JEDI Visual Component Library (JVCL)

The toolkit is designed around a strict separation of interfaces and implementations.

• Interfaces: All survey operations are controlled through interface instances defined in JvSurveyIntf.pas. The core interface is IJvSurvey.
• Implementation: The default implementation is provided in JvSurveyImpl.pas (and JvSurveyUtils.pas), which uses XML files for storage.
• Factory Pattern: To create an IJvSurvey instance, the application uses a function pointer named CreateSurvey defined in JvSurveyIntf.

Developer Note: When building applications using this toolkit, you must include the JvSurveyImpl unit in your project. This ensures that the CreateSurvey function pointer is assigned a valid factory function at runtime. Because the interfaces use COM/OLE/Automation compatible data types, you can implement alternative storage backends (e.g., via SOAP or COM) without changing the application logic.

When the server needs to update appointment data from physical storage, it fires specific events. You must implement handlers for these events to retrieve data and update the appointment properties.

• OnRefreshAppt: Fired when a specific appointment object in memory needs updating. The appointment's Modified property is set to False before the event fires.
• OnRefreshSched: Fired when the server needs to refresh all appointments linked to a specific schedule (provided via the Sched parameter). The Modified property for each linked appointment is set to False before the event fires.

If you need to manually mark an appointment as changed, call TJvTFAppt.SetModified.

// Example: Handling OnRefreshAppt to reload data from disk
procedure TMyManager.ScheduleManagerOnRefreshAppt(Appt: TJvTFAppt); 
begin
  // Retrieve data from physical storage
  Appt.Description := LoadDescriptionFromDB(Appt.ID);
  // ... set other properties
end;

TJvTFDaysPrinter provides several events that allow you to perform manual drawing on the grid components.

Important: Buffering and Canvas Usage All drawing in TJvTFDaysPrinter is buffered to eliminate flicker. Because of this buffering, you MUST use the canvas supplied by the aCanvas parameter provided in the event. Do NOT use the control's own canvas for custom drawing.

Available drawing events include:

• OnDrawAppt: Fires after the grid draws an appointment but before it is committed to the canvas. Use this to manually draw appointments.
• OnDrawApptBar: Fires immediately after the appointment bar is drawn. Provides Appt (the appointment), Col (column index), BarRect (bounding rectangle), and TimeStampRect (rectangle representing actual start/length).
• OnDrawColHdr: Fires after the column header is drawn.
• OnDrawCorner: Fires after a grid corner is drawn.
• OnDrawDataCell: Fires after a data cell is drawn.
• OnDrawGroupHdr: Fires immediately after a group header is drawn.
• OnDrawMajorRowHdr: Fires after the major row header is drawn (only if RowHdrType is rhFancy). Index is set to the last row of the hour.
• OnDrawMinorRowHdr: Fires after the minor row header is drawn (only if RowHdrType is rhFancy).
• OnDrawRowHdr: Fires after the row header is drawn (only if RowHdrType is rhGrid).