How to load opengl custom layer?

[Aashik0808]

This is the c++ code I'm using. I'm able to render Triangle. But it is not transforming acording to map interaction like zoom (or) pan.
I want to know how to convert QMapbox::CustomLayerRenderParameters to MVP, so that I can use it inside Shader.
` class TestLayer : public QMapbox::CustomLayerHostInterface {

    GLuint program = 0;
    GLuint vertexShader = 0;
    GLuint fragmentShader = 0;
    GLuint buffer = 0;
    GLuint a_pos = 0;

    const GLchar *vertexShaderSource =
        "#version 300 es\n"
        "uniform mat4 u_matrix;"
        "in vec2 a_pos;"
        "void main() { "
            "gl_Position = vec4(a_pos, 0, 1);"
        "}";
    const GLchar *fragmentShaderSource =
        "#version 300 es\n"
        "out mediump vec4 fragColor;"
        "void main() {"
            "fragColor = vec4(1.0, 0.0, 0.0, 0.5);"
        "}";

    virtual void initialize() {
        int maxAttrib;
        GL_CHECK_ERROR(glGetIntegerv(GL_MAX_VERTEX_ATTRIBS, &maxAttrib));

        vertexShader = GL_CHECK_ERROR(glCreateShader(GL_VERTEX_SHADER));
        GL_CHECK_ERROR(glShaderSource(vertexShader, 1, &vertexShaderSource, nullptr));
        GL_CHECK_ERROR(glCompileShader(vertexShader));
        checkCompileStatus(vertexShader);

        fragmentShader = GL_CHECK_ERROR(glCreateShader(GL_FRAGMENT_SHADER));
        GL_CHECK_ERROR(glShaderSource(fragmentShader, 1, &fragmentShaderSource, nullptr));
        GL_CHECK_ERROR(glCompileShader(fragmentShader));
        checkCompileStatus(fragmentShader);

        program = GL_CHECK_ERROR(glCreateProgram());
        GL_CHECK_ERROR(glAttachShader(program, vertexShader));
        GL_CHECK_ERROR(glAttachShader(program, fragmentShader));
        GL_CHECK_ERROR(glLinkProgram(program));
        checkLinkStatus(program);

        a_pos = GL_CHECK_ERROR(glGetAttribLocation(program, "a_pos"));

        GLfloat background[] = {0.5694555555555555,0.28906703939214295,0.5372305555555555,0.3277633358931997,0.5847166666666667,0.33679357865410225};
        GL_CHECK_ERROR(glGenBuffers(1, &buffer));
        GL_CHECK_ERROR(glBindBuffer(GL_ARRAY_BUFFER, buffer));
        GL_CHECK_ERROR(glBufferData(GL_ARRAY_BUFFER, 8 * sizeof(GLfloat), background, GL_STATIC_DRAW));
    }
    virtual void render(const QMapbox::CustomLayerRenderParameters &params) {
        glUseProgram(program);
        glBindBuffer(GL_ARRAY_BUFFER, buffer);
        glEnableVertexAttribArray(a_pos);
        glVertexAttribPointer(a_pos, 2, GL_FLOAT, GL_FALSE, 0, NULL);
        glEnable(GL_BLEND);
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);


        GL_CHECK_ERROR(glDrawArrays(GL_TRIANGLE_STRIP, 0, 3));

    }
    virtual void deinitialize() {
    }
};

map->addCustomLayer("MyLayer", std::make_unique<TestLayer>());`

Thank you.