SetGadgetEventCallback(#Gadget, @CallbackProcedure())

[Sirius-2337]

I would like to have a callback for gadgets that would be called whenever an event occurs (like MouseDown / MouseMove / etc.) or when a gadget function is called (like SetGadgetColor / FreeGadget / ...).
With this callback and the Canvas gadget we could create custom gadgets that would be as easy to use as PBs own gadgets.

A callback procedure could then look like this (Pseudo-Code)

Code: Select all

Structure PB_EventData_AddGadgetItem ;This Structure would be Predefined by PB
  Position.i
  Text.s
  ImageID.i
  Flags.i
EndStructure

Structure PB_EventData_AddGadgetColumn ;This Structure would be Predefined by PB
  Position.i
  Title.s
  Width.i
EndStructure

Structure PB_GadgetEventCallback_EventData ;This Structure would be Predefined by PB
  StructureUnion
    AddGadgetItem.PB_EventData_AddGadgetItem
    AddGadgetColumn.PB_EventData_AddGadgetColumn
  EndStructureUnion
EndStructure

Procedure GadgetEventCallback(#Gadget, EventType, *EventData.PB_GadgetEventCallback_EventData)
  
  If EventType = #Event_LeftClick
    ;Depending on Mouse-Position Post a Custom Event
    
  ElseIf EventType = #Event_AddGadgetItem
    Select *EventData\AddGadgetItem\Position
      Case -1
      Case  0
      Default
    EndSelect
    ;Add a new item to the Custom Gadget or return Null if not possible for this Gadget
    
  ElseIf EventType = #Event_GadgetHeight
    ProcedureReturn #PB_ProcessPureBasicEvents ;Since PB knows the gadgets height we dont need to react on this event
    
  ElseIf EventType = #Event_FreeGadget
    ;Do some Cleanup
    
  EndIf
  
EndProcedure