Table columns are resizable

packages/devtools_app/lib/src/shared/table/_flat_table.dart

@@ -305,7 +305,7 @@ class FlatTableState<T> extends State<FlatTable<T>> with AutoDisposeMixin {
       fillWithEmptyRows: widget.fillWithEmptyRows,
       enableHoverHandling: widget.enableHoverHandling,
     );
-    if (widget.sizeColumnsToFit || tableController.columnWidths == null) {
+    if (tableController.columnWidths == null) {
       return LayoutBuilder(
         builder: (context, constraints) => buildTable(
           tableController.computeColumnWidthsSizeToFit(constraints.maxWidth),

packages/devtools_app/lib/src/shared/table/_table_row.dart

@@ -37,6 +37,7 @@ class TableRow<T> extends StatefulWidget {
        sortDirection = null,
        secondarySortColumn = null,
        onSortChanged = null,
+       onColumnResize = null,
        _rowType = _TableRowType.data,
        tall = false;
 
@@ -58,6 +59,7 @@ class TableRow<T> extends StatefulWidget {
        sortDirection = null,
        secondarySortColumn = null,
        onSortChanged = null,
+       onColumnResize = null,
        searchMatchesNotifier = null,
        activeSearchMatchNotifier = null,
        tall = false,
@@ -75,6 +77,7 @@ class TableRow<T> extends StatefulWidget {
     required this.sortColumn,
     required this.sortDirection,
     required this.onSortChanged,
+    this.onColumnResize,
     this.secondarySortColumn,
     this.onPressed,
     this.tall = false,
@@ -100,6 +103,7 @@ class TableRow<T> extends StatefulWidget {
     required this.sortColumn,
     required this.sortDirection,
     required this.onSortChanged,
+    this.onColumnResize,
     this.secondarySortColumn,
     this.onPressed,
     this.tall = false,
@@ -176,6 +180,8 @@ class TableRow<T> extends StatefulWidget {
   })?
   onSortChanged;
 
+  final void Function(int, double)? onColumnResize;
+
   final ValueListenable<List<T>>? searchMatchesNotifier;
 
   final ValueListenable<T?>? activeSearchMatchNotifier;
@@ -527,9 +533,32 @@ class _TableRowState<T> extends State<TableRow<T>>
                 widget.columnWidths[index],
               );
             case _TableRowPartDisplayType.columnSpacer:
-              return const SizedBox(
-                width: columnSpacing,
-                child: VerticalDivider(width: columnSpacing),
+              final columnIndex = columnIndexMap[i - 1];
+              final onColumnResize = widget.onColumnResize;
+              final isResizable = columnIndex != null && onColumnResize != null;
+              return MouseRegion(
+                cursor: isResizable
+                    ? SystemMouseCursors.resizeColumn
+                    : SystemMouseCursors.basic,
+                child: GestureDetector(
+                  behavior: HitTestBehavior.opaque,
+                  onHorizontalDragUpdate: (details) {
+                    if (isResizable) {
+                      setState(() {
+                        final newWidth = _calculateNewColumnWidth(
+                          width: widget.columnWidths[columnIndex],
+                          delta: details.delta.dx,
+                          minWidth: widget.columns[columnIndex].minWidthPx,
+                        );
+                        onColumnResize(columnIndex, newWidth);
+                      });
+                    }
+                  },
+                  child: const SizedBox(
+                    width: columnSpacing,
+                    child: VerticalDivider(width: columnSpacing),
+                  ),
+                ),
               );
             case _TableRowPartDisplayType.columnGroupSpacer:
               return const _ColumnGroupSpacer();
@@ -560,4 +589,13 @@ class _TableRowState<T> extends State<TableRow<T>>
 
   @override
   bool shouldShow() => widget.isShown;
+
+  double _calculateNewColumnWidth({
+    required double width,
+    required double delta,
+    double? minWidth,
+  }) => (width + delta).clamp(
+    minWidth ?? DevToolsTable.columnMinWidth,
+    double.infinity,
+  );
 }

packages/devtools_app/lib/src/shared/table/table.dart

@@ -104,34 +104,40 @@ class DevToolsTable<T> extends StatefulWidget {
   final bool fillWithEmptyRows;
   final bool enableHoverHandling;
 
+  static const columnMinWidth = 50.0;
+
   @override
   DevToolsTableState<T> createState() => DevToolsTableState<T>();
 }
 
 @visibleForTesting
 class DevToolsTableState<T> extends State<DevToolsTable<T>>
     with AutoDisposeMixin {
+  static const _resizingDebounceDuration = Duration(milliseconds: 200);
+
   late ScrollController scrollController;
   late ScrollController pinnedScrollController;
   late ScrollController _horizontalScrollbarController;
 
   late List<T> _data;
 
-  /// An adjusted copy of `widget.columnWidths` where any variable width columns
-  /// may be increased so that the sum of all column widths equals the available
-  /// screen space.
-  ///
-  /// This must be calculated where we have access to the Flutter view
-  /// constraints (e.g. the [LayoutBuilder] below).
+  late Debouncer _resizingDebouncer;
+
   @visibleForTesting
-  late List<double> adjustedColumnWidths;
+  List<double> get columnWidths => _columnWidths;
+
+  late List<double> _columnWidths;
+
+  double? _previousViewWidth;
 
   @override
   void initState() {
     super.initState();
 
     _initDataAndAddListeners();
 
+    _resizingDebouncer = Debouncer(duration: _resizingDebounceDuration);
+
     final initialScrollOffset = widget.preserveVerticalScrollPosition
         ? widget.tableController.tableUiState.scrollOffset
         : 0.0;
@@ -148,7 +154,7 @@ class DevToolsTableState<T> extends State<DevToolsTable<T>>
 
     pinnedScrollController = ScrollController();
 
-    adjustedColumnWidths = List.of(widget.columnWidths);
+    _columnWidths = List.of(widget.columnWidths);
   }
 
   @override
@@ -166,7 +172,9 @@ class DevToolsTableState<T> extends State<DevToolsTable<T>>
       _initDataAndAddListeners();
     }
 
-    adjustedColumnWidths = List.of(widget.columnWidths);
+    if (!collectionEquals(widget.columnWidths, oldWidget.columnWidths)) {
+      _columnWidths = List.of(widget.columnWidths);
+    }
   }
 
   void _initDataAndAddListeners() {
@@ -252,93 +260,91 @@ class DevToolsTableState<T> extends State<DevToolsTable<T>>
     super.dispose();
   }
 
+  void _handleColumnResize(int columnIndex, double newWidth) {
+    setState(() {
+      _columnWidths[columnIndex] = newWidth;
+    });
+  }
+
   /// The width of all columns in the table with additional padding.
-  double get _tableWidthForOriginalColumns {
+  double get _currentTableWidth {
     var tableWidth = 2 * defaultSpacing;
     final numColumnGroupSpacers =
         widget.tableController.columnGroups?.numSpacers ?? 0;
     final numColumnSpacers =
         widget.tableController.columns.numSpacers - numColumnGroupSpacers;
     tableWidth += numColumnSpacers * columnSpacing;
     tableWidth += numColumnGroupSpacers * columnGroupSpacingWithPadding;
-    for (final columnWidth in widget.columnWidths) {
+    for (final columnWidth in _columnWidths) {
       tableWidth += columnWidth;
     }
     return tableWidth;
   }
 
-  /// Modifies [adjustedColumnWidths] so that any available view space greater
-  /// than [_tableWidthForOriginalColumns] is distributed evenly across variable
-  /// width columns.
+  /// Adjusts the column widths to fit the new [viewWidth].
+  ///
+  /// This method will attempt to distribute any extra space (positive or
+  /// negative) amongst the variable-width columns. If there are no
+  /// variable-width columns, it will distribute the space amongst all columns.
   void _adjustColumnWidthsForViewSize(double viewWidth) {
-    final extraSpace = viewWidth - _tableWidthForOriginalColumns;
-    if (extraSpace <= 0) {
-      adjustedColumnWidths = List.of(widget.columnWidths);
+    final extraSpace = _currentTableWidth - viewWidth;
+    if (extraSpace == 0) {
       return;
     }
 
-    final adjustedColumnWidthsByIndex = <int, double>{};
-
-    /// Helper method to evenly distribute [space] among the columns at
-    /// [columnIndices].
-    ///
-    /// This method stores the adjusted width values in
-    /// [adjustedColumnWidthsByIndex].
-    void evenlyDistributeColumnSizes(List<int> columnIndices, double space) {
-      final targetSize = space / columnIndices.length;
-
-      var largestColumnIndex = -1;
-      var largestColumnWidth = 0.0;
-      for (final index in columnIndices) {
-        final columnWidth = widget.columnWidths[index];
-        if (columnWidth >= largestColumnWidth) {
-          largestColumnIndex = index;
-          largestColumnWidth = columnWidth;
-        }
-      }
-      if (targetSize < largestColumnWidth) {
-        // We do not have enough extra space to evenly distribute to all
-        // columns. Remove the largest column and recurse.
-        adjustedColumnWidthsByIndex[largestColumnIndex] = largestColumnWidth;
-        final newColumnIndices = List.of(columnIndices)
-          ..remove(largestColumnIndex);
-        return evenlyDistributeColumnSizes(
-          newColumnIndices,
-          space - largestColumnWidth,
-        );
-      }
-
-      for (int i = 0; i < columnIndices.length; i++) {
-        final columnIndex = columnIndices[i];
-        adjustedColumnWidthsByIndex[columnIndex] = targetSize;
-      }
-    }
-
-    final variableWidthColumnIndices = <int>[];
-    var sumVariableWidthColumnSizes = 0.0;
+    final variableWidthColumnIndices = <(int, double)>[];
     for (int i = 0; i < widget.tableController.columns.length; i++) {
       final column = widget.tableController.columns[i];
       if (column.fixedWidthPx == null) {
-        variableWidthColumnIndices.add(i);
-        sumVariableWidthColumnSizes += widget.columnWidths[i];
+        variableWidthColumnIndices.add((i, _columnWidths[i]));
       }
     }
-    final totalVariableWidthColumnSpace =
-        sumVariableWidthColumnSizes + extraSpace;
 
-    evenlyDistributeColumnSizes(
-      variableWidthColumnIndices,
-      totalVariableWidthColumnSpace,
+    // If the table contains variable width columns, then distribute the extra
+    // space between them. Otherwise, distribute the extra space between all the
+    // columns.
+    _distributeExtraSpace(
+      extraSpace,
+      indexedColumns: variableWidthColumnIndices.isNotEmpty
+          ? variableWidthColumnIndices
+          : _columnWidths.indexed,
     );
+  }
 
-    adjustedColumnWidths.clear();
-    for (int i = 0; i < widget.columnWidths.length; i++) {
-      final originalWidth = widget.columnWidths[i];
-      final isVariableWidthColumn = variableWidthColumnIndices.contains(i);
-      adjustedColumnWidths.add(
-        isVariableWidthColumn ? adjustedColumnWidthsByIndex[i]! : originalWidth,
+  /// Distributes [extraSpace] evenly between the given [indexedColumns].
+  ///
+  /// The [extraSpace] will be subtracted from each column's width. The
+  /// remainder of the division is subtracted from the last column to ensure a
+  /// perfect fit.
+  ///
+  /// This method respects the `minWidthPx` of each column.
+  void _distributeExtraSpace(
+    double extraSpace, {
+    required Iterable<(int, double)> indexedColumns,
+  }) {
+    final newWidths = List.of(_columnWidths);
+    final delta = extraSpace / indexedColumns.length;
+    final remainder = extraSpace % indexedColumns.length;
+
+    for (var i = 0; i < indexedColumns.length; i++) {
+      final columnIndex = indexedColumns.elementAt(i).$1;
+      var newWidth = indexedColumns.elementAt(i).$2;
+
+      newWidth -= delta;
+      if (i == indexedColumns.length - 1) {
+        newWidth -= remainder;
+      }
+
+      final column = widget.tableController.columns[columnIndex];
+      newWidths[columnIndex] = max(
+        newWidth,
+        column.minWidthPx ?? DevToolsTable.columnMinWidth,
       );
     }
+
+    setState(() {
+      _columnWidths = newWidths;
+    });
   }
 
   double _pinnedDataHeight(BoxConstraints tableConstraints) => min(
@@ -372,7 +378,7 @@ class DevToolsTableState<T> extends State<DevToolsTable<T>>
     return widget.rowBuilder(
       context: context,
       index: index,
-      columnWidths: adjustedColumnWidths,
+      columnWidths: _columnWidths,
       isPinned: isPinned,
       enableHoverHandling: widget.enableHoverHandling,
     );
@@ -406,7 +412,12 @@ class DevToolsTableState<T> extends State<DevToolsTable<T>>
     return LayoutBuilder(
       builder: (context, constraints) {
         final viewWidth = constraints.maxWidth;
-        _adjustColumnWidthsForViewSize(viewWidth);
+        if (_previousViewWidth != null && viewWidth != _previousViewWidth) {
+          _resizingDebouncer.run(
+            () => _adjustColumnWidthsForViewSize(viewWidth),
+          );
+        }
+        _previousViewWidth = viewWidth;
         return Scrollbar(
           controller: _horizontalScrollbarController,
           thumbVisibility: true,
@@ -415,14 +426,15 @@ class DevToolsTableState<T> extends State<DevToolsTable<T>>
             controller: _horizontalScrollbarController,
             child: SelectionArea(
               child: SizedBox(
-                width: max(viewWidth, _tableWidthForOriginalColumns),
+                width: max(viewWidth, _currentTableWidth),
                 child: Column(
                   crossAxisAlignment: CrossAxisAlignment.stretch,
                   children: [
                     if (showColumnGroupHeader)
                       TableRow<T>.tableColumnGroupHeader(
                         columnGroups: columnGroups,
-                        columnWidths: adjustedColumnWidths,
+                        columnWidths: _columnWidths,
+                        onColumnResize: _handleColumnResize,
                         sortColumn: sortColumn,
                         sortDirection: tableUiState.sortDirection,
                         secondarySortColumn:
@@ -436,7 +448,8 @@ class DevToolsTableState<T> extends State<DevToolsTable<T>>
                       key: const Key('Table header'),
                       columns: widget.tableController.columns,
                       columnGroups: columnGroups,
-                      columnWidths: adjustedColumnWidths,
+                      columnWidths: _columnWidths,
+                      onColumnResize: _handleColumnResize,
                       sortColumn: sortColumn,
                       sortDirection: tableUiState.sortDirection,
                       secondarySortColumn:

packages/devtools_app/release_notes/NEXT_RELEASE_NOTES.md

@@ -17,6 +17,8 @@ To learn more about DevTools, check out the
 
 - Added a horizontal scrollbar to data tables to help with navigation.  -
   [#9482](https://github.com/flutter/devtools/pull/9482)
+- Made it possible to resize data table columns by dragging the header separators.  -
+  [#9845](https://github.com/flutter/devtools/pull/9485)
 
 ## Inspector updates