SDL2 OpenGL3如何在函數內部初始化SDL

Question

我正在試驗新的SDL2 beta和OpenGL3上下文，但遇到一個奇怪的問題：

如果我在main（）函數中運行SDL初始化代碼，則可以正常工作，但是我想將此代碼放在單獨的init_sdl（）函數中。

如果我將初始化代碼放在單獨的init_sdl（）函數中，然后從main（）調用此函數，則背景顏色將永遠不會繪制，並且程序開始瘋狂消耗我所有的系統資源。

有人可以指出一個工作示例，其中在單獨的函數中初始化SDL嗎？ 我似乎找不到一個……也許這不可能嗎？ 我想我模糊地記得SDL 1.2遇到過類似的問題，但是自從使用它已有幾年了，我認為我從未找到解決方案。 實際上，這可能就是我選擇改用SFML的原因。

我真的想使用SDL2而不是SFML，因為它可以在更多平台上運行，但是對我來說，無法將其分解為小功能是很麻煩的。 這應該很容易，我是否缺少明顯的東西？

編輯：

這有效：

#include <iostream>
#include <GL/glew.h>
#include <SDL.h>
#define PROGRAM_NAME "SDL2 OpenGL3 Example"

int main(int argc, char** argv)
{
    SDL_Window* sdl2_window = 0;
    SDL_GLContext opengl3_context;

    SDL_Init(SDL_INIT_VIDEO);

    // set the opengl context version
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);

    // turn on double buffering set the depth buffer to 24 bits
    // you may need to change this to 16 or 32 for your system
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);

    // create the sdl2 window
    sdl2_window = SDL_CreateWindow(PROGRAM_NAME, SDL_WINDOWPOS_CENTERED,
            SDL_WINDOWPOS_CENTERED, 512, 512,
            SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN);

    // create the opengl3 context
    opengl3_context = SDL_GL_CreateContext(sdl2_window);

    GLenum status = glewInit();
    if (status != GLEW_OK)
    {
        std::cerr << "GLEW Error: " << glewGetErrorString(status) << "\n";
        exit(1);
    }

    // sync buffer swap with monitor's vertical refresh rate
    SDL_GL_SetSwapInterval(1);

    // set background color
    glClearColor( 1.0, 0.0, 0.0, 1.0 );

    while (true)
    {
        int status = 0;

        glClear( GL_COLOR_BUFFER_BIT );

        SDL_GL_SwapWindow(sdl2_window);

        SDL_Event event;

        while (SDL_PollEvent(&event))
        {
            switch (event.type)
            {
            case SDL_KEYDOWN:
                break;
            case SDL_KEYUP:
                // if escape is pressed, quit
                if (event.key.keysym.sym == SDLK_ESCAPE)
                    status = 1; // set status to 1 to exit main loop
                break;
            case SDL_QUIT:
                status = 1;
                break;
            }
        }

        if (status == 1) // if received instruction to quit
            break;
    }

    // delete opengl3 context, destroy sdl2 window, and shut down sdl subsystems
    SDL_GL_DeleteContext(opengl3_context);
    SDL_DestroyWindow(sdl2_window);
    SDL_Quit();

    return 0;
}

這不起作用：

#include <iostream>
#include <GL/glew.h>
#include <SDL.h>
#define PROGRAM_NAME "SDL2 OpenGL3 Example"

void init_sdl(SDL_Window* sdl2_window, SDL_GLContext& opengl3_context)
{
    SDL_Init(SDL_INIT_VIDEO);

    // set the opengl context version
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);

    // turn on double buffering set the depth buffer to 24 bits
    // you may need to change this to 16 or 32 for your system
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);

    // create the sdl2 window
    sdl2_window = SDL_CreateWindow(PROGRAM_NAME, SDL_WINDOWPOS_CENTERED,
            SDL_WINDOWPOS_CENTERED, 512, 512,
            SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN);

    // create the opengl3 context
    opengl3_context = SDL_GL_CreateContext(sdl2_window);
}

int main(int argc, char** argv)
{
    SDL_Window* sdl2_window = 0;
    SDL_GLContext opengl3_context;

    init_sdl(sdl2_window, opengl3_context);

    GLenum status = glewInit();
    if (status != GLEW_OK)
    {
        std::cerr << "GLEW Error: " << glewGetErrorString(status) << "\n";
        exit(1);
    }

    // sync buffer swap with monitor's vertical refresh rate
    SDL_GL_SetSwapInterval(1);

    // set background color
    glClearColor( 1.0, 0.0, 0.0, 1.0 );

    while (true)
    {
        int status = 0;

        glClear( GL_COLOR_BUFFER_BIT );

        SDL_GL_SwapWindow(sdl2_window);

        SDL_Event event;

        while (SDL_PollEvent(&event))
        {
            switch (event.type)
            {
            case SDL_KEYDOWN:
                break;
            case SDL_KEYUP:
                // if escape is pressed, quit
                if (event.key.keysym.sym == SDLK_ESCAPE)
                    status = 1; // set status to 1 to exit main loop
                break;
            case SDL_QUIT:
                status = 1;
                break;
            }
        }

        if (status == 1) // if received instruction to quit
            break;
    }

    // delete opengl3 context, destroy sdl2 window, and shut down sdl subsystems
    SDL_GL_DeleteContext(opengl3_context);
    SDL_DestroyWindow(sdl2_window);
    SDL_Quit();

    return 0;
}

Answer 1

void init_sdl(SDL_Window* sdl2_window, SDL_GLContext& opengl3_context)

您的第一個參數也應該是參考。 否則，當您返回main() sdl2_window仍為零。

Answer 2

您確定上下文沒有錯誤嗎？

int flags = SDL_WINDOW_OPENGL | SDL_WINDOW_BORDERLESS | SDL_WINDOW_SHOWN;
win = SDL_CreateWindow("3Doodle", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 1024, 768, flags);
SDL_assert(win != NULL);

context = SDL_GL_CreateContext(win);
SDL_assert(context != NULL);