//

// left top 这里设置的默认是左上角

//

void push_view2d(int left, int top, int width, int height)

{

    //glPushAttrib(GL_TRANSFORM_BIT|GL_VIEWPORT_BIT);

    glPushAttrib(GL_ALL_ATTRIB_BITS);

    glMatrixMode(GL_PROJECTION);

    glPushMatrix();

    glLoadIdentity();

    //直角坐标系

    //glOrtho(left, width, top, height, 0, INT_MAX);

    //十字坐标系

    //glOrtho(-width/2, width/2, -height/2, height/2, 0, INT_MAX);//

    //windows坐标系

    //glOrtho(left, width, height, top, -1.0, 1000000.0);

    //这里的-1要去掉，不然绘制会有舍入偏差

    //glOrtho(left, left+width-1, top+height-1, top, 0, INT_MAX);

    glOrtho(left, left+width, top+height, top, , INT_MAX);

    //glOrtho(0, width-1, -height+1, 0, 0, INT_MAX);

    //glTranslatef(0, -height+1, 0);

    //重新设置正面，默认GL_CCW

    //glFrontFace(GL_CW);

    //反转屏幕

    //glScalef(1.0f, -1.0f, 1.0f);

    //glTranslatef(0.0f, -height, 0.0f);

    glMatrixMode(GL_MODELVIEW);

    glLoadIdentity();

    glDisable(GL_DEPTH_TEST);//关闭深度测试

    glDisable(GL_CULL_FACE); //关闭面剔除

}

//恢复视口映射设置

void pop_view2d()

{

    glMatrixMode(GL_PROJECTION);

    glPopMatrix();

    glMatrixMode(GL_MODELVIEW);

    glPopAttrib();

}

#define CGL_LOWER_LEFT 0    //左下角起始（默认）

#define CGL_UPPER_LEFT 1    //左上角起始（Windows）

#define CGL_COORDINATE CGL_LOWER_LEFT    //定义左上角起始

/*

struct vec4f

{

    float r, g, b, a;

};

struct vertex_type

{

    float x, y, z;

    float u, v;

    vec4f color;

};

*/

void glcontext::draw_image(GLuint image, float x, float y, float width, float height,

    float u1, float v1, float u2, float v2)

{

    vertex_type vtx[] = {

        #if CGL_COORDINATE == CGL_LOWER_LEFT//左下角为原点

        vertex_type(x,         y,          0.0f, u1, v2, color),

        vertex_type(x + width, y,          0.0f, u2, v2, color),

        vertex_type(x + width, y + height, 0.0f, u2, v1, color),

        vertex_type(x        , y + height, 0.0f, u1, v1, color)

        #else//右下角为原点，OpenGL默认

        vertex_type(x,         y,          0.0f, u1, v1, color),

        vertex_type(x + width, y,          0.0f, u2, v1, color),

        vertex_type(x + width, y + height, 0.0f, u2, v2, color),

        vertex_type(x,         y + height, 0.0f, u1, v2, color)

        #endif

    };

    this->bind_texture(image);

    this->draw_arrays(GL_TRIANGLE_FAN, vtx, , );

}