perf: optimize DataGridView scroll performance (#522)

* perf: optimize DataGridView scroll by pre-computing column metadata and warming display cache

* fix: address review — complete cell property guard, prevent division by zero

Author: datlechin

TablePro/Models/Query/RowProvider.swift

@@ -217,6 +217,23 @@ final class InMemoryRowProvider: RowProvider {
         return columnIndex < rowCache.count ? rowCache[columnIndex] : nil
     }
 
+    @MainActor
+    func preWarmDisplayCache(upTo rowCount: Int) {
+        let count = min(rowCount, totalRowCount)
+        for row in 0..<count {
+            let cacheKey = resolveCacheKey(for: row)
+            guard displayCache[cacheKey] == nil else { continue }
+            let src = sourceRow(at: row)
+            let columnCount = columns.count
+            var rowCache = [String?](repeating: nil, count: columnCount)
+            for col in 0..<min(src.count, columnCount) {
+                let ct = col < columnTypes.count ? columnTypes[col] : nil
+                rowCache[col] = CellDisplayFormatter.format(src[col], columnType: ct)
+            }
+            displayCache[cacheKey] = rowCache
+        }
+    }
+
     /// Invalidate entire display cache (after settings change, full reload).
     func invalidateDisplayCache() {
         displayCache.removeAll()

TablePro/Views/Results/DataGridCellFactory.swift

@@ -230,8 +230,12 @@ final class DataGridCellFactory {
             isNewCell = true
         }
 
-        // Re-apply single-line properties (editing may reset these on reused cells)
-        if !isNewCell {
+        if !isNewCell && (
+            cell.lineBreakMode != .byTruncatingTail ||
+            cell.maximumNumberOfLines != 1 ||
+            cell.cell?.truncatesLastVisibleLine != true ||
+            cell.cell?.usesSingleLineMode != true
+        ) {
             cell.lineBreakMode = .byTruncatingTail
             cell.maximumNumberOfLines = 1
             cell.cell?.truncatesLastVisibleLine = true

TablePro/Views/Results/DataGridCoordinator.swift

@@ -95,6 +95,8 @@ final class TableViewCoordinator: NSObject, NSTableViewDelegate, NSTableViewData
     var lastReapplyVersion: Int = -1
     private(set) var cachedRowCount: Int = 0
     private(set) var cachedColumnCount: Int = 0
+    private(set) var enumOrSetColumns: Set<Int> = []
+    private(set) var fkColumns: Set<Int> = []
     var isSyncingSortDescriptors: Bool = false
     /// Suppresses selection delegate callbacks during programmatic selection sync
     var isSyncingSelection = false
@@ -263,6 +265,30 @@ final class TableViewCoordinator: NSObject, NSTableViewDelegate, NSTableViewData
         cachedColumnCount = rowProvider.columns.count
     }
 
+    func rebuildColumnMetadataCache() {
+        var enumSet = Set<Int>()
+        var fkSet = Set<Int>()
+        let columns = rowProvider.columns
+        let types = rowProvider.columnTypes
+        let enumValues = rowProvider.columnEnumValues
+        let fkKeys = rowProvider.columnForeignKeys
+
+        for i in 0..<columns.count {
+            let name = columns[i]
+            if i < types.count {
+                let ct = types[i]
+                if (ct.isEnumType || ct.isSetType) && enumValues[name]?.isEmpty == false {
+                    enumSet.insert(i)
+                }
+            }
+            if fkKeys[name] != nil {
+                fkSet.insert(i)
+            }
+        }
+        enumOrSetColumns = enumSet
+        fkColumns = fkSet
+    }
+
     // MARK: - Font Updates
 
     /// Update fonts on existing visible cell views in-place.

TablePro/Views/Results/DataGridView.swift

@@ -174,6 +174,7 @@ struct DataGridView: NSViewRepresentable {
         scrollView.documentView = tableView
         context.coordinator.tableView = tableView
         context.coordinator.onMoveRow = onMoveRow
+        context.coordinator.rebuildColumnMetadataCache()
         if let connectionId {
             context.coordinator.observeTeardown(connectionId: connectionId)
         }
@@ -280,6 +281,16 @@ struct DataGridView: NSViewRepresentable {
         }
 
         coordinator.updateCache()
+        coordinator.rebuildColumnMetadataCache()
+
+        if previousIdentity == nil || previousIdentity?.rowCount == 0 {
+            let rowH = tableView.rowHeight
+            if rowH > 0 {
+                let visibleRows = Int(tableView.visibleRect.height / rowH) + 5
+                coordinator.rowProvider.preWarmDisplayCache(upTo: visibleRows)
+            }
+        }
+
         coordinator.changeManager = changeManager
         coordinator.isEditable = isEditable
         coordinator.onRefresh = onRefresh

TablePro/Views/Results/Extensions/DataGridView+Columns.swift

@@ -43,20 +43,8 @@ extension TableViewCoordinator {
         let isDropdown = dropdownColumns?.contains(columnIndex) == true
         let isTypePicker = typePickerColumns?.contains(columnIndex) == true
 
-        let isEnumOrSet: Bool = {
-            guard columnIndex < rowProvider.columnTypes.count,
-                  columnIndex < rowProvider.columns.count else { return false }
-            let ct = rowProvider.columnTypes[columnIndex]
-            let columnName = rowProvider.columns[columnIndex]
-            guard ct.isEnumType || ct.isSetType else { return false }
-            return rowProvider.columnEnumValues[columnName]?.isEmpty == false
-        }()
-
-        let isFKColumn: Bool = {
-            guard columnIndex < rowProvider.columns.count else { return false }
-            let columnName = rowProvider.columns[columnIndex]
-            return rowProvider.columnForeignKeys[columnName] != nil
-        }()
+        let isEnumOrSet = enumOrSetColumns.contains(columnIndex)
+        let isFKColumn = fkColumns.contains(columnIndex)
 
         return cellFactory.makeDataCell(
             tableView: tableView,