/* Simple demo of computing textures as arrays of values and
   texture-mapping them onto a 2D quad.  This shows that texture
   parameters (modes) can be associated with a texture id, because the
   checkerboard flag uses repeat and linear, while the flag uses clamp and
   nearest.

   Scott D. Anderson
   Fall 2000 original
   Fall 2003 adapted to use TW
*/

#include <stdio.h>
#include <tw.h>

bool USflag = false;                // which flag to show

void toggleFlag(unsigned char key, int x, int y) {
    USflag = !USflag;
    glutPostRedisplay();
}

/* ================================================================
   Checkerboard Texture variables
*/

const int CheckFlagWidth  = 8;
const int CheckFlagHeight = 8;

GLubyte CheckFlagArray[CheckFlagHeight][CheckFlagWidth];

void init_check_flag() {
    for(int i=0; i<CheckFlagWidth; i++) 
        for(int j=0; j<CheckFlagWidth; j++) 
            CheckFlagArray[i][j] = ((i+j)&1)==0 ? 0xFF : 0;
}

/* ================================================================ */

const int NUM_TEXTURES = 2;     // The number of textures (size of the array)
GLuint textureIDs[NUM_TEXTURES]; // The array of texture IDs.  Each
                                 // texture has a unique ID, assigned by OpenGL

void init() {
    glGenTextures(NUM_TEXTURES,textureIDs);

    glBindTexture(GL_TEXTURE_2D,textureIDs[0]);
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    twUSflag();
    
    glBindTexture(GL_TEXTURE_2D,textureIDs[1]);
    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);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    init_check_flag();
    glTexImage2D(GL_TEXTURE_2D, 0, 3, CheckFlagWidth, CheckFlagHeight, 0,
                 GL_LUMINANCE, GL_UNSIGNED_BYTE, CheckFlagArray);
}

/* ================================================================ */

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

    glPushAttrib(GL_ALL_ATTRIB_BITS);

    // this is the more efficient way, using texture binding.
    if(USflag) {
        glBindTexture(GL_TEXTURE_2D,textureIDs[0]);
    } else {
        glBindTexture(GL_TEXTURE_2D,textureIDs[1]);
    }

    glEnable(GL_TEXTURE_2D);
    glBegin(GL_QUADS);
    glTexCoord2f(0,2); glVertex3f( 0,0,0); 
    glTexCoord2f(2,2); glVertex3f(10,0,0); 
    glTexCoord2f(2,0); glVertex3f(10,5,0); 
    glTexCoord2f(0,0); glVertex3f( 0,5,0); 
    glEnd();

    glPopAttrib();
    glFlush();
    glutSwapBuffers();
}

/* ================================================================ */
int main(int argc, char **argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    twInitWindowSize(500, 500);
    glutCreateWindow(argv[0]);
    init();
    glutDisplayFunc(display);
    twBoundingBox(0,10,0,5,-1,1);
    twMainInit();
    twKeyCallback('u',toggleFlag,"toggle which flag to show");
    glutMainLoop();                   
}