/* Demo of two partly coincident quads, to show color speckling.

The red one is drawn first, then the green one.

Implemented Fall 2005
Scott D. Anderson
*/

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

bool BgBlack = true;
bool DepthTest = true;

float TextLeft = -0.2;          // X coordinate for left end of text
float TextTop  = -0.2;          // Y coordinate for first line of text

void RedThenGreenQuads() {
    glBegin(GL_QUADS);

    glColor4f(1,0,0,1);                // solid red
    glVertex2f(0,0);        // lower left, then CCW
    glVertex2f(2,0);
    glVertex2f(2,2);
    glVertex2f(0,2);
    glColor4f(0,1,0,1);                // solid green
    glVertex2f(1,0);        // lower left, then CCW
    glVertex2f(3,0);
    glVertex2f(3,2);
    glVertex2f(1,2);

    glEnd();
}

void depthTest() {
    twColorName(BgBlack?TW_WHITE:TW_BLACK);
    if(DepthTest) {
        glEnable(GL_DEPTH_TEST);
        twDrawString(TextLeft,TextTop,0, "Depth Test ON - 'd' toggles");
    } else {
        glDisable(GL_DEPTH_TEST);
        twDrawString(TextLeft,TextTop,0, "Depth Test OFF - 'd' toggles");
    }
}

void display(void) {
    if(BgBlack) 
        glClearColor(0,0,0,0);        // transparent black
    else
        glClearColor(1,1,1,1);        // opaque white
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    twCamera();
    depthTest();

    RedThenGreenQuads();

    glFlush();
    glutSwapBuffers();
}

void keys(unsigned char k, int, int) {
    switch(k) {
    case 'b': BgBlack = !BgBlack; break;
    case 'd': DepthTest = !DepthTest; break;
    }
    glutPostRedisplay();
}

int main(int argc, char** argv) {
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  twInitWindowSize(500,500);
  glutCreateWindow(argv[0]);
  glutDisplayFunc(display);
  twBoundingBox(0,3,0,2,0,0);
  twMainInit();            
  twKeyCallback('b',keys,"toggle black/white background");
  twKeyCallback('d',keys,"toggle depth test");
  glutMainLoop();
  return 0;
}