opengl中简单的画图程序，类似于绘图，有菜单可以选择绘制不同图形-opengl in the simple drawing program, similar to the drawings, there is the menu you can choose to draw different shapes

简单的图形绘制软件包示例程序：要求能实现画文本、画线、三角形、矩形和点的绘制及菜单。-Simple drawing package sample program: Request to draw text, draw lines, triangles, rectangles, and points to draw menu