Leland Richardson and Chuck Jasky, both key members of Google's Compose team, dive into performance optimization for the Compose toolkit. They discuss groundbreaking features like Pausable Composition, which automates updates and enhances rendering speed. The duo also tackles the challenges of managing mutable versus immutable objects and the intricacies of equality in Kotlin. Additionally, they touch on the balance between stability and performance, and highlight new diagnostic tools improving the developer experience in Android app development.
The introduction of Pausable Composition allows developers to manage composition tasks more effectively, reducing jank during rendering operations.
Optimizing prefetching strategies in Compose enables smoother scrolling experiences and enhances performance during fast user interactions with lists.
The implementation of strong skipping improves performance by allowing mutable data types to be treated as stable during composition.
Deep dives
Pausable Composition and Performance Optimization
A new feature called Pausable Composition has been developed to enhance performance during composition tasks by allowing tasks that require multiple frames to be broken down and managed more effectively. This feature automatically manages the stopping points during composition, allowing developers to focus on writing composable functions without needing to implement complex threading or buffering logic. By pausing and resuming composition during idle times, it reduces the chances of jank, especially in scenarios like scrolling lists where large items may take longer to render. This approach is akin to how coroutines operate, but it is specifically optimized for the Compose framework.
Strategic Prefetching for Improved User Experience
The podcast discusses the existing prefetching strategies in Compose, which aim to anticipate the content a user will scroll to and begin loading these elements in advance. The current prefetch behavior typically allows for pre-fetching a single item at a time, which could lead to performance bottlenecks during fast scrolls or if items require substantial processing time. By optimizing prefetching methods and possibly allowing prefetching in both scroll directions, developers can enhance smooth scrolling experiences and better handle visual elements like lazy lists. Future adjustments are being explored to refine this logic, aiming for a more adaptive and effective pre-fetching strategy.
Strong Skipping for Enhanced Stability in Composition
The introduction of strong skipping allows Compose to treat certain mutable data types as stable, improving performance during composition. This change enables developers to directly utilize mutable objects, on the assumption that they will not be modified during composition unless specified otherwise. By reevaluating how Compose interprets mutable state, performance can be improved without forcing developers to duplicate their data in immutable formats. This change also aligns more closely with common developer expectations about how state management should function in Compose applications.
Optimization and Monitoring of Composition Performance
The discussion emphasizes the ongoing efforts to enhance performance metrics within the Compose framework, focusing on reducing overhead and streamlining the information collected during the composition process. By refining how the runtime tracks data and manages state reading, improved performance during initial compositions is anticipated. These optimizations help developers gain clarity on their applications' behaviors and identify potential bottlenecks in their composition logic. Emphasizing a balance between maintaining informational efficiency and providing actionable feedback to developers is part of the broader goal to improve the Compose user experience.
Enhanced Diagnostics and Error Handling in Compose
The conversation highlights the efforts to improve exception tracking and diagnostics in Compose, allowing developers to understand the origins of issues more clearly. By correlating exceptions with specific parts of the composition lifecycle, developers can receive more meaningful feedback when errors occur. Additionally, there is a focus on providing contextual information about state reads and data flows within composables to help diagnose performance issues. This commitment to better diagnostics supports developers in maintaining robust applications while optimizing performance effectively.
In this episode, Tor and Romain chat with Leland and Chuck from the Compose team about performance -- recent optimizations, upcoming optimizations, and challenges.
