GLfloat blockSize = 0.1f;

//正方形四个点的坐标
GLfloat vVerts[] = {
    -blockSize, -blockSize, 0.0f,
    blockSize, -blockSize, 0.0f,
    blockSize, blockSize, 0.0f,
    -blockSize, blockSize, 0.0f,
};

//将 GL_TRIANGLES 修改为 GL_TRIANGLE_FAN ,4个顶点
    triangleBatch.Begin(GL_TRIANGLE_FAN, 4);

//key 枚举值，x、y是位置
void SpecialKeys(int key, int x, int y){
    //步长
    GLfloat stepSize = 0.025f;

    //相对点的坐标
    GLfloat blockX = vVerts[0];
    GLfloat blockY = vVerts[10];

    printf("v[0] = %f\n",blockX);
    printf("v[10] = %f\n",blockY);

    //根据移动方向，更新相对坐标
    if (key == GLUT_KEY_UP) {
        blockY += stepSize;
    }
    if (key == GLUT_KEY_DOWN) {
        blockY -= stepSize;
    }
    if (key == GLUT_KEY_LEFT) {
        blockX -= stepSize;
    }
    if (key == GLUT_KEY_RIGHT) {
        blockX += stepSize;
    }

    //触碰到边界（4个边界）的处理

    //当正方形移动超过最左边的时候
    if (blockX < -1.0f) {
        blockX = -1.0f;
    }
    //当正方形移动到最右边时
    //1.0 - blockSize * 2 = 总边长 - 正方形的边长 = 最左边点的位置
    if (blockX > (1.0f - blockSize * 2)) {
        blockX = 1.0f - blockSize * 2;
    }
    //当正方形移动到最下面时
    //-1.0 - blockSize * 2 = Y（负轴边界） - 正方形边长 = 最下面点的位置
    if (blockY < -1.0f + blockSize * 2) {
        blockY = -1.0f + blockSize * 2;
    }
    //当正方形移动到最上面时
    if (blockY > 1.0f) {
        blockY = 1.0f;
    }

    printf("blockX = %f\n",blockX);
    printf("blockY = %f\n",blockY);

    //重新计算正方形的位置
    //一个顶点有三个数 x、y、z
    vVerts[0] = blockX;
    vVerts[1] = blockY - blockSize * 2;
    printf("(%f,%f)\n",vVerts[0],vVerts[1]);

    vVerts[3] = blockX + blockSize * 2;
    vVerts[4] = blockY - blockSize * 2;
    printf("(%f,%f)\n",vVerts[3],vVerts[4]);

    vVerts[6] = blockX + blockSize * 2;
    vVerts[7] = blockY;
    printf("(%f,%f)\n",vVerts[6],vVerts[7]);

    vVerts[9] = blockX;
    vVerts[10] = blockY;
    printf("(%f,%f)\n",vVerts[9],vVerts[10]);

    //更新顶点数据
    triangleBatch.CopyVertexData3f(vVerts);

    //重新渲染提交 --> RenderScene
    glutPostRedisplay();

}

//记录移动图形时，在x轴上平移的距离
GLfloat xPos = 0.0f;
//记录移动图形时，在y轴上平移的距离
GLfloat yPos = 0.0f;

GLfloat stepSize = 0.025f;

//使用矩阵方式（一起搞定），不需要修改每个顶点，只需要记录移动步长，碰撞检测
void SpecialKeys(int key, int x, int y){

    GLfloat stepSize = 0.025f;

    if (key == GLUT_KEY_UP) {

        yPos += stepSize;
    }

    if (key == GLUT_KEY_DOWN) {
        yPos -= stepSize;
    }

    if (key == GLUT_KEY_LEFT) {
        xPos -= stepSize;
    }

    if (key == GLUT_KEY_RIGHT) {
        xPos += stepSize;
    }

    //碰撞检测 xPos是平移距离，即移动量
    if (xPos < (-1.0f + blockSize)) {

        xPos = -1.0f + blockSize;
    }

    if (xPos > (1.0f - blockSize)) {
        xPos = 1.0f - blockSize;
    }

    if (yPos < (-1.0f + blockSize)) {
        yPos = -1.0f + blockSize;
    }

    if (yPos > (1.0f - blockSize)) {
        yPos = 1.0f - blockSize;
    }

    glutPostRedisplay();

}

//开始渲染
void RenderScene(void)

{
    //1.清除一个或者一组特定的缓存区
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

    //1.设置颜色RGBA
    GLfloat vRed[] = {1.0f, 0.5f, 0.0f, 1.0f};

    //定义矩阵
    M3DMatrix44f mTransformMatrix;

    //平移矩阵
    m3dTranslationMatrix44(mTransformMatrix, xPos, yPos, 0.0f);

    //当单元着色器不够用时，使用平面着色器
    //参数1：存储着色器类型
    //参数2：使用什么矩阵变换
    //参数3：颜色
    shaderManager.UseStockShader(GLT_SHADER_FLAT, mTransformMatrix, vRed);

    //提交着色器
    triangleBatch.Draw();
    glutSwapBuffers();
}