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Start Host Notification (23)
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This function enables you to notify your WinHLLAPI application of changes in the Host Session Presentation Space (PS) or Operation Information Area (OIA).
Prerequisite Functions
There are no prerequisite functions for this function.
Syntax
WinHLLAPIAsync (hWnd, lpwFunction, lpbyString, lpwLength, lpwReturnCode)
Call Parameters
Parameter
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Description
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Data String
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A 7-byte string in the following format:
| • | Byte 1 Short name session ID of the desired Host session, or space or null for the current Host session. |
| • | Byte 2 Notification mode. "P" for presentation space update only, "O" for OIA update only, "B" for both presentation space and OIA updates. When calling WinHLLAPIAsync, this position can be "A". |
| • | Byte 3-6 Not used. Provided for compatibility with older applications. |
| • | Byte 7 Reserved or replaced with one of the following if using WinHLLAPIAsync and A in byte 2: P for presentation space update only, O for OIA update only; and B for both presentation space and OIA updates. |
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Data Length
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Length of Host event buffer (256 recommended).
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PS Position
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NA
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Return Parameters
Parameter
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Description
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Data String
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Same as Data String on the call.
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Return Codes
Code
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Description
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WHLLOK
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Host notification enabled.
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WHLLNOTCONNECTED
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The specified Host session is invalid.
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WHLLPARAMETERERROR
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One of more parameters are invalid.
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WHLLSYSERROR
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The function failed due to a system error.
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WHLLCANCEL
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The asynchronous function was cancelled.
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Remarks
Once enabled, Host notification is enabled until you call Stop Host Notification (25) or WinHLLAPICancelAsyncRequest(). The function initiates host notification and immediately returns control to your Windows HLLAPI application. This frees your application to perform other tasks while waiting for host updates. When an update occurs, the function will notify the window specified by hWnd with the registered message WinHLLAPIAsync.
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