System Topic - Win32 Programmer's Reference

Custom Search

System Topic

The System topic provides a context for information of general interest to any DDE client. It is recommended that server applications support the System topic at all times. The System topic is defined in the DDEML.H header file as SZDDESYS_TOPIC.

To determine which servers are present and the kinds of information they can provide, a client application can request a conversation on the System topic upon starting, setting the device name to NULL. Such wildcard conversations are costly in terms of system performance, so they should be kept to a minimum. For more information about initiating DDE conversations, see Conversation Management.

A server must support the following item names within the System topic and any other item names that are useful to a client.

Item	Description
SZDDE_ITEM_ITEMLIST	A list of the items supported under a non-System topic. (This list may vary from moment to moment and from topic to topic.)
SZDDESYS_ITEM_FORMATS	A tab-delimited list of strings representing all clipboard formats potentially supported by the service application. Strings that represent predefined clipboard formats are equivalent to the CF_ values with the "CF_" prefix removed. For example, the CF_TEXT format is represented by the string "TEXT". These strings must be uppercase to further identify them as predefined formats. The list of formats must appear in the order of most rich in content to least rich in content.
	For more information about clipboard formats and rendering data, see Clipboard.
SZDDESYS_ITEM_HELP	User-readable information of general interest. This item must contain, at a minimum, information on how to use the server application's DDE features. This information may include, but is not limited to, how to specify items within topics, what execute strings the server can perform, what poke transactions are allowed, and how to find help on other System topic items.
SZDDESYS_ITEM_RTNMSG	Supporting detail for the most recently used WM_DDE_ACK message. This item is useful when more than 8 bits of application-specific return data are required.
SZDDESYS_ITEM_STATUS	An indication of the current status of the server. Typically, this item supports only the CF_TEXT format and contains the Ready or Busy string.
SZDDESYS_ITEM_SYSITEMS	A list of the items supported under the System topic by this server.
SZDDESYS_ITEM_TOPICS	A list of the topics supported by the server at the current time. (This list may vary from moment to moment.)

These item names are values defined in the DDEML.H header file. To obtain string handles for these strings, an application must use the DDEML string-management functions, just as it would for any other string in a DDEML application. For more information about managing strings, see String Management.

Last news from Greatis Software

    Nostalgia .Net     .Net is powerful, but not all-powerful, so sometimes we need to use Win32 API for our .Net applications. It's simple enough with Platform Invoke if you have Win32 skill, but we do not always have time to dig the ancient documentation, declare the special types that are compatible with Win32, find the values of the Win32's constants and so on. Nostalgia .Net offers several simple-to-use classes, and components that will allow you to forget about the headache of Win32 and just use the power of Win32 in your application the same way as you use the native. Net classes. More »

Recommended software for developers

    Ultimate Pack     Component pack for Delphi and C++ Builder that contains runtime form designer, runtime object inspector, print suite and much more for the very special price. More »

    Form Designer .Net     Unique runtime form design solution that allows to edit any form in .Net WinForms application at runtime with full source codes for only 300 euro! More »

    Print Suite .Net     Print Suite .Net is a set of components for easy printing texts, images and grids from your WinForms applications. Full C# source codes are available More »

    Gradient Controls .Net     Gradient Controls .Net offers controls with gradient background feature. Labels, panels and so on... Full C# source codes are available More »

    Greatis iGrid     iGrid plots drawing grid right over your desktop, so you can use it everywhere, with any drawing application without any special plugins for different graphic editors. More »

All the contacts and projects

Dmitry Vasiliev (just.dmitry)

More Online Helps

Win32 Programmer's Reference
Win32 Multimedia Programmer's Reference
OLE Programmer's Reference
Microsoft Windows Pen API Programmer's Reference
Microsoft Windows Sockets 2 Reference
Microsoft Windows Telephony API (TAPI) Programmer's Reference
Unix Manual Pages

greatis just4fun network