从 SDL_Window* 到 Uint32 的转换无效？

Question

我正在 cpp 中创建一个分形。对于渲染器，我使用 SDL2，但出现一个我不明白的错误：

35:49: error: invalid conversion from 'SDL_Window*' to 'Uint32' {aka 'unsigned int'} [-fpermissive]

这是我的代码：

#include <SDL2/SDL.h>
#include <numeric>
#include <complex>
#include <cmath>
#include <iostream>

int isInSet(std::complex<double> c) 
{
    std::complex<double> z(0,0);
    for (int i = 0; i < 25; i++)
    {
        z = std::pow(z, 2) + c;
        if (std::norm(z) > 10)
        {
            return i;
        }
    }
    return 0;
}

int main() 
{
    SDL_Init(SDL_INIT_EVERYTHING);
    SDL_Window* window = nullptr;
    SDL_Renderer* renderer = nullptr;
    /*SDL_Window* window = SDL_CreateWindow(
    "An SDL2 window", // window title
    SDL_WINDOWPOS_UNDEFINED, // initial x position
    SDL_WINDOWPOS_UNDEFINED, // initial y position
    640, // width, in pixels
    480, // height, in pixels
    SDL_WINDOW_FULLSCREEN // flags - see below
    );*/
    //SDL_Renderer* renderer = SDL_CreateRenderer(window , -1, SDL_RENDERER_PRESENTVSYNC);
    SDL_CreateWindowAndRenderer(2000, 2000, window, renderer); // here error: invalid conversion from 'SDL_Window*' to 'Uint32' {aka 'unsigned int'} [-fpermissive]
    SDL_RenderSetScale(renderer, 2, 2);

    for (double x = 0.0; x < 1.0; x = x + 0.01)
    {
        for (double y = 0.0; y < 1.0; y = y + 0.01)
        {
            double point_x = std::lerp(-2.0, 2.0, x);
            double point_y = std::lerp(-2.0, 2.0, y);
            int iters = isInSet(std::complex<double>(point_x, point_y));
            if (iters == 0)
            {
                SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
                SDL_RenderDrawPointF(renderer, x * 1000, y * 1000);
            }
            else
            {
                SDL_SetRenderDrawColor(renderer, 255-iters,255-iters,255-iters, 255);
                SDL_RenderDrawPointF(renderer, x * 1000, y * 1000);
            }
        }

        SDL_RenderPresent(renderer);
        SDL_Delay(10000);
    }
    return 0;
}

// g++.exe -fdiagnostics-color=always -g J:\Info\cpp.cpp\MyProjects\fractales\Mandelbrot\mandelbrot.cpp -o J:\Info\cpp.cpp\MyProjects\fractales\Mandelbrot\mandelbrot.exe && J:\Info\cpp.cpp\MyProjects\fractales\Mandelbrot\mandelbrot.exe
// g++.exe -std=c20++ J:\Info\cpp.cpp\MyProjects\fractales\Mandelbrot\mandelbrot.cpp -IC:\Users\user.PC-SKAMRA\cpp\SDL2\x86_64-w64-mingw32\include -LC:\Users\user.PC-SKAMRA\cpp\SDL2\x86_64-w64-mingw32\lib -Wall -lmingw32 -lSDL2main -lSDL2 -o J:\Info\cpp.cpp\MyProjects\fractales\Mandelbrot\mandelbrot.exe

为什么我会收到此错误？

Answer 1

根据文档，这是

SDL_CreateWindowAndRenderer

的签名：

int SDL_CreateWindowAndRenderer(
    int width, int height, Uint32 window_flags,
    SDL_Window **window, SDL_Renderer **renderer);

所以需要五个参数......但你只给出四个。您将

window

作为第三个传递，但该函数需要标志，并且您无法将指针转换为

Uint32

。

解决方案是传递这些标志。如果您不需要任何特定选项，可以使用

0

。这些

window

和

renderer

参数也是指向指针的指针，因此您需要传递指针变量的地址：

SDL_CreateWindowAndRenderer(2000, 2000, 0, &window, &renderer);