Specifies the protocol for getting system colours for use in text views. A class which implements this protocol allows an application (or a thread, because a pointer to the object is held in thread-local storage) to use system colours in text views.

You should create an object of an MFormParam-derived class which implements the SystemColor() function. Then, pass a pointer to the object to the static function MFormParam::Set(). The MFormParam-derived object is owned by the caller of Set(). When system colours are no longer needed, you should cancel them by calling MFormParam::Set(NULL). It is the caller's responsibility to cause the text view to be redrawn after system colours are changed.

CTextLayout uses the colour translation function SystemColor() (if an MFormParam-derived object is present) to set the pen and brush colours for drawing components of the text view. It calls MFormParam::Get() before each draw. This enables an application to introduce system colours, change the parameter object, or abolish system colours, and redraw everything correctly; no information is left over from the last draw.