Compute Pressure API

This directory contains the service-side implementation of the Compute Pressure API.

Code map

The system is made up of the following components.

device::mojom::PressureManager, defined in Services, is the interface between the renderer and the services sides of the API implementation.

device::PressureManagerImpl is the top-level class for the services side implementation. The class is responsible for handling the communication between the renderer process and services.

device::mojom::PressureClient is the interface that client of the device::mojom::PressureManager interface must implement to receive device::mojom::PressureUpdate.

device::mojom::PressureUpdate represents the device's compute pressure update, composed of the device::mojom::PressureState and the timestamp. This information is collected by device::CpuProbe and bubbled up by device::PlatformCollector to device::PressureManagerImpl, which broadcasts the information to the blink::PressureObserverManager instances.

device::CpuProbe is an abstract base class that drives measuring the device's compute pressure state from the operating system. The class is responsible for invoking platform-specific measurement code at regular intervals, and for straddling between sequences to meet the platform-specific code's requirements. This interface is also a dependency injection point for tests.

blink::PressureObserver implements bindings for the PressureObserver interface. There can be more than one PressureObserver per frame.

blink::PressureObserverManager keeps track of blink::PressureClientImpl and the connection to the device::mojom::PressureManager remote.

blink::PressureClientImpl implements the device::mojom::PressureClient interface to receive device::mojom::PressureUpdate from device::PressureManagerImpl and broadcasts the information to active blink::PressureObserver. This class also keeps track of State and active blink::PressureObserver per source type.