Module stack 

A thread-safe collection for managing multiple progress indicators.

The ProgressStack serves as the central registry for “Multi-Bar” applications. It allows a renderer to iterate over a dynamic list of active tasks without fighting the worker threads for locks.

Synchronization Strategy

The stack uses a coarse-grained RwLock to protect the list of handles. Individual progress updates (incrementing counters) do not lock the stack.

• Workers: Only acquire the stack lock when adding/removing a bar (rare).
• Renderers: Acquire a read lock on the stack once per frame to clone the handles, then iterate independently.

Structs

ProgressStack

A thread-safe, shared-clonable collection of Progress instances.

ProgressStackSnapshot

A snapshot of the state of the entire progress stack at a specific point in time.