vim73/src/option.c

option.c

/*
 * Return "dark" or "light" depending on the kind of terminal.
 * This is just guessing!  Recognized are:
 * "linux"          Linux console
 * "screen.linux"   Linux console with screen
 * "cygwin"         Cygwin shell
 * "putty"          Putty program
 * We also check the COLORFGBG environment variable, which is set by
 * rxvt and derivatives. This variable contains either two or three
 * values separated by semicolons; we want the last value in either
 * case. If this value is 0-6 or 8, our background is dark.
 */
    static char_u *
term_bg_default()
{
#if defined(MSDOS) || defined(OS2) || defined(WIN3264)
    /* DOS console nearly always black */
    return (char_u *)"dark";
#else
    char_u      *p;

    if (STRCMP(T_NAME, "linux") == 0
            || STRCMP(T_NAME, "screen.linux") == 0
            || STRCMP(T_NAME, "cygwin") == 0
            || STRCMP(T_NAME, "putty") == 0
            || ((p = mch_getenv((char_u *)"COLORFGBG")) != NULL
                && (p = vim_strrchr(p, ';')) != NULL
                && ((p[1] >= '0' && p[1] <= '6') || p[1] == '8')
                && p[2] == NUL))
        return (char_u *)"dark";
    return (char_u *)"light";
#endif
}