#TJHSST ~ Mouse-Driven Triangle Input

triinput.c

/*
  Triangle Input
*/
#include <graphics.h>
#include <math.h>
#include <string.h>
#include "mouse.h"

struct point {
  long int x,y;
};

#define sqr(x) ((x)*(x))

double getarea(double,double,double);

main()
{
  int gdriver,gmode;
  double px,py,pz,dpx,dpy,dpz,d01,d12,d20,areat;
  int x,y,lastx=(-1),lasty=(-1),cnt;
  char ostrx[20],ostry[20],ostrz[20],strx[20],stry[20],strz[20];
  struct point origs[3];

  origs[0].x=20;
  origs[0].y=180;
  origs[1].x=2;
  origs[1].y=20;
  origs[2].x=280;
  origs[2].y=180;
  d01=sqrt((double)(sqr(origs[0].x-origs[1].x)+sqr(origs[0].y-origs[1].y)));
  d12=sqrt((double)(sqr(origs[1].x-origs[2].x)+sqr(origs[1].y-origs[2].y)));
  d20=sqrt((double)(sqr(origs[2].x-origs[0].x)+sqr(origs[2].y-origs[0].y)));
  areat=getarea(d01,d12,d20);
  gdriver=CGA;
  gmode=CGA;
  initgraph(&gdriver,&gmode,"");
  setcolor(1);
  for(cnt=0;cnt<3;cnt++)
    line(origs[cnt].x,origs[cnt].y,origs[(cnt+1)%3].x,origs[(cnt+1)%3].y);
  curson();
  while(!getbutton(MOUSE2))  {
    if(getbutton(MOUSE1))  {
      x=getvaluator(MOUSEX)/2;
      y=getvaluator(MOUSEY);
      if(lastx!=x||lasty!=y)  {
	dpx=sqrt((double)(sqr(x-origs[0].x)+sqr(y-origs[0].y)));
	dpy=sqfrt((double)(sqr(x-origs[1].x)+sqr(y-origs[1].y)));
	dpz=sqrt((double)(sqr(x-origs[2].x)+sqr(y-origs[2].y)));
	px=getarea(dpy,dpz,d12);
	py=getarea(dpx,dpz,d20);
	pz=getarea(dpx,dpy,d01);
	px=px/areat;
	py=py/areat;
	pz=pz/areat;
	setcolor(0);
	cursoff();
	for(cnt=0;cnt<3;cnt++)
	  line(lastx,lasty,origs[cnt].x,origs[cnt].y);
	outtextxy(280,10,ostrx);
	outtextxy(280,30,ostry);
	outtextxy(280,50,ostrz);
	curson();
	sprintf(strx,"%5.4lf",px);
	sprintf(stry,"%5.4lf",py);
	sprintf(strz,"%5.4lf",pz);
	cursoff();
	setcolor(2);
	for(cnt=0;cnt<3;cnt++)
	  line(x,y,origs[cnt].x,origs[cnt].y);
	setcolor(1);
	for(cnt=0;cnt<3;cnt++)
	  line(origs[cnt].x,origs[cnt].y,origs[(cnt+1)%3].x,origs[(cnt+1)%3].y);
        outtextxy(280,10,strx);
	outtextxy(280,30,stry);
	outtextxy(280,50,strz);
	curson();
	strcpy(ostrx,strx);
	strcpy(ostry,stry);
	strcpy(ostrz,strz);
	lastx=x;
	lasty=y;
      }
    }
  }
  cursoff();
  closegraph();
}

double getarea(a,b,c)
double a,b,c;
{
  double s,area;

  s=(a+b+c)/2;
  area=s*(s-a)*(s-b)*(s-c);
  area=sqrt(area);
  return area;
}

A C program found on an old 5.25 floppy disk from when I was a nerd at Thomas Jefferson High School for Science and Technology between 1988 and 1992.

http://en.wikipedia.org/wiki/Ternary_plot
http://en.wikipedia.org/wiki/Phase_diagram

Anyone can do whatever they'd like to with this program--if anything.

I remain a three-sided nerd.