Event Handling in ProvideX

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Griffin Tyler
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1 Event Handling in ProvideX Presented by: Brett Condy

2 Overview OOP and COM Objects Properties and Methods How does the COM Interface work? COM Events Additional TCB Values ProvideX Type Library Browser NOMADS Interface Language Level Event Extensions Limitations Future Enhancements

3 OOP and COM Objects What is an Object? Fundamentally, an Object is a self-contained entity that contains: Data referred to as Properties Functions referred to as Methods. OOP Objects Created using Object Oriented Programming concepts in ProvideX. COM Objects Use the Microsoft 'COM' (Common Object Module) interface. Supports OLE, OCX and ActiveX technologies.

4 OOP Objects Based on an Object model. OOP incorporates the following concepts: Encapsulation All aspects of an Object are self-contained Inheritance Objects may be derived from other similar objects Polymorphism The ability to react differently, or override functionality derived from another object Object Oriented Programming Direxions 2002 Presentation

5 OOP Objects OOP Example A Customer Object would contain... Properties: Name Address City Salesperson. Methods: Add Delete Find Fax.

6 OOP Objects General Syntax for OOP Objects Object Definition Directives DEF CLASS PROPERTY LOCAL FUNCTION LIKE PROGRAM PRECISION STATIC Object Creation and Deletion NEW( ) REF( ) DROP OBJECT Defines the object class. Declares data/properties. Declares private data/properties. Declares methods. Declares inherited class. Declares default programs. Declares precision. Dynamically declares LOCAL variables. Instantiates an object. Controls reference counts. Deletes an object.

7 OOP Objects Sample Object DEF CLASS "Customer" LOCAL Customer_File PROPERTY Cust_No$ SET Change_Cust PROPERTY Name$,Addr$,City$,SalesPerson$ PROPERTY Amt_Owing GET ";CheckSecurity" SET ERR FUNCTION Find(X$)Get_Customer FUNCTION Update()Update_Customer END DEF On_Create: IF Customer_File=0 THEN OPEN (GFN,IOL=*)"cstfile"; Customer_File=LFO RETURN On_Delete: CLOSE (Customer_File); Customer_File=0; RETURN..cont d

8 OOP Objects Sample Object..cont d Get_Customer: ENTER C$ READ (Customer_File,KEY=C$)! Loads all variables RETURN 1 Change_Cust: ENTER C$ READ DATA FROM "" TO IOL=IOL(Customer_File) Cust_No$=C$; READ (Customer_File,KEY=C$,DOM=*END) RETURN Update_Customer: WRITE (Customer_File); RETURN 1 CheckSecurity: IF %Security_OK THEN RETURN Amt_Owing EXIT 52 Note: Use of %Security_OK violates rules of Encapsulation.

9 COM Objects Separately compiled utilities that provide a service, function, or control. Similar to a DLL. Automation interface: Allows access to Objects, Properties, Methods and Events. Supports any Object or Control that exposes an IDispatch interface. Limited to the Windows version of ProvideX. Automation in ProvideX COM Interface Documentation

10 COM Objects General Syntax for COM Objects DEF OBJECT directive is used to instantiate a COM Object. DELETE OBJECT directive is used to disconnect from the COM Object. DROP OBJECT is an alternative for the DELETE OBJECT directive. The following syntax allows you to select from a list of available 32-bit OLE and ActiveX controls: DEF OBJECT x,"*"

11 Properties and Methods Used with COM and OOP Objects. Accessed via the dynamic property operator: ' x$ = Customer'Name$! Property Get Customer'Name$="Abc Co."! Property Set Customer'Add( )! Invoke a Method A comma-separated list of properties and methods can be obtained by querying tick-star internal property: '* Methods identified by a "( )" appended to name.

12 Properties and Methods Generally speaking, properties and methods are handled the same for OOP and COM objects, with a few exceptions: Helper properties and methods are provided for COM objects and prefixed with PVX; e.g, PvxName$, PvxTop, PvxWidth COM interface accepts "invoke hints" (.get,.put,.putref) to help differentiate between getting or setting properties, or invoking a method; e.g, x=grid'cell.get(row, Col) Optional parameters are supported by the COM interface with an asterisk * as placeholder; e.g, x=grid'setvalue(*, *, Row)

13 How does the COM interface work? DEF OBJECT Instantiate Object ProvideX PVXOCX32.DLL COM Object Expose Properties & Methods Dispatch Handle Instantiating a COM Object

14 COM Events What are Events? Provide a means for interacting with COM Objects. A COM control signals an application when a given action occurs by sending a message. This message is referred to as an Event. The process of sending the message is commonly referred to as Event firing. One of the most common Events supported by controls with a user interface is a mouse click.

15 COM Events Working with Events Events must be responded to immediately. This is a standard requirement for COM. Events can fire at any time! When is determined by the COM Object. Unlike accessing properties and methods which is controlled by the application. Events can fire when an application is reading or updating files, processing data, printing reports, or waiting for user input. Note: An Event can also fire while the application is in the process of servicing a previous Event! To prevent an application from looping endlessly, a limit of 64 nested Events has been imposed.

16 COM Events The OOP Approach Knowing that... Events can fire at any time and, must be responded to immediately, and OOP Objects are self-contained... associating a COM Object to an OOP Object is a perfect fit. This allows ProvideX to issue a method call without affecting the underlying application. When an Event fires, ProvideX will suspend the current task, process the Event, then return control to the current task.

17 COM Events ProvideX Data Entry Suspend current operation COM Object Event Triggers Display Process OOP Method for the Event Processing WAIT or WI Resume current operation Event Processing

18 COM Events Syntax for Event Support Associating COM Object with OOP Object: ON EVENT FROM com_id PROCESS oop_id Where: com_id oop_id CTL value of the COM Object CTL value of the OOP Object

19 COM Events Syntax for Event Support Activating support for individual Events in an OOP Object: FUNCTION func_name ( args ) prog_ref FOR EVENT { str_var SAME } Where: func_name Function / Method name args Optional function arguments prog_ref Program/Statement label str_var Event name or keyword SAME

20 COM Events Calendar Event Object DEF CLASS "Calendar" LOCAL EventListBox PROPERTY CalCTL PROPERTY CalDay,CalMonth,CalYear,CalValue$! Event Functions FUNCTION Click()";Click" FOR EVENT SAME FUNCTION DblClick()";DblClick" FOR EVENT SAME FUNCTION SelChange()";SelChange" FOR EVENT SAME FUNCTION DateDblClick()";DateDblClick" FOR EVENT SAME! Regular Functions FUNCTION ShowEvents()";ShowEvents" FUNCTION HideEvents()";HideEvents" END DEF..cont d

21 COM Events Calendar Event Object..cont d On_Create: DEF OBJECT CalCTL,@(40,0,22,20), "MSComCtl2.MonthView.2" ON EVENT FROM CalCTL PROCESS _Obj RETURN On_Delete: IF CalCTL \ THEN DROP OBJECT CalCTL; CalCTL=0 GOSUB HideEvents RETURN..cont d

22 COM Events Calendar Event Object..cont d Click: EventProcessed$="Click" GOTO ReturnFromEvent DblClick: EventProcessed$="DblClick" GOTO ReturnFromEvent SelChange: EventProcessed$="SelChange" GOTO ReturnFromEvent DateDblClick: EventProcessed$="DateDblClick" GOSUB ReturnFromEvent MSGBOX "Date Selected: "+ClickValue$ RETURN..cont d

23 COM Events Calendar Event Object..cont d ShowEvents: IF EventListBox=0 \ THEN EventListBox=100; LIST_BOX EventListBox,@(64,0,24,20),SEP="," LIST_BOX LOAD EventListBox,CalCTL'PvxEvents$ RETURN HideEvents: IF EventListBox \ THEN LIST_BOX REMOVE EventListBox; EventListBox=0 RETURN ReturnFromEvent: CalValue$=CalCTL'Value$, CalDay=CalCTL'DayOfWeek CalMonth=CalCTL'Month, CalYear=CalCTL'Year RETURN

24 COM Events The PvxEvents$ Property A list of Events supported by a given COM control are available in the PvxEvents$ property. Active Events are noted with leading plus sign + Inactive Events are preceded with minus sign - This property is populated only after executing: ON EVENT FROM com_id PROCESS oop_id

25 Additional TCB values TCB Information for Event Support TCB(120) TCB(121) TCB(122) TCB(123) CTL value of the COM object which triggered the event. Number of COM events processed for this session Current level of processing in the event queue. While this should normally be one, receiving an event within an event will increment the level. Number of COM events ignored due to excessive event requests.

26 Language Level Event Extensions New syntax to simplify the Event interface. Eliminates the need to create an OOP object to manage the Events. Generates CTL signal when a given Event is received. Used by the NOMADS interface. Syntax to generate the CTL value: ON EVENT "EvtName " FROM com_id PREINPUT ctl_val Where: EvtName Event Name com_id CTL value of the COM Object ctl_val CTL value to PREINPUT Syntax to remove an Event: ON EVENT "EvtName " FROM com_id REMOVE

27 Language Level Event Extensions New Object to control internal ProvideX Events known as "*system" : DEF OBJECT com_id,"*system" Available Methods: SetTimer(nn) nn indicates the # of seconds Supported Events: Timeout( ) triggered when SetTimer expires FileClose(file_no) file_no is the channel # being closed FileOpen(file_no, file_name) file_no is the channel # being opened file_name is the file being opened

28 ProvideX Type Library Browser The Type Library Browser (PvxTLB) provides extended type information for COM objects. It can also be used to create ProvideX OOP objects to simplify the handling of COM events. PvxTLB is freely downloadable. While it simplifies working with COM objects, it is not a replacement for documentation. Type Library Browser TLB Documentation

29 ProvideX Type Library Browser Output from PvxTLB DEF CLASS "DMonthViewEvents" PROPERTY EventCaller GET GetEventCaller SET ERR PROPERTY EventStack GET GetEventStack SET ERR PROPERTY EventsDispatched GET GetEventsDispatched SET ERR PROPERTY EventsDiscarded GET GetEventsDiscarded SET ERR FUNCTION Event_DateDblClick(dbl_DateDblClicked) Event_DateDblClick FOR EVENT "DateDblClick" FUNCTION Event_SelChange (dbl_startdate,dbl_enddate,int_cancel) Event_SelChange FOR EVENT "SelChange" FUNCTION Event_Click()Event_Click FOR EVENT "Click" FUNCTION Event_DblClick()Event_DblClick FOR EVENT "DblClick" END DEF STOP..cont d

30 ProvideX Type Library Browser Output from PvxTLB..cont d On_Create:! CONSTRUCTOR On_Create! < Insert code here > RETURN On_Delete:! DESTRUCTOR On_Delete! < Insert code here > RETURN GetEventCaller:! PROPERTY EventCaller (GET) RETURN TCB(120) GetEventStack:! PROPERTY EventStack (GET) RETURN TCB(122) GetEventsDispatched:! PROPERTY EventsDispatched (GET) RETURN TCB(121) GetEventsDiscarded:! PROPERTY EventsDiscarded (GET) RETURN TCB(123)..cont d

31 ProvideX Type Library Browser Output from PvxTLB..cont d! EVENT DateDblClick - Occurs when the user presses and releases a mouse button and then presses and releases it again over a valid date. Event_DateDblClick: ENTER dbl_datedblclicked! < Insert code here > RETURN! EVENT SelChange - Occurs when the user selects a new date or range of dates. Event_SelChange: ENTER dbl_startdate,dbl_enddate,int_cancel! < Insert code here > RETURN

32 NOMADS Interface COM support has replaced VBX support in NOMADS Replaces the existing VBX Controls. Supports Properties, Method calls and Event handling. All Properties and Events are presented in Grid. Default values for Properties can be specified as Fixed or Expression. Logic for Events includes: Ignore, Link, Perform, Call and Execute. Post-create logic also available. NOMADS Enhancements Direxions 2004 Presentation

33 NOMADS Interface Sample Panel and Program! NomCal -- Calendar Events in NOMADS Click: EventType$="Click"; GOTO ReturnFromEvent DblClick: EventType$="DblClick"; GOTO ReturnFromEvent NOMADS_DateDblClick: EventType$="DateDblClick"; GOSUB ReturnFromEvent MSGBOX "Date: "+ClickValue$,"NOMADS PREINPUT Event" cmd_str$="end" RETURN..cont d

34 NOMADS Interface Sample Panel and Program..cont d SelChange: EventType$="SelChange" GOTO ReturnFromEvent ReturnFromEvent: ClickValue$=MonthView.ctl'Value$ x=monthview.ctl'dayofweek NewDay$=MID(MSG(134),TBL(x<>1,7,x-1)*4-3,3) NewDay$=STR(x)+" - "+NewDay$ x=monthview.ctl'month NewMonth$=STR(x)+" - "+MID(MSG(133),x*4-3,3) NewYear$=MonthView.ctl'Year$ LIST_BOX LOAD EventList.ctl,0,EventType$ x=eventlist.ctl'itemcount LIST_BOX WRITE EventList.ctl,x Refresh_flg=1; RETURN

35 NOMADS Interface Working with Events that supply parameters Previous example did not use an OOP object to service the Events, but instead made use of the ON EVENT PREINPUT syntax. This approach does not allow parameters passed by the COM control to be intercepted. The only means for doing this is to add an OOP object to the mix. This can be done in the POST-CREATE logic for the COM control.

36 NOMADS Interface Add following changes to NomCal and save it as NomCal.Pvc. Add PERFORM ";Initialize_MonthView" to COM post-create logic.! NomCal.pvc -- Calendar Events in NOMADS DEF CLASS "NomCal" FUNCTION DateDblClick(x)";DateDblClick" FOR EVENT SAME END DEF DateDblClick: ENTER x y=x+jul(1900,1,1)-2,x$=dte(y:"%dl, %Ml, %D, %Yl") MSGBOX "Date: "+x$,"datedblclick FUNCTION ON Event" RETURN Initialize_MonthView: NomCalOOP=NEW("NomCal") ON EVENT FROM MonthView.ctl PROCESS NomCalOOP RETURN

37 Cautions and Limitations As Events can fire rapidly, it is important to service the event as quickly as possible, and, without user intervention. Events are not supported across a WindX connection. Primarily due to timing... sending packets between the host and the client does not allow for immediate response to the Event. Internal ProvideX Events are not currently supported on UNIX/Linux platforms.

38 Future Enhancements Internal ProvideX Events on UNIX/Linux platforms. Additional triggers in ProvideX as required or requested.

39 End of Presentation THANK YOU!

Object Oriented Programming

Object Oriented Programming (OOP) is a different approach to application development. In OOP, an Object is an entity that consists of properties and functions. Properties are the data portion of an Object,