Core Foundation is a framework that provides fundamental software services useful to application services, application environments, and to applications themselves. Core Foundation also provides abstractions for common data types, facilitates internationalization with Unicode string storage, and offers a suite of utilities such as plug-in support, XML property lists, URL resource access, and preferences.

The Core Graphics framework is based on the Quartz advanced drawing engine. It provides low-level, lightweight 2D rendering with unmatched output fidelity. You use this framework to handle path-based drawing, transformations, color management, offscreen rendering, patterns, gradients and shadings, image data management, image creation, and image masking, as well as PDF document creation, display, and parsing.

Core Text provides a low-level programming interface for laying out text and handling fonts. The Core Text layout engine is designed for high performance, ease of use, and close integration with Core Foundation. The text layout API provides high-quality typesetting, including character-to-glyph conversion, with ligatures, kerning, and so on. The complementary Core Text font technology provides automatic font substitution (cascading), font descriptors and collections, easy access to font metrics and glyph data, and many other features.

The Foundation framework provides a base layer of functionality for apps and frameworks, including data storage and persistence, text processing, date and time calculations, sorting and filtering, and networking. The classes, protocols, and data types defined by Foundation are used throughout the macOS, iOS, watchOS, and tvOS SDKs.

macOS Launch Services is an API that enables a running app to open other apps or their document files, similar to the Finder or the Dock.Launch Services eliminates apps having to query the Finder to open an app, document, or URL for them. The macOS Finder itself uses Launch Services to perform such tasks. Because the Finder performs no additional processing beyond calling Launch Services, any client using Launch Services for these purposes behaves identically to the Finder.

Allow users to browse, edit, and save images, using slideshows and Core Image filters.The Quartz Composer API supports processing and rendering graphical data and allows developers to create custom patches for the Quartz Composer developer tool. ImageKit provides user interface support for browsing, editing, and saving images, showing slideshows, and browsing and previewing Core Image filters. PDFKit is a technology that allows applications to display and manipulate PDF documents.

WebKit provides a set of classes to display web content in windows, and implements browser features such as following links when clicked by the user, managing a back-forward list, and managing a history of pages recently visited.

The Message UI framework provides specialized view controllers for presenting standard composition interfaces for email and SMS (Short Messaging Service) text messages. Use these interfaces to add message delivery capabilities without requiring the user to leave your app.

The UIKit framework (UIKit.framework) provides the crucial infrastructure needed to construct and manage iOS apps. This framework provides the window and view architecture needed to manage an app’s user interface, the event handling infrastructure needed to respond to user input, and the app model needed to drive the main run loop and interact with the system.

Gradient View is a simple UIView wrapper around CGGradient.