There are two subclasses, Fl_Line_Dial and Fl_Fill_Dial.
Fl_Dial(int x,int y,int w,int h, const char *l = 0); int value(float); float value() const {return value_;} void bounds(float *a, float *b) const {*a = min; *b = max;} void bounds(float, float); float step() const {return step_;} void step(float a) {step_ = a;} void angles(short a, short b) {a1=a; a2=b;} void direction(uchar d) {direction_ = d;} uchar direction() const {return direction_;}