dtk_create_circle_str man page
dtk_create_circle_str — Create and modify circular strip
dtk_hshape dtk_create_circle_str(dtk_hshape shp,
float cx, float cy, float r, float thick,
const float *color, unsigned int numpoints);
dtk_create_circle_str() creates an approximation of a circular strip of radius r centered at (cx,cy) using num_points vertices. The radius r is always referred to the outer circle.
thick represents the thickness of the strip. If thick is negative or greater than r, the call fails.
shp and color have the same usage and meaning as for other shape creation function:
shp can be used to modify a previously created shape. If it is non-null, the handle will be used to modify the shape referenced by shp. If shp is NULL, the function will attempt to create a new shape.
color should point to a 4 float array containing a normalized RGBA value (i.e. each component is between 0.0 and 1.0).
In case of success these functions return the handle to the newly created or modified shape. If the shp argument is non-null, the handle returned is the same value. In case of error, NULL is returned. If thick is negative or greater than r, NULL is returned.