#ifndef _WASM_H_DEF
#define _WASM_H_DEF
#include <stdio.h>
#include <math.h>
struct Canvas {
  double width,  height;
  double xscale, yscale;
  double xofset, yofset;
  float xt (const double x) const {
    return float (xscale * (x - xofset));
  }
  float yt (const double y) const {
    return float (height - yscale * (y - yofset));
  }
};
static const char * multipliers  [] = {"f","p","n","μ","m","","k","M","G","T","P"};
struct Stepping {
  double b,e,s;
  char fmtbuf [16];
  explicit Stepping (const double from, const double to) {
    double lp;
    const double  z = log10 (fabs (to - from));
    const double fp = modf (z, & lp);
    if      (fp < 0.30103) s = 1.0;
    else if (fp > 0.69897) s = 5.0;
    else                   s = 2.0;
    int ip = int (lp) - 1;
    if (z < 0.0) ip -= 1;
    s *= ::pow (10.0, double (ip));
    do {
      const int k = int (fabs(to - from) / s);
      b = round (from / s) * s;
      e = round (to   / s) * s;
      if (k > 50) s *= 10.0;    // prevence přeplnění osy, nevím proč, ale tohle to odstraní
      else        break;        // patrně log10() nedává přesně to, co bych čekal
    } while (true);
  }
  void f () {printf("stepping = %g, b = %g, e = %g\n", s, b, e);}
  char * ing (const double x, int n=0) {
    if (fabs(x) < 0.5 * s) {
      fmtbuf[n++] = ' ';
      fmtbuf[n++] = '\0';
      return fmtbuf;
    }
    if (x < 0.0) {
      fmtbuf[n++] = '-';
      return ing (-x, n);
    }
    if (x > 0.0) {
      double ip;
      const double fp = modf(log10(x), & ip);
      int pi = ip, ofs = 5 * 3;
      if (pi < -ofs) pi = -ofs;
      if (pi > 18  ) pi = 18;
      const div_t dt = div(pi + ofs, 3);
      n += snprintf (fmtbuf + n, 16 - n, "%g%s", ::pow (10.0, fp + double (dt.rem)), multipliers [dt.quot]);
    }
    return fmtbuf;
  }
};
#endif // _WASM_H_DEF