class RectPainter:

def init(self):

self.start_x = 0

self.start_y = 0

self.end_x = 0

self.end_y = 0

self.clear_flag = False

def prepare(self):

vshader_src = """

#version 330 core

layout (location = 0) in vec3 aPos;

        void main()
        {
            gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
            // gl_Position是内置变量}