[Buttons] Addition of a FAB shape themer (#5131)

This is an addition of a FAB shape themer.

This resolves issue #5055

components/Buttons/src/ShapeThemer/MDCFloatingButtonShapeThemer.h

@@ -0,0 +1,35 @@
+// Copyright 2018-present the Material Components for iOS authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <UIKit/UIKit.h>
+
+#import "MaterialButtons.h"
+#import "MaterialShapeLibrary.h"
+#import "MaterialShapeScheme.h"
+
+/**
+ The Material Design shape system's themer for instances of MDCFloatingButton.
+ */
+@interface MDCFloatingButtonShapeThemer : NSObject
+
+/**
+ Applies a shape scheme's properties to an MDCFloatingButton.
+
+ @param shapeScheme The shape scheme to apply to the component instance.
+ @param button A component instance to which the shape scheme should be applied.
+ */
++ (void)applyShapeScheme:(nonnull id<MDCShapeScheming>)shapeScheme
+                toButton:(nonnull MDCFloatingButton *)button;
+
+@end

components/Buttons/src/ShapeThemer/MDCFloatingButtonShapeThemer.m

@@ -0,0 +1,32 @@
+// Copyright 2018-present the Material Components for iOS authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "MDCFloatingButtonShapeThemer.h"
+
+static const CGFloat kFloatingButtonBaselineShapePercentageValue = 0.5f;
+
+@implementation MDCFloatingButtonShapeThemer
+
++ (void)applyShapeScheme:(nonnull id<MDCShapeScheming>)shapeScheme
+                toButton:(nonnull MDCFloatingButton *)button {
+  // This is an override of the default scheme to fit the baseline values.
+  MDCRectangleShapeGenerator *rectangleShape = [[MDCRectangleShapeGenerator alloc] init];
+  MDCCornerTreatment *cornerTreatment =
+      [MDCCornerTreatment cornerWithRadius:kFloatingButtonBaselineShapePercentageValue
+                                 valueType:MDCCornerTreatmentValueTypePercentage];
+  [rectangleShape setCorners:cornerTreatment];
+  button.shapeGenerator = rectangleShape;
+}
+
+@end

components/Buttons/src/ShapeThemer/MaterialButtons+ShapeThemer.h

@@ -13,3 +13,4 @@
 // limitations under the License.
 
 #import "MDCButtonShapeThemer.h"
+#import "MDCFloatingButtonShapeThemer.h"

components/Buttons/tests/unit/ButtonsShapeThemerTests.m

@@ -56,6 +56,27 @@ - (void)testMDCButtonShapeThemer {
                         self.shapeScheme.smallSurfaceShape.bottomRightCorner);
 }
 
+- (void)testMDCFloatingButtonShapeThemer {
+  // Given
+  MDCFloatingButton *FAB = [[MDCFloatingButton alloc] initWithFrame:CGRectZero
+                                                              shape:MDCFloatingButtonShapeDefault];
+  self.shapeScheme.smallSurfaceShape =
+      [[MDCShapeCategory alloc] initCornersWithFamily:MDCShapeCornerFamilyAngled andSize:10];
+  FAB.shapeGenerator = [[MDCRectangleShapeGenerator alloc] init];
+
+  // When
+  [MDCFloatingButtonShapeThemer applyShapeScheme:self.shapeScheme toButton:FAB];
+
+  // Then
+  MDCRectangleShapeGenerator *rect = (MDCRectangleShapeGenerator *)FAB.shapeGenerator;
+  MDCCornerTreatment *corner = [MDCCornerTreatment cornerWithRadius:0.5f];
+  corner.valueType = MDCCornerTreatmentValueTypePercentage;
+  XCTAssertEqualObjects(rect.topLeftCorner, corner);
+  XCTAssertEqualObjects(rect.topRightCorner, corner);
+  XCTAssertEqualObjects(rect.bottomLeftCorner, corner);
+  XCTAssertEqualObjects(rect.bottomRightCorner, corner);
+}
+
 - (void)testBackgroundColorAfterButtonTheming {
   // Given
   UIColor *bgColor = [UIColor blueColor];