/* Simplest demo of reading in an image and texture-mapping it onto
   something; in this case, a quad.

   Scott D. Anderson
   Fall 2005
*/

#include <math.h>
#include <stdio.h>              // for printf
#include <stdlib.h>             // for exit
#include <tw.h>

char* filename = "USflag.ppm";

void texinit() {
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

    twPPM_Tex2D(filename,true);
}    

void display() {
    twDisplayInit();
    twCamera();

    glEnable(GL_TEXTURE_2D);

    // this is a *square*, so the aspect ratio may not match the texture's aspect-ratio
    glBegin(GL_QUADS);
    glTexCoord2f(0,0); glVertex3f( -1, 1,0); // upper left vertex is 0,0 in texture space
    glTexCoord2f(0,1); glVertex3f( -1,-1,0); // lower left is 0,1 in texture space
    glTexCoord2f(1,1); glVertex3f(  1,-1,0); // lower right is 1,1
    glTexCoord2f(1,0); glVertex3f(  1, 1,0); // upper right is 1,0
    glEnd();

    glFlush();
    glutSwapBuffers();
}

int main(int argc, char **argv) {
    if(argc >= 2) {
        filename=argv[1];
    }
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    twInitWindowSize(500, 500);
    glutCreateWindow(argv[0]);
    glutDisplayFunc(display);
    twBoundingBox(-1,+1,-1,+1,0,0.01);
    twMainInit();
    texinit();                  // load the texture from the file
    glutMainLoop();                   
}