You can set tab stops in a multiline edit control by using the EM_SETTABSTOPS message. The default for a tab stop is eight characters. When you add text to the edit control, tab characters in the text automatically generate space up to the next tab stop. The EM_SETTABSTOPS message does not automatically cause Windows to redraw the text. To do that, you can call the InvalidateRect function. The EM_SETTABSTOPS message applies to multiline edit controls only.
You can set the width of the left and right margins for an edit control by using the EM_SETMARGINS message. After sending this message, Windows redraws the edit control to reflect the new margin settings. You can retrieve the width of the left or right margin by sending the EM_GETMARGINS message. By default, the edit control margins are set to be just wide enough to accommodate the largest character horizontal overhang, known as a negative ABC width, for the font currently in use in the edit control.