enum Control {
    PushButton,
    RadioButton,
    DropList,
    ...
};

enum State {
    Normal,
    Default,
    Pressed,
    Focused,
    Hot, // MouseOver
    Disabled    
};

enum SysInfo
{
    HaveAnimations,
    AnimationTime,
    Composited,
    //...
};


enum PixelMetric
{
    PushButtonMargin,
    PushButtonDefaultHeight, // MacOSX...
    //...

};

class Camo
{
public:
    void drawControl(Draw& w, Control c , State s, Rect bounds, Rect clip);
    int pixelMetric(PixelMetric pm);
    int getInfo(SysInfo);
    Color getColor(Control c, State s, ... );
    // ....
    // ....
};

// CamoWin.cpp , CamoGtk.cpp, CamoMacOS.cpp, CamoUpp.cpp ,etc.