Refactor Material build method (#147430)

Only a code quality change, improves readability using `switch`.

Author: nate-thegrate

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

@@ -431,38 +431,24 @@ class Material extends StatefulWidget {
 class _MaterialState extends State<Material> with TickerProviderStateMixin {
   final GlobalKey _inkFeatureRenderer = GlobalKey(debugLabel: 'ink renderer');
 
-  Color? _getBackgroundColor(BuildContext context) {
-    final ThemeData theme = Theme.of(context);
-    Color? color = widget.color;
-    if (color == null) {
-      switch (widget.type) {
-        case MaterialType.canvas:
-          color = theme.canvasColor;
-        case MaterialType.card:
-          color = theme.cardColor;
-        case MaterialType.button:
-        case MaterialType.circle:
-        case MaterialType.transparency:
-          break;
-      }
-    }
-    return color;
-  }
-
   @override
   Widget build(BuildContext context) {
     final ThemeData theme = Theme.of(context);
-    final Color? backgroundColor = _getBackgroundColor(context);
-    final Color modelShadowColor = widget.shadowColor ?? (theme.useMaterial3 ? theme.colorScheme.shadow : theme.shadowColor);
-    // If no shadow color is specified, use 0 for elevation in the model so a drop shadow won't be painted.
-    final double modelElevation = widget.elevation;
+    final Color? backgroundColor = widget.color ?? switch (widget.type) {
+      MaterialType.canvas => theme.canvasColor,
+      MaterialType.card => theme.cardColor,
+      MaterialType.button || MaterialType.circle || MaterialType.transparency => null,
+    };
+    final Color modelShadowColor = widget.shadowColor
+        ?? (theme.useMaterial3 ? theme.colorScheme.shadow : theme.shadowColor);
     assert(
       backgroundColor != null || widget.type == MaterialType.transparency,
       'If Material type is not MaterialType.transparency, a color must '
       'either be passed in through the `color` property, or be defined '
       'in the theme (ex. canvasColor != null if type is set to '
       'MaterialType.canvas)',
     );
+
     Widget? contents = widget.child;
     if (contents != null) {
       contents = AnimatedDefaultTextStyle(
@@ -486,6 +472,10 @@ class _MaterialState extends State<Material> with TickerProviderStateMixin {
       ),
     );
 
+    ShapeBorder? shape = widget.borderRadius != null
+        ? RoundedRectangleBorder(borderRadius: widget.borderRadius!)
+        : widget.shape;
+
     // PhysicalModel has a temporary workaround for a performance issue that
     // speeds up rectangular non transparent material (the workaround is to
     // skip the call to ui.Canvas.saveLayer if the border radius is 0).
@@ -495,31 +485,39 @@ class _MaterialState extends State<Material> with TickerProviderStateMixin {
     // specified rectangles (e.g shape RoundedRectangleBorder with radius 0, but
     // we choose not to as we want the change from the fast-path to the
     // slow-path to be noticeable in the construction site of Material.
-    if (widget.type == MaterialType.canvas && widget.shape == null && widget.borderRadius == null) {
-      final Color color = Theme.of(context).useMaterial3
+    if (widget.type == MaterialType.canvas && shape == null) {
+      final Color color = theme.useMaterial3
         ? ElevationOverlay.applySurfaceTint(backgroundColor!, widget.surfaceTintColor, widget.elevation)
         : ElevationOverlay.applyOverlay(context, backgroundColor!, widget.elevation);
 
       return AnimatedPhysicalModel(
         curve: Curves.fastOutSlowIn,
         duration: widget.animationDuration,
         clipBehavior: widget.clipBehavior,
-        elevation: modelElevation,
+        elevation: widget.elevation,
         color: color,
         shadowColor: modelShadowColor,
         animateColor: false,
         child: contents,
       );
     }
 
-    final ShapeBorder shape = _getShape();
+    shape ??= switch (widget.type) {
+      MaterialType.circle => const CircleBorder(),
+      MaterialType.canvas || MaterialType.transparency => const RoundedRectangleBorder(),
+      MaterialType.card || MaterialType.button => const RoundedRectangleBorder(
+          borderRadius: BorderRadius.all(Radius.circular(2.0)),
+        ),
+    };
 
     if (widget.type == MaterialType.transparency) {
-      return _transparentInterior(
-        context: context,
-        shape: shape,
+      return ClipPath(
+        clipper: ShapeBorderClipper(
+          shape: shape,
+          textDirection: Directionality.maybeOf(context),
+        ),
         clipBehavior: widget.clipBehavior,
-        contents: contents,
+        child: _ShapeBorderPaint(shape: shape, child: contents),
       );
     }
 
@@ -536,56 +534,6 @@ class _MaterialState extends State<Material> with TickerProviderStateMixin {
       child: contents,
     );
   }
-
-  static Widget _transparentInterior({
-    required BuildContext context,
-    required ShapeBorder shape,
-    required Clip clipBehavior,
-    required Widget contents,
-  }) {
-    final _ShapeBorderPaint child = _ShapeBorderPaint(
-      shape: shape,
-      child: contents,
-    );
-    return ClipPath(
-      clipper: ShapeBorderClipper(
-        shape: shape,
-        textDirection: Directionality.maybeOf(context),
-      ),
-      clipBehavior: clipBehavior,
-      child: child,
-    );
-  }
-
-  // Determines the shape for this Material.
-  //
-  // If a shape was specified, it will determine the shape.
-  // If a borderRadius was specified, the shape is a rounded
-  // rectangle.
-  // Otherwise, the shape is determined by the widget type as described in the
-  // Material class documentation.
-  ShapeBorder _getShape() {
-    if (widget.shape != null) {
-      return widget.shape!;
-    }
-    if (widget.borderRadius != null) {
-      return RoundedRectangleBorder(borderRadius: widget.borderRadius!);
-    }
-    switch (widget.type) {
-      case MaterialType.canvas:
-      case MaterialType.transparency:
-        return const RoundedRectangleBorder();
-
-      case MaterialType.card:
-      case MaterialType.button:
-        return RoundedRectangleBorder(
-          borderRadius: widget.borderRadius ?? kMaterialEdges[widget.type]!,
-        );
-
-      case MaterialType.circle:
-        return const CircleBorder();
-    }
-  }
 }
 
 class _RenderInkFeatures extends RenderProxyBox implements MaterialInkController {
@@ -899,7 +847,7 @@ class _MaterialInterior extends ImplicitlyAnimatedWidget {
   final Color color;
 
   /// The target shadow color.
-  final Color? shadowColor;
+  final Color shadowColor;
 
   /// The target surface tint color.
   final Color? surfaceTintColor;
@@ -930,13 +878,11 @@ class _MaterialInteriorState extends AnimatedWidgetBaseState<_MaterialInterior>
       widget.elevation,
       (dynamic value) => Tween<double>(begin: value as double),
     ) as Tween<double>?;
-    _shadowColor =  widget.shadowColor != null
-      ? visitor(
-          _shadowColor,
-          widget.shadowColor,
-          (dynamic value) => ColorTween(begin: value as Color),
-        ) as ColorTween?
-      : null;
+    _shadowColor = visitor(
+      _shadowColor,
+      widget.shadowColor,
+      (dynamic value) => ColorTween(begin: value as Color),
+    ) as ColorTween?;
     _surfaceTintColor = widget.surfaceTintColor != null
       ? visitor(
           _surfaceTintColor,
@@ -958,16 +904,15 @@ class _MaterialInteriorState extends AnimatedWidgetBaseState<_MaterialInterior>
     final Color color = Theme.of(context).useMaterial3
       ? ElevationOverlay.applySurfaceTint(widget.color, _surfaceTintColor?.evaluate(animation), elevation)
       : ElevationOverlay.applyOverlay(context, widget.color, elevation);
-    // If no shadow color is specified, use 0 for elevation in the model so a drop shadow won't be painted.
-    final double modelElevation = widget.shadowColor != null ? elevation : 0;
-    final Color shadowColor = _shadowColor?.evaluate(animation) ?? const Color(0x00000000);
+    final Color shadowColor = _shadowColor!.evaluate(animation)!;
+
     return PhysicalShape(
       clipper: ShapeBorderClipper(
         shape: shape,
         textDirection: Directionality.maybeOf(context),
       ),
       clipBehavior: widget.clipBehavior,
-      elevation: modelElevation,
+      elevation: elevation,
       color: color,
       shadowColor: shadowColor,
       child: _ShapeBorderPaint(