tack



tack(1M)                                                              tack(1M)




NAME

       tack - terminfo action checker


SYNOPSIS

       tack [-itV] [term]


DESCRIPTION

       The  tack  program has three purposes: (1) to help you build a new ter-
       minfo entry describing an unknown terminal, (2) to test the correctness
       of an existing entry, and (3) to develop the correct pad timings needed
       to ensure that screen updates  don’t  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.

   OPTIONS
       -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.

       -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.


OVERVIEW

       Since tack is designed to test terminfo’s it is not possible to rely on
       the correctness of the terminfo data base.  Because of this the menuing
       system used with tack is vary primitive.  When a  menu  is  printed  it
       will  scroll  the  entire  screen.  To compensate for this verbose 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  ques-
       tion mark (?) is a good character to type.  A carriage return will exe-
       cute 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 tack is designed to rely on as little of the
       terminfo entry as possible.


CREATING NEW ENTRIES

       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’
       entry.

       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.


VERIFYING AN EXISTING ENTRY

       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
       check.

       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
       offending  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 dis-
       play which caps cannot be tested.  This menu also allows you  to  write
       the  newly  modified  terminfo to disc.  If you have made any modifica-
       tions 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.



CORRECTING PAD TIMINGS

   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  pro-
       cess  them.   In either case, when the terminal cannot process them and
       can’t tell the host to stop soon enough, it will just drop  them.   The
       dropped  characters could be text, escape sequences or the escape char-
       acter 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
       line.

       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
       worse.

       (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
       attributes’.

          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 Tektronics 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-
       tively.

       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).



NOTE

       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.


FILES

       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.


SEE ALSO

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


BUGS

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


AUTHOR

       Concept,  design,  and  original  implementation   by   Daniel   Weaver
       <danw@znyx.com>.  Portions of the code and documentation are by Eric S.
       Raymond <esr@snark.thyrsus.com>.



                                                                      tack(1M)

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