ref: a946b00aa91ed059a1e9aad367bb6e872dcd1c1a
author: rodri <rgl@antares-labs.eu>
date: Mon May 11 05:59:39 EDT 2020
new toy: triangles
--- /dev/null
+++ b/mkfile
@@ -1,0 +1,7 @@
+</$objtype/mkfile
+
+BIN=/$objtype/bin/etoys
+TARG=\
+ triangles\
+
+</sys/src/cmd/mkmany
--- /dev/null
+++ b/triangles.c
@@ -1,0 +1,236 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <event.h>
+#include <keyboard.h>
+
+typedef struct Point2 Point2;
+typedef struct Triangle Triangle;
+typedef struct Circle Circle;
+typedef struct Object Object;
+
+struct Point2
+{+ double x, y, w;
+};
+
+struct Triangle
+{+ Point2 p0, p1, p2;
+};
+
+struct Circle
+{+ Point2 c;
+ double r;
+};
+
+struct Object
+{+ Triangle t;
+ Circle c;
+};
+
+enum {+ Cbg,
+ Ctri,
+ Ccir,
+ NCOLOR
+};
+
+Image *pal[NCOLOR];
+Object *tris;
+ulong ntri;
+Point2 pts[3];
+int npt;
+
+Point2
+Pt2(double x, double y, double w)
+{+ return (Point2){x,y,w};+}
+
+Point2
+addpt2(Point2 p, Point2 q)
+{+ return (Point2){p.x+q.x,p.y+q.y,p.w+q.w};+}
+
+Point2
+subpt2(Point2 p, Point2 q)
+{+ return (Point2){p.x-q.x,p.y-q.y,p.w-q.w};+}
+
+Point2
+mulpt2(Point2 p, double s)
+{+ return (Point2){p.x*s,p.y*s,p.w*s};+}
+
+Point2
+divpt2(Point2 p, double s)
+{+ return (Point2){p.x/s,p.y/s,p.w/s};+}
+
+double
+veclen(Point2 p)
+{+ return sqrt(p.x*p.x + p.y*p.y);
+};
+
+Point2
+crossvec(Point2 p, Point2 q)
+{+ return (Point2){+ p.y*q.w - p.w*q.y,
+ p.w*q.x - p.x*q.w,
+ p.x*q.y - p.y*q.x
+ };
+}
+
+void
+addobj(Triangle t, Circle c)
+{+ tris = realloc(tris, ++ntri*sizeof(Object));
+ tris[ntri-1].t = t;
+ tris[ntri-1].c = c;
+}
+
+double
+triperi(Triangle t)
+{+ return veclen(subpt2(t.p0, t.p1))
+ + veclen(subpt2(t.p1, t.p2))
+ + veclen(subpt2(t.p2, t.p0));
+};
+
+double
+triarea(Triangle t)
+{+ Point2 p;
+ double r;
+
+ p = crossvec(t.p0, t.p1);
+ p = addpt2(p, crossvec(t.p1, t.p2));
+ p = addpt2(p, crossvec(t.p2, t.p0));
+ r = sqrt(p.x*p.x + p.y*p.y + p.w*p.w);
+ return r/2;
+}
+
+Point
+toscreen(Point2 p)
+{+ return addpt(screen->r.min, Pt(p.x,p.y));
+}
+
+Point2
+fromscreen(Point p)
+{+ p = subpt(p, screen->r.min);
+ return (Point2){p.x,p.y,0};+}
+
+void
+triangle(Triangle t)
+{+ Point p[4];
+
+ p[0] = toscreen(t.p0);
+ p[1] = toscreen(t.p1);
+ p[2] = toscreen(t.p2);
+ p[3] = p[0];
+ poly(screen, p, nelem(p), Endsquare, Endsquare, 0, pal[Ctri], ZP);
+}
+
+void
+circle(Circle c)
+{+ ellipse(screen, toscreen(c.c), c.r, c.r, 0, pal[Ccir], ZP);
+}
+
+void
+initpalette(void)
+{+ pal[Cbg] = allocimage(display, Rect(0,0,1,1), screen->chan, 1, 0x000000ff);
+ pal[Ctri] = allocimage(display, Rect(0,0,1,1), screen->chan, 1, 0x00ff00ff);
+ pal[Ccir] = allocimage(display, Rect(0,0,1,1), screen->chan, 1, 0xff0000ff);
+}
+
+void
+redraw(void)
+{+ int i;
+
+ draw(screen, screen->r, pal[Cbg], nil, ZP);
+ for(i = 0; i < ntri; i++){+ triangle(tris[i].t);
+ circle(tris[i].c);
+ }
+ for(i = 0; i < npt; i++)
+ fillellipse(screen, toscreen(pts[i]), 2, 2, pal[Ctri], ZP);
+ flushimage(display, 1);
+}
+
+void
+usage(void)
+{+ fprint(2, "usage: %s\n", argv0);
+ exits("usage");+}
+
+void
+main(int argc, char *argv[])
+{+ Event e;
+ Triangle t;
+ Circle c;
+
+ ARGBEGIN{+ default: usage();
+ }ARGEND;
+ if(argc > 0)
+ usage();
+ if(initdraw(nil, nil, nil) < 0)
+ sysfatal("initdraw: %r");+ initpalette();
+ einit(Emouse|Ekeyboard);
+ redraw();
+ for(;;)
+ switch(event(&e)){+ case Emouse:
+ if((e.mouse.buttons&1) != 0){+ pts[npt++] = fromscreen(e.mouse.xy);
+ if(npt >= nelem(pts)){+ t.p0 = pts[0];
+ t.p1 = pts[1];
+ t.p2 = pts[2];
+ c.c = divpt2(addpt2(addpt2(mulpt2(t.p0, veclen(subpt2(t.p1, t.p2))),
+ mulpt2(t.p1, veclen(subpt2(t.p2, t.p0)))),
+ mulpt2(t.p2, veclen(subpt2(t.p0, t.p1)))),
+ triperi(t));
+ c.r = 2*triarea(t)/triperi(t);
+ addobj(t, c);
+ npt = 0;
+ }
+ redraw();
+ }
+ break;
+ case Ekeyboard:
+ switch(e.kbdc){+ case 'q':
+ case Kdel:
+ exits(0);
+ }
+ break;
+ }
+}
+
+void
+eresized(int)
+{+ if(getwindow(display, Refnone) < 0)
+ sysfatal("resize failed");+ redraw();
+}