Allow Drawer width to be customized (#99777)

* Add ability to customize Drawer width

* Fix formatting

* More formatting

* Formatting again

* Add width to DrawerThemeData and add associated tests

* Fix test formatting

packages/flutter/lib/src/material/drawer.dart

@@ -144,6 +144,7 @@ class Drawer extends StatelessWidget {
     this.backgroundColor,
     this.elevation,
     this.shape,
+    this.width,
     this.child,
     this.semanticLabel,
   }) : assert(elevation == null || elevation >= 0.0),
@@ -172,6 +173,12 @@ class Drawer extends StatelessWidget {
   /// is also null, then it falls back to [Material]'s default.
   final ShapeBorder? shape;
 
+  /// The width of the drawer.
+  ///
+  /// If this is null, then [DrawerThemeData.width] is used. If that is also
+  /// null, then it falls back to the Material spec's default (304.0).
+  final double? width;
+
   /// The widget below this widget in the tree.
   ///
   /// Typically a [SliverList].
@@ -212,7 +219,7 @@ class Drawer extends StatelessWidget {
       explicitChildNodes: true,
       label: label,
       child: ConstrainedBox(
-        constraints: const BoxConstraints.expand(width: _kWidth),
+        constraints: BoxConstraints.expand(width: width ?? drawerTheme.width ?? _kWidth),
         child: Material(
           color: backgroundColor ?? drawerTheme.backgroundColor,
           elevation: elevation ?? drawerTheme.elevation ?? 16.0,

packages/flutter/lib/src/material/drawer_theme.dart

@@ -36,6 +36,7 @@ class DrawerThemeData with Diagnosticable {
     this.scrimColor,
     this.elevation,
     this.shape,
+    this.width,
   });
 
   /// Overrides the default value of [Drawer.backgroundColor].
@@ -50,6 +51,9 @@ class DrawerThemeData with Diagnosticable {
   /// Overrides the default value of [Drawer.shape].
   final ShapeBorder? shape;
 
+  /// Overrides the default value of [Drawer.width].
+  final double? width;
+
   /// Creates a copy of this object with the given fields replaced with the
   /// new values.
   DrawerThemeData copyWith({
@@ -57,12 +61,14 @@ class DrawerThemeData with Diagnosticable {
     Color? scrimColor,
     double? elevation,
     ShapeBorder? shape,
+    double? width,
   }) {
     return DrawerThemeData(
       backgroundColor: backgroundColor ?? this.backgroundColor,
       scrimColor: scrimColor ?? this.scrimColor,
       elevation: elevation ?? this.elevation,
       shape: shape ?? this.shape,
+      width: width ?? this.width,
     );
   }
 
@@ -80,6 +86,7 @@ class DrawerThemeData with Diagnosticable {
       scrimColor: Color.lerp(a?.scrimColor, b?.scrimColor, t),
       elevation: lerpDouble(a?.elevation, b?.elevation, t),
       shape: ShapeBorder.lerp(a?.shape, b?.shape, t),
+      width: lerpDouble(a?.width, b?.width, t),
     );
   }
 
@@ -89,6 +96,7 @@ class DrawerThemeData with Diagnosticable {
     scrimColor,
     elevation,
     shape,
+    width,
   );
 
   @override
@@ -101,7 +109,8 @@ class DrawerThemeData with Diagnosticable {
         && other.backgroundColor == backgroundColor
         && other.scrimColor == scrimColor
         && other.elevation == elevation
-        && other.shape == shape;
+        && other.shape == shape
+        && other.width == width;
   }
 
   @override
@@ -111,6 +120,7 @@ class DrawerThemeData with Diagnosticable {
     properties.add(ColorProperty('scrimColor', scrimColor, defaultValue: null));
     properties.add(DoubleProperty('elevation', elevation, defaultValue: null));
     properties.add(DiagnosticsProperty<ShapeBorder>('shape', shape, defaultValue: null));
+    properties.add(DoubleProperty('width', width, defaultValue: null));
   }
 }
 

packages/flutter/test/material/drawer_test.dart

@@ -445,4 +445,45 @@ void main() {
     await tester.pumpAndSettle();
     expect(find.text('endDrawer'), findsNothing);
   });
+
+  testWidgets('Drawer width defaults to Material spec', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: Scaffold(
+          drawer: Drawer(),
+        ),
+      ),
+    );
+
+    final ScaffoldState state = tester.firstState(find.byType(Scaffold));
+    state.openDrawer();
+
+    await tester.pump();
+    await tester.pump(const Duration(seconds: 1));
+
+    final RenderBox box = tester.renderObject(find.byType(Drawer));
+    expect(box.size.width, equals(304.0));
+  });
+
+  testWidgets('Drawer width can be customized by parameter', (WidgetTester tester) async {
+    const double smallWidth = 200;
+
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: Scaffold(
+          drawer: Drawer(
+            width: smallWidth,
+          ),
+        ),
+      ),
+    );
+
+    final ScaffoldState state = tester.firstState(find.byType(Scaffold));
+    state.openDrawer();
+
+    await tester.pumpAndSettle();
+
+    final RenderBox box = tester.renderObject(find.byType(Drawer));
+    expect(box.size.width, equals(smallWidth));
+  });
 }

packages/flutter/test/material/drawer_theme_test.dart

@@ -31,6 +31,7 @@ void main() {
       scrimColor: Color(0x00000098),
       elevation: 5.0,
       shape: RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(2.0))),
+      width: 200.0,
     ).debugFillProperties(builder);
 
     final List<String> description = builder.properties
@@ -43,6 +44,7 @@ void main() {
       'scrimColor: Color(0x00000098)',
       'elevation: 5.0',
       'shape: RoundedRectangleBorder(BorderSide(Color(0xff000000), 0.0, BorderStyle.none), BorderRadius.circular(2.0))',
+      'width: 200.0',
     ]);
   });
 
@@ -63,6 +65,7 @@ void main() {
     expect(_drawerMaterial(tester).elevation, 16.0);
     expect(_drawerMaterial(tester).shape, null);
     expect(_scrim(tester).color, Colors.black54);
+    expect(_drawerRenderBox(tester).size.width, 304.0);
   });
 
   testWidgets('DrawerThemeData values are used when no Drawer properties are specified', (WidgetTester tester) async {
@@ -70,6 +73,7 @@ void main() {
     const Color scrimColor = Color(0x00000002);
     const double elevation = 7.0;
     const RoundedRectangleBorder shape = RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(16.0)));
+    const double width = 200.0;
 
     final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey<ScaffoldState>();
     await tester.pumpWidget(
@@ -80,6 +84,7 @@ void main() {
             scrimColor: scrimColor,
             elevation: elevation,
             shape: shape,
+            width: width,
           ),
         ),
         home: Scaffold(
@@ -95,6 +100,7 @@ void main() {
     expect(_drawerMaterial(tester).elevation, elevation);
     expect(_drawerMaterial(tester).shape, shape);
     expect(_scrim(tester).color, scrimColor);
+    expect(_drawerRenderBox(tester).size.width, width);
   });
 
   testWidgets('Drawer values take priority over DrawerThemeData values when both properties are specified', (WidgetTester tester) async {
@@ -102,6 +108,7 @@ void main() {
     const Color scrimColor = Color(0x00000002);
     const double elevation = 7.0;
     const RoundedRectangleBorder shape = RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(16.0)));
+    const double width = 200.0;
 
     final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey<ScaffoldState>();
     await tester.pumpWidget(
@@ -112,6 +119,7 @@ void main() {
             scrimColor: Color(0x00000004),
             elevation: 13.0,
             shape: RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(29.0))),
+            width: 400.0,
           ),
         ),
         home: Scaffold(
@@ -121,6 +129,7 @@ void main() {
             backgroundColor: backgroundColor,
             elevation: elevation,
             shape: shape,
+            width: width,
           ),
         ),
       ),
@@ -132,6 +141,7 @@ void main() {
     expect(_drawerMaterial(tester).elevation, elevation);
     expect(_drawerMaterial(tester).shape, shape);
     expect(_scrim(tester).color, scrimColor);
+    expect(_drawerRenderBox(tester).size.width, width);
   });
 
   testWidgets('DrawerTheme values take priority over ThemeData.drawerTheme values when both properties are specified', (WidgetTester tester) async {
@@ -139,6 +149,7 @@ void main() {
     const Color scrimColor = Color(0x00000002);
     const double elevation = 7.0;
     const RoundedRectangleBorder shape = RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(16.0)));
+    const double width = 200.0;
 
     final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey<ScaffoldState>();
     await tester.pumpWidget(
@@ -149,6 +160,7 @@ void main() {
             scrimColor: Color(0x00000004),
             elevation: 13.0,
             shape: RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(29.0))),
+            width: 400.0
           ),
         ),
         home: DrawerTheme(
@@ -157,6 +169,7 @@ void main() {
             scrimColor: scrimColor,
             elevation: elevation,
             shape: shape,
+            width: width,
           ),
           child: Scaffold(
             key: scaffoldKey,
@@ -172,6 +185,7 @@ void main() {
     expect(_drawerMaterial(tester).elevation, elevation);
     expect(_drawerMaterial(tester).shape, shape);
     expect(_scrim(tester).color, scrimColor);
+    expect(_drawerRenderBox(tester).size.width, width);
   });
 }
 
@@ -200,3 +214,8 @@ Container _scrim(WidgetTester tester) {
     ),
   );
 }
+
+// The RenderBox representing the Drawer.
+RenderBox _drawerRenderBox(WidgetTester tester) {
+  return tester.renderObject(find.byType(Drawer));
+}