Material Design

Shapes Core

This library consists of several classes that are often used together to implement Shape behavior on a component. Concretely, to create a shape object, you’ll need to create an object that implements the MDCShapeGenerating protocol. MDCShapeGenerating only has one method, (CGPath *)pathForSize:(CGSize)size that returns the shape’s CGPath for the expected size.

Our components support shapes by providing a property called id<MDCShapeGenerating> shapeGenerator and applies the provided shape to the component.

Table of contents


Overview

Listed below are classes that can be used to create an object that implements the MDCShapeGenerating protocol.

MDCPathGenerator

At the core there is MDCPathGenerator, which provides helper methods for building a CGPath. By providing a start point and end point, and using its different APIs to draw lines/curves between points, a CGPath is created.

MDCShapedShadowLayer

An MDCShapedShadowLayer class is used as the main layer class of the component’s view instead of MDCShadowLayer to allow shapes to work well with shadows, borders, and background color.

The same way we override the layer in our components with MDCShadowLayer to achieve a shadow, we instead use MDCShapedShadowLayer like so:

@interface Component ()
@property(nonatomic, readonly, strong) MDCShapedShadowLayer *layer;
@end

@implementation Component

@dynamic layer;

+ (Class)layerClass {
  return [MDCShapedShadowLayer class];
}
@end

MDCShapedView

MDCShapedView is a base UIView that incorporates MDCShapedShadowLayer, a shapeGenerator object, and elevation, to provide a minimal view that has full shape support. This can be used as a building block for components that need shape support.

MDCCornerTreatment and MDCEdgeTreatment

MDCCornerTreatment and MDCEdgeTreatment are both classes that provide a modular approach for defining specifically the CGPath for a specific edge or corner.

MDCRectangleShapeGenerator

The last class in the Shapes Core library is MDCRectangleShapeGenerator. It is a shapeGenerator on its own (meaning it implements MDCShapeGenerating), and generates a CGPath but allows good customization as part of its implementation. It allows to set each of its corners and edges by using its MDCCornerTreatments and MDCEdgeTreatment. With this class we can basically build any Shape we want.

Usage

You’ll typically create an MDCRectangleShapeGenerator instance that you set your component with. Components that support the shape system will have a id<MDCShapeGenerating> shapeGenerator property as part of their API. By setting the shapeGenerator property with your MDCRectangleShapeGenerator, you will provide the defined shape to your component.

Swift

let card = MDCCard()
let shapeGenerator = MDCRectangleShapeGenerator()
card.shapeGenerator = MDCRectangleShapeGenerator()

Objective-C

MDCCard *card = [[MDCCard alloc] init];
MDCRectangleShapeGenerator *shapeGenerator = [[MDCRectangleShapeGenerator alloc] init];
card.shapeGenerator = shapeGenerator;