dOPCAE.TdOPCEvent.ChangeMask

ChangeMask indicates what properties of the condition have changed and forced the server to send the event notification.

Delphi

property ChangeMask: integer;

C++

__property int ChangeMask;

Remarks

Value	Description
opc_Change_Active_State	the condition's active state has changed
opc_Change_Ack_State	the condition's acknowledgment state has changed
opc_Change_Enable_State	the condition's enabled state has changed
opc_Change_Quality	the condition's quality has changed
opc_Change_Severity	the severity level has changed
opc_Change_Subcondition	the condition has transitioned into a new sub-condition
opc_Change_Message	the event message has changed (compared to prior event notifications related to this condition)
opc_Change_Attribute	one or more event attributes have changed (compared to prior event notifications related to this condition)

If the event notification is the result of a refresh, these bits have to be ignored. For a "new event", opc_Change_Active_State is the only bit which will always be set. Other values are server-specific. (A "new event" is any event resulting from the related condition leaving the Inactive and Acknowledged state.)