: I6ac5c3304bcd22e23f298c4dbdd65358aa1c64f7

2 files changed, 36 insertions, 2 deletions

diff --git a/client/src/com/vaadin/client/widget/escalator/ScrollbarBundle.java b/client/src/com/vaadin/client/widget/escalator/ScrollbarBundle.java
index 21f56c6c4d..2345641408 100644
--- a/client/src/com/vaadin/client/widget/escalator/ScrollbarBundle.java
+++ b/client/src/com/vaadin/client/widget/escalator/ScrollbarBundle.java
@@ -335,7 +335,7 @@ public abstract class ScrollbarBundle implements DeferredWorker {
 
     private boolean isLocked = false;
 
-    /** @deprecarted access via {@link #getHandlerManager()} instead. */
+    /** @deprecated access via {@link #getHandlerManager()} instead. */
     @Deprecated
     private HandlerManager handlerManager;
 
@@ -515,6 +515,15 @@ public abstract class ScrollbarBundle implements DeferredWorker {
     }
 
     /**
+     * Should be called whenever this bundle is attached to the DOM (typically,
+     * from the onLoad of the containing widget). Used to ensure the DOM scroll
+     * position is maintained when detaching and reattaching the bundle.
+     */
+    public void onLoad() {
+        internalSetScrollPos(toInt32(scrollPos));
+    }
+
+    /**
      * Truncates a double such that no decimal places are retained.
      * <p>
      * E.g. {@code trunc(2.3d) == 2.0d} and {@code trunc(-2.3d) == -2.0d}.
diff --git a/client/src/com/vaadin/client/widgets/Escalator.java b/client/src/com/vaadin/client/widgets/Escalator.java
index a81d0f3e18..129100e073 100644
--- a/client/src/com/vaadin/client/widgets/Escalator.java
+++ b/client/src/com/vaadin/client/widgets/Escalator.java
@@ -47,6 +47,7 @@ import com.google.gwt.dom.client.TableRowElement;
 import com.google.gwt.dom.client.TableSectionElement;
 import com.google.gwt.event.shared.HandlerRegistration;
 import com.google.gwt.logging.client.LogConfiguration;
+import com.google.gwt.user.client.Command;
 import com.google.gwt.user.client.DOM;
 import com.google.gwt.user.client.Window;
 import com.google.gwt.user.client.ui.RequiresResize;
@@ -4479,7 +4480,28 @@ public class Escalator extends Widget implements RequiresResize, DeferredWorker
 
         header.paintInsertRows(0, header.getRowCount());
         footer.paintInsertRows(0, footer.getRowCount());
-        recalculateElementSizes();
+
+        // recalculateElementSizes();
+
+        Scheduler.get().scheduleDeferred(new Command() {
+            @Override
+            public void execute() {
+                /*
+                 * Not a faintest idea why we have to defer this call, but
+                 * unless it is deferred, the size of the escalator will be 0x0
+                 * after it is first detached and then reattached to the DOM.
+                 * This only applies to a bare Escalator; inside a Grid
+                 * everything works fine either way.
+                 * 
+                 * The three autodetectRowHeightLater calls above seem obvious
+                 * suspects at first. However, they don't seem to have anything
+                 * to do with the issue, as they are no-ops in the
+                 * detach-reattach case.
+                 */
+                recalculateElementSizes();
+            }
+        });
+
         /*
          * Note: There's no need to explicitly insert rows into the body.
          * 
@@ -4506,6 +4528,9 @@ public class Escalator extends Widget implements RequiresResize, DeferredWorker
             footer.reapplyColumnWidths();
         }
 
+        verticalScrollbar.onLoad();
+        horizontalScrollbar.onLoad();
+
         scroller.attachScrollListener(verticalScrollbar.getElement());
         scroller.attachScrollListener(horizontalScrollbar.getElement());
         scroller.attachMousewheelListener(getElement());