Linux中SDL2空白透明窗口

Question

Linux中SDL2空白透明窗口

3

这是一段我尝试在我的Linux计算机上运行的SDL2示例代码，我的操作系统是Ubuntu 18.04，并且使用了KDE Plasma桌面环境（我安装了多个桌面环境以备不时之需）。

#include<iostream>
#include<SDL2/SDL.h>

int main(int argc, char** argv)
{
    if(SDL_Init(SDL_INIT_VIDEO) != 0){
        std::cerr << "SDL_Init() Error: " << SDL_GetError() << std::endl;
        return 1;
    }

    SDL_Window* win = SDL_CreateWindow(
        "Hello world",
        SDL_WINDOWPOS_CENTERED,
        SDL_WINDOWPOS_CENTERED,
        640,480,
        0
    );

    if(win == nullptr){
        std::cerr << "SDL_CreateWindow() Error: " << SDL_GetError() << std::endl;
        return 1;  
    }

    //Create and init the renderer
    SDL_Renderer* ren = SDL_CreateRenderer(win, -1, 0);
    if(ren == nullptr){
        std::cerr << "SDL_CreateRenderer() Error: " << SDL_GetError() << std::endl;
        SDL_DestroyWindow(win);
        return 1;
    }

    //Render something
    SDL_RenderSetLogicalSize(ren,640,480);

    //Set colour of renderer
    SDL_SetRenderDrawColor(ren,255,0,0,255);

    //Clear the screen to the set colour
    SDL_RenderClear(ren);

    //Show all the has been done behind the scenes
    SDL_RenderPresent(ren);

    //Delay so that we can see what is on the screen
    SDL_Delay(5000);

    //Clean Up
    SDL_DestroyRenderer(ren);
    SDL_DestroyWindow(win);
    SDL_Quit();

    return 0;
}

当我第一次运行程序时，应该出现的红窗口只出现了一次。所有后续执行都会产生一个透明的空窗口，并将背景中的任何内容拖动到窗口中。我在SDL_CreateWindow()中尝试使用SDL_WINDOW_SHOWN标志以及SDL_CreateRenderer()中的SDL_RENDER_ACCELERATED标志。唯一再次出现红屏幕的方法是重新启动系统。即使我使用IDE（CodeLite）编译并运行此代码，仍然得到相同的结果。这个SO上的问题与此类似，但OP不使用Linux，问题也不完全相同。这个网站上的其他帖子提到事件处理，但我还没有深入了解。如果必要的话，我会感激一些关于它的资源，因为文档没有解释得很清楚。更新：该程序在另一台运行Lubuntu 18.10的计算机上可以正常运行。

- DS2830

1个回答

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可以查看英文原文，
原文链接

- genpfault · Accepted Answer

将阻塞所有事件处理（如通知X11/Wayland和窗口管理器您的进程仍在运行）的SDL_Delay()替换为循环调用SDL_PumpEvents()，可以直接（如下所示）或间接地通过SDL_PollEvent()/SDL_WaitEvent()调用：

const Uint32 startMs = SDL_GetTicks();
while( SDL_GetTicks() - startMs < 5000 )
{
    SDL_PumpEvents();

    //Render something
    SDL_RenderSetLogicalSize(ren,640,480);

    //Set colour of renderer
    SDL_SetRenderDrawColor(ren,255,0,0,255);

    //Clear the screen to the set colour
    SDL_RenderClear(ren);

    //Show all the has been done behind the scenes
    SDL_RenderPresent(ren);
}

全部在一起：

#include <iostream>
#include <SDL2/SDL.h>

int main( int argc, char** argv )
{
    if( SDL_Init( SDL_INIT_VIDEO ) != 0 )
    {
        std::cerr << "SDL_Init() Error: " << SDL_GetError() << std::endl;
        return 1;
    }

    SDL_Window* win = SDL_CreateWindow
        (
        "Hello world",
        SDL_WINDOWPOS_CENTERED,
        SDL_WINDOWPOS_CENTERED,
        640, 480,
        0
        );

    if( win == nullptr )
    {
        std::cerr << "SDL_CreateWindow() Error: " << SDL_GetError() << std::endl;
        return 1;
    }

    //Create and init the renderer
    SDL_Renderer* ren = SDL_CreateRenderer( win, -1, 0 );
    if( ren == nullptr )
    {
        std::cerr << "SDL_CreateRenderer() Error: " << SDL_GetError() << std::endl;
        SDL_DestroyWindow( win );
        return 1;
    }

    const Uint32 startMs = SDL_GetTicks();
    while( SDL_GetTicks() - startMs < 5000 )
    {
        SDL_PumpEvents();

        //Render something
        SDL_RenderSetLogicalSize( ren, 640, 480 );

        //Set colour of renderer
        SDL_SetRenderDrawColor( ren, 255, 0, 0, 255 );

        //Clear the screen to the set colour
        SDL_RenderClear( ren );

        //Show all the has been done behind the scenes
        SDL_RenderPresent( ren );
    }

    //Clean Up
    SDL_DestroyRenderer( ren );
    SDL_DestroyWindow( win );
    SDL_Quit();

    return 0;
}