There are four programs in directory src/:
    1. test_window -- test:
            the functions hit_test and calc_we_area, 
            window element attributes changing,
            window renderer changing.
            window border style changing.

    2. test_draw_menu -- test:
            the menu with radio or check mark,
            drawing functions in renderer.

    3. test_calccolor -- test:
            function HSV2RGB and RGB2HSV use fixed point decimal fraction,
            calc_3dbox_color in renderer.
            The program use assert() to test correctness of calculating.

    4. ctrldemo -- the same as ctrldemo in mde, but the default renderer 
            can be changed by menubar.
