// cp_vt.c //// Copyright (c) 2006, Mike Acton <macton@cellperformance.com>// // Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated // documentation files (the "Software"), to deal in the Software without restriction, including without// limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of// the Software, and to permit persons to whom the Software is furnished to do so, subject to the following// conditions://// The above copyright notice and this permission notice shall be included in all copies or substantial// portions of the Software.//// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT// LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO// EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN// AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE// OR OTHER DEALINGS IN THE SOFTWARE.// NOTES:// From http://www.linuxjournal.com/article/2597////     "Console ttys are used when the keyboard and monitor are directly connected to the system without running//     the X Window System. Since you can have several virtual consoles, the devices are tty0 through tty63. In//     theory you can have 64 virtual consoles, but most people use only a few. The device /dev/console is//     identical to tty0 and is needed for historical reasons. If your system lets you log in on consoles 1//     through 6, then when you run X Windows System, X uses console 7, so you'll need /dev/tty1 through /dev///     tty7 on your system. I recommend having files up through /dev/tty12. For more information on using//     virtual consoles, see the article Keyboards, Consoles and VT Cruising by John Fisk in the November 1996//     issue of Linux Journal"#include <stdio.h>#include <stdint.h>#include <fcntl.h>#include <unistd.h>#include <sys/ioctl.h>#include <linux/vt.h>#include <linux/kd.h>#include "cp_vt.h"static inline const char*select_error_str( int existing_error, const char* const existing_error_str, int new_error, const char* const new_error_str ){  // Only report the first error found - any error that follows is probably just a cascading effect.  const char* error_str = (char*)( (~(intptr_t)existing_error & (intptr_t)new_error & (intptr_t)new_error_str)                                 |  ((intptr_t)existing_error & (intptr_t)existing_error_str) );  return (error_str);}intcp_vt_open_graphics(cp_vt* restrict vt){  const char*    error_str      = NULL;  int            error          = 0;  // Open the current tty   // From http://tldp.org/HOWTO/Text-Terminal-HOWTO-6.html#ss6.3  // (An excellent overview by David S. Lawyer)  //  //     "In Linux the PC monitor is usually called the console and has several device special files associated  //     with it: vc/0 (tty0), vc/1 (tty1), vc/2 (tty2), etc. When you log in you are on vc/1. To go to vc/2  //     (on the same screen) press down the 2 keys Alt(left)-F3. For vc/3 use Left Alt-F3, etc. These (vc/1,  //     vc/2, vc/3, etc.) are called "virtual terminals". vc/0 (tty0) is just an alias for the current virtual  //     terminal and it's where messages from the system are sent. Thus messages from the system will be seen  //     on the console (monitor) regardless of which virtual terminal it is displaying."  const int   cur_tty                = open( "/dev/tty0", O_RDWR );  const int   open_cur_tty_error     = (cur_tty >> ((sizeof(int)*8)-1));  const char* open_cur_tty_error_str = "Could not open /dev/tty0. Check permissions.";    error_str = select_error_str( error, error_str, open_cur_tty_error, open_cur_tty_error_str );  error     = error | open_cur_tty_error;  // From: http://www.linuxjournal.com/article/2783  // (A little out of date, but a nice primer.)  //  //     "VT_GETSTATE returns the state of all VT's in the kernel in the structure:  //  //         struct vt_stat {  //               ushort v_active;   //               ushort v_signal;   //               ushort v_state;  //          };  //  //      v_active        the currently active VT   //      v_state         mask of all the opened VT's  //  //      v_active holds the number of the active VT (starting from 1), while v_state   //      holds a mask where there is a 1 for each VT that has been opened by some process.   //      Note that VT 0 is always opened in this scenario, since it refers to the current VT.  //  //      Bugs:  //      The v_signal member is unsupported."  struct vt_stat  vts;  const int   get_state_error     = ioctl( cur_tty, VT_GETSTATE, &vts );  const char* get_state_error_str = "VT_GETSTATE failed on /dev/tty0";  error_str = select_error_str( error, error_str, get_state_error, get_state_error_str );  error     = error | get_state_error;  vt->prev_tty_ndx = vts.v_active;  // From: http://opensolaris.org/os/project/vconsole/vt.7i.txt  // (Close enough to Linux and a pretty good source of documentation.)  //  // "VT_OPENQRY  //     This call is used to find an available VT.    The argu-  //     ment to the    ioctl is a pointer to an integer.  The integer  //     will be filled in with the number of the first avail-  //     able VT that no other process has open (and    hence, is  //     available to be opened).  If there are no available  //     VTs, then -1 will be filled in."  const int   open_query_error     = ioctl( cur_tty, VT_OPENQRY, &vt->tty_ndx);  const char* open_query_error_str = "No open ttys available";  error_str = select_error_str( error, error_str, open_query_error, open_query_error_str );  error     = error | open_query_error;  const int   close_cur_tty_error     = close( cur_tty );  const char* close_cur_tty_error_str = "Could not close parent tty";  error_str = select_error_str( error, error_str, close_cur_tty_error, close_cur_tty_error_str );  error     = error | close_cur_tty_error;  char tty_file_name[11];  (void)snprintf( tty_file_name, 11, "/dev/tty%d", vt->tty_ndx );  const int   tty                = open( tty_file_name, O_RDWR );  const int   open_tty_error     = (cur_tty >> ((sizeof(int)*8)-1));  const char* open_tty_error_str = "Could not open tty";  error_str = select_error_str( error, error_str, open_tty_error, open_tty_error_str );  error     = error | open_tty_error;  vt->tty = tty;  // From: http://opensolaris.org/os/project/vconsole/vt.7i.txt  // (Close enough to Linux and a pretty good source of documentation.)  //  // "VT_ACTIVATE  //    This call has the effect of making the VT specified in  //    the argument the active VT. The VT manager will cause  //    a switch to occur in the same manner as if a hotkey had  //    initiated the switch.  If the specified VT is not open  //    or does not exist the call will fail and errno will be  //    set to ENXIO."  //  // "VT_WAITACTIVE  //    If the specified VT is already active, this call  //    returns immediately. Otherwise, it will sleep until  //    the specified VT becomes active, at which point it will  //    return."  const int   activate_tty_error     = ioctl( vt->tty, VT_ACTIVATE, vt->tty_ndx );  const char* activate_tty_error_str = "Could not activate tty";  error_str = select_error_str( error, error_str, activate_tty_error, activate_tty_error_str );  error     = error | activate_tty_error;  const int   waitactive_tty_error     = ioctl( vt->tty, VT_WAITACTIVE, vt->tty_ndx );  const char* waitactive_tty_error_str = "Could not switch to tty";  error_str = select_error_str( error, error_str, waitactive_tty_error, waitactive_tty_error_str );  error     = error | waitactive_tty_error;  // From: http://opensolaris.org/os/project/vconsole/vt.7i.txt  // (Close enough to Linux and a pretty good source of documentation.)  //  //  "KDSETMODE  //   This call is used to set the text/graphics mode to the VT.  //  //      KD_TEXT indicates that console text will be displayed on the screen  //      with this VT. Normally KD_TEXT is combined with VT_AUTO mode for  //      text console terminals, so that the console text display will  //      automatically be saved and restored on the hot key screen switches.  //  //      KD_GRAPHICS indicates that the user/application, usually Xserver,  //      will have direct control of the display for this VT in graphics  //      mode. Normally KD_GRAPHICS is combined with VT_PROCESS mode for  //      this VT indicating direct control of the display in graphics mode.  //      In this mode, all writes to this VT using the write system call are  //      ignored, and the user is responsible for saving and restoring the  //      display on the hot key screen switches."  // Save the current VT mode. This is most likely KD_TEXT.  const int   kdgetmode_error     = ioctl( vt->tty, KDGETMODE, &vt->prev_kdmode );  const char* kdgetmode_error_str = "Could not get mode for tty";  error_str = select_error_str( error, error_str, kdgetmode_error, kdgetmode_error_str );  error     = error | kdgetmode_error;    // Set VT to GRAPHICS (user draw) mode  const int   kdsetmode_graphics_error     = ioctl( vt->tty, KDSETMODE, KD_GRAPHICS );  const char* kdsetmode_graphics_error_str = "Could not set graphics mode for tty";  error_str = select_error_str( error, error_str, kdsetmode_graphics_error, kdsetmode_graphics_error_str );  error     = error | kdsetmode_graphics_error;  //  // Not bothering with VT_PROCESS, VT_AUTO is fine for our purposes.  //   // If vt blanking is active, for example when running this program from a remote terminal,   // setting KD_GRAPHICS will not disable the blanking. Reset to KD_TEXT from KD_GRAPHICS will  // force disable blanking. Then return to KD_GRAPHICS for drawing.  //  // Note: KD_TEXT (default) to KD_TEXT will do nothing, so blanking will not be disable unless  // the mode is changing. i.e. the initial set to KD_GRAPHICS above is useful.  const int   kdsetmode_text_error     = ioctl( vt->tty, KDSETMODE, KD_TEXT );  const char* kdsetmode_text_error_str = "Could not set text mode for tty";  error_str = select_error_str( error, error_str, kdsetmode_text_error, kdsetmode_text_error_str );  error     = error | kdsetmode_text_error;  const int   kdsetmode_graphics_reset_error     = ioctl( vt->tty, KDSETMODE, KD_GRAPHICS );  const char* kdsetmode_graphics_reset_error_str = "Could not reset graphics mode for tty";  error_str = select_error_str( error, error_str, kdsetmode_graphics_reset_error, kdsetmode_graphics_reset_error_str );  error     = error | kdsetmode_graphics_reset_error;  if ( error == -1 )  {      printf("ERROR: vt_graphics_open: %s\n",error_str);      return (-1);  }  return (0);}intcp_vt_close(cp_vt* restrict vt){  const char*    error_str      = NULL;  int            error          = 0;  // Reset previous mode on tty (likely KD_TEXT)  const int   kdsetmode_error     = ioctl( vt->tty, KDSETMODE, vt->prev_kdmode );  const char* kdsetmode_error_str = "Could not reset previous mode for tty";  error_str = select_error_str( error, error_str, kdsetmode_error, kdsetmode_error_str );  error     = error | kdsetmode_error;  // Restore previous tty  const int   activate_tty_error     = ioctl( vt->tty, VT_ACTIVATE, vt->prev_tty_ndx );  const char* activate_tty_error_str = "Could not activate previous tty";  error_str = select_error_str( error, error_str, activate_tty_error, activate_tty_error_str );  error     = error | activate_tty_error;  const int   waitactive_tty_error     = ioctl( vt->tty, VT_WAITACTIVE, vt->prev_tty_ndx );  const char* waitactive_tty_error_str = "Could not switch to previous tty";  error_str = select_error_str( error, error_str, waitactive_tty_error, waitactive_tty_error_str );  error     = error | waitactive_tty_error;  // Close tty  const int   close_tty_error     = close( vt->tty );  const char* close_tty_error_str = "Could not close tty";  error_str = select_error_str( error, error_str, close_tty_error, close_tty_error_str );  error     = error | close_tty_error;  if ( error == -1 )  {      printf("ERROR: vt_close: %s\n",error_str);      return (-1);  }  return (0);}