MMIOM_REDO
The MMIOM_REDO message is sent to a Multimedia I/O (MMIO) procedure to request that the last logical editing action reversed by an MMIOM_UNDO message be reapplied to the media file or data stream.
Syntax
rc = mmioSendMessage(hmmio, MMIOM_REDO, lParam1, 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_REDO`.
- lParam1 (LONG)
- This parameter is not used.
- lParam2 (LONG)
- This parameter is not used.
Return Value
- rc (ULONG)
- Return codes indicating success or failure:
- MMIO_SUCCESS: The previously undone editing operation was successfully redone.
- MMIO_ERROR: An error occurred, or there are no available operations in the undo history stack to redo.
Remarks
- **Transaction History Stack**: This message relies on the internal undo/redo multi-level tracking stacks managed by digital media engines or custom I/O procedures supporting non-destructive destructive editing (such as waveforms or digital video streams).
- **State Advancement**: When an application calls a redo sequence, the I/O procedure shifts forward one step in the operational history timeline, reapplying modifications like MMIOM_CUT, MMIOM_PASTE, or MMIOM_WRITE changes back onto the active media layout.