Minimal low-CPU desktop style SDL2 mainloop with drawing, with mouse use

main.cpp

#include <SDL2/SDL.h>
#undef main
#include <stdio.h>
#include <stdint.h>

SDL_Rect d = {0, 0, 800, 600};
int mouse_x = 0;
int mouse_y = 0;

int main()
{
    SDL_Window * window;
    SDL_Renderer * renderer;

    SDL_CreateWindowAndRenderer(d.w, d.h, SDL_WINDOW_RESIZABLE, &window, &renderer);
    
    bool damage = true;
    for(;;)
    {
        SDL_Event event;
        while(SDL_PollEvent(&event))
        {
            if (event.type == SDL_QUIT)
                exit(0);
            
            if (event.type == SDL_WINDOWEVENT)
            {
                damage = true;
                if (event.window.event == SDL_WINDOWEVENT_SIZE_CHANGED)
                    d.w = event.window.data1, d.h = event.window.data2;
            }
            
            if (event.type == SDL_MOUSEMOTION or event.type == SDL_MOUSEBUTTONDOWN or event.type == SDL_MOUSEBUTTONUP or event.type == SDL_MOUSEWHEEL)
                SDL_GetMouseState(&mouse_x, &mouse_y), damage = true;
        }
        if(damage)
        {
            damage = false;
            
            SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x00, 0xFF);
            SDL_RenderFillRect(renderer, &d);
            
            SDL_SetRenderDrawColor(renderer, 0xFF, 0xFF, 0xFF, 0xFF);
            SDL_RenderDrawLine(renderer, 0, 0, d.w, d.h);
            SDL_RenderDrawLine(renderer, mouse_x-5, mouse_y-5, mouse_x+5, mouse_y+5);
            SDL_RenderDrawLine(renderer, mouse_x-5, mouse_y+5, mouse_x+5, mouse_y-5);
            
            SDL_RenderPresent(renderer);
        }
        else
            SDL_Delay(1);
    }
}