3.7画封闭的线,一次连接个顶点

void fl_polygon(int x, int y, int x1, int y1, int x2, int y2)
void fl_polygon(int x, int y, int x1, int y1, int x2, int y2, int x3, int y3)

Fill a 3 or 4-sided polygon. The polygon must be convex.