new toy: ptinpoly

2 files changed, 238 insertions, 0 deletions

diff --git a/mkfile b/mkfile
index 54c39da..9e967c6 100644
--- a/mkfile
+++ b/mkfile
@@ -11,6 +11,7 @@ TARG=\
 	chain\
 	imagelerp\
 	rframeviz\
+	ptinpoly\
 
 HFILES=\
 	libgeometry/geometry.h\
diff --git a/ptinpoly.c b/ptinpoly.c
new file mode 100644
index 0000000..7f60f1c
--- /dev/null
+++ b/ptinpoly.c
@@ -0,0 +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();
+}