Moved default elevation logic into MDCButton+Subclassing.h.

Author: ajsecord

components/Buttons/src/MDCButton.h

@@ -93,13 +93,14 @@
 @property(nonatomic) UIEdgeInsets hitAreaInsets;
 
 /**
- * This is the color of the view behind the button. It's used by flat buttons to calculate accessible text colors.
+ * The color of the view behind the button, used to calculate accessible text colors.
  *
- * For Flat buttons, this is the color of both the surrounding area and the button's background.
- * For Raised and Floating buttons, this is the color of view underneath the button.
+ * For flat buttons with the default transparent background, this is the color of the surrounding
+ * area (and thus the button's background). For all other buttons, this is the color of view
+ * underneath the button.
  *
- * The default is nil, but if left unset, Raised/Floating buttons will have possibly-incorrect
- * disabled state, and flat buttons will additionally have incorrect text colors.
+ * The default is nil.  If left unset, buttons will likely have an incorrect appearance when
+ * disabled. Additionally, flat buttons will have incorrect text colors.
  */
 @property(nonatomic, strong, nullable) UIColor *underlyingColor;
 

components/Buttons/src/MDCButton.m

@@ -454,24 +454,7 @@ - (void)setBackgroundColor:(UIColor *)backgroundColor forState:(UIControlState)s
 
 - (CGFloat)elevationForState:(UIControlState)state {
   NSNumber *elevation = _userElevations[@(state)];
-
-  if (elevation) {
-    return [elevation floatValue];
-  }
-  if (state & UIControlStateSelected) {
-    CGFloat elevationForNormal = [self elevationForState:UIControlStateNormal];
-    // TODO(ajsecord): Why is this using the raised button values for all buttons?
-    // This should just be a factor of 2, I believe.
-    if (MDCButtonFloatIsExactlyZero(elevationForNormal)) {
-      return MDCShadowElevationRaisedButtonPressed;
-    } else {
-      CGFloat pressedDeltaForRaisedButton = MDCShadowElevationRaisedButtonPressed -
-                                            MDCShadowElevationRaisedButtonResting;
-      return elevationForNormal + pressedDeltaForRaisedButton;
-    }
-  } else {
-    return MDCShadowElevationNone;
-  }
+  return elevation ? [elevation floatValue] : [self defaultElevationForState:state];
 }
 
 - (void)setElevation:(CGFloat)elevation forState:(UIControlState)state {
@@ -563,6 +546,10 @@ - (UIEdgeInsets)defaultContentEdgeInsets {
   return UIEdgeInsetsMake(8, 16, 8, 16);
 }
 
+- (CGFloat)defaultElevationForState:(UIControlState)state {
+  return 0;
+}
+
 - (BOOL)shouldHaveOpaqueBackground {
   BOOL isFlatButton = MDCButtonFloatIsExactlyZero([self elevationForState:UIControlStateNormal]);
   return !isFlatButton;

components/Buttons/src/MDCFloatingButton.m

@@ -110,4 +110,10 @@ - (UIEdgeInsets)defaultContentEdgeInsets {
   }
 }
 
+- (CGFloat)defaultElevationForState:(UIControlState)state {
+  return (state & UIControlStateSelected) == UIControlStateSelected ?
+      MDCShadowElevationFABPressed :
+      MDCShadowElevationFABResting;
+}
+
 @end

components/Buttons/src/MDCRaisedButton.m

@@ -33,4 +33,12 @@ - (instancetype)initWithFrame:(CGRect)frame {
   return self;
 }
 
+#pragma mark - Subclassing
+
+- (CGFloat)defaultElevationForState:(UIControlState)state {
+  return (state & UIControlStateSelected) == UIControlStateSelected ?
+      MDCShadowElevationRaisedButtonPressed :
+      MDCShadowElevationRaisedButtonResting;
+}
+
 @end

components/Buttons/src/Private/MDCButton+Subclassing.h

@@ -57,4 +57,9 @@
  */
 - (UIEdgeInsets)defaultContentEdgeInsets;
 
+/**
+ The default elevation for a particular button state (if not set by the calling code).
+ */
+- (CGFloat)defaultElevationForState:(UIControlState)state;
+
 @end