Comments on: SDL Coordinates and Bliting

By: tim

tim — Sun, 14 Feb 2010 03:46:54 +0000

Not all linux users have to do that…I’m running Ubuntu Karmic ( not on a netbook ) and programming in Code::Blocks.
#include works for me. With libSDL.so added in the linker.

By: phoff

phoff — Tue, 09 Feb 2010 01:31:28 +0000

Do this on Linux too (I’m using Kubuntu Karmic and HP’s netbook distro, which is also Debian-based).

By: Tim Jones

Tim Jones — Tue, 19 Jan 2010 12:03:52 +0000

Glad you figured it out. You’re correct, you need both of them. What we are doing is called overloading the function.

By: Restler

Restler — Sun, 03 Jan 2010 01:08:39 +0000

Hi again, I think I missunderstood the code, the second OnDraw(…) wasn’t supposed to replace the the first one in CSurface.cpp right?

To draw a part of a picture you said:
“Open back up CSurface.cpp, and add the following function:

bool CSurface::OnDraw(SDL_Surface* Surf_Dest, SDL_Surface* Surf_Src, int X, int Y, int X2, int Y2, int W, int H) {…”

The first OnDraw wasnät there so I thought I was supposed to replace it with the new one. Sorry!
Well, now it works fine!
Thanks again for the tutorial!!

By: Restler

Restler — Sun, 03 Jan 2010 00:46:59 +0000

Hello, I have exactly the same problem as #27 had, and I use VC++ 2008 too (I’ve never used any other IDE before so I wanted to go with the safest choice for now).

I get 2 linking errors:
1>CApp_OnRender.obj : error LNK2019: unresolved external symbol “public: static bool __cdecl CSurface::OnDraw(struct SDL_Surface *,struct SDL_Surface *,int,int)” (?OnDraw@CSurface@@SA_NPAUSDL_Surface@@0HH@Z) referenced in function “public: void __thiscall CApp::OnRender(void)” (?OnRender@CApp@@QAEXXZ)
1> fatal error LNK1120: 1 unresolved externals

But just like #27, when I erase “CSurface::OnDraw(surf_Display, surf_Test, 0, 0);”
it all works fine..?

By: SeedGameMaster

SeedGameMaster — Wed, 16 Dec 2009 01:10:25 +0000

Hi !
As many of your readers/alumns, i am starting in this SDL programming “stuff”, i find your tutorials very clear and intuitive so far. I just wanted to say “Great Job” and thanks for your dedication to this…

PS: Please Forgive my bad “English” … i will work on improve it

By: Sam

Sam — Fri, 16 Oct 2009 18:36:36 +0000

thanks i dont understand why but there were just some spaces between the functions arguments and the commas i was bored so i removed them and now it works didn’t think tht wud matter but thanks for the help about the error

By: Tim Jones

Tim Jones — Thu, 15 Oct 2009 13:15:39 +0000

Sam,
It means that you didn’t actually define the function inside CSurface.cpp – hence the error: “unresolved external symbol.” Unresolved means it cannot find it, external symbol “[stuff here]” is what it can’t find. Make sure all the parameters match exactly.

By: Sam

Sam — Wed, 14 Oct 2009 13:51:13 +0000

I’m attempting to use VC++ but everything worked perfectly until i introduced the second OnDraw function

my code is identical to yours but im getting an error that i don’t understand whatsoever if you could just look at the error and see if you understand it thtat would help because googling hasen’t

>OnRender.obj : error LNK2019: unresolved external symbol “public: static bool __cdecl CSurface::OnDraw(struct SDL_Surface *,struct SDL_Surface *,int,int,int,int,int,int)” (?OnDraw@CSurface@@SA_NPAUSDL_Surface@@0HHHHHH@Z) referenced in function “public: void __thiscall CApp::OnRender(void)” (?OnRender@CApp@@QAEXXZ)

It might be linked to VC settings but i have no idea

The reason im using VC by the way is because codeblocks just won’t compile says it can’t find my mingw-g++.exe file but its defenitly where i have told codeblocks to look

By: Josh

Josh — Wed, 14 Oct 2009 10:42:24 +0000

If your using Dev C++ like me replace,
#include “SDL.h” with
#include “SDL/SDL.h”