SDL_GL_GetAttribute(SDL_GL_RED_SIZE, &red) 返回 OpenGL 错误 502 [关闭]

Question

SDL 版本 2.26.2

OpenGL核心版本4.0

我正在使用 SDL 为 OpenGL 项目创建窗口和上下文。我将 RGB 设置为 8 位，双缓冲，然后创建我的窗口和上下文。创建上下文后，我使用 SDL_GL_GetAttribute() 检索像素“形状”，这样我就知道我在使用什么。然而，每次我这样做，我都会得到一个错误，说明

Failed to retrieve red size. Error message:
        OpenGL error: 00000502
["alpha":8, "blue":8, "red":0, "green":8]

我在循环中使用正确的值调用 SDL_GL_GetAttribute()，但我每次都会收到此错误。在查看 OpenGL 文档时，我发现错误 502 表示“无效操作”，但我不知道无效操作可能是什么。任何帮助或建议将不胜感激。

编辑

在尝试为此最小化代码时，错误更改为以下内容：

[warning] source\app.d:61:main Attempt to read red size failed, OpenGL error: GL_INVALID_ENUM

生成该警告的代码如下：

import std.stdio;
import std.experimental.logger;
import std.conv;

import bindbc.sdl;
import bindbc.opengl;

SDL_Window* window;
SDL_Renderer* render;
SDL_GLContext context;

void main()
{
    auto support = loadSDL();
    if (support != sdlSupport) {
        if (support == SDLSupport.noLibrary) {
            writeln("the library could not be found");
        }
        else if (support == SDLSupport.badLibrary) {
            writeln("the version of SDL library loaded does not match the expected version");
        }
        else {
            writeln("Something bad happened here...");
        }
        
    }
    loadSDL("SDL2.lib");
    
    SDL_Init(SDL_INIT_EVERYTHING);

    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);

    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);

    SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8); 

    window = SDL_CreateWindow("testbed", 
        SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 1024, 768, 
        SDL_WINDOW_SHOWN  | SDL_WINDOW_OPENGL
    );

    
    context = SDL_GL_CreateContext(window);

    auto ogl_support = loadOpenGL();


    SDL_GL_SetSwapInterval(1);
    SDL_ShowWindow(window);

    SDL_Event event;
    bool running = true;

    int red, green, blue;

    if (SDL_GL_GetAttribute(SDL_GL_RED_SIZE, &red) < 0)
        log(LogLevel.warning, "Attempt to read red size failed, " ~ to!string(SDL_GetError()));
    if (SDL_GL_GetAttribute(SDL_GL_GREEN_SIZE, &green) < 0)
        log(LogLevel.warning, "Attempt to read green size failed, " ~ to!string(SDL_GetError()));
    if (SDL_GL_GetAttribute(SDL_GL_BLUE_SIZE, &blue) < 0)
        log(LogLevel.warning, "Attempt to read red size failed, " ~ to!string(SDL_GetError()));
    

    writeln(text(red), " ", text(green), " ", text(blue));

    
    while(running) {
        SDL_GL_SwapWindow(window);

        while(SDL_PollEvent(&event)) {
            if(event.type == SDL_QUIT) {
                running = false;
                break;
            }
        }
    }

    SDL_Quit();
}

再一次，当我尝试使用 SDL_GL_GetAttribute(SDL_GL_RED_SIZE, ...) 时发生错误，但在其他方面似乎可以很好地检索绿色和蓝色等价物。