Notices

 file:sdlgl.c
/* Including math.h is not bad. It may become useful somehow */
#include <math.h>
/* what about establishing a surface? */
SDL_Surface *surface;
/* variable context, better or worse? */
/* perspective replacement for opengles? */
void gluPerspective(double fovy,double aspect,double zNear,double zFar)
{
double xmin,xmax,ymin,ymax;
ymax = zNear * tan(fovy * M_PI / 360);
ymin=-ymax;
xmin=ymin*aspect;
xmax=ymax*aspect;
glFrustumf(xmin,xmax,ymin,ymax,zNear,zFar);
}
/* defining screen resolution? */
#define SCREEN_WIDTH 800
#define SCREEN_HEIGHT 480
#define SCREEN_BPP 16
int resizeWindow(int width,int height)
{
GLfloat ratio;
if(height==0)
height =1;
ratio=(GLfloat)width/(GLfloat)height;
glViewport(0,0,(GLsizei)width,(GLsizei)height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f,ratio,0.1f,100.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
return(1);
}
/* a function for later use */
int initGL(GLvoid)
{
static int gles_init ...
SDL_GLES_MakeCurrent(context);
/* maybe some applications require background color and smoothing? */
glShadeModel(GL_SMOOTH);
glClearColor(0.0f,0.0f,0.0f,0.0f);
glHint(GL_PERSPECTIVE_CORRECTION,GL_NICEST);
glEnableClientState(GL_VERTEX_ARRAY);
return(1);
}
/* buffer cleaning might be needed */
glClear(GL_COLOR_BUFFER_BIT);

SDL_GL_SetAttribute( SDL_GL_RED_SIZE, 5 );
SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, 5 );
SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, 5 );
SDL_GL_SetAttribute( SDL_GL_DEPTH_SIZE, 16 );
SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );

/* Using additional function */
int FilterEvents(const SDL_Event *event) {
    static int boycott = 1;

    /* This quit event signals the closing of the window */
    if ( (event->type == SDL_QUIT) && boycott ) {
        printf("Quit event filtered out -- try again.\n");
        boycott = 0;
        return(0);
    }
    if ( event->type == SDL_MOUSEMOTION ) {
        printf("Mouse moved to (%d,%d)\n",
                event->motion.x, event->motion.y);
        return(0);    /* Drop it, we've handled it */
    }
    return(1);
}

SDL_SetEventFilter(FilterEvents);