Is it expected behaviour for

SDL_BlitSurface(source, 0, target, 0);

to increment the refcount of target? Just because I’ve blitted source to target does that necessarily mean that target ‘has a reference’ to source?

(As I call FreeSurface on my source~s the refcount of target does decrease)

Here is a simple demonstration


#include "SDL.h"

void test(int x)
{
    SDL_Surface *image1 = SDL_CreateRGBSurface(0, 100,100, 32, 0, 0, 0, 0);
    SDL_Surface *image2 = SDL_CreateRGBSurface(0, 100,100, 32, 0, 0, 0, 0);
    printf("%d load: image1 %d image2 %d\n", x, image1->refcount, image2->refcount);
    SDL_BlitSurface(image1, 0, image2, 0);
    printf("%d blit: image1 %d image2 %d\n", x, image1->refcount, image2->refcount);
    if (x == 0)
    {
        SDL_FreeSurface(image1);
        SDL_FreeSurface(image2);
    }
    else
    {
        SDL_FreeSurface(image2);
        SDL_FreeSurface(image1);
    }
    printf("%d free: image1 %d image2 %d\n", x, image1->refcount, image2->refcount);
}

int main(int argc, char* argv[])
{
    test(0);
    test(1);
}

Compile with

g++ -o sdleg3 sdleg3.c -LSDL2 -I/usr/include/SDL2 -lSDL2

Output is

0 load: image1 1 image2 1
0 blit: image1 1 image2 2
0 free: image1 0 image2 0
1 load: image1 1 image2 1
1 blit: image1 1 image2 2
1 free: image1 0 image2 -1

So deleting the target surface first leads to a refcount of -1