blob: 88bace09dc945de34cbf3be94ef465cfa6a834af [file] [log] [blame]
 #include #include #include #include /* * adapted from Paul Heckbert's algorithm on p 657-659 of * Andrew S. Glassner's book, "Graphics Gems" * ISBN 0-12-286166-3 * */ #include "tickmarks.h" #define MAX(a, b) (((a) < (b)) ? (b) : (a)) static double nicenum(double x, int round) { int exp; /* exponent of x */ double f; /* fractional part of x */ exp = floor(log10(x)); f = x / pow(10.0, exp); if (round) { if (f < 1.5) return 1.0 * pow(10.0, exp); if (f < 3.0) return 2.0 * pow(10.0, exp); if (f < 7.0) return 5.0 * pow(10.0, exp); return 10.0 * pow(10.0, exp); } if (f <= 1.0) return 1.0 * pow(10.0, exp); if (f <= 2.0) return 2.0 * pow(10.0, exp); if (f <= 5.0) return 5.0 * pow(10.0, exp); return 10.0 * pow(10.0, exp); } static void shorten(struct tickmark *tm, int nticks, int *power_of_ten, int use_KMG_symbols, int base_offset) { const char shorten_chr[] = { 0, 'K', 'M', 'G', 'P', 'E', 0 }; int i, l, minshorten, shorten_idx = 0; char *str; minshorten = 100; for (i = 0; i < nticks; i++) { str = tm[i].string; l = strlen(str); if (strcmp(str, "0") == 0) continue; if (l > 9 && strcmp(&str[l - 9], "000000000") == 0) { *power_of_ten = 9; shorten_idx = 3; } else if (6 < minshorten && l > 6 && strcmp(&str[l - 6], "000000") == 0) { *power_of_ten = 6; shorten_idx = 2; } else if (l > 3 && strcmp(&str[l - 3], "000") == 0) { *power_of_ten = 3; shorten_idx = 1; } else { *power_of_ten = 0; } if (*power_of_ten < minshorten) minshorten = *power_of_ten; } if (minshorten == 0) return; if (!use_KMG_symbols) shorten_idx = 0; else if (base_offset) shorten_idx += base_offset; for (i = 0; i < nticks; i++) { str = tm[i].string; l = strlen(str); str[l - minshorten] = shorten_chr[shorten_idx]; if (shorten_idx) str[l - minshorten + 1] = '\0'; } } int calc_tickmarks(double min, double max, int nticks, struct tickmark **tm, int *power_of_ten, int use_KMG_symbols, int base_offset) { char str[100]; int nfrac; double d; /* tick mark spacing */ double graphmin, graphmax; /* graph range min and max */ double range, x; int count, i; /* we expect min != max */ range = nicenum(max - min, 0); d = nicenum(range / (nticks - 1), 1); graphmin = floor(min / d) * d; graphmax = ceil(max / d) * d; nfrac = MAX(-floor(log10(d)), 0); snprintf(str, sizeof(str)-1, "%%.%df", nfrac); count = ((graphmax + 0.5 * d) - graphmin) / d + 1; *tm = malloc(sizeof(**tm) * count); i = 0; for (x = graphmin; x < graphmax + 0.5 * d; x += d) { (*tm)[i].value = x; sprintf((*tm)[i].string, str, x); i++; } shorten(*tm, i, power_of_ten, use_KMG_symbols, base_offset); return i; } #if 0 static void test_range(double x, double y) { int nticks, i; struct tickmark *tm = NULL; printf("Testing range %g - %g\n", x, y); nticks = calc_tickmarks(x, y, 10, &tm); for (i = 0; i < nticks; i++) printf(" (%s) %g\n", tm[i].string, tm[i].value); printf("\n\n"); free(tm); } int main(int argc, char *argv[]) { test_range(0.0005, 0.008); test_range(0.5, 0.8); test_range(5.5, 8.8); test_range(50.5, 80.8); test_range(-20, 20.8); test_range(-30, 700.8); } #endif