void myActions() { // actions to be executed at each frame
    scribe("Jarek Rossignac's triangle / tringle Booleans (starting point for project)");         //*:01 prints text at top of the graphic window (see TAB UI), line 0
    if ((mousePressed)&&(!keyPressed)) dragPoint();    // while mouse pressed moves the selected point by mouse displacement (in TAB polygon)
    fill(black);              //*:05 reset fill color to black (for writing text in the windows)
    pt A=P[0], B=P[2], C=P[4], D=P[1], E=P[3], F=P[5]; 
    stroke(dblue); fill(cyan,200); strokeWeight(2); showTriangle(A,B,C); showTriangle(D,E,F);
    A.show(2); B.show(2); C.show(2); D.show(2); E.show(2); F.show(2);
    fill(black); A.showLabel("A"); B.showLabel("B"); C.showLabel("C"); D.showLabel("D"); E.showLabel("E"); F.showLabel("F");  
 // INTERSECTION
    pushMatrix();
    translate(width/2,0);
    stroke(dblue); noFill(); strokeWeight(2); showTriangle(A,B,C); showTriangle(D,E,F);
    fill(red,220); stroke(black); strokeWeight(4); showIntersection(A,B,C,D,E,F); 
    popMatrix();
// DIFFERENCE
    pushMatrix();
    translate(0,height/2);
    stroke(dblue); noFill(); strokeWeight(2); showTriangle(A,B,C); showTriangle(D,E,F);
    fill(blue,220); stroke(black); strokeWeight(4); showDifference(A,B,C,D,E,F);  
    popMatrix();
// UNION
    pushMatrix();
    translate(width/2,height/2);
    stroke(dblue); noFill(); strokeWeight(2); showTriangle(A,B,C); showTriangle(D,E,F);
    fill(green,220); stroke(black); strokeWeight(4); showUnion(A,B,C,D,E,F); 
    popMatrix();
    };
    
void showTriangle(pt A, pt B, pt C) {beginShape();  A.v(); B.v(); C.v(); endShape(CLOSE); };    

void showIntersection(pt A, pt B, pt C, pt D, pt E, pt F) { 
  // Jarek's cheat! Replace with proper code for computing the loop(s) of the intersection and rendering them 
  beginShape(); EE(A,B,D,E).v(); EE(B,C,D,E).v(); EE(B,C,E,F).v(); EE(C,A,E,F).v(); EE(C,A,F,D).v(); EE(A,B,F,D).v(); endShape(CLOSE); 
 
  };
  
void showDifference(pt A, pt B, pt C, pt D, pt E, pt F) { 
  // Jarek's cheat! Replace with proper code for computing the loop(s) of the difference and rendering them 
  showTriangle(A,B,C);  stroke(white); fill(white); showTriangle(D,E,F);
  
  };
  
void showUnion(pt A, pt B, pt C, pt D, pt E, pt F) { 
  // Jarek's cheat! Replace with proper code for computing the loop(s) of the union and rendering them 
  strokeWeight(4); showTriangle(A,B,C); showTriangle(D,E,F);   noStroke(); showTriangle(A,B,C); showTriangle(D,E,F);

  };
  
boolean ordered(pt A, pt B, pt C) {return (0<dot(V(A,B),V(A,C))) && (dot(V(A,B),V(A,C))<dot(V(A,C),V(A,C))); }  // tests whether B falls between A and C
boolean edgesCross(pt A, pt B, pt C, pt D) {return (dot(U(R(V(A,B))),V(A,C))>0 != dot(U(R(V(A,B))),V(A,D))>0) // tests whether two edges cross
                                                && (dot(U(R(V(C,D))),V(C,A))>0 != dot(U(R(V(C,D))),V(C,B))>0) ; }

pt EE(pt A, pt B, pt C, pt D) {        // returns intersection point between two edges assuming it exists
    vec T=V(A,B);                      // make vector T=AB
    vec N = R(V(C,D));                 // makes vector N by rotating CD by 90 degrees 
    vec AC = V(A,C);
    float t = dot(AC,N) / dot(T,N);    // compute intersection parameter
    return S(A,t,T);                   // returns intersection. S() computes a point on a line (see TAB geo2D)
   }