Retrieves the state of the button. Returns TRUE if button is grayed, FALSE otherwise.

NOTE: Grayed is not the same thing as disabled. Grayed has a meaning for radio buttons and checkboxes. To be more precise - it applies only if the button has the BS_3STATE or BS_AUTO3STATE style. Grayed means that its state is indeterminate. In order to check if the button is enabled, use IsWindowEnabled.