ref: 5633da27ae4132550959fc7135f7d19afa519a70
parent: a829fc8b5a2ab396fe46ffbe8c01dcdb9d3038f6
author: rodri <rgl@antares-labs.eu>
date: Fri Jan 19 11:46:32 EST 2024
new toy: lineXcircle.
--- /dev/null
+++ b/lineXcircle.c
@@ -1,0 +1,265 @@
+#include <u.h>
+#include <libc.h>
+#include <thread.h>
+#include <draw.h>
+#include <mouse.h>
+#include <keyboard.h>
+#include <geometry.h>
+
+enum {+ PCBg,
+ PCFg,
+ PCLine,
+ PCLineseg,
+ PCCin,
+ PCCout,
+ PCPt,
+ NCOLORS
+};
+
+Rectangle UR = {0,0,1,1}; /* unit rectangle */+RFrame worldrf;
+Image *pal[NCOLORS];
+Point2 theline[2], thecircle[2];
+int npts;
+Point2 Xpts[2];
+int nXpts;
+
+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);
+}
+
+double
+sgn(double n)
+{+ return n < 0? -1: 1;
+}
+
+int
+lineXcircle(Point2 *r)
+{+ Point2 p0, p1, dp;
+ double dr, D, cr, Δ;
+
+ p0 = subpt2(theline[0], thecircle[0]);
+ p1 = subpt2(theline[1], thecircle[0]);
+ dp = subpt2(p1, p0);
+ dr = vec2len(dp);
+ D = p0.x*p1.y - p0.y*p1.x;
+ cr = vec2len(subpt2(thecircle[1], thecircle[0]));
+ Δ = cr*cr*dr*dr - D*D;
+
+ if(Δ < 0) /* imaginary */
+ return 0;
+ else if(Δ == 0){ /* tangent */+ r[0].x = (D*dp.y + sgn(dp.y)*dp.x*sqrt(Δ))/(dr*dr);
+ r[0].y = (-D*dp.x + fabs(dp.y)*sqrt(Δ))/(dr*dr);
+ r[0] = addpt2(r[0], thecircle[0]);
+ return 1;
+ }else{ /* secant */+ r[0].x = (D*dp.y + sgn(dp.y)*dp.x*sqrt(Δ))/(dr*dr);
+ r[0].y = (-D*dp.x + fabs(dp.y)*sqrt(Δ))/(dr*dr);
+ r[0] = addpt2(r[0], thecircle[0]);
+ r[1].x = (D*dp.y - sgn(dp.y)*dp.x*sqrt(Δ))/(dr*dr);
+ r[1].y = (-D*dp.x - fabs(dp.y)*sqrt(Δ))/(dr*dr);
+ r[1] = addpt2(r[1], thecircle[0]);
+ return 2;
+ }
+}
+
+void
+initpalette(void)
+{+ pal[PCBg] = allocimage(display, UR, screen->chan, 1, DWhite);
+ pal[PCFg] = allocimage(display, UR, screen->chan, 1, DBlack);
+ pal[PCLine] = allocimage(display, UR, screen->chan, 1, 0xEEEEEEFF);
+ pal[PCLineseg] = allocimage(display, UR, screen->chan, 1, DDarkblue);
+ pal[PCCin] = allocimage(display, UR, screen->chan, 1, DPalebluegreen);
+ pal[PCCout] = allocimage(display, UR, screen->chan, 1, DDarkyellow);
+ pal[PCPt] = allocimage(display, UR, screen->chan, 1, DRed);
+}
+
+void
+drawline(void)
+{+ Point pts[2], dp;
+ int i;
+
+ for(i = 0; i < nelem(pts); i++) pts[i] = toscreen(theline[i]);
+ dp = subpt(pts[1], pts[0]);
+
+ line(screen, pts[0], pts[1], 0, 0, 1, pal[PCLineseg], ZP);
+ for(i = 0; i < nelem(pts); i++){+ line(screen, pts[i], addpt(mulpt(dp, i == 0? -10: 10), pts[i]), 0, 0, 0, pal[PCLine], ZP);
+ fillellipse(screen, pts[i], 2, 2, pal[PCPt], ZP);
+ }
+}
+
+void
+drawcircle(void)
+{+ Point p;
+ double r;
+
+ p = toscreen(thecircle[0]);
+ r = vec2len(subpt2(thecircle[1], thecircle[0]));
+
+ fillellipse(screen, p, r, r, pal[PCCin], ZP);
+ ellipse(screen, p, r, r, 0, pal[PCCout], ZP);
+ fillellipse(screen, p, 2, 2, pal[PCPt], ZP);
+}
+
+void
+drawX(void)
+{+ int i;
+
+ if(nXpts < 1)
+ return;
+
+ for(i = 0; i < nelem(Xpts); i++)
+ fillellipse(screen, toscreen(Xpts[i]), 2, 2, pal[PCPt], ZP);
+}
+
+void
+redraw(void)
+{+ lockdisplay(display);
+ draw(screen, screen->r, pal[PCBg], nil, ZP);
+ if(npts >= 4){+ drawcircle();
+ drawX();
+ }
+ if(npts >= 2)
+ drawline();
+ flushimage(display, 1);
+ unlockdisplay(display);
+}
+
+void
+rmb(Mousectl *mc)
+{+ USED(mc);
+}
+
+void
+lmb(Mousectl *mc)
+{+ if(npts >= 4)
+ npts = 0;
+ if(npts >= 0 && npts < 2)
+ theline[npts++] = fromscreen(mc->xy);
+ else if(npts >= 2 && npts < 4)
+ thecircle[npts++ & 1] = fromscreen(mc->xy);
+ if(npts >= 4)
+ nXpts = lineXcircle(Xpts);
+}
+
+void
+mouse(Mousectl *mc)
+{+ static Mouse om;
+
+ if(mc->buttons == om.buttons)
+ return;
+
+ if((mc->buttons&1) != 0)
+ lmb(mc);
+ if((mc->buttons&4) != 0)
+ rmb(mc);
+ om = mc->Mouse;
+}
+
+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);
+
+ 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();
+}
--- a/mkfile
+++ b/mkfile
@@ -14,5 +14,6 @@
ptinpoly\
ptintriangle\
barycentric\
+ lineXcircle\
</sys/src/cmd/mkmany