From e22ca2af047391e62195d2d3f07217ead8d88dd6 Mon Sep 17 00:00:00 2001
From: Artur Signell <artur@vaadin.com>
Date: Tue, 25 Oct 2016 18:27:20 +0300
Subject: [PATCH] Ensure #cell[N] always scrolls row N into view (#20423)

Change-Id: I99347ee1d0f2f13fcb8e110d2e7192590e4f9456
---
 .../com/vaadin/client/widgets/Escalator.java  | 22 +++++++++++--------
 .../basicfeatures/server/GridScrollTest.java  |  6 +++++
 2 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/client/src/main/java/com/vaadin/client/widgets/Escalator.java b/client/src/main/java/com/vaadin/client/widgets/Escalator.java
index 8dbbfc437d..9eaa7ddd36 100644
--- a/client/src/main/java/com/vaadin/client/widgets/Escalator.java
+++ b/client/src/main/java/com/vaadin/client/widgets/Escalator.java
@@ -6682,15 +6682,19 @@ 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")) {
@@ -6834,4 +6838,4 @@ public class Escalator extends Widget
     double getMinCellWidth(int colIndex) {
         return columnConfiguration.getMinCellWidth(colIndex);
     }
-}
\ No newline at end of file
+}
diff --git a/uitest/src/test/java/com/vaadin/tests/components/grid/basicfeatures/server/GridScrollTest.java b/uitest/src/test/java/com/vaadin/tests/components/grid/basicfeatures/server/GridScrollTest.java
index fbd36f87f9..815d6f72a6 100644
--- a/uitest/src/test/java/com/vaadin/tests/components/grid/basicfeatures/server/GridScrollTest.java
+++ b/uitest/src/test/java/com/vaadin/tests/components/grid/basicfeatures/server/GridScrollTest.java
@@ -68,4 +68,10 @@ public class GridScrollTest extends GridBasicFeaturesTest {
                 active);
     }
 
+    @Test
+    public void scrollIntoViewThroughSubPart() {
+        openTestURL("theme=valo");
+        GridElement grid = $(GridElement.class).first();
+        assertEquals("(10, 0)", grid.getCell(10, 0).getText());
+    }
 }
-- 
2.39.5