Programming : SDL_Window* into std::shared_ptr

I've had a little bit of a brain fart this morning, so to save you all the trouble, I'll go through it... First of all, I am working on an isolated system, therefore I had no internet, no clues, and importantly no books... This is a drag, because mainly I'll check things out look things up and just make sure I get things right... When things go wrong.

Unfortunately, things went wrong, and it was very early (for me) and I was unable to see the problem.

extern "C"

{

    #include <SDL.h>

}

SDL_Window* theWindow = SDL_CreateWindow (

    "The Window Title,

    SDL_WINDOWPOS_UNDEFINED,

    SDL_WINDOWPOS_UNDEFINED,

    800,

    600,

    SDL_WINDOW_SHOWN);

This code will create an SDL window at a unspecified location, with a size of 800x600 and the imaginative title "The Window Title".

This is fine, however, I hate seeing raw pointers, that "theWindow" variable irks me, it's just wrong to see that in modern C++ code; even if I am using a C based library.

So, I wanted to set about wrapping that into a smart pointer:

#include <memory>

namespace Xelous

{

    using SDLWindowPtr = std::shared_ptr<SDL_Window>;

}

This is my wanted type, "SDLWindowPtr", I know what this means to me, and I wanted to have a creating function wrap this for me:

The trouble?... This is considered an incomplete type, when we pass "SDL_CreateWindow" to the smart pointer ctor, it reports "incomplete type".

You can see the full error above, click to zoom in on the image.

So, what have I done wrong?... Well, the brain fart is to forget that "SDL_Window*" does not contain a standard destructor, it actually needs to be passed to SDL_DestroyWindow to close it down & release all resources.

I had totally forgotten this detail, I was too focussing too much upon the creation step and not thinking about the window objects life cycle.  The result was about 20 minutes wasted time banding my head wondering why this was happening.

Two cups of coffee and a pint of water, plus a wander down the corridor later, and I had that moment of realisation about this.

And so my code evolved, giving the solution to create a nullptr smart pointer result, then reset it to use the newly created window and instruct the smart pointer to use the SDL_DestroyWindow call for the clean up.

The complete code for a user might be more like this:

#include <string>

#include <memory>

extern "C"

{

    #include <SDL.h>

}

using SDLWindowPtr = std::shared_ptr<SDL_Window>;

SDLWindowPtr CreateWindowPtr (

    const std::string& p_Title,

    const unsigned int& p_X,

    const unsigned int& p_Y,

    const unsigned int& p_Width,

    const unsigned int& p_Height)

{

    auto l_result = SDLWindowPtr(nullptr);

    l_result.reset (

        SDL_CreateWindow(

            p_Title.c_str(),

            p_X,

            p_Y,

            p_Width,

            p_Height,

            SDL_WINDOW_SHOWN),

        SDL_DestroyWindow);

    return l_result;

}

int main ()

{

    SDLWindowPtr theWindow = CreateWindowPtr(

        "Hello World",

        10,

        10,

        800,

        600);

    SDL_Delay(5000);

}

We don't need to remember to SDL_DestroyWindow, we don't need to worry about forgetting to clean up, the smart pointer will do it for us when the reference count drops to zero.