SDL OpenGL issue

Question

我正在 youtube 上学习教程，但问题是教程的制作者使用的是 SDL 1.2，而 Im 使用的是 2.00，所以我不得不按照 SDL 迁移指南对代码进行一点更改。但是，我的代码没有做它应该做的事情，即绘制一个三角形。就这么简单。我得到的只是一个白屏。

======

=主要==

==========

#include "stdafx.h"

void init()
{
    glClearColor(0.0, 0.0, 0.0, 1.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45, 640.0 / 480.0, 1.0, 500.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}
void display()
{
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
    glBegin(GL_TRIANGLES);
    glVertex3f(0.0, 2.0, -5.0);
    glVertex3f(-2.0, -2.0, -5.0);
    glVertex3f(2.0, -2.0, -5.0);
    glEnd();
}
int main(int argc, char* argv[]){
SDL_Init(SDL_INIT_EVERYTHING); 
    SDL_Window * window;
    window = SDL_CreateWindow("OpenGLTest", 300, 300, 640, 480, SDL_WINDOW_SHOWN |       SDL_WINDOW_OPENGL);
    init();
    SDL_Event * mainEvent;
    mainEvent = new SDL_Event;
    while (true){
        SDL_PollEvent(mainEvent);
        display();
        SDL_GL_SwapWindow(window);
        if (mainEvent->type == SDL_QUIT){
            break;
        }
    }
return 0;
}

====

=stdafx

=========

#pragma once
#include <iostream>
#include <SDL.h>
#include <Windows.h>
#include <gl/GL.h>
#include <gl/GLU.h>
#define PI 3.14159265
using namespace std;

知道我做错了什么吗？

Answer 1

仅SDL_WINDOW_OPENGL是必要的，但还不够。

使用 SDL_GL_CreateContext() 创建一个 GL 上下文，并通过 SDL_GL_MakeCurrent() 使其处于当前状态：

#include <GL/glew.h>
#include <SDL/SDL.h>
int main( int argc, char *argv[] )
{
    SDL_Init(SDL_INIT_EVERYTHING); 
    SDL_Window * window = SDL_CreateWindow
        (
        "OpenGLTest", 
        300, 300, 
        640, 480, 
        SDL_WINDOW_SHOWN | SDL_WINDOW_OPENGL
        );
    SDL_GLContext context = SDL_GL_CreateContext( window );
    SDL_GL_MakeCurrent( window, context );
    glewInit();
    bool running = true;
    while( running )
    {
        SDL_Event ev;
        while( SDL_PollEvent( &ev ) )
        {
            if ( ev.type == SDL_QUIT)
                running = false;
        }
        glClearColor(0.0, 0.0, 0.0, 1.0);
        glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        gluPerspective(45, 640.0 / 480.0, 1.0, 500.0);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        glBegin(GL_TRIANGLES);
        glVertex3f(0.0, 2.0, -5.0);
        glVertex3f(-2.0, -2.0, -5.0);
        glVertex3f(2.0, -2.0, -5.0);
        glEnd();
        SDL_GL_SwapWindow(window);
    }
    SDL_GL_DeleteContext( context );
    SDL_DestroyWindow( window );
    SDL_Quit();
    return 0;
}