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Annotation of researchv9/jerq/src/lib/j/disc.c, revision 1.1.1.1

1.1       root        1: #ifndef        MUX
                      2: #define        Jcursinhibit()  cursinhibit()
                      3: #define        Jcursallow()    cursallow()
                      4: #define        lrectf(l, r, f) rectf(l, r, f)
                      5: #endif
                      6: 
                      7: #include <jerq.h>
                      8: #define        DB              ((Word *)0x700000)
                      9: #define        ONSCREEN(b)     (b->base>=DB && b->base<DB+XMAX/WORDSIZE*YMAX)
                     10: /*     Fill a disc of radius r centered at x1,y1
                     11:  *     The boundary is a sequence of vertically, horizontally,
                     12:  *     or diagonally adjacent points that minimize 
                     13:  *     abs(x^2+y^2-r^2).
                     14:  *
                     15:  *     The circle is guaranteed to be symmetric about
                     16:  *     the horizontal, vertical, and diagonal axes
                     17:  */
                     18: disc(b, p, r, f)
                     19:        Bitmap *b;
                     20:        Point p;
                     21: {
                     22:        register x1=p.x, y1=p.y;
                     23:        register eps = 0;       /* x^2 + y^2 - r^2 */
                     24:        int dxsq = 1;           /* (x+dx)^2-x^2*/
                     25:        int dysq = 1 - 2*r;
                     26:        int exy;
                     27:        short inhibited;
                     28:        register x0 = x1;
                     29:        register y0 = y1 - r;
                     30:        x1++;           /* to offset jerq's half-open lines*/
                     31:        y1 += r;
                     32:        inhibited=0;
                     33:        if(f!=F_XOR && ONSCREEN(b)){
                     34:                Jcursinhibit();
                     35:                inhibited=1;
                     36:        }
                     37:        while(y1 > y0) {
                     38:                exy = eps + dxsq + dysq;
                     39:                if(-exy <= eps+dxsq) {
                     40:                        lrectf(b, Rect(x0, y0, x1, y0+1), f);
                     41:                        lrectf(b, Rect(x0, y1, x1, y1+1), f);
                     42:                        y1--;
                     43:                        y0++;
                     44:                        eps += dysq;
                     45:                        dysq += 2;
                     46:                }
                     47:                if(exy <= -eps) {
                     48:                        x1++;
                     49:                        x0--;
                     50:                        eps += dxsq;
                     51:                        dxsq += 2;
                     52:                }
                     53:        }
                     54:        lrectf(b, Rect(x0, y0, x1, y0+1), f);
                     55:        if(inhibited)
                     56:                Jcursallow();
                     57: }

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