This message inserts the text string at the currently selected text, visually deleting that selection. Unlike in the English mode, deletion does not occur in the same manner as typing at the keyboard would. This is because typing Arabic in overwrite mode would replace characters in logical order not visual order.
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.