CoCreate Modeling FAQ: DDE

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<a name="DdeToOsdm"></a>
<a name="dde"></a>
---+++ %ENGLISH% How do I talk to <nop>CoCreate Modeling via DDE?

<nop>CoCreate Modeling services DDE requests, and you can also send DDE requests 
from <nop>CoCreate Modeling
via Integration Kit functionality. See the section "DDE Interface" in
the Integration Kit documentation for details.

DDE is a fairly old interprocess communication protocol. It is still
used both in Windows applications and in the operating system, though.
As an example, the 
[[http://www.angelfire.com/biz/rhaminisys/ddeapps.html#DDEShell][Windows shell uses DDE]] 
to notify running applications when a user double-clicks a file which is associated
with the application.

DDE uses messages which are sent to an application's message queue. The
DDE protocol requires all DDE-enabled applications to continually process
messages, or else DDE communication in the system will be blocked. While
an DDE-enabled application is busy doing other things (parsing a file,
processing a spreadsheet, or, in <nop>CoCreate Modeling's case, blending complex edges),
it may not react to DDE messages for a while, and as a consequence,
even DDE conversations with _other_ apps may block for some time.

For this reason, use DDE sparingly, and only in circumstances where
losing a message at least does not have catastrophic effects. That said,
here is a simple example in VBA which shows how to open a conversation
with <nop>CoCreate Modeling and have it execute a command.

<pre>
  Sub dde()
    Dim nChannelNumber As Variant
    nChannelNumber = DDEInitiate("PESD", "GENERAL")
    DDEExecute nChannelNumber, "(CREATE_PART :name ""dde_test_part"" :owner ""/"")"
    DDETerminate nChannelNumber
  End Sub
</pre>

By the way, if you want to try out DDE communication from a shell window,
check out the command-line tool =ddeclient.exe= which is
[[http://www.opensource.apple.com/darwinsource/WWDC2004/emacs-56/emacs/nt/ddeclient.c][part of the Emacs distribution]]:

<pre>
  $ echo '(CREATE_PART :name "dde_test_part" :owner "/")' | ddeclient PESD GENERAL
</pre>

-- Main.ClausBrod - 14 Jul 2005

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<a name="OsdmToDde"></a>
---+++ %ENGLISH% How do I talk to other applications from <nop>CoCreate Modeling via DDE?

The Integration Kit provides the following DDE functionality to talk to
external applications which support DDE:

   * =sd-dde-initiate=
   * =sd-dde-execute=
   * =sd-dde-poke=
   * =sd-dde-request=
   * =sd-dde-close=
   * =sd-dde-request-timeout=
   * =sd-dde-execute-timeout=

The exact commands to be sent via DDE differ from application to application.
The [[http://www.angelfire.com/biz/rhaminisys/ddeinfo.html][DDE FAQ]] provides
information on many such applications and is a good starting point for further
search.

A typical DDE session usually involves three steps:

   1 Initialization
   2 Communication phase
   3 Teardown

In phase 1, you contact the external application using =sd-dde-initiate=:
<pre>
  (setf dde (oli:sd-dde-initiate "EXCEL" "System")) ;; connect to Excel
</pre>

In phase 2, you send commands using =sd-dde-execute= and inquire data from
the external application using =sd-dde-request=.
<pre>
  (oli:sd-dde-execute dde "[Select(\"r1c1:r2c2\")]")) ;; select range
</pre>

In phase 3, you close the session using =sd-dde-close=.
<pre>
  (oli:sd-dde-close dde)
</pre>

-- Main.ClausBrod - 21 Jul 2005

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---+++ %ENGLISH% How do I talk to Excel using DDE?

See the sample code at MacroHelloExcel.

-- Main.ClausBrod - 11 Apr 2007

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