c++ - 设置窗口大小后，SDL 未渲染到整个窗口

Question

下面是我使用SDL加载图片的步骤。

1. 创建窗口并以默认大小呈现，例如 100x100
2. 使用 IMG_LoadTexture 从图像创建纹理
3. 查询纹理信息并获取纹理尺寸，例如 800x600，然后使用 SDL_SetWindowSize 调整到所需尺寸
4. 执行渲染

结果是SDL在窗口创建时只渲染到100x100区域，其他部分不渲染。

如何在 SDL_SetWindowSize 之后让 SDL 渲染到整个窗口？

下面是我的示例代码

#include <iostream>
#include <SDL_image.h>
#include "SDL.h"

int main(int argc, char *argv[])
{
SDL_Window* sdlWindow;
SDL_Renderer* sdlRenderer;
SDL_CreateWindowAndRenderer(100, 100, 0, &sdlWindow, &sdlRenderer);

IMG_Init(IMG_INIT_JPG);

SDL_Texture* sdlTexture = IMG_LoadTexture(sdlRenderer, "test-wallpaper-800x600.jpg");

Uint32 format;
int access, w, h;
if (SDL_QueryTexture(sdlTexture, &format, &access, &w, &h) == 0) {
    SDL_SetWindowSize(sdlWindow, w, h);
    SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "linear");
    SDL_RenderSetLogicalSize(sdlRenderer, w, h);
}

SDL_RenderClear(sdlRenderer);
SDL_RenderCopy(sdlRenderer, sdlTexture, NULL, NULL);
SDL_RenderPresent(sdlRenderer);

SDL_Event sdlEvent;
while (SDL_WaitEvent(&sdlEvent)) {
    if (sdlEvent.type == SDL_WINDOWEVENT
        && sdlEvent.window.event == SDL_WINDOWEVENT_CLOSE) {
        break;
    }
    if (sdlEvent.type == SDL_KEYDOWN
            && sdlEvent.key.keysym.sym == SDLK_ESCAPE) {
        break;
    }
}

SDL_DestroyRenderer(sdlRenderer);
SDL_DestroyWindow(sdlWindow);
return 0;
}

Answer 1

您看不到更新的渲染，因为您只在帧循环之前渲染了一次。要解决此问题，请将渲染移动到帧循环中，如下所示:

SDL_Event sdlEvent;
while (SDL_WaitEvent(&sdlEvent))
{
    if (sdlEvent.type == SDL_WINDOWEVENT
        && sdlEvent.window.event == SDL_WINDOWEVENT_CLOSE) {
        break;
    }
    if (sdlEvent.type == SDL_KEYDOWN
            && sdlEvent.key.keysym.sym == SDLK_ESCAPE) {
        break;
    }

    // Render here
    SDL_RenderClear(sdlRenderer);
    SDL_RenderCopy(sdlRenderer, sdlTexture, NULL, NULL);
    SDL_RenderPresent(sdlRenderer);
}