This message inserts the text string at the current selection, deleting that selection in the same manner as typing at the keyboard would. The text string must be in CF_TEXT format (or one of the formats acceptable to MLM_IMPORT) and null-terminated. The line-break (CR LF, LF, and so on) is counted as one byte, regardless of the number of bytes occupied in the buffer, and the null terminator is not counted.

This interacts with the format rectangle and text limits, and a return of less than the full count can be the result. If so, a notification message is sent.