Notification System Architecture

The notification system allows dashboard components to communicate without direct coupling:

• Transmitters send messages with type and optional payload
• Receivers register handlers for specific message types
• No broadcast - direct transmitter-to-receiver connections only
• Type-safe - TMessageType enum defines all valid messages

Location: Framework/COMMON/WEBSITE/Intf.Supports.Messages.pas

TMessageType enum defines all message categories:

Card Actions

Canvas Actions

Data Actions

IMessageTransmitter Interface

TYPE
   IMessageTransmitter = INTERFACE
      ['{GUID}']
      PROCEDURE TransmitMessage(MessageType: TMessageType; 
         Payload: TCardPayload = NIL);
      PROCEDURE ConnectReceiver(Receiver: IMessageReceiver);
      PROCEDURE DisconnectReceiver(Receiver: IMessageReceiver);
   END;

Implementation

TYPE
   TMessageTransmitter = CLASS(TInterfacedObject, IMessageTransmitter)
   PRIVATE
      FReceivers: TList<IMessageReceiver>;
   PUBLIC
      PROCEDURE TransmitMessage(MessageType: TMessageType; 
         Payload: TCardPayload = NIL);
      BEGIN
         FOR Receiver IN FReceivers DO
            Receiver.HandleMessage(MessageType, Payload);
      END;
   END;

IMessageReceiver Interface

TYPE
   IMessageReceiver = INTERFACE
      ['{GUID}']
      PROCEDURE HandleMessage(MessageType: TMessageType; 
         Payload: TCardPayload);
   END;

Implementation in Component

TYPE
   TDashboardCanvas = CLASS(TCoreDiv, IMessageReceiver)
   PRIVATE
      PROCEDURE HandleMessage(MessageType: TMessageType; 
         Payload: TCardPayload);
   END;

PROCEDURE TDashboardCanvas.HandleMessage(MessageType: TMessageType; 
   Payload: TCardPayload);
BEGIN
   CASE MessageType OF
      mtCanvasMaximize:
         MaximizeCard(Payload.CardID);
      mtCanvasMinimize:
         RestoreCard(Payload.CardID);
      mtCardDelete:
         DeleteCard(Payload.CardID);
      mtAdjustLayout:
         RecalculateLayout;
   END;
END;

TCardPayload Class

TYPE
   TCardPayload = CLASS
   PUBLIC
      CardID: Integer;           /// Affected card ID
      SourceComponent: TObject;  /// Sender reference
      Data: TJSObject;           /// Optional JSON data
      StringValue: STRING;       /// Optional string data
      IntValue: Integer;         /// Optional integer data
      
      CONSTRUCTOR Create(ACardID: Integer);
   END;

Creating Payload

VAR
   Payload: TCardPayload;
BEGIN
   Payload := TCardPayload.Create(Card.CardID);
   Payload.SourceComponent := Self;
   Payload.StringValue := 'additional info';
   
   Transmitter.TransmitMessage(mtCardDelete, Payload);
END;

Header Button → Canvas

/// In THeaderButton (transmitter)
PROCEDURE THeaderButton.DoOnClick;
VAR
   Payload: TCardPayload;
BEGIN
   Payload := TCardPayload.Create(OwnerCard.CardID);
   Payload.SourceComponent := Self;
   
   CASE Action OF
      mtCanvasMaximize:
         FTransmitter.TransmitMessage(mtCanvasMaximize, Payload);
      mtCardShowGrid:
         FTransmitter.TransmitMessage(mtCardShowGrid, Payload);
   END;
END;

Card → Canvas Connection

/// When card is created
PROCEDURE TDashboardCanvas.AddCard(Card: TDashboardCard);
BEGIN
   /// Connect card's transmitter to canvas receiver
   Card.Transmitter.ConnectReceiver(Self);
   FCards.Add(Card);
END;

/// When card is removed
PROCEDURE TDashboardCanvas.RemoveCard(Card: TDashboardCard);
BEGIN
   Card.Transmitter.DisconnectReceiver(Self);
   FCards.Remove(Card);
END;

Sidebar → All Cards

/// Sidebar filter change broadcasts to all cards
PROCEDURE TSidebar.OnDateRangeChange(NewStart, NewEnd: TDateTime);
VAR
   Payload: TCardPayload;
BEGIN
   Payload := TCardPayload.Create(0);  /// 0 = all cards
   Payload.Data := TJSObject.new;
   Payload.Data['startDate'] := DateToISO(NewStart);
   Payload.Data['endDate'] := DateToISO(NewEnd);
   
   FTransmitter.TransmitMessage(mtDateRangeChanged, Payload);
END;