Confused on SDL_CreateRGBSurface() width and height parameters - height

Question

So, after fooling around with the width and height numbers on the SDL_CreateRGBSurface() function, i am really confused on how they work. According to SDL Wiki the width and height refer to the width and height of the surface, however when I say SCREENWIDTH / 2, or SCREENHEIGHT / 2, it shows bigger than without the division. This is the code I was messing around with:
#include <iostream>
#include <SDL.h>
const int WIN_WIDTH = 640;
const int WIN_HEIGHT = 480;
int main(int argc, char **argv){
if (SDL_Init(SDL_INIT_EVERYTHING) != 0){
std::cerr << "SDL_Init failed: " << SDL_GetError() << "\n";
return 1;
}
SDL_Window *win = SDL_CreateWindow("Rendering to a texture!", SDL_WINDOWPOS_CENTERED,
SDL_WINDOWPOS_CENTERED, WIN_WIDTH, WIN_HEIGHT, 0);
SDL_Renderer *renderer = SDL_CreateRenderer(win, -1,
SDL_RENDERER_ACCELERATED | SDL_RENDERER_TARGETTEXTURE);
SDL_Surface* s;
SDL_Color c = { 155, 0, 0 };
SDL_Rect r = { 0, 0, 100, 100 };
s = SDL_CreateRGBSurface(0, WIN_WIDTH / 2, WIN_HEIGHT, 32, 0, 0, 0, 0);
SDL_FillRect(s, &r, SDL_MapRGB(s->format, c.r, c.g, c.b));
SDL_Texture* t;
t = SDL_CreateTextureFromSurface(renderer, s);
SDL_SetRenderDrawColor(renderer, 0xFF, 0xFF, 0xFF, 0xFF);
SDL_RenderClear(renderer);
SDL_RenderCopy(renderer, t, NULL, NULL);
SDL_RenderPresent(renderer);
SDL_Delay(2000);
SDL_FreeSurface(s);
SDL_DestroyTexture(t);
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(win);
SDL_Quit();
return 0;
}
All I really want is a rect with a width of 100 and height of 100, but to have it appear correctly on the screen, the width and height must be specified to the width and height of the window. Why is that?

Answer 1

SDL_RenderCopy will stretch the source texture to fit into the destination renderer. So it will stretch your surface over the entire window. If you want to draw a 100x100 pixel rectangle, your SDL surface should be the same size as the window you're copying it to; that way no stretching will take place and the surface will be presented 1:1.