Question

我正在尝试使用SDL渲染一个点，我似乎无法得到渲染点。我没有在代码中出现任何错误，它正在编译，但窗口上没有出现任何问题。

代码：

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

using namespace std;

int main() {
    const int windowHeight = 600;
    const int windowWidth = 800;

    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        return 1;
        cout << "Initialization failed" << endl;
    }

    SDL_Window *window = SDL_CreateWindow("Practice making sdl Window",
            SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, windowWidth,
            windowHeight, SDL_WINDOW_SHOWN);

    if (window == NULL) {
        SDL_Quit();
        return 2;
    }
    SDL_Renderer *s;
    const int pointLocationx = windowWidth/2;
    const int pointLocationy = windowHeight/2;
    SDL_RenderDrawPoint(s, pointLocationx, pointLocationy);

    bool quit = false;
    SDL_Event event;
    while (!quit) {
        //drawing particles
        //setting up objects
        //repeated over and over again

        while (SDL_PollEvent(&event)) {
            if (event.type == SDL_QUIT) {
                quit = true;
            }
        }
    }

    SDL_DestroyWindow(window);
    SDL_Quit();

}

以上是我的代码。任何建议表示赞赏，并且非常感谢帮助。

Answer 1

你错过了几件事。第一个也是最重要的是你的渲染器没有被初始化，这是用SDL_CreateRenderer完成的。现在我们准备好画在窗户上了。为此，您需要在渲染器上设置颜色（此颜色用于RenderDrawPoint和RenderDrawLine等函数）。

在绘制完你的观点之后，我们将颜色设置为之前的颜色。我选择黑色作为背景，白色作为点的颜色，你可以选择你需要的任何东西，在渲染器中设置颜色的功能是SDL_SetRenderDrawColor。

现在我们可以绘制，但在每次绘制之前你必须clear你的屏幕，对渲染器进行所有绘制调用，然后show绘制你所绘制的内容。

这是一个完整的示例，其中包含有关您缺少的部分的注释部分，我还将您的drawPoint移动到主循环中，因为在一天结束时您可能想要它。

但是（非常罕见的使用）如果你想画一次并且永远不再改变屏幕上的什么，那么你可以把它带到墙外，打电话给清楚并出现一次并完成它。

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

using namespace std;

int main() {
    const int windowHeight = 600;
    const int windowWidth = 800;

    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        return 1;
        cout << "Initialization failed" << endl;
    }

    SDL_Window *window = SDL_CreateWindow("Practice making sdl Window",
            SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, windowWidth,
            windowHeight, SDL_WINDOW_SHOWN);

    if (window == NULL) {
        SDL_Quit();
        return 2;
    }

    // We create a renderer with hardware acceleration, we also present according with the vertical sync refresh.
    SDL_Renderer *s = SDL_CreateRenderer(window, 0, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC) ;

    const int pointLocationx = windowWidth/2;
    const int pointLocationy = windowHeight/2;

    bool quit = false;
    SDL_Event event;

    while (!quit) {
        //drawing particles
        //setting up objects
        //repeated over and over again

        while (SDL_PollEvent(&event)) {
            if (event.type == SDL_QUIT) {
                quit = true;
            }
        }

        // We clear what we draw before
        SDL_RenderClear(s);
        // Set our color for the draw functions
        SDL_SetRenderDrawColor(s, 0xFF, 0xFF, 0xFF, 0xFF);
        // Now we can draw our point
        SDL_RenderDrawPoint(s, pointLocationx, pointLocationy);
        // Set the color to what was before
        SDL_SetRenderDrawColor(s, 0x00, 0x00, 0x00, 0xFF);
        // .. you could do some other drawing here
        // And now we present everything we draw after the clear.
        SDL_RenderPresent(s);
    }

    SDL_DestroyWindow(window);
    // We have to destroy the renderer, same as with the window.
    SDL_DestroyRenderer(s);
    SDL_Quit();

}

如何在sdl2中渲染一个点

1 个答案: