OpenGL 2.1 glCreateShader未定义

Question

我刚开始在FLTK的帮助下学习OpenGL，因为我需要一些GUI功能。我的IDE是Windows 7上的VS13，我的显卡驱动程序支持OpenGL 2.1。

我所做的只是运行他们的一个示例并尝试稍微修改它但是它无法使用非常基本的东西进行编译 - 包含在OpenGL 2.1中的glCreateShader方法，它说“错误：标识符“glCreateShader”未定义“尽管还有许多其他gl-功能被识别。这是代码，我的功能在最后。如果我发表评论它会构建并运行：

//
// "$Id: cube.cxx 8864 2011-07-19 04:49:30Z greg.ercolano $"
//
// Another forms test program for the Fast Light Tool Kit (FLTK).
//
// Modified to have 2 cubes to test multiple OpenGL contexts
//
// Copyright 1998-2010 by Bill Spitzak and others.
//
// This library is free software. Distribution and use rights are outlined in
// the file "COPYING" which should have been included with this file.  If this
// file is missing or damaged, see the license at:
//
//     http://www.fltk.org/COPYING.php
//
// Please report all bugs and problems on the following page:
//
//     http://www.fltk.org/str.php
//

#include <config.h>
#include <FL/Fl.H>
#include <FL/Fl_Window.H>
#include <FL/Fl_Box.H>
#include <FL/Fl_Button.H>
#include <FL/Fl_Radio_Light_Button.H>
#include <FL/Fl_Slider.H>
#include <stdlib.h>
#include <string>


#include <FL/Fl_Gl_Window.H>
#include <FL/gl.h>

class cube_box : public Fl_Gl_Window {
    void draw();
    int handle(int);
public:
    double lasttime;
    int wire;
    double size;
    double speed;
    cube_box(int x, int y, int w, int h, const char *l = 0)
        : Fl_Gl_Window(x, y, w, h, l) {
        lasttime = 0.0;
    }
};

/* The cube definition */
float v0[3] = { 0.0, 0.0, 0.0 };
float v1[3] = { 1.0, 0.0, 0.0 };
float v2[3] = { 1.0, 1.0, 0.0 };
float v3[3] = { 0.0, 1.0, 0.0 };
float v4[3] = { 0.0, 0.0, 1.0 };
float v5[3] = { 1.0, 0.0, 1.0 };
float v6[3] = { 1.0, 1.0, 1.0 };
float v7[3] = { 0.0, 1.0, 1.0 };

#define v3f(x) glVertex3fv(x)

void drawcube(int wire) {
    /* Draw a colored cube */
    glBegin(wire ? GL_LINE_LOOP : GL_POLYGON);
    glColor3ub(0, 0, 255);
    v3f(v0); v3f(v1); v3f(v2); v3f(v3);
    glEnd();
    glBegin(wire ? GL_LINE_LOOP : GL_POLYGON);
    glColor3ub(0, 255, 255); v3f(v4); v3f(v5); v3f(v6); v3f(v7);
    glEnd();
    glBegin(wire ? GL_LINE_LOOP : GL_POLYGON);
    glColor3ub(255, 0, 255); v3f(v0); v3f(v1); v3f(v5); v3f(v4);
    glEnd();
    glBegin(wire ? GL_LINE_LOOP : GL_POLYGON);
    glColor3ub(255, 255, 0); v3f(v2); v3f(v3); v3f(v7); v3f(v6);
    glEnd();
    glBegin(wire ? GL_LINE_LOOP : GL_POLYGON);
    glColor3ub(0, 255, 0); v3f(v0); v3f(v4); v3f(v7); v3f(v3);
    glEnd();
    glBegin(wire ? GL_LINE_LOOP : GL_POLYGON);
    glColor3ub(255, 0, 0); v3f(v1); v3f(v2); v3f(v6); v3f(v5);
    glEnd();
}

void cube_box::draw() {
    lasttime = lasttime + speed;
    if (!valid()) {
        glLoadIdentity();
        glViewport(0, 0, w(), h());
        glEnable(GL_DEPTH_TEST);
        glFrustum(-1, 1, -1, 1, 2, 10000);
        glTranslatef(0, 0, -10);
        gl_font(FL_HELVETICA_BOLD, 16);
    }
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glPushMatrix();
    glRotatef(float(lasttime*1.6), 0, 0, 1);
    glRotatef(float(lasttime*4.2), 1, 0, 0);
    glRotatef(float(lasttime*2.3), 0, 1, 0);
    glTranslatef(-1.0, 1.2f, -1.5);
    glScalef(float(size), float(size), float(size));
    drawcube(wire);
    glPopMatrix();
    gl_color(FL_GRAY);
    glDisable(GL_DEPTH_TEST);
    gl_draw(wire ? "Cube: wire" : "Cube: flat", -4.5f, -4.5f);
    glEnable(GL_DEPTH_TEST);
}

int cube_box::handle(int e) {
    switch (e) {
    case FL_ENTER: cursor(FL_CURSOR_CROSS); break;
    case FL_LEAVE: cursor(FL_CURSOR_DEFAULT); break;
    }
    return Fl_Gl_Window::handle(e);
}

Fl_Window *form;
Fl_Slider *speed, *size;
Fl_Button *button, *wire, *flat;
cube_box *cube;

void makeform(const char *name) {
    form = new Fl_Window(510 + 390, 390, name);
    new Fl_Box(FL_DOWN_FRAME, 20, 20, 350, 350, "");
    new Fl_Box(FL_DOWN_FRAME, 510, 20, 350, 350, "");
    speed = new Fl_Slider(FL_VERT_SLIDER, 390, 90, 40, 220, "Speed");
    size = new Fl_Slider(FL_VERT_SLIDER, 450, 90, 40, 220, "Size");
    wire = new Fl_Radio_Light_Button(390, 20, 100, 30, "Wire");
    flat = new Fl_Radio_Light_Button(390, 50, 100, 30, "Flat");
    button = new Fl_Button(390, 340, 100, 30, "Exit");
    cube = new cube_box(23, 23, 344, 344, 0);
    Fl_Box *b = new Fl_Box(FL_NO_BOX, cube->x(), size->y(),
        cube->w(), size->h(), 0);
    form->resizable(b);
    b->hide();
    form->end();
}

int main(int argc, char **argv) {
    makeform(argv[0]);
    // added to demo printing
    form->begin();

    form->end();
    // end of printing demo
    speed->bounds(4, 0);
    speed->value(cube->speed = 1.0);
    size->bounds(4, 0.01);
    size->value(cube->size = 1.0);
    flat->value(1); 
    cube->wire = 0; 
    form->label("cube");
    form->show(argc, argv);
    cube->show();

    for (;;) {
        if (form->visible() && speed->value()) {
            if (!Fl::check()) break;
        }   // returns immediately
        else                 {
if (!Fl::wait()) break;}    // waits until something happens
    cube->wire = wire->value();
    cube->size = size->value();
    cube->speed = speed->value();
    cube->redraw();
    if (Fl::readqueue() == button) break;
  }
  return 0;
}



//////////////////////////// Testing



GLuint CreateShader(GLenum eShaderType, const std::string &strShaderFile)
{
    GLuint shader = glCreateShader(eShaderType);

    return shader;
}