perf: Enhance performance content size calculation, fixes #1223

src/models/gridOption.interface.ts

@@ -25,6 +25,7 @@ export interface CustomDataView<T = any> {
   getItem: (index: number) => T;
   getItemMetadata(row: number, cell?: boolean | number): ItemMetadata | null;
   getLength: () => number;
+  getCellValue?: (index: number, field: string) => T[keyof T];
 }
 
 export interface CssStyleHash {

src/slick.grid.ts

@@ -2738,7 +2738,7 @@ export class SlickGrid<TData = any, C extends Column<TData> = Column<TData>, O e
     rowInfo.startIndex = 0;
     rowInfo.endIndex = rowInfo.rowCount - 1;
     rowInfo.valueArr = null;
-    rowInfo.getRowVal = (j: number) => this.getDataItem(j)[columnDef.field as keyof TData];
+    rowInfo.getRowVal = (j: number) => this.getCellValue(j, columnDef.field as string);
 
     const rowSelectionMode = (isInit ? autoSize.rowSelectionModeOnInit : undefined) || autoSize.rowSelectionMode;
 
@@ -3404,6 +3404,29 @@ export class SlickGrid<TData = any, C extends Column<TData> = Column<TData>, O e
     }
   }
 
+  /**
+   * Returns the value of a single field for a given row index.
+   *
+   * When the databinding source is a `CustomDataView` that implements the optional
+   * `getCellValue(index, field)` accessor, that method is used directly. This allows
+   * column-oriented (or otherwise non row-materializing) data sources to return a
+   * single cell value without first having to build a full row object via `getItem()`,
+   * which can be expensive when called repeatedly (e.g. during column content auto-sizing).
+   *
+   * Falls back to `getDataItem(i)[field]` for plain arrays or data sources that don't
+   * implement `getCellValue`.
+   *
+   * @param {Number} i Item row index.
+   * @param {String} field Column field name.
+   */
+  getCellValue(i: number, field: string): TData[keyof TData] {
+    const customDataView = this.data as CustomDataView<TData>;
+    if (customDataView.getCellValue) {
+      return customDataView.getCellValue(i, field) as TData[keyof TData];
+    }
+    return this.getDataItem(i)[field as keyof TData];
+  }
+
   /**  Are we using a DataView? */
   hasDataView() {
     return !Array.isArray(this.data);