void SDL_GL_Enter2DMode(GLuint w, GLuint h) {
glPushAttrib(GL_ENABLE_BIT | GL_VIEWPORT_BIT | GL_SCISSOR_BIT);
glDisable(GL_DEPTH_TEST);
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
glOrtho(0.0, (GLdouble)w, (GLdouble)h, 0.0, 0.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();
// glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
}
void SDL_GL_Leave2DMode()
{
glMatrixMode(GL_MODELVIEW);
glPopMatrix();
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glPopAttrib();
}