Function opc_write_values 

pub fn opc_write_values(
    pid: PidParameters,
    controller_type: ControllerType,
    integral_type: IntegralType,
) -> OpcWriteValues

The literal integral/derivative values to write back to the DCS/PLC for one PidParameters, given the controller type the run was configured for. Pure port of the controller-type-conditional part of WritePIDparametersToOPCtags — proportional is always pid.proportional, so this only exists to decide integral/derivative, which ControllerType::P/ControllerType::Pi algorithms don’t use:

• Integral: a ControllerType::P-only run never writes pid.integral (it was computed but is meaningless for an algorithm with no integral term). Instead it writes a sentinel that disables integral action in whatever representation the template uses — 9999 for IntegralType::ResetTime (an effectively-infinite reset time), or 0 for IntegralType::ResetRate/IntegralType::ResetGain (a zero rate/gain has the same disabling effect). ControllerType::Pi/ControllerType::Pid always write the real calculated value.
• Derivative: only a ControllerType::Pid run writes pid.derivative; P/Pi always write 0.