What Are GUI Hints:

GUI Hints are recommendations to the window manager about the window functionality and appearance.   There are some properties under the Functional group   which enable you to make these recommendations. If the present window manager supports the specific Graphical User Interface Hint property and it is set to yes then Form Builder uses it.  Thus if the window manage does not support the property and the Form Builder ignores it.

Note:  A Minimize Allowed properties have to be set yes in the sequence for Icon file name to be valid.