MMIOM_WINMSG
The MMIOM_WINMSG message is sent to a Multimedia I/O (MMIO) procedure to forward standard Presentation Manager (PM) window messages from a window procedure or a Media Control Driver (MCD). This facilitates communication regarding user interface or system environmental shifts—such as clipboard modifications—that directly impact the active I/O storage mechanism.
Syntax
rc = mmioSendMessage(hmmio, MMIOM_WINMSG, (LONG)pMmioWinMsg, lParam2);
Parameters
- pmmioinfo (PMMIOINFO)
- A pointer to an MMIOINFO data structure maintaining the current runtime state of the open file channel.
- usMsg (USHORT)
- The message identifier, set to `MMIOM_WINMSG`.
- lParam1 (LONG)
- A pointer to an MMIO_WINMSG data structure containing the specific PM window message parameters being forwarded to the stream handler.
- lParam2 (LONG)
- This parameter is not used.
Return Value
- rc (ULONG)
- Return codes indicating success or routing status:
- MMIO_SUCCESS: The forwarded window message was accepted and handled successfully by the I/O procedure.
- MMIO_ERROR: An error occurred during the internal processing of the window event context.
Remarks
- **Clipboard Synchronization**: This interface is primarily utilized to forward the `WM_DESTROYCLIPBOARD` window message to the I/O procedure. When received, the I/O procedure can cleanly execute appropriate cleanup actions, such as freeing memory or temporary backing storage allocations previously allocated for clipboard copy/paste sharing operations.
- **Optional Implementation**: Handling this message is entirely optional for custom I/O procedures. Because many file format drivers operate completely independently of the presentation or windowing sub-systems, callers should gracefully catch and ignore any error return codes generated by an unsupportive media handler.