Power Programmierung 2/Power-Programmierung CD 2 (Tewi)(1994).iso/c/library/windows/ddelib/ddedemos.prn

Text File | 1990-09-17 | 6.3 KB | 178 lines

                            Dynamic Data Exchange Demos


                             Horizon Technologies Inc.


            Overview:


            The Dynamic Data Exchange (DDE) demo programs illustrate the

              concept of inter-program communications in a Microsoft

              Windows environment.  Source code for three programs is

              included.  All interactions between these programs are

              accomplished via the process of message passing in

              accordance with the DDE protocol defined by Microsoft.  A

              dynamic link library, DDELIB, developed by Horizon

              Technologies Inc., has been utilized in each of these

              programs to significantly reduce development time and

              program complexity.  The following material builds upon

              the information presented in the Overview of the  DDELIB

              documentation.



            AccExcel:



            ACCEXCEL is a menu driven application that shows the basics

              of a DDE connection to EXCEL.  EXCEL is a popular Windows

              spreadsheet application written by Microsoft.  The

              ACCEXCEL pull-down menu "DDE" lists four items; Initiate,

              Poke, Advise and Terminate.


            Initiate will establish a DDE session with a spreadsheet in

              EXCEL.  The name of the spreadsheet is entered into a

              dialog box presented by ACCEXCEL.  Poke will send data to

              the spreadsheet.  A dialog box will allow the

              specification of the cell range and the comma separated

              data values.  Advise will set up an advise circuit with a

              cell range in EXCEL.  When any data is modified in this

              range, EXCEL will advise ACCEXCEL which in turn will

              display a message box with the modified data.  Terminate

              simply closes the DDE session established with Initiate.



            Sub:



            SUB is a DDE client application that talks to the server

              application FISH.  FISH, supplied by Microsoft, displays

              fish swimming in a tank.  When FISH establishes a session

              with a client, it reveals a yellow submarine.  This

              submarine can then be manipulated by the client to move

              up, down, left, right and even fire a torpedo.  To


         DDE DEMOS - Copyright (C) September 12, 1990 Horizon

         Technologies Inc.  All rights reserved.  [phone]    Page 1






              augment this capability, the client can also obtain the

              current position of a fish in x,y coordinates.  With a

              simple sneak-up-from-behind-and-fire strategy, SUB easily

              controls the submarine in a mission to liquidate fish.


            Technically, SUB initiates two sessions with fish;  one for

              sub control and reporting, the other for fish position

              monitoring.  A DDE advise circuit for fish number zero is

              established.  The callback routine Fish() is called by

              DDELIB every time the fish moves.  In this routine, a

              request for the current sub position is made.  This

              results in a callback to the Sub() routine.  Once the

              current fish and sub positions are known, a call to

              MoveSub() is made.  Here, a command is sent to the sub

              for positioning and firing.  Note that the sub must be

              moving up or down, left or right.  Therefore, if the sub

              needs to maintain elevation, it must oscillate up and

              down.



            Session and SessUtil:



            SESSION is a DDE server application that provides a means

              for clients to store and retrieve string variable

              contents by name.  SESSION accepts DDE pokes, requests,

              and advises.  Commands are not supported.


            SESSION accomplishes this by registering the topic

              Variables.  The callback routine Session() is invoked by

              DDELIB every time a new client establishes a session,

              terminates a session, pokes or requests data, establishes

              an advise circuit, or sends a command.  SESSION processes

              these events to provide its services, such as saving the

              contents of a poke or advising a client of a change in

              the variable.


            SESSUTIL is a DDE client application that communicates with

              the SESSION application.  SESSUTIL shows the current

              contents of the User variable, as provided by SESSION, on

              its client area.  The user can set the contents of the

              User variable by selecting the ______
                                             Modify item from the ____
                                                                  File

              menu.  The new value is displayed on every instance of

              SESSUTIL running.


            SESSUTIL initially establishes a DDE advise circuit with

              SESSION on the variable User.  This causes the callback

              routine User() to be invoked by DDELIB whenever SESSION

              performs an advise.  User() will update its own copy of

              the value and then force a repaint of the client area,

              resulting in the new value of the User variable to be


         DDE DEMOS - Copyright (C) September 12, 1990 Horizon

         Technologies Inc.  All rights reserved.  [phone]    Page 2






              displayed.  When the user selects OK from the modify

              dialog box, the Poke() routine is called.  This sends the

              new variable to SESSION, which in turn advises SESSUTIL,

              which then displays the new value.


            Microsoft Word for Windows can eavesdrop in on the

              conversation, displaying the current contents of the User

              variable.  Simply insert a field of the form {ddeauto

              SESSION Variables User}.












































         DDE DEMOS - Copyright (C) September 12, 1990 Horizon

         Technologies Inc.  All rights reserved.  [phone]    Page 3