[Shadows] Code improvements for the new Shadow component.

PiperOrigin-RevId: 367871950

components/Shadow/examples/ShadowTypicalUseExample.swift

@@ -29,14 +29,15 @@ final class ShadowedView: UIView {
 
   override func layoutSubviews() {
     super.layoutSubviews()
-    MDCConfigureShadow(for: self, color: MDCShadowColor(), elevation: 2)
+    MDCConfigureShadow(
+      for: self, shadow: MDCShadowForElevation(1, MDCShadowsCollectionDefault()),
+      color: MDCShadowColor())
   }
 }
 
 /// Typical use-case for a shaped view with Material Shadows.
 final class ShapedView: UIView {
   let shapeLayer = CAShapeLayer()
-  let shadow = MDCShadowForElevation(2)
 
   override init(frame: CGRect) {
     super.init(frame: frame)
@@ -61,14 +62,17 @@ final class ShapedView: UIView {
     super.layoutSubviews()
     guard let path = polygonPath(bounds: self.bounds, numSides: 3, numPoints: 3) else { return }
     shapeLayer.path = path
-    MDCConfigureShadow(for: self, color: MDCShadowColor(), shadow: shadow, path: path)
+
+    MDCConfigureShadow(
+      for: self, shadow: MDCShadowForElevation(1, MDCShadowsCollectionDefault()),
+      color: MDCShadowColor(),
+      path: path)
   }
 }
 
 /// More complex use-case for a view with a custom shape which animates.
 final class AnimatedShapedView: UIView {
   let shapeLayer = CAShapeLayer()
-  let shadow = MDCShadowForElevation(2)
   let firstNumSides = 3
   let lastNumSides = 12
   let animationStepDuration: CFTimeInterval = 0.6
@@ -104,7 +108,10 @@ final class AnimatedShapedView: UIView {
         bounds: bounds, numSides: firstNumSides, numPoints: lastNumSides)
     else { return }
     shapeLayer.path = startPath
-    MDCConfigureShadow(for: self, color: MDCShadowColor(), shadow: shadow, path: startPath)
+    MDCConfigureShadow(
+      for: self, shadow: MDCShadowForElevation(1, MDCShadowsCollectionDefault()),
+      color: MDCShadowColor(),
+      path: startPath)
 
     var polygonPaths = (firstNumSides...lastNumSides).map {
       polygonPath(bounds: bounds, numSides: $0, numPoints: lastNumSides)

components/Shadow/src/MDCShadow.h

@@ -15,11 +15,14 @@
 #import <UIKit/UIKit.h>
 
 /**
- Immutable value type holding shadow metrics to apply to a view's layer. Use
- `MDCShadowForElevation()` or `MDCShadowBuilder` to create this object.
+ An immutable shadow object that consists of shadow properties (opacity, radius, offset).
+
+ To generate a shadow instance, please use the MDCShadowBuilder APIs.
  */
 __attribute__((objc_subclassing_restricted)) @interface MDCShadow : NSObject
 
+- (nonnull instancetype)init NS_UNAVAILABLE;
+
 /** CALayer.shadowOpacity */
 @property(nonatomic, readonly) CGFloat opacity;
 
@@ -29,8 +32,6 @@ __attribute__((objc_subclassing_restricted)) @interface MDCShadow : NSObject
 /** CALayer.shadowOffset */
 @property(nonatomic, readonly) CGSize offset;
 
-- (nonnull instancetype)init NS_UNAVAILABLE;
-
 @end
 
 /**
@@ -50,15 +51,9 @@ __attribute__((objc_subclassing_restricted)) @interface MDCShadowBuilder : NSObj
 /** Returns an immutable value type containing a snapshot of the values in this object. */
 - (nonnull MDCShadow *)build;
 
-@end
-
-/**
- Default color for a Material shadow. On iOS >= 13, this is a dynamic color.
- */
-FOUNDATION_EXTERN UIColor *_Nonnull MDCShadowColor(void);
+/** Returns a builder with the provided opacity, radius, and offset properties. */
++ (nonnull MDCShadowBuilder *)builderWithOpacity:(CGFloat)opacity
+                                          radius:(CGFloat)radius
+                                          offset:(CGSize)offset;
 
-/**
- Returns an `MDCShadow` representing the Material shadow metrics for the given elevation (in
- points).
- */
-FOUNDATION_EXTERN MDCShadow *_Nonnull MDCShadowForElevation(CGFloat elevation);
+@end

components/Shadow/src/MDCShadow.m

@@ -14,9 +14,6 @@
 
 #import "MDCShadow.h"
 
-#import "MaterialAvailability.h"
-#import "MDCShadow+Internal.h"
-
 @implementation MDCShadow
 
 - (instancetype)initWithOpacity:(CGFloat)opacity radius:(CGFloat)radius offset:(CGSize)offset {
@@ -59,68 +56,14 @@ - (MDCShadow *)build {
   return [[MDCShadow alloc] initWithOpacity:self.opacity radius:self.radius offset:self.offset];
 }
 
-@end
-
-static UIColor *LightStyleShadowColor(void) {
-  static UIColor *lightStyleShadowColor;
-  static dispatch_once_t onceToken;
-  dispatch_once(&onceToken, ^{
-    lightStyleShadowColor = [UIColor colorWithRed:0.235 green:0.251 blue:0.263 alpha:1];
-  });
-  return lightStyleShadowColor;
-}
-
-UIColor *MDCShadowColor(void) {
-#if MDC_AVAILABLE_SDK_IOS(13_0)
-  if (@available(iOS 13.0, *)) {
-    return [UIColor colorWithDynamicProvider:^(UITraitCollection *traitCollection) {
-      switch (traitCollection.userInterfaceStyle) {
-        case UIUserInterfaceStyleUnspecified:
-          __attribute__((fallthrough));
-        case UIUserInterfaceStyleLight:
-          return LightStyleShadowColor();
-        case UIUserInterfaceStyleDark:
-          return UIColor.blackColor;
-      }
-      __builtin_unreachable();
-    }];
-  }
-#endif  // MDC_AVAILABLE_SDK_IOS(13_0)
-  return LightStyleShadowColor();
++ (MDCShadowBuilder *)builderWithOpacity:(CGFloat)opacity
+                                  radius:(CGFloat)radius
+                                  offset:(CGSize)offset {
+  MDCShadowBuilder *builder = [[MDCShadowBuilder alloc] init];
+  builder.opacity = opacity;
+  builder.radius = radius;
+  builder.offset = offset;
+  return builder;
 }
 
-static int ShadowElevationToLevel(CGFloat elevation) {
-  if (elevation < 1) {
-    return 0;
-  }
-  if (elevation < 3) {
-    return 1;
-  }
-  if (elevation < 6) {
-    return 2;
-  }
-  if (elevation < 8) {
-    return 3;
-  }
-  if (elevation < 12) {
-    return 4;
-  }
-  return 5;
-}
-
-MDCShadow *MDCShadowForElevation(CGFloat elevation) {
-  static NSArray *shadowLevels;
-  static dispatch_once_t onceToken;
-  dispatch_once(&onceToken, ^{
-    shadowLevels = @[
-      [[MDCShadow alloc] initWithOpacity:0 radius:0 offset:CGSizeMake(0, 0)],
-      [[MDCShadow alloc] initWithOpacity:0.43 radius:2.5 offset:CGSizeMake(0, 1)],
-      [[MDCShadow alloc] initWithOpacity:0.4 radius:3.25 offset:CGSizeMake(0, 1.25)],
-      [[MDCShadow alloc] initWithOpacity:0.34 radius:4.75 offset:CGSizeMake(0, 2.25)],
-      [[MDCShadow alloc] initWithOpacity:0.42 radius:6 offset:CGSizeMake(0, 3)],
-      [[MDCShadow alloc] initWithOpacity:0.4 radius:7.25 offset:CGSizeMake(0, 5)],
-    ];
-  });
-  int shadowLevel = ShadowElevationToLevel(elevation);
-  return shadowLevels[shadowLevel];
-}
+@end