Crate lay_rs

Layers Engine

Layers is an animation and rendering engine designed for user interfaces. It utilizes a scene graph for efficient, retained mode rendering of UI elements, optimizing common interpolations such as opacity, 2D transformations, and blending.

Key Features

• Scene Graph: Manages nodes (graphical layers) including text, simple shapes (e.g., rectangles), and external textures.
• Animatable Properties: Nodes have properties that can be animated, with changes scheduled and executed by the engine using a Command pattern. This ensures a consistent API for both immediate and animated changes.
• Optimized Rendering: Uses a display list for efficient rendering commands.
• Animation Hooks: The API exposes hooks at different stages of the animation progress.
• Layout Engine: Uses the Taffy library for layout calculations.
• Multi-threaded: Supports concurrent updates to layer properties.
• Spring Physics Animations: Supports spring physics for animations.
• Easing Functions: Includes a variety of easing functions for animations.
• Incremental Rendering: Only redraws the portions of the scene that have changed.
• Debugger: The engine has a built-in debugger for visualizing the scene graph

Layer

A Layer is a 2D object in the engine with the following capabilities:

• Rasterized Content: Can contain rasterized images or be a container for other layers.
• Transformations: Supports positioning, rotation, scaling, and animation.
• Nesting: Layers can be nested to create complex 2D objects, similar to the DOM in web browsers.
• Drawing Properties: Includes properties such as border, background, shadow, and opacity.

Rendering Model

• Retained Mode: The engine maintains a tree of layers and only redraws those that have changed.
• Display List: Uses a display list to optimize rendering commands.
• Damage tracking: On every update, the damage of the scene is calculated.

Multi-threaded Support

• Concurrent Updates: Layer properties are updated across multiple threads.

Backend Support (Skia)

• Drawing Library: Uses the Skia library.
• Supported Backends:
  • OpenGL: Using FBO (Framebuffer Objects)
  • EGL: For OpenGL ES contexts
  • Image: For testing purposes

Taffy Layout

• Layout Engine: Utilizes the Taffy library, based on the Flexbox model.

Re-exports

• pub extern crate skia_bindings as sb;
• pub extern crate skia_safe as skia;
• pub extern crate taffy;

Modules

• api
  Safe interface to C API (under development)
• drawing
  Drawing related code for Layer, Scene, and Text. The functions in this module are used to draw into a Skia canvas independent from the backend
• engine
  Contains all the logic for running the animations, execute the scheduled changes to the models, and prepare the render tree The scene is drawn in 4 stages:
• prelude
• renderer
  Renderers that use skia to draw the models to different backends. currently the backends available are gl framebuffer objects and images.
• types
  Types used in the library to describe Layers properties
• utils
• view
  Helper struct to build complex layer hierarchies that change over time

Macros

• layer_trees
• layer_trees_opt