From f2dbe1f103588aa3e430fefecf676512e5f47300 Mon Sep 17 00:00:00 2001
From: Jan Prochazka <jan.prochazka@gmail.com>
Date: Thu, 14 Jan 2021 10:45:24 +0100
Subject: [PATCH] performance comments

---
 packages/web/src/datagrid/DataGrid.js     | 8 +++++++-
 packages/web/src/datagrid/DataGridCore.js | 3 +++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/packages/web/src/datagrid/DataGrid.js b/packages/web/src/datagrid/DataGrid.js
index abe6750b9..b4f25e8a3 100644
--- a/packages/web/src/datagrid/DataGrid.js
+++ b/packages/web/src/datagrid/DataGrid.js
@@ -45,7 +45,13 @@ export default function DataGrid(props) {
               <ReferenceManager {...props} managerSize={managerSize} />
             </WidgetColumnBarItem>
           )}
-          <WidgetColumnBarItem title="Cell data" name="cellData" collapsed>
+          <WidgetColumnBarItem
+            title="Cell data"
+            name="cellData"
+            // cell data must be collapsed by default, because of performance reasons
+            // when not collapsed, onSelectionChanged of grid is set and RERENDER of this component is done on every selection change
+            collapsed
+          >
             {isFormView ? (
               <CellDataView selectedValue={formSelection} />
             ) : (
diff --git a/packages/web/src/datagrid/DataGridCore.js b/packages/web/src/datagrid/DataGridCore.js
index d9823e5b5..8c2df0039 100644
--- a/packages/web/src/datagrid/DataGridCore.js
+++ b/packages/web/src/datagrid/DataGridCore.js
@@ -1062,6 +1062,9 @@ export default function DataGridCore(props) {
           {_.range(firstVisibleRowScrollIndex, firstVisibleRowScrollIndex + visibleRowCountUpperBound).map(
             (rowIndex) => (
               <DataGridRow
+                // this component use React.memo
+                // when adding props, check, whether they are correctly memoized and row is not rerendered
+                // uncomment line console.log('RENDER ROW', rowIndex); in  DataGridRow.js for check
                 key={rowIndex}
                 grider={grider}
                 rowIndex={rowIndex}