A deep dive into the Panel Controller side of Android Automotive OS's Scalable UI framework. Covers how DecorPanelControllerBase and BaseTaskPanelController work, how to wire a custom View and Controller into CarSystemUI via Dagger, and how to build imperative panel behavior. Two proof-of-concept implementations are walked through: FlameSun, an animated AGSL shader rendered inside a DecorPanel with minimal controller logic, and FocusGlow, a dynamic glow border that tracks window focus using TaskStackListener, PanelPool, PanelUpdateConsumer, and AutoSurfaceTransaction to reposition its surface at runtime. Limitations such as no RRO-only View shipping, full CarSystemUI rebuilds for code changes, and no persistent state across SystemUI restarts are also discussed.
