Summary

The Thermostat cluster server does not update the three SetpointChange tracking attributes when a setpoint write occurs:

According to the Matter specification (section 4.3.9), these attributes shall be updated whenever OccupiedHeatingSetpoint, OccupiedCoolingSetpoint, UnoccupiedHeatingSetpoint, or UnoccupiedCoolingSetpoint is written.

Expected behavior

After a write to one of the four setpoint attributes:

• SetpointChangeAmount is set to new_value − previous_value.
• SetpointChangeSourceTimestamp is set to the current CHIP epoch time.
• SetpointChangeSource reflects who triggered the change:
  • Manual (default) when no delegate override is present.
  • Schedule or External when the application delegate signals so.

Proposed solution

1. Add a GetSetpointChangeSource() virtual method to ThermostatDelegate (default returns Manual) so applications can report the source.
2. Save the pre-change value in MatterThermostatClusterServerPreAttributeChangedCallback (if validation succeeds).
3. In MatterThermostatClusterServerAttributeChangedCallback, compute and write the three attributes using the saved value.
4. Enable the three attributes (RAM storage) in the thermostat example ZAP configuration and regenerate the .matter file.

Related PR

A first implementation of this feature was proposed in #43643, but the thermostat cluster server has since been refactored (split into ThermostatCluster.cpp, ThermostatClusterPresets.cpp, etc.), so a fresh port is needed.

Testing

• Verify attributes are updated after a write to OccupiedCoolingSetpoint or OccupiedHeatingSetpoint.
• Verify SetpointChangeAmount reflects the correct delta (new − previous value).
• Verify SetpointChangeSourceTimestamp is set to the current CHIP epoch time.
• Verify SetpointChangeSource defaults to Manual when no delegate is set.
• Verify a custom delegate can override GetSetpointChangeSource().