From aeae310b7e16f40745992e075626fc19ca90321d Mon Sep 17 00:00:00 2001
From: Aleksi Hietanen <aleksi@vaadin.com>
Date: Tue, 29 Nov 2016 16:58:17 +0200
Subject: [PATCH] Migrate Escalator changes to compatibility escalator

Change-Id: Ie19f0f2c2202dcdcaebc67dd5d16df91c18633be
---
 .../vaadin/v7/client/widgets/Escalator.java   | 38 ++++++++++++++-----
 1 file changed, 28 insertions(+), 10 deletions(-)

diff --git a/compatibility-client/src/main/java/com/vaadin/v7/client/widgets/Escalator.java b/compatibility-client/src/main/java/com/vaadin/v7/client/widgets/Escalator.java
index 0804a0ad5e..f343d45f6f 100644
--- a/compatibility-client/src/main/java/com/vaadin/v7/client/widgets/Escalator.java
+++ b/compatibility-client/src/main/java/com/vaadin/v7/client/widgets/Escalator.java
@@ -859,8 +859,8 @@ public class Escalator extends Widget
                 if (position instanceof AbsolutePosition) {
                     /*
                      * we don't want to put "top: 0" on the footer, since it'll
-                     * render wrong, as we already have
-                     * "bottom: $footer-height".
+                     * render wrong, as we already have "bottom: $footer-height"
+                     * .
                      */
                     footElem.getStyle().setLeft(-scrollLeft, Unit.PX);
                 } else {
@@ -5584,8 +5584,22 @@ public class Escalator extends Widget
         // init default dimensions
         setHeight(null);
         setWidth(null);
+
+        publishJSHelpers(root);
+    }
+
+    private int getBodyRowCount() {
+        return getBody().getRowCount();
     }
 
+    private native void publishJSHelpers(Element root)
+    /*-{
+        var self = this;
+        root.getBodyRowCount = $entry(function () {
+           return self.@Escalator::getBodyRowCount()();
+        });
+    }-*/;
+
     private void setupScrollbars(final Element root) {
 
         ScrollHandler scrollHandler = new ScrollHandler() {
@@ -6630,15 +6644,19 @@ public class Escalator extends Widget
         } else if (type.equalsIgnoreCase("cell")) {
             // If wanted row is not visible, we need to scroll there.
             Range visibleRowRange = getVisibleRowRange();
-            if (indices.length > 0 && !visibleRowRange.contains(indices[0])) {
-                try {
-                    scrollToRow(indices[0], ScrollDestination.ANY, 0);
-                } catch (IllegalArgumentException e) {
-                    getLogger().log(Level.SEVERE, e.getMessage());
+            if (indices.length > 0) {
+                // Contains a row number, ensure it is available and visible
+                boolean rowInCache = visibleRowRange.contains(indices[0]);
+
+                // Scrolling might be a no-op if row is already in the viewport
+                scrollToRow(indices[0], ScrollDestination.ANY, 0);
+
+                if (!rowInCache) {
+                    // Row was not in cache, scrolling caused lazy loading and
+                    // the caller needs to wait and call this method again to be
+                    // able to get the requested element
+                    return null;
                 }
-                // Scrolling causes a lazy loading event. No element can
-                // currently be retrieved.
-                return null;
             }
             container = getBody();
         } else if (type.equalsIgnoreCase("footer")) {
-- 
2.39.5