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1#include <stdio.h>
2#include <math.h>
3#include <malloc.h>
17ba3e42 4#include <string.h>
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5
6/*
7 * adapted from Paul Heckbert's algorithm on p 657-659 of
8 * Andrew S. Glassner's book, "Graphics Gems"
9 * ISBN 0-12-286166-3
10 *
11 */
12
13#include "tickmarks.h"
14
15#define MAX(a, b) (((a) < (b)) ? (b) : (a))
16
17static double nicenum(double x, int round)
18{
19 int exp; /* exponent of x */
20 double f; /* fractional part of x */
21
22 exp = floor(log10(x));
23 f = x / pow(10.0, exp);
24 if (round) {
25 if (f < 1.5)
26 return 1.0 * pow(10.0, exp);
27 if (f < 3.0)
28 return 2.0 * pow(10.0, exp);
29 if (f < 7.0)
30 return 5.0 * pow(10.0, exp);
31 return 10.0 * pow(10.0, exp);
32 }
33 if (f <= 1.0)
34 return 1.0 * pow(10.0, exp);
35 if (f <= 2.0)
36 return 2.0 * pow(10.0, exp);
37 if (f <= 5.0)
38 return 5.0 * pow(10.0, exp);
39 return 10.0 * pow(10.0, exp);
40}
41
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42static void shorten(struct tickmark *tm, int nticks, int *power_of_ten,
43 int use_KMG_symbols)
17ba3e42 44{
7175d91d 45 int i, l, minshorten;
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46 char *str;
47 char shorten_char = '?';
48
49 minshorten = 100;
50 for (i = 0; i < nticks; i++) {
51 str = tm[i].string;
52 l = strlen(str);
53
54 if (l > 9 && strcmp(&str[l - 9], "000000000") == 0) {
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55 *power_of_ten = 9;
56 shorten_char = use_KMG_symbols ? 'G' : '\0';
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57 } else if (6 < minshorten && l > 6 &&
58 strcmp(&str[l - 6], "000000") == 0) {
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59 *power_of_ten = 6;
60 shorten_char = use_KMG_symbols ? 'M' : '\0';
1e1ffcc4 61 } else if (l > 3 && strcmp(&str[l - 3], "000") == 0) {
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62 *power_of_ten = 3;
63 shorten_char = use_KMG_symbols ? 'K': '\0';
1e1ffcc4 64 } else {
7175d91d 65 *power_of_ten = 0;
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66 }
67
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68 if (*power_of_ten < minshorten)
69 minshorten = *power_of_ten;
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70 }
71
72 if (minshorten == 0)
73 return;
74
75 for (i = 0; i < nticks; i++) {
76 str = tm[i].string;
77 l = strlen(str);
78 str[l - minshorten] = shorten_char;
79 str[l - minshorten + 1] = '\0';
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80 }
81}
82
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83int calc_tickmarks(double min, double max, int nticks, struct tickmark **tm,
84 int *power_of_ten, int use_KMG_symbols)
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85{
86 char str[100];
87 int nfrac;
88 double d; /* tick mark spacing */
89 double graphmin, graphmax; /* graph range min and max */
90 double range, x;
91 int count, i;
92
93 /* we expect min != max */
94 range = nicenum(max - min, 0);
95 d = nicenum(range / (nticks - 1), 1);
96 graphmin = floor(min / d) * d;
97 graphmax = ceil(max / d) * d;
98 nfrac = MAX(-floor(log10(d)), 0);
99 snprintf(str, sizeof(str)-1, "%%.%df", nfrac);
100
101 count = ((graphmax + 0.5 * d) - graphmin) / d + 1;
102 *tm = malloc(sizeof(**tm) * count);
103
104 i = 0;
105 for (x = graphmin; x < graphmax + 0.5 * d; x += d) {
106 (*tm)[i].value = x;
107 sprintf((*tm)[i].string, str, x);
108 i++;
109 }
7175d91d 110 shorten(*tm, i, power_of_ten, use_KMG_symbols);
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111 return i;
112}
113
114#if 0
115
116static void test_range(double x, double y)
117{
118 int nticks, i;
119
120 struct tickmark *tm = NULL;
121 printf("Testing range %g - %g\n", x, y);
122 nticks = calc_tickmarks(x, y, 10, &tm);
123
124 for (i = 0; i < nticks; i++) {
125 printf(" (%s) %g\n", tm[i].string, tm[i].value);
126 }
127 printf("\n\n");
128 free(tm);
129}
130
131int main(int argc, char *argv[])
132{
133 test_range(0.0005, 0.008);
134 test_range(0.5, 0.8);
135 test_range(5.5, 8.8);
136 test_range(50.5, 80.8);
137 test_range(-20, 20.8);
138 test_range(-30, 700.8);
139}
140#endif