MMIOM_CLEAR
The MMIOM_CLEAR message is sent to a Multimedia I/O (MMIO) procedure to request that a specific range of data be permanently deleted from a file. Unlike a cut operation, this deletion is destructive and bypasses the system clipboard entirely.
Syntax
rc = mmioSendMessage(hmmio, MMIOM_CLEAR, (LONG)pEditParms, lParam2);
Parameters
- pmmioinfo (PMMIOINFO)
- A pointer to an MMIOINFO data structure maintaining the current state of the open file.
- usMsg (USHORT)
- The message identifier, set to `MMIOM_CLEAR`.
- lParam1 (LONG)
- A pointer to an MMIO_EDIT_PARMS structure that specifies the exact range of data to be cleared.
- lParam2 (LONG)
- This parameter is not used.
Return Value
- rc (ULONG)
- Return codes indicating success or failure:
- MMIO_SUCCESS: The specified media data range was successfully deleted.
- MMIO_ERROR: An error occurred, and the file contents remain unmodified.
Remarks
- **Target Range**: The exact segment to clear is determined by the `ulStartTime` and `ulDuration` fields inside the MMIO_EDIT_PARMS structure.
- **Duration Rule**: The `ulDuration` field must be non-zero. Attempting to send this message with a duration of zero will result in an error.
- **Media Pointer Update**: Following a successful clear operation, the internal file or media position pointer is automatically updated to sit at the location designated by the `ulStartTime` value.
- **Non-Clipboard Operation**: This message handles direct data truncation and compression within the file. If you wish to retain a copy of the removed data for pasting elsewhere, use MMIOM_CUT instead.