Hover over cell

frontend/src/components/data-table/cell-hover-template/feature.ts

@@ -0,0 +1,14 @@
+/* Copyright 2025 Marimo. All rights reserved. */
+"use no memo";
+
+import type { InitialTableState, TableFeature } from "@tanstack/react-table";
+import type { CellHoverTemplateTableState } from "./types";
+
+export const CellHoverTemplateFeature: TableFeature = {
+  getInitialState: (state?: InitialTableState): CellHoverTemplateTableState => {
+    return {
+      ...state,
+      cellHoverTemplate: null,
+    };
+  },
+};

frontend/src/components/data-table/cell-hover-template/types.ts

@@ -0,0 +1,11 @@
+/* Copyright 2025 Marimo. All rights reserved. */
+/* eslint-disable @typescript-eslint/no-empty-interface */
+
+export interface CellHoverTemplateTableState {
+  cellHoverTemplate: string | null;
+}
+
+// Use declaration merging to add our new feature APIs
+declare module "@tanstack/react-table" {
+  interface TableState extends CellHoverTemplateTableState {}
+}

frontend/src/components/data-table/data-table.tsx

@@ -24,6 +24,7 @@ import { Table } from "@/components/ui/table";
 import type { GetRowIds } from "@/plugins/impl/DataTablePlugin";
 import { cn } from "@/utils/cn";
 import type { PanelType } from "../editor/chrome/panels/context-aware-panel/context-aware-panel";
+import { CellHoverTemplateFeature } from "./cell-hover-template/feature";
 import { CellSelectionFeature } from "./cell-selection/feature";
 import type { CellSelectionState } from "./cell-selection/types";
 import { CellStylingFeature } from "./cell-styling/feature";
@@ -63,6 +64,7 @@ interface DataTableProps<TData> extends Partial<DownloadActionProps> {
   rowSelection?: RowSelectionState;
   cellSelection?: CellSelectionState;
   cellStyling?: CellStyleState | null;
+  hoverTemplate?: string | null;
   onRowSelectionChange?: OnChangeFn<RowSelectionState>;
   onCellSelectionChange?: OnChangeFn<CellSelectionState>;
   getRowIds?: GetRowIds;
@@ -103,6 +105,7 @@ const DataTableInternal = <TData,>({
   rowSelection,
   cellSelection,
   cellStyling,
+  hoverTemplate,
   paginationState,
   setPaginationState,
   downloadAs,
@@ -176,6 +179,7 @@ const DataTableInternal = <TData,>({
       ColumnFormattingFeature,
       CellSelectionFeature,
       CellStylingFeature,
+      CellHoverTemplateFeature,
       CopyColumnFeature,
       FocusRowFeature,
     ],
@@ -237,6 +241,7 @@ const DataTableInternal = <TData,>({
       cellSelection,
       cellStyling,
       columnPinning: columnPinning,
+      cellHoverTemplate: hoverTemplate,
     },
   });
 

frontend/src/components/data-table/renderers.tsx

@@ -101,6 +101,25 @@
         cell.getUserStyling?.() || {},
         pinningstyle,
       );
+      const hoverTemplate = table.getState().cellHoverTemplate || undefined;
+      let title: string | undefined;
+      if (hoverTemplate) {
+        title = hoverTemplate;
+        const variableRegex = /{{(\w+)}}/g;
+        const matches = [...hoverTemplate.matchAll(variableRegex)];
+        for (const match of matches) {
+          // if match is in the row, replace it in the string
+          const matchTerm = match[1];
+          const currentCell = cells.find(
+            (cell) => cell.column.id === matchTerm,
+          );
+          if (currentCell) {
+            const cellValue = currentCell.getValue();
+            title = title.replace(match[0], cellValue as string);
+          }
+          console.log(matchTerm, columns);
+        }
+      }
       return (
         <TableCell
           tabIndex={0}
@@ -114,6 +133,7 @@
             className,
           )}
           style={style}
+          title={title}
           onMouseDown={(e) => handleCellMouseDown(e, cell)}
           onMouseUp={handleCellMouseUp}
           onMouseOver={(e) => handleCellMouseOver(e, cell)}

frontend/src/plugins/impl/DataTablePlugin.tsx

@@ -254,6 +254,7 @@ export const DataTablePlugin = createPlugin<S>("marimo-table")
       maxColumns: z.union([z.number(), z.literal("all")]).default("all"),
       hasStableRowId: z.boolean().default(false),
       cellStyles: z.record(z.record(z.object({}).passthrough())).optional(),
+      hoverTemplate: z.string().optional(),
       // Whether to load the data lazily.
       lazy: z.boolean().default(false),
       // If lazy, this will preload the first page of data
@@ -385,6 +386,7 @@ interface DataTableProps<T> extends Data<T>, DataTableFunctions {
   // Filters
   enableFilters?: boolean;
   cellStyles?: CellStyleState | null;
+  hoverTemplate?: string | null;
   toggleDisplayHeader?: () => void;
   host: HTMLElement;
   cellId?: CellId | null;
@@ -707,6 +709,7 @@ const DataTableComponent = ({
   totalColumns,
   get_row_ids,
   cellStyles,
+  hoverTemplate,
   toggleDisplayHeader,
   calculate_top_k_rows,
   preview_column,
@@ -904,6 +907,7 @@ const DataTableComponent = ({
             rowSelection={rowSelection}
             cellSelection={cellSelection}
             cellStyling={cellStyles}
+            hoverTemplate={hoverTemplate}
             downloadAs={showDownload ? downloadAs : undefined}
             enableSearch={enableSearch}
             searchQuery={searchQuery}

marimo/_plugins/ui/_impl/table.py

@@ -332,6 +332,7 @@ def style_cell(_rowId, _columnName, value):
         on_change (Callable[[Union[List[JSONType], Dict[str, List[JSONType]], IntoDataFrame, List[TableCell]]], None], optional):
             Optional callback to run when this element's value changes.
         style_cell (Callable[[str, str, Any], Dict[str, Any]], optional): A function that takes the row id, column name and value and returns a dictionary of CSS styles.
+        hover_template (str, optional): A template for the hover text of the table.
         max_columns (int, optional): Maximum number of columns to display. Defaults to the
             configured default_table_max_columns (50 by default). Set to None to show all columns.
         label (str, optional): A descriptive name for the table. Defaults to "".
@@ -439,6 +440,7 @@ def __init__(
             ]
         ] = None,
         style_cell: Optional[Callable[[str, str, Any], dict[str, Any]]] = None,
+        hover_template: Optional[str] = None,
         # The _internal_* arguments are for overriding and unit tests
         # table should take the value unconditionally
         _internal_column_charts_row_limit: Optional[int] = None,
@@ -666,6 +668,7 @@ def __init__(
                 "wrapped-columns": wrapped_columns,
                 "has-stable-row-id": self._has_stable_row_id,
                 "cell-styles": search_result_styles,
+                "hover-template": hover_template,
                 "lazy": _internal_lazy,
                 "preload": _internal_preload,
             },