ref: 11b5a9d404f0d53e3ba0306ea35cebe0dea534f4
parent: 1c93e86c01eaad0143ee193cf11dec5dee82b6c9
author: rodri <rgl@antares-labs.eu>
date: Sun Jun 28 12:50:26 EDT 2020
new toy: ptintriangle
--- a/mkfile
+++ b/mkfile
@@ -12,6 +12,7 @@
imagelerp\
rframeviz\
ptinpoly\
+ ptintriangle\
HFILES=\
libgeometry/geometry.h\
--- /dev/null
+++ b/ptintriangle.c
@@ -1,0 +1,252 @@
+#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 Triangle Triangle;
+
+struct Triangle
+{+ Point2 p0, p1, p2;
+};
+
+Rectangle UR = {0,0,1,1}; /* unit rectangle */+RFrame worldrf;
+Image *pal[NCOLORS];
+Triangle thetriangle;
+Point2 thepoint;
+int isinside;
+
+void resized(void);
+
+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);
+}
+
+/*
+ * comparison of a point p with an edge [e0 e1]
+ * p to the right: +
+ * p to the left: -
+ * p on the edge: 0
+ */
+static int
+edgeptcmp(Point2 e0, Point2 e1, Point2 p)
+{+ Point3 e0p, e01, r;
+
+ p = subpt2(p, e0);
+ e1 = subpt2(e1, e0);
+ e0p = Vec3(p.x,p.y,0);
+ e01 = Vec3(e1.x,e1.y,0);
+ r = crossvec3(e0p, e01);
+
+ /* clamp to avoid overflow */
+ return fclamp(r.z, -1, 1); /* e0.x*e1.y - e0.y*e1.x */
+}
+
+int
+ptintriangle(Point2 p, Triangle t)
+{+ /* counter-clockwise check */
+ return edgeptcmp(t.p0, t.p2, p) <= 0 &&
+ edgeptcmp(t.p2, t.p1, p) <= 0 &&
+ edgeptcmp(t.p1, t.p0, p) <= 0;
+}
+
+Triangle
+Trianpt(Point2 p0, Point2 p1, Point2 p2)
+{+ return (Triangle){p0, p1, p2};+};
+
+void
+triangle(Image *dst, Triangle t, int thick, Image *src, Point sp)
+{+ Point pl[4];
+
+ pl[0] = toscreen(t.p0);
+ pl[1] = toscreen(t.p1);
+ pl[2] = toscreen(t.p2);
+ pl[3] = pl[0];
+
+ poly(dst, pl, nelem(pl), Endsquare, Endsquare, thick, src, sp);
+}
+
+void
+filltriangle(Image *dst, Triangle t, Image *src, Point sp)
+{+ Point pl[3];
+
+ pl[0] = toscreen(t.p0);
+ pl[1] = toscreen(t.p1);
+ pl[2] = toscreen(t.p2);
+
+ fillpoly(dst, pl, nelem(pl), 0, src, sp);
+}
+
+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, DPalebluegreen);
+ 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)
+{+ lockdisplay(display);
+ draw(screen, screen->r, pal[PCBg], nil, ZP);
+ filltriangle(screen, thetriangle, pal[PCPoly], ZP);
+ triangle(screen, thetriangle, 1, pal[PCPolydark], ZP);
+ fillellipse(screen, toscreen(thetriangle.p0), 2, 2, pal[PCPolydark], ZP);
+ fillellipse(screen, toscreen(thetriangle.p1), 2, 2, pal[PCPolydark], ZP);
+ fillellipse(screen, toscreen(thetriangle.p2), 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 = ptintriangle(thepoint, thetriangle);
+}
+
+void
+lmb(Mousectl *mc)
+{+ USED(mc);
+}
+
+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;
+ Point2 tmp;
+
+ GEOMfmtinstall();
+ 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);
+ tmp = Pt2(Dx(screen->r)/2,Dy(screen->r)/2,1);
+ thetriangle = Trianpt(tmp, addpt2(tmp, Vec2(200,0)), addpt2(tmp, Vec2(0,-160)));
+
+ 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();
+}