Fix hierarchical grid export to handle multiple child islands per record

Fixed issue where each record could have multiple child islands (different owners)
but only one was being rendered. The code now:

- Groups grandchildren by their owner (each owner represents a different child island)
- Renders a separate nested child table for each island/owner
- Maintains proper recursive structure for unlimited nesting depth
- Each island gets its own headers and proper indentation

This ensures that hierarchical grids with multiple child grids per parent row
export correctly, with all child islands rendered as separate nested tables.

Co-authored-by: kdinev <[email protected]>

Author: Copilot

projects/igniteui-angular/src/lib/services/pdf/pdf-exporter.ts

@@ -326,28 +326,28 @@ export class IgxPdfExporterService extends IgxBaseExporter {
 
             // Check if this child record has its own children (next level in hierarchy)
             const childRecordIndex = allData.indexOf(childRecord);
-            const grandchildRecords: IExportRecord[] = [];
-            let grandchildOwner: string | null = null;
+            const grandchildrenByOwner = new Map<string, IExportRecord[]>();
 
             if (childRecordIndex >= 0 && childRecordIndex + 1 < allData.length) {
-                // Look for grandchildren
+                // Look for grandchildren and group them by owner (each owner represents a different child island)
                 let k = childRecordIndex + 1;
 
-                // Collect all grandchildren that belong to this child
+                // Collect all grandchildren that belong to this child, grouped by owner
                 while (k < allData.length && allData[k].level > childRecord.level) {
                     // Only include direct children (next level)
                     if (allData[k].level === childRecord.level + 1 && !allData[k].hidden) {
-                        grandchildRecords.push(allData[k]);
-                        if (!grandchildOwner) {
-                            grandchildOwner = allData[k].owner.toString();
+                        const owner = allData[k].owner.toString();
+                        if (!grandchildrenByOwner.has(owner)) {
+                            grandchildrenByOwner.set(owner, []);
                         }
+                        grandchildrenByOwner.get(owner)!.push(allData[k]);
                     }
                     k++;
                 }
             }
 
-            // If this child has grandchildren, render them as a nested child table
-            if (grandchildRecords.length > 0 && grandchildOwner) {
+            // If this child has grandchildren, render them as nested child tables (one per owner/island)
+            if (grandchildrenByOwner.size > 0) {
                 // Check if we need a new page for parent row
                 if (yPosition + rowHeight > pageHeight - margin) {
                     pdf.addPage();
@@ -361,21 +361,23 @@ export class IgxPdfExporterService extends IgxBaseExporter {
                 this.drawDataRow(pdf, childRecord, childColumns, childTableX, yPosition, childColumnWidth, rowHeight, 0, options);
                 yPosition += rowHeight;
 
-                // Recursively draw grandchildren as a nested child table
-                yPosition = this.drawHierarchicalChildren(
-                    pdf,
-                    allData,
-                    grandchildRecords,
-                    grandchildOwner,
-                    yPosition,
-                    margin,
-                    indentPerLevel + 30, // Increase indentation for next level
-                    usableWidth,
-                    pageHeight,
-                    headerHeight,
-                    rowHeight,
-                    options
-                );
+                // Recursively draw each island's grandchildren as a separate nested child table
+                for (const [grandchildOwner, grandchildRecords] of grandchildrenByOwner) {
+                    yPosition = this.drawHierarchicalChildren(
+                        pdf,
+                        allData,
+                        grandchildRecords,
+                        grandchildOwner,
+                        yPosition,
+                        margin,
+                        indentPerLevel + 30, // Increase indentation for next level
+                        usableWidth,
+                        pageHeight,
+                        headerHeight,
+                        rowHeight,
+                        options
+                    );
+                }
             } else {
                 // No grandchildren, just draw this child as a regular row
                 // Check if we need a new page