🚀 go-pugleaf

You must have a valid rendering context before you can call glGetString.
Open up a window, get a context, and then call glGetString and you will
get the correct behavior.

-- Marcin



"Dr. Antoni Kajetan Wisor" wrote:
> 
> Hi folks!
> 
> I have a small problem with OpenGL. Because I am not very deep in this topic, I
> do not know what to do further. If any one can help me, please post it. Here is
> an excerpt of my problem, which should run without any problem after
> compilation:
> 
> #include <stdio.h>              //Standard C I/O functions
> #include <windows.h>            //For Win32-API Applications
> #include <gl/gl.h>              //OpenGL
> 
> /* Declaration of prototypes */
> LONG __cdecl main();
> 
> /* Mainprog */
> 
> LONG __cdecl main()
> {
>   char* vendor = (char*)glGetString((GLenum)GL_VENDOR);
>   char* renderer = (char*)glGetString((GLenum)GL_RENDERER);
>   char* version = (char*)glGetString((GLenum)GL_VERSION);
>   char* extensions = (char*)glGetString((GLenum)GL_EXTENSIONS);
> 
>   glFlush();
> 
>   printf("Vendor: %s\n", vendor);
>   printf("Renderer: %s\n", renderer);
>   printf("Version: %s\n", version);
>   printf("Extensions: %s", extensions);
> 
>   return (LONG)0;
> }
> 
> Thanks!
> 
> Jakob Wisor

Dr. Antoni Kajetan Wisor wrote:
> 
> Hi folks!
> 
> I have a small problem with OpenGL. Because I am not very deep in this topic, I
> do not know what to do further. If any one can help me, please post it. Here is
> an excerpt of my problem, which should run without any problem after
> compilation:

You are wrong, this program should NOT run.

> 
> #include <stdio.h>              //Standard C I/O functions
> #include <windows.h>            //For Win32-API Applications
> #include <gl/gl.h>              //OpenGL
> 
> /* Declaration of prototypes */
> LONG __cdecl main();

First, the proper prototype for main is:

int main(int argc, char **argv);

> /* Mainprog */
> 
> LONG __cdecl main()
> {
>   char* vendor = (char*)glGetString((GLenum)GL_VENDOR);
>   char* renderer = (char*)glGetString((GLenum)GL_RENDERER);
>   char* version = (char*)glGetString((GLenum)GL_VERSION);
>   char* extensions = (char*)glGetString((GLenum)GL_EXTENSIONS);

You cannot call OpenGL functions without creating a context and making
it current. To create a context you need to create a window, so you
might as well start with a full Windows app instead of a console app. Or
use GLUT to avoid the Windows API.

> 
>   glFlush();

There is no reason to cal glFlush if you have not rendered anything.

> 
>   printf("Vendor: %s\n", vendor);
>   printf("Renderer: %s\n", renderer);
>   printf("Version: %s\n", version);
>   printf("Extensions: %s", extensions);
> 
>   return (LONG)0;
> }
> 
> Thanks!
> 
> Jakob Wisor


Phil Frisbie, Jr.
Hawk Software
http://www.hawksoft.com