tack - terminfo action checker


       tack [-diltV] [term]


       The tack program has three purposes:

       (1) to help you build a new terminfo entry describing an unknown termi-

       (2) to test the correctness of an existing entry, and

       (3) to develop the correct pad timings needed  to  ensure  that  screen
           updates do not fall behind the incoming data stream.

       Tack presents a series of screen-painting and interactive tests in ways
       which are intended to make any mismatches between  the  terminfo  entry
       and  reality  visually obvious.  Tack also provides tools that can help
       in understanding how the terminal operates.


       -d     Start tack with the debug-file "debug.log" opened.

       -i     Usually tack will send the reset and init strings to the  termi-
              nal  when the program starts up.  The -i option will inhibit the
              terminal initialization.

       -l     Start tack with the log-file "tack.log" opened.  This is also  a
              menu item.

       -t     Tell  tack  to override the terminfo settings for basic terminal
              functions.  When this option is set, tack will translate

              (cr) to \r,
              (cud1) to \n,
              (ind) to \n,
              (nel) to \r\n,
              (cub1) to \b,
              (bel) to \007,
              (ff) to \f and
              (ht) to \t.

       -V     Display the version information and exit.

       term   Terminfo terminal name to be tested.  If not present,  then  the
              $TERM environment variable will be used.


       Since  tack  is designed to test terminfo entries it is not possible to
       rely on the correctness of the terminfo data base.   Because  of  this,
       the  menuing  system  used with tack is very primitive.  When a menu is
       printed, it will scroll the entire screen.  To compensate for this ver-
       bose  menu  system,  tack  permits  menu  selection type ahead.  If you
       already know what action you would like tack to perform  then  you  can
       enter that value immediately and avoid the menu display.  When in doubt
       the question mark (?) is a good character to type.  A  carriage  return
       will execute the default action.  These default actions are designed to
       run all the standard tests.

       When tack first comes up it will display some basic  information  about
       the  terminal.   Take  some  time to verify this information.  If it is
       wrong many of the subsequent tests will fail.  The most important  item
       is  the screen size.  If the screen size is wrong, there is no point in
       proceeding.  (home) and (clear) are also critical  to  the  success  of
       subsequent  tests.  The values of (cr) (ind) (cub1) and (ht) may effect
       the tests if they are defined incorrectly.  If they are undefined  tack
       will set them to reasonable defaults.  The last two entries on the dis-
       play are the enquire and acknowledge strings.  These strings are  taken
       from the user strings (u9) and (u8).

       By  now  you  must  be wondering why the terminfo names are enclosed in
       parenthesis.  This has no profound meaning other  than  it  makes  them
       stand  out.  The tack program uses this convention any time it displays
       a terminfo name.  Remember that tack is designed to rely on  as  little
       of the terminfo entry as possible.


       Tack has a number of tools that are designed to help gather information
       about the terminal.  Although these functions are not dependent on ter-
       minal  type,  you may wish to execute tack with options -it.  This will
       turn off initialization and default the standard entries.

       These tools may be reached from the main menu by selecting the  "tools"

       Echo tool:  All data typed from the keyboard will be echoed back to the
       terminal.  Control characters are not translated to the up arrow format
       but  are sent as control characters.  This allows you to test an escape
       sequence and see what it actually does.  You may also elect  to  enable
       hex  output  on echo tool this will echo the characters in hexadecimal.
       Once the test is running you may enter the "lines"  or  "columns"  key-
       words  which  will  display a pattern that will help you determine your
       screen size.  A complete list of keywords will be  displayed  when  the
       test starts.  Type "help" to redisplay the list of available commands.

       Reply  tool:  This tool acts much like the echo tool, but control char-
       acters that are sent from the terminal more than one character after  a
       carriage  return  will be expanded to the up arrow format.  For example
       on a standard ANSI terminal you may type:

                 CR ESC [ c

       and the response will be echoed as something like:

                 ^[ [ ? 6 c

       ANSI sgr display:  This test assumes you have  an  ANSI  terminal.   It
       goes  through  attribute  numbers  0 to 79, displaying each in turn and
       using that SGR number to write the text.  This shows you which  of  the
       SGR  modes are actually implemented by the terminal.  Note: some termi-
       nals (such as Tektronix color) use the private use characters  to  aug-
       ment  the  functionality of the SGR command.  These private use charac-
       ters may be interjected into the escape sequence by typing the  charac-
       ter ( <, =, >, ? ) after the original display has been shown.

       ANSI  status  reports:   This  test  queries  the  terminal in standard
       ANSI/VT-100 fashion.  The results of this test may help determine  what
       options are supported by your terminal.

       ANSI  character  sets:  This test displays the character sets available
       on a ANSI/VT-100 style terminal.  Character sets on a real VT-100  ter-
       minal  are  usually  defined with smacs=\E(0 and rmacs=\E(B.  The first
       character after the escape defines the font bank.  The second character
       defines  the  character  set.   This test allows you to view any of the
       possible combinations.  Private use character sets are defined  by  the
       digits.  Standard character sets are located in the alphabetic range.


       You  can  verify  the  correctness of an entry with the "begin testing"
       function.  This entry is the default action and will be chosen  if  you
       hit  carriage  return  (or enter).  This will bring up a secondary menu
       that allows you to select more specific tests.

       The general philosophy of the program is, for each capability, to  send
       an  appropriate test pattern to the terminal then send a description of
       what the user should expect.  Occasionally (as when checking  function-
       key  capabilities)  the  program  will ask you to enter input for it to

       If the test fails then you have the option of dynamically changing  the
       terminfo  entry  and  re-running the test.  This is done with the "edit
       terminfo" menu item.  The edit submenu allows you to change the offend-
       ing  terminfo  entry  and  immediately retest the capability.  The edit
       menu lets you do other things with the terminfo, such as;  display  the
       entire  terminfo entry, display which caps have been tested and display
       which caps cannot be tested.  This menu also allows you  to  write  the
       newly modified terminfo to disc.  If you have made any modifications to
       the terminfo tack will ask you if you want to save  the  file  to  disc
       before  it  exits.  The filename will be the same as the terminal name.
       After the program exits you can run the tic(1M)  compiler  on  the  new
       terminfo to install it in the terminfo data base.


Theory of Overruns and Padding

       Some  terminals require significant amounts of time (that is, more than
       one transmitted-character interval) to do screen  updates  that  change
       large  portions  of the screen, such as screen clears, line insertions,
       line deletions, and scrolls (including scrolls triggered by line  feeds
       or a write to the lowest, right-hand-most cell of the screen).

       If  the computer continues to send characters to the terminal while one
       of these time-consuming operations is going on, the screen may be  gar-
       bled.   Since  the  length  of  a  character  transmission  time varies
       inversely with transmission speed in cps,  entries  which  function  at
       lower speeds may break at higher speeds.

       Similar  problems  result if the host machine is simply sending charac-
       ters at a sustained rate  faster  than  the  terminal  can  buffer  and
       process  them.   In  either case, when the terminal cannot process them
       and cannot tell the host to stop soon enough, it will just  drop  them.
       The  dropped  characters  could be text, escape sequences or the escape
       character itself, causing some really strange-looking  displays.   This
       kind of glitch is called an overrun.

       In  terminfo entries, you can attach a pad time to each string capabil-
       ity that is a number of milliseconds to delay after sending  it.   This
       will give the terminal time to catch up and avoid overruns.

       If  you  are  running  a software terminal emulator, or you are on an X
       pseudo-tty, or your terminal is on an RS-232C line which correctly han-
       dles  RTS/CTS  hardware flow control, then pads are not strictly neces-
       sary.  However, some display packages (such as ncurses(3X)) use the pad
       counts  to  calculate  the  fastest way to implement certain functions.
       For example: scrolling the screen may be faster than deleting  the  top

       One  common  way  to  avoid overruns is with XON/XOFF handshaking.  But
       even this handshake may have problems at high baud rates.   This  is  a
       result  of the way XON/XOFF works.  The terminal tells the host to stop
       with an XOFF.  When the host gets this  character,  it  stops  sending.
       However,  there  is a small amount of time between the stop request and
       the actual stop.  During this window, the  terminal  must  continue  to
       accept  characters  even  though  it has told the host to stop.  If the
       terminal sends the stop request too late, then its internal buffer will
       overflow.   If it sends the stop character too early, then the terminal
       is not getting the most efficient use out of its internal buffers.   In
       a  real application at high baud rates, a terminal could get a dozen or
       more characters before the host gets around to suspending transmission.
       Connecting  the  terminal  over  a  network  will make the problem much

       (RTS/CTS handshaking does not have this problem because the  UARTs  are
       signal-connected and the "stop flow" is done at the lowest level, with-
       out software intervention).

Timing your terminal

       In order to get accurate timings from your terminal tack needs to  know
       when  the terminal has finished processing all the characters that were
       sent.  This requires a different type of handshaking than the  XON/XOFF
       that  is  supported by most terminals.  Tack needs to send a request to
       the terminal and wait for its reply.  Many terminals will respond  with
       an  ACK  when  they receive an ENQ.  This is the preferred method since
       the sequence is short.  ANSI/VT-100  style  terminals  can  mimic  this
       handshake  with  the  escape  sequence  that  requests  "primary device

          ESC [ c

       The terminal will respond with a sequence like:

          ESC [ ? 1 ; 0 c

       Tack assumes that (u9) is the enquire sequence and  that  (u8)  is  the
       acknowledge  string.   A  VT-100  style  terminal could set u9=\E[c and
       u8=\E[?1;0c.  Acknowledge strings fall into two categories.

       1)  Strings with a unique terminating character and,

       2)  strings of fixed length.

       The acknowledge string for the VT-100 is of the  first  type  since  it
       always  ends  with the letter "c".  Some Tektronix terminals have fixed
       length acknowledge strings.  Tack supports both  types  of  strings  by
       scanning for the terminating character until the length of the expected
       acknowledge string has arrived.  (u8) should be  set  to  some  typical
       acknowledge that will be returned when (u9) is sent.

       Tack will test this sequence before running any of the pad tests or the
       function key tests.  Tack will ask you the following:

           Hit lower case g to start testing...

       After it sends this message it will send the enquire string.   It  will
       then read characters from the terminal until it sees the letter g.

Testing and Repairing Pad Timings

       The  pad  timings  in distributed terminfo entries are often incorrect.
       One major motivation for this program is to make it relatively easy  to
       tune these timings.

       You  can  verify and edit the pad timings for a terminal with the "test
       string capabilities" function (this is also part of  the  "normal  test
       sequence" function).

       The key to determining pad times is to find out the effective baud rate
       of the terminal.  The effective baud  rate  determines  the  number  of
       characters per second that the terminal can accept without either hand-
       shaking or losing data.  This rate is frequently less than the  nominal
       cps rate on the RS-232 line.

       Tack uses the effective baud rate to judge the duration of the test and
       how much a particular escape sequence will perturb the terminal.

       Each pad test has two associated variables that can be tweaked to  help
       verify the correctness of the pad timings.  One is the pad test length.
       The other is the pad multiplier,  which  is  used  if  the  pad  prefix
       includes  "*".   In  curses use, it is often the first parameter of the
       capability (if there is one).  For a capability like (dch) or (il) this
       will  be  the  number of character positions or lines affected, respec-

       Tack will run the pad tests and display the results  to  the  terminal.
       On capabilities that have multipliers tack will not tell you if the pad
       needs the multiplier or not.  You must make this decision  yourself  by
       rerunning the test with a different multiplier.  If the padding changes
       in proportion to the multiplier than the multiplier  is  required.   If
       the  multiplier  has  little or no effect on the suggested padding then
       the multiplier is not needed.  Some capabilities will take several runs
       to  get  a  good feel for the correct values.  You may wish to make the
       test longer to get more accurate results.  System load will also effect
       the  results  (a  heavily loaded system will not stress the terminal as
       much, possibly leading to pad timings that are too short).


       The tests done at the beginning of the program are assumed to  be  cor-
       rect  later  in  the  code.  In particular, tack displays the number of
       lines and columns indicated in the terminfo entry as part of  its  ini-
       tial  output.   If  these values are wrong a large number of tests will
       fail or give incorrect results.


       tack.log    If logging is enabled then all characters  written  to  the
                   terminal  will also be written to the log file.  This gives
                   you the ability to see how the tests were performed.   This
                   feature is disabled by default.

       term        If  you  make  changes to the terminfo entry tack will save
                   the new terminfo to a file.  The file will  have  the  same
                   name as the terminal name.


       terminfo(5),  ncurses(3X),  tic(1M), infocmp(1M).  You should also have
       the documentation supplied by the terminal manufacturer.


       If the screen size is incorrect, many of the tests will fail.


       Concept, design, and original implementation by Daniel Weaver

       Portions of the code and documentation are by Eric S. Raymond

       Refactored by Thomas E. Dickey to eliminate dependency on ncurses
       internal functions, and to allow tack to work with other
       implementations of curses and terminfo than ncurses.