ref: 77043bdafc8d7cec0dac4b9375885be2f323f4f9
parent: cb1bc5e9b37b5f302221252e4078f8a68d30585b
author: rodri <rgl@antares-labs.eu>
date: Mon Jun 22 05:29:11 EDT 2020
new toy: ptinpoly
--- a/mkfile
+++ b/mkfile
@@ -11,6 +11,7 @@
chain\
imagelerp\
rframeviz\
+ ptinpoly\
HFILES=\
libgeometry/geometry.h\
--- /dev/null
+++ b/ptinpoly.c
@@ -1,0 +1,237 @@
+#include <u.h>
+#include <libc.h>
+#include <thread.h>
+#include <draw.h>
+#include <mouse.h>
+#include <keyboard.h>
+#include <geometry.h>
+
+enum {+ PCBg,
+ PCFg,
+ PCPoly,
+ PCPolydark,
+ PCAux,
+ NCOLORS
+};
+
+typedef struct Polygon Polygon;
+
+struct Polygon
+{+ Point2 *pts;
+ Point *scrpts;
+ int npts;
+
+ void (*push)(Polygon*, Point2);
+};
+
+Rectangle UR = {0,0,1,1}; /* unit rectangle */+RFrame worldrf;
+Image *pal[NCOLORS];
+Polygon *thepoly;
+Point2 thepoint;
+int isinside;
+
+void resized(void);
+Point toscreen(Point2);
+
+void
+polygonpush(Polygon *poly, Point2 p)
+{+ poly->pts = realloc(poly->pts, ++poly->npts*sizeof(Point2));
+ poly->pts[poly->npts-1] = p;
+ poly->scrpts = realloc(poly->scrpts, poly->npts*sizeof(Point));
+ poly->scrpts[poly->npts-1] = toscreen(p);
+}
+
+Polygon*
+newpolygon(Point2 *pts, int npts)
+{+ Polygon *poly;
+ int i;
+
+ poly = malloc(sizeof(Polygon));
+ if(pts == nil){+ poly->pts = nil;
+ poly->scrpts = nil;
+ poly->npts = 0;
+ }else{+ poly->pts = pts;
+ poly->scrpts = malloc(npts*sizeof(Point));
+ for(i = 0; i < npts; i++)
+ poly->scrpts[i] = toscreen(poly->pts[i]);
+ poly->npts = npts;
+ }
+ poly->push = polygonpush;
+ return poly;
+}
+
+int
+ptinpoly(Point2 p, Polygon poly)
+{+ int i, j, c;
+
+ for(i = c = 0, j = poly.npts-1; i < poly.npts; j = i++)
+ if(p.y < poly.pts[i].y != p.y < poly.pts[j].y &&
+ p.x < (poly.pts[j].x - poly.pts[i].x) * (p.y - poly.pts[i].y)/(poly.pts[j].y - poly.pts[i].y) + poly.pts[i].x)
+ c ^= 1;
+ return c;
+}
+
+Point
+toscreen(Point2 p)
+{+ p = invrframexform(p, worldrf);
+ return Pt(p.x,p.y);
+}
+
+Point2
+fromscreen(Point p)
+{+ return rframexform(Pt2(p.x,p.y,1), worldrf);
+}
+
+void
+initpalette(void)
+{+ pal[PCBg] = allocimage(display, UR, screen->chan, 1, DWhite);
+ pal[PCFg] = allocimage(display, UR, screen->chan, 1, DBlack);
+ pal[PCPoly] = allocimage(display, UR, screen->chan, 1, DPaleblue);
+ pal[PCPolydark] = allocimage(display, UR, screen->chan, 1, DDarkblue);
+ pal[PCAux] = allocimage(display, UR, screen->chan, 1, DRed);
+}
+
+void
+drawbanner(void)
+{+ static char *msgs[] = {+ "THE POINT IS OUTSIDE",
+ "THE POINT IS INSIDE"
+ }, *s;
+
+ s = msgs[isinside];
+ string(screen, toscreen(Pt2(Dx(screen->r)/2 - strlen(s)/2*font->width,10,1)), pal[PCFg], ZP, font, s);
+}
+
+void
+redraw(void)
+{+ int i;
+
+ lockdisplay(display);
+ draw(screen, screen->r, pal[PCBg], nil, ZP);
+ fillpoly(screen, thepoly->scrpts, thepoly->npts, 1, pal[PCPoly], ZP);
+ poly(screen, thepoly->scrpts, thepoly->npts, Enddisc, Enddisc, 1, pal[PCPolydark], ZP);
+ for(i = 0; i < thepoly->npts; i++)
+ fillellipse(screen, thepoly->scrpts[i], 2, 2, pal[PCPolydark], ZP);
+ fillellipse(screen, toscreen(thepoint), 2, 2, pal[PCAux], ZP);
+ drawbanner();
+ flushimage(display, 1);
+ unlockdisplay(display);
+}
+
+void
+rmb(Mousectl *mc)
+{+ thepoint = fromscreen(mc->xy);
+ isinside = ptinpoly(thepoint, *thepoly);
+}
+
+void
+lmb(Mousectl *mc)
+{+ thepoly->push(thepoly, fromscreen(mc->xy));
+}
+
+void
+mouse(Mousectl *mc)
+{+ if((mc->buttons&1) != 0)
+ lmb(mc);
+ if((mc->buttons&4) != 0)
+ rmb(mc);
+}
+
+void
+key(Rune r)
+{+ switch(r){+ case Kdel:
+ case 'q':
+ threadexitsall(nil);
+ }
+}
+
+void
+usage(void)
+{+ fprint(2, "usage: %s\n", argv0);
+ exits("usage");+}
+
+void
+threadmain(int argc, char *argv[])
+{+ Mousectl *mc;
+ Keyboardctl *kc;
+ Rune r;
+
+ ARGBEGIN{+ default: usage();
+ }ARGEND;
+ if(argc > 0)
+ usage();
+
+ if(initdraw(nil, nil, nil) < 0)
+ sysfatal("initdraw: %r");+ if((mc = initmouse(nil, screen)) == nil)
+ sysfatal("initmouse: %r");+ if((kc = initkeyboard(nil)) == nil)
+ sysfatal("initkeyboard: %r");+ initpalette();
+
+ worldrf.p = Pt2(screen->r.min.x,screen->r.min.y,1);
+ worldrf.bx = Vec2(1,0);
+ worldrf.by = Vec2(0,1);
+ thepoly = newpolygon(nil, 0);
+
+ display->locking = 1;
+ unlockdisplay(display);
+ redraw();
+
+ for(;;){+ enum { MOUSE, RESIZE, KEYBOARD };+ Alt a[] = {+ {mc->c, &mc->Mouse, CHANRCV},+ {mc->resizec, nil, CHANRCV},+ {kc->c, &r, CHANRCV},+ {nil, nil, CHANEND}+ };
+
+ switch(alt(a)){+ case MOUSE:
+ mouse(mc);
+ break;
+ case RESIZE:
+ resized();
+ break;
+ case KEYBOARD:
+ key(r);
+ break;
+ }
+
+ redraw();
+ }
+}
+
+void
+resized(void)
+{+ lockdisplay(display);
+ if(getwindow(display, Refnone) < 0)
+ sysfatal("couldn't resize");+ unlockdisplay(display);
+ worldrf.p = Pt2(screen->r.min.x,screen->r.min.y,1);
+ redraw();
+}