# 04: PipeWire volume This example tracks the default audio sink, displays its state, and binds a slider to its volume. The slider writes back only from `onMoved`, so initialization and service-driven updates do not cause writes. The write checks that the audio object exists. Static check: ```sh qmllint -I /usr/lib/qt6/qml examples/04-pipewire-volume/shell.qml ``` This does not exercise PipeWire discovery or volume mutation. A runtime service test needs an isolated PipeWire environment and explicit interaction assertions.