更新：Ubuntu SDL SetVideoMode失败，找不到匹配的GLX Visual

Question

I have been tracking down this issue to the best of my abilities and I think I have found the culprit but I am unable to fix it.

Basically I am trying to run my simple game engine in Ubuntu 12.04. The engine is a static library and it is linked to the using game. Everything compiles (in Ubuntu) fine but when I run the program it never opens a window and immediately closes. In CodeBlocks I get the error "Process terminated with status 255". I believe SetVideoMode is returning null as checked by this line in the Init code:

if((Surf_Display = SDL_SetVideoMode(WindowWidth, WindowHeight, 32,SDL_GL_DOUBLEBUFFER | SDL_OPENGL)) == NULL){
        return false;
   }

I think this because I previously forgot to add the double equals before the NULL and in this condition the app does not terminate, only never creates a window bu the program is evidently running in the system monitor.

I also noticed something interesting. The Debug version of the static library is 350 odd kb and the program itself is only 150kb. On windows the program is always more than the size of the library, this assuming the library is built into the executable. This maybe how Linux works though.

Here is the engines initialization code:

#include "Scales.h"
#include "SDL/SDL.h"
#include "GL/gl.h"
#include "GL/glu.h"
#include "SDL/SDL_opengl.h"
#include <iostream>

Engine *scalesEngine;

bool OnInit(int WindowHeight, int WindowWidth){

    SDL_Surface* Surf_Display;

    if(SDL_Init(SDL_INIT_EVERYTHING) < 0) {
        return false;
   }
    SDL_GL_SetAttribute(SDL_GL_RED_SIZE,        8);
    SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE,      8);
    SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE,       8);
    SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE,      8);

    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE,      16);
    SDL_GL_SetAttribute(SDL_GL_BUFFER_SIZE,        32);

    SDL_GL_SetAttribute(SDL_GL_ACCUM_RED_SIZE,    8);
    SDL_GL_SetAttribute(SDL_GL_ACCUM_GREEN_SIZE,    8);
    SDL_GL_SetAttribute(SDL_GL_ACCUM_BLUE_SIZE,    8);
    SDL_GL_SetAttribute(SDL_GL_ACCUM_ALPHA_SIZE,    8);

    SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS,  1);
    SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES,  2);

   if((Surf_Display = SDL_SetVideoMode(WindowWidth, WindowHeight, 32,SDL_GL_DOUBLEBUFFER | SDL_OPENGL)) == NULL){
        return false;
   }

   glClearColor(0.422f,0.576f,1.0f,1.0f);
   glClearDepth(1.0f);

   glViewport(0, 0, WindowWidth, WindowHeight);

   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();

   glOrtho(0, WindowWidth, WindowHeight, 0, 1, -1);

   glMatrixMode(GL_MODELVIEW);

   glEnable(GL_TEXTURE_2D);

   glLoadIdentity();

   game_Init();

   return true;
}

int main(int argc, char* argv[]){

    scalesEngine = new Engine;

    game_preload();

    if(OnInit(scalesEngine->WindowHeight(), scalesEngine->WindowWidth()) == false){
        return -1;
    }

    SDL_Event Event;

    //Main Game Loop
    while(scalesEngine->Running){

        while(SDL_PollEvent(&Event)){
            scalesEngine->OnEvent(&Event);
        }


        scalesEngine->Update();
        scalesEngine->Render();
    }

    scalesEngine->OnCleanUp();
    delete scalesEngine;

    return 0;
}

All the function calls prefixed with "game" are extern functions in the actual program. The above code is in the engines library.

If you require further information please ask.

EDIT: After further hunting down of the issue I noticed SDL give this error:

Couldn't Find Matching GLX Visual

What Does this mean and how on earth do I fix it?

Answer 1

SDL_SetVideoMode(WindowWidth, WindowHeight, 32,SDL_GL_DOUBLEBUFFER | SDL_OPENGL))

SDL_GL_DOUBLEBUFFER is in no way a valid flags argument to SDL_SetVideoMode() .

---

Also, you're specifying a huge number of GL attributes. Try removing all of the SDL_GL_SetAttribute() calls. If that works add them back in one at a time to figure out which one your GL implementation doesn't like.

Answer 2

(I know this is old but I finally cracked it and it has been bothering me for months.)

Remove all the attribute sets for "SDL_GL_ACCUM*", removing these you should that setting multisamples works.

Also remember to enable GL_MULTISAMPLE, GL_LINE_SMOOTH and GL_POLYGON_SMOOTH and perhaps provide hints for line/polygon smoothing.

You may find you don't see effects of AA when in windowed mode and with some graphics drivers (my catalyst drivers don't seem to do anything.)

These are the attributes I use:

SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);

SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
SDL_GL_SetAttribute(SDL_GL_BUFFER_SIZE, 32);

//SDL_GL_SetAttribute(SDL_GL_ACCUM_RED_SIZE, 8);
//SDL_GL_SetAttribute(SDL_GL_ACCUM_GREEN_SIZE, 8);
//SDL_GL_SetAttribute(SDL_GL_ACCUM_BLUE_SIZE, 8);
//SDL_GL_SetAttribute(SDL_GL_ACCUM_ALPHA_SIZE, 8);

//SDL_GL_SetAttribute(SDL_GL_ACCELERATED_VISUAL, 1);

SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1);
SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES, 4);