The multi-line entry field control window procedure responds to this message by setting formatting dimensions and mode.

Any addition of text that causes the text to exceed the rectangle limits causes a notification before proceeding (see MLN_PIXHORZOVERFLOW and MLN_PIXVERTOVERFLOW).

Any activity that would cause the rectangle to be unable to contain the existing text (resize, undo, increasing font size, or word-wrap on or off) is rejected and results in a notification message for information (see MLN_OVERFLOW).