c++ - SDL2 程序仅在使用 SDL_RENDERER_SOFTWARE 创建渲染器时才有效

Question

我使用 C++ 和 SDL2 编写了一个程序:

1. 创建一个窗口
2. 获取窗口的表面
3. 为窗口创建渲染器
4. 在窗口上渲染一些填充的矩形
5. 从窗口的表面创建一个纹理
6. 清除屏幕
7. 在窗口上渲染一些实心圆
8. 从窗口的表面创建第二个纹理
9. 进入一个事件循环，每次按下一个键时:
10. 如果当前正在显示圆形，则使用 SDL_RenderCopy() 将正方形纹理复制到窗口。
11. 否则，如果当前正在显示正方形，则将圆形纹理复制到窗口。

如果渲染器是使用 SDL_RENDERER_SOFTWARE 标志创建的，该程序将完美运行。

如果渲染器是使用 SDL_RENDERER_ACCELERATED 标志创建的，我发现虽然我可以直接渲染到屏幕，但如果我从窗口表面创建几个不同的纹理然后尝试复制它们使用 SDL_RenderCopy() 回到窗口；我只看到一个黑色的窗口。

我找不到任何失败的 SDL 调用。

我想知道纹理格式和渲染器之间是否可能存在一些不兼容 - 但我不确定如何跟进。

有什么帮助或建议吗？

我的环境是:

• Windows 10
• 2015 年 Visual Studio 社区
• SDL2 版本 2.0.4

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

附加信息和源代码:

我添加了简化的源代码来演示下面的问题。

请注意，为了减小大小，我删除了所有错误检查并将相关代码合并到一个主函数中。

我得到的是，如果我取消注释第 40 行，那么程序会按预期工作，以便我使用 SDL_RENDERER_SOFTWARE 标志调用 SDL_CreateRenderer。

如果我取消注释任何其他 SDL_CreateRenderer 行(第 41-43 行:使用硬件加速)，我会在最初呈现到屏幕时看到红色和蓝色方 block 。

但是当我按键时，我看到的不是窗口在红色和蓝色方 block 之间闪烁，而是黑色窗口。

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

#include <SDL.h>
#include <SDL_image.h>
#include <stdio.h>
#include <string>


//Screen dimension constants
const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;


int main(int argc, char* args[])
{

    //The window we'll be rendering to
    SDL_Window* gWindow = NULL;

    //The surface contained by the window
    SDL_Surface* gScreenSurface = NULL;

    //And two textures, one for a red square, on for a blue square
    SDL_Texture* texture_red = NULL;
    SDL_Texture* texture_blue = NULL;

    //The window renderer
    SDL_Renderer* gRenderer = NULL;


    //Initialize SDL
    SDL_Init(SDL_INIT_VIDEO);

    //Create window
    gWindow = SDL_CreateWindow("SDL Tutorial", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);

    //Get the screen surface
    gScreenSurface = SDL_GetWindowSurface(gWindow);


    //Create renderer for window
    gRenderer = SDL_CreateRenderer(gWindow, -1, SDL_RENDERER_SOFTWARE);
    //gRenderer = SDL_CreateRenderer(gWindow, -1, SDL_RENDERER_ACCELERATED);
    //gRenderer = SDL_CreateRenderer(gWindow, -1, SDL_RENDERER_PRESENTVSYNC);
    //gRenderer = SDL_CreateRenderer(gWindow, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_TARGETTEXTURE);

    /*###########################################################################################
    # I can not figure out how to make this program work with hardware acceleration. It works   #
    # fine when I define the renderer using SDL_RENDERER_SOFTWARE, but doesn't display anything #
    # if I define the renerer using the SDL_RENDERER_ACCELERATED flag                           #
    ###########################################################################################*/

    //Initialize renderer color
    SDL_SetRenderDrawColor(gRenderer, 0xFF, 0xFF, 0xFF, 0xFF);


    //Clear screen
    SDL_SetRenderDrawColor(gRenderer, 0xFF, 0xFF, 0xFF, 0xFF);
    SDL_RenderClear(gRenderer);

    //Render red filled quad
    SDL_Rect fillRect = { 100, 75, 100, 100 };
    SDL_SetRenderDrawColor(gRenderer, 0xFF, 0x00, 0x00, 0xFF);
    SDL_RenderFillRect(gRenderer, &fillRect);

    //Update the rendered image on screen
    SDL_RenderPresent(gRenderer);

    //Pause long enough to see it
    SDL_Delay(200);

    //Create texture_red texture from the screen surface
    texture_red = SDL_CreateTextureFromSurface(gRenderer, gScreenSurface);


    //Clear screen
    SDL_SetRenderDrawColor(gRenderer, 0xFF, 0xFF, 0xFF, 0xFF);
    SDL_RenderClear(gRenderer);

    //Render blue filled quad
    fillRect = { 225, 250, 100, 100 };
    SDL_SetRenderDrawColor(gRenderer, 0x00, 0x00, 0xFF, 0xFF);
    SDL_RenderFillRect(gRenderer, &fillRect);

    //Update the rendered image on screen
    SDL_RenderPresent(gRenderer);

    //Pause long enough to see it
    SDL_Delay(200);

    //Create texture_red texture from the screen surface
    texture_blue = SDL_CreateTextureFromSurface(gRenderer, gScreenSurface);


    //Main loop flag
    bool quit = false;

    //Flag to keep track of which colour we're currently looking at
    bool blue = true;

    //Event handler
    SDL_Event e;

    //While application is running
    while (!quit)
    {
        //Handle events on queue
        while (SDL_PollEvent(&e) != 0)
        {
            //User requests quit
            if (e.type == SDL_QUIT)
            {
                quit = true;
            }
            //User presses a key
            else if (e.type == SDL_KEYDOWN)
            {
                //Select surfaces based on key press
                switch (e.key.keysym.sym)
                {

                case SDLK_ESCAPE:
                    quit = true;
                    break;

                default:
                    if (blue)
                    {
                        //Copy surface used to store red image onto the screen surface
                        SDL_RenderCopy(gRenderer, texture_red, NULL, NULL);

                        //Update current colour flag
                        blue = false;
                    }
                    else
                    {

                        //Copy surface used to store blue image onto the screen surface
                        SDL_RenderCopy(gRenderer, texture_blue, NULL, NULL);

                        //Update current colour flag
                        blue = true;
                    }

                    //Update the screen with recent render activity
                    SDL_RenderPresent(gRenderer);

                    break;
                }
            }
        }
    }


    //Deallocate surfaces
    SDL_FreeSurface(gScreenSurface);

    //Destroy window
    SDL_DestroyWindow(gWindow);
    gWindow = NULL;

    //Quit SDL subsystems
    SDL_Quit();

    return 0;
}

Answer 1

SDL_GetWindowSurface() header comment特别禁止将其与 SDL_Renderer 功能一起使用:

/**
 *  \brief Get the SDL surface associated with the window.
 *
 *  \return The window's framebuffer surface, or NULL on error.
 *
 *  A new surface will be created with the optimal format for the window,
 *  if necessary. This surface will be freed when the window is destroyed.
 *
 *  \note You may not combine this with 3D or the rendering API on this window.
 *
 *  \sa SDL_UpdateWindowSurface()
 *  \sa SDL_UpdateWindowSurfaceRects()
 */
extern DECLSPEC SDL_Surface * SDLCALL SDL_GetWindowSurface(SDL_Window * window);

使用SDL_RENDERER_TARGETTEXTURE & SDL_SetRenderTarget()如果您想捕获 SDL_Renderer 输出。

您可以使用 SDL_GetRendererInfo()查询兼容的纹理格式。或者直接使用 SDL_PIXELFORMAT_ARGB8888 like testrendertarget.c does并希望最好的:)