bl.c

   1 /*
   2  * Copyright (c) 2017, S. Gilles <sgilles@math.umd.edu>
   3  *
   4  * Permission to use, copy, modify, and/or distribute this software
   5  * for any purpose with or without fee is hereby granted, provided
   6  * that the above copyright notice and this permission notice appear
   7  * in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
  10  * WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
  11  * WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
  12  * AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
  13  * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
  14  * OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
  15  * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
  16  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18 #include <errno.h>
  19 #include <stdint.h>
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <termios.h>
  24 #include <unistd.h>
  25
  26 #define STR2(x) #x
  27 #define STR(x) STR2(x)
  28 #define L(x) __FILE__ ":" STR(__LINE__) ": " x
  29
  30 static int16_t brightness;
  31
  32 #define STEP 2
  33
  34 #define BAR_WIDTH 72
  35 #define BAR_PRE " ┝"
  36 #define BAR_POST "┤ "
  37 #define FINAL "\033[G"
  38 #define BRIGHT_CELL "━"
  39 #define DARK_CELL "─"
  40
  41 static void output(void)
  42 {
  43         printf("%s%s", "\033[G", BAR_PRE);
  44
  45         for (int j = 0; j < BAR_WIDTH; ++j) {
  46                 if (j * 128 <= brightness * BAR_WIDTH) {
  47                         printf("%s", BRIGHT_CELL);
  48                 } else {
  49                         printf("%s", DARK_CELL);
  50                 }
  51         }
  52
  53         printf("%s%d/128   %s", BAR_POST, (int) brightness, FINAL);
  54         fflush(stdout);
  55 }
  56
  57 int main(void)
  58 {
  59         int ret = 0;
  60         FILE *sf = 0;
  61         struct termios in_t = { 0 };
  62         struct termios stored_in_t = { 0 };
  63         struct termios stored_out_t = { 0 };
  64         int in_fd = fileno(stdin);
  65         int out_fd = fileno(stdout);
  66         char buf[2];
  67         int c;
  68
  69         errno = 0;
  70
  71         /* Get the /sys entry to manipulate */
  72         if (!(sf = fopen(BACKLIGHT_PATH, "w+"))) {
  73                 ret = errno;
  74                 perror(L("fopen(\"" BACKLIGHT_PATH "\", \"a+\")"));
  75                 goto err_pre_tty;
  76         }
  77
  78         /* Read initial backlight value */
  79         buf[0] = '\0';
  80         brightness = 0;
  81
  82         while (!feof(sf) &&
  83                !ferror(sf)) {
  84                 if (fread(buf, 1, 1, sf) > 0) {
  85                         if (buf[0] <= '9' &&
  86                             buf[0] >= '0') {
  87                                 brightness = brightness * 10 + (buf[0] - '0');
  88                         }
  89                 }
  90         }
  91
  92         if (brightness < 0 ||
  93             brightness > 128) {
  94                 fprintf(stderr, L("impossible backlight value\n"));
  95                 goto err_pre_tty;
  96         }
  97
  98         /* Set up the terminal for pretty */
  99         if (!isatty(in_fd)) {
 100                 ret = errno;
 101                 fprintf(stderr, L("stdin is not a tty\n"));
 102                 goto err_pre_tty;
 103         }
 104
 105         if (tcgetattr(in_fd, &stored_in_t)) {
 106                 ret = errno;
 107                 perror(L("tcgetattr"));
 108                 goto err_pre_tty;
 109         }
 110
 111         memcpy(&in_t, &stored_in_t, sizeof in_t);
 112
 113         if (!isatty(out_fd)) {
 114                 ret = errno;
 115                 fprintf(stderr, L("stdout is not a tty\n"));
 116                 goto err_pre_tty;
 117         }
 118
 119         if (tcgetattr(out_fd, &stored_out_t)) {
 120                 ret = errno;
 121                 perror(L("tcgetattr"));
 122                 goto err_pre_tty;
 123         }
 124
 125         /* cfmakeraw() is nonstandard, and I want ^C anyway. */
 126         in_t.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR |
 127                           ICRNL | IXON);
 128         in_t.c_oflag &= ~OPOST;
 129         in_t.c_lflag &= ~(ECHO | ECHONL | ICANON);
 130         in_t.c_cflag &= ~(CSIZE | PARENB);
 131         in_t.c_cflag |= CS8;
 132
 133         /* Technically, it is necessary to check these one by one. That's a pain */
 134         if (tcsetattr(in_fd, TCSANOW, &in_t)) {
 135                 ret = errno;
 136                 perror(L("tcsetattr"));
 137                 goto err_pre_tty;
 138         }
 139
 140         printf("\033[?25l");
 141         output();
 142
 143         while ((c = getchar()) != EOF) {
 144                 switch (c) {
 145                 case 'q':
 146                 case 'Q':
 147                         goto done;
 148                         break;
 149                 case 005:
 150                 case 'j':
 151                 case 'J':
 152                         brightness -= (2 * STEP);
 153                 case 031:
 154                 case 'k':
 155                 case 'K':
 156                         brightness += STEP;
 157
 158                         if (brightness < 0) {
 159                                 brightness = 0;
 160                         } else if (brightness > 128) {
 161                                 brightness = 128;
 162                         }
 163
 164                         fprintf(sf, "%d\n", (int) brightness);
 165                         fflush(sf);
 166                         break;
 167                 default:
 168                         break;
 169                 }
 170
 171                 output();
 172         }
 173
 174 done:
 175         tcsetattr(in_fd, TCSANOW, &stored_in_t);
 176         printf("\033[?25h\n");
 177 err_pre_tty:
 178
 179         if (sf) {
 180                 fclose(sf);
 181         }
 182
 183         return ret;
 184 }