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NAME

       tepam - An introduction into TEPAM, Tcl's Enhanced Procedure and Argument Manager

DESCRIPTION

       This  document  is  an informal introduction into version 0.2 of TEPAM, the Tcl's Enhanced
       Procedure and Argument Manager. Detailed information to the TEPAM package is  provided  in
       the tepam::procedure and tepam::argument_dialogbox reference manuals.

OVERVIEW

       This  package  provides  a  new  Tcl  procedure  declaration  syntax  that  simplifies the
       implementation of procedure subcommands  and  the  handling  of  the  different  types  of
       procedure  arguments  like  flags  or  switches,  options, unnamed arguments, optional and
       mandatory options and arguments,  default  values,  etc.  Procedure  declarations  can  be
       enriched with detailed information about the procedure and its arguments. This information
       is used later for the following purposes:

       First of all, an argument manager that is automatically added to a  procedure  implemented
       with  TEPAM  checks  the  argument types and values before the procedure body is executed.
       Then, the information is used to generate  help  and  usage  texts  if  requested,  or  to
       generate  clear  error  message in case an argument validation fails. The information also
       allows generating automatically graphical forms that allows an interactive  definition  of
       all  arguments,  in  case a procedure is called interactively. And finally, the additional
       information helps self-commenting in a clean way the declaration of a procedure and of all
       its arguments.

       The  graphical  form generator that creates the necessary argument specification forms for
       the interactive procedure calls is also available for other purposes  than  for  procedure
       argument specifications. It allows creating code efficiently complex parameter entry forms
       that are usable independently from TEPAM's new procedure definition feature.

       Here is a short overview about all major TEPAM features:

       ·      New self-documenting procedure declaration syntax: The  additional  information  to
              declare properly a procedure has not to be provided with additional statements, but
              can be added in a natural syntax directly into the procedure header.

       ·      Easy way to specify subcommands: A subcommand is declared like a procedure,  simply
              with  a  procedure name composed by a base name followed by a subcommand name. Sub-
              subcommands are created identically using simply  procedure  names  composed  by  3
              words.

       ·      Flexible   usage  of  flags  (switches),  options  (named  arguments)  and  unnamed
              arguments. Option names are optionally automatically completed.

       ·      Support for default values, mandatory/optional options and arguments, choice lists,
              valid value ranges, multiple usable options/arguments.

       ·      Choice  of a named arguments first, unnamed arguments later procedure calling style
              (typical for Tcl commands) or of an unnamed arguments first, named arguments  later
              procedure calling style (typical for Tk commands).

       ·      In case the named arguments first, unnamed arguments later style (Tcl) is selected:
              Clear separation between options and arguments  via  the  "--"  flag.  The  unnamed
              arguments can optionally be accessed as options (named arguments).

       ·      Automatic  type  and value check before the procedure body is executed, taking into
              account validation ranges, choice lists and custom validation commands.  Generation
              of clear error message if necessary.

       ·      Many  predefined  types  exist  (integer, boolean, double, color, file, font, ...).
              Other application specific types can easily be added.

       ·      Automatic help and usage text generation when a procedure is called with the  -help
              flag.

       ·      Automatic  generation  of  an  interactive  argument  definition  form,  in  case a
              procedure is called with the -interactive flag.

       ·      Powerful and code efficient generation of complex parameter definition forms.

PROCEDURE DECLARATION

       TEPAM's procedure declaration syntax is simple and self-explaining. Instead of declaring a
       procedure  with  the  Tcl  key  word  proc, a procedure is declared with the TEPAM command
       procedure which takes as proc also 3 arguments: The procedure name, the  procedure  header
       and the procedure body.

       The  following  example  declares  the  subcommand  message of the procedure display. This
       command has several named and unnamed arguments:

              tepam::procedure {display message} {
                 -return            -
                 -short_description "Displays a simple message box"
                 -description       "This procedure allows displaying a configurable message box.
                 -args {
                    {-mtype -default Warning -choices {Info Warning Error} -description "Message type"}
                    {-font -type font -default {Arial 10 italic} -description "Message text font"}
                    {-level -type integer -optional -range {1 10} -description "Message level"}
                    {-fg -type color -default black -description "Message color"}
                    {-bg -type color -optional -description "Background color"}
                    {-no_border -type none -description "Use a splash window style (no border)"}
                    {-log_file -type file -optional -description "Optional message log file"}
                    {text -type string -multiple -description "Multiple text lines to display"}
                 }
              } {
                 puts "display message:"
                 foreach var {mtype font level fg bg no_border log_file text} {
                    if {[info exists $var]} {
                       puts  "  $var=[set $var]"
                    }
                 }
              }
       When a procedure that has been declared in this way is called, the TEPAM argument  manager
       is  automatically  invoked  before  the  procedure  body is executed. The argument manager
       parses the provided arguments, validates them, completes them eventually with some default
       values, and makes them finally available to the procedure body as local variables. In case
       an argument is missing or has a wrong  type,  the  argument  manager  generates  an  error
       message that explains the reason for the error.

       As  the example above shows, the TEPAM command procedure accepts subcommand definitions as
       procedure name and allows defining much more  information  than  just  the  argument  list
       inside  the  procedure header. The procedure body on the other hand is identical between a
       command declared with proc or with procedure.

       The procedure  header  allows  defining  in  addition  to  the  arguments  some  procedure
       attributes,  like  a  description,  information  concerning  the  return  value, etc. This
       information is basically used for the automatic generation of comprehensive help and usage
       texts.

       A  list  of  argument definition statements assigned to the -args argument is defining the
       procedure arguments. Each argument definition statement starts  with  the  argument  name,
       optionally followed by some argument attributes.

       Three types of arguments can be defined: Unnamed arguments, named arguments and flags. The
       distinction between the named and unnamed arguments is made by  the  first  argument  name
       character  which  is  simply  "-" for named arguments. Flags are defined as named argument
       that has a type set to none.

       Named and unnamed arguments are mandatory, unless they are  declared  with  the  -optional
       flag  and  unless  they  have  a  default  value specified with the -default option. Named
       arguments and the last unnamed argument can have the attribute -multiple, which means that
       they  can be defined multiple times. The expected argument data type is specified with the
       -type option. TEPAM defines a large set  of  standard  data  types  which  can  easily  be
       completed with application specific data types.

       The  argument  declaration  order has only an importance for unnamed arguments that are by
       default parsed after the named arguments (Tcl style).  A  variable  allows  changing  this
       behavior  in a way that unnamed arguments are parsed first, before the named arguments (Tk
       style).

PROCEDURE HELP

       The declared procedure can simply be called with the -help option to get  the  information
       about the usage of the procedure and its arguments:

              display message -help
                ->
              NAME
                    display message - Displays a simple message box
              SYNOPSYS
                    display message
                          [-mtype <mtype>] :
                             Message type, default: "Warning", choices: {Info Warning Error}
                          [-font <font>] :
                             Message text font, type: font, default: Arial 10 italic
                          [-level <level>] :
                             Message level, type: integer, range: 1..10
                          [-fg <fg>] :
                             Message color, type: color, default: black
                          [-bg <bg>] :
                             Background color, type: color
                          [-no_border ] :
                             Use a splash window style (no border)
                          [-log_file <log_file>] :
                             Optional message log file, type: file
                          <text> :
                             Multiple text lines to display, type: string
              DESCRIPTION
                    This procedure allows displaying a configurable message box.

PROCEDURE CALL

       The specified procedure can be called in many ways. The following listing shows some valid
       procedure calls:

              display message "The document hasn't yet been saved!"
              -> display message:
                   mtype=Warning
                   font=Arial 10 italic
                   fg=black
                   no_border=0
                   text={The document hasn't yet been saved!}

              display message -fg red -bg black "Please save first the document"
              -> display message:
                   mtype=Warning
                   font=Arial 10 italic
                   fg=red
                   bg=black
                   no_border=0
                   text={Please save first the document}

              display message -mtype Error -no_border "Why is here no border?"
              -> display message:
                   mtype=Error
                   font=Arial 10 italic
                   fg=black
                   no_border=1
                   text={Why is here no border?}

              display message -font {Courier 12} -level 10 \
                 "Is there enough space?" "Reduce otherwise the font size!"
              -> display message:
                   mtype=Warning
                   font=Courier 12
                   level=10
                   fg=black
                   no_border=0
                   text={Is there enough space?} {Reduce otherwise the font size!}
       The next lines show how  wrong  arguments  are  recognized.  The  text  argument  that  is
       mandatory is missing in the first procedure call:

              display message -font {Courier 12}
                -> display message: Required argument is missing: text
       Only valid arguments are accepted:

              display message -category warning Hello
                -> display message: Argument '-category' not known
       Argument  types  are  automatically  checked and an error message is generated in case the
       argument type is not satisfied.

              display message -fg MyColor "Hello"
                -> display message: Argument 'fg' requires type 'color'. \
                          Provided value: 'MyColor'
       Selection choices have to be respected...

              display message -mtype Fatal Hello
                -> display message: Argument (mtype) has to be one of the \
                          following elements: Info, Warning, Error
       ... as well as valid value ranges:

              display message -level 12 Hello
                -> display message: Argument (level) has to be between 1 and 10

INTERACTIVE ARGUMENT DEFINITION

       The most intuitive way to call the procedure is using  an  interactive  form  that  allows
       specifying  all  arguments.  This  form  will automatically be generated when the declared
       procedure is called with the -interactive flag.

              display message -interactive
       The generated form contains for each argument a data entry widget that is adapted  to  the
       argument type. Check buttons are used to specify flags, radio boxes for tiny choice lists,
       disjoint list boxes for larger choice lists and files, directories, fonts and  colors  can
       be selected with dedicated browsers.

       After  acknowledging  the  specified  argument data via an OK button, the entered data are
       first validated, before the provided arguments are transformed into  local  variables  and
       the  procedure  body  is executed. In case the entered data are invalid, a message appears
       and the user can correct them until they are valid.

FLEXIBLE ARGUMENT DIALOG BOX

       The form generator that creates in the previous example the argument dialog  box  for  the
       interactive procedure call is also available for other purposes than for the definition of
       procedure arguments. Even if Tk is well known for its code efficient way  to  build  GUIs,
       the  presented  argument dialog box allows crating complex parameter definition forms in a
       still much more efficient way.

       The following example tries to illustrate the simplicity  to  create  complex  data  entry
       forms.  It  creates  an  input  mask  that allows specifying a file to copy, a destination
       folder as well as a checkbox that allows specifying if an eventual existing  file  can  be
       overwritten.  Comfortable  browsers  can  be  used  to  select  files and directories. And
       finally, the form offers also the possibility to accept and decline the selection. Here is
       the code snippet that is doing all this:

              tepam::argument_dialogbox \
                 -existingfile {-label "Source file" -variable SourceFile} \
                 -existingdirectory {-label "Destination folder" -variable DestDir} \
                 -checkbutton {-label "Overwrite existing file" -variable Overwrite}
       The  argument_dialogbox returns ok when the entered data are validated and cancel when the
       data  entry  has  been  canceled.  After  the  validation  of  the   entered   data,   the
       argument_dialogbox  defines  all  the specified variables with the entered data inside the
       calling context.

       A pair of arguments has to be provided to argument_dialogbox for each variable that has to
       be  specified by this last one. The first argument defines the entry widget type to use to
       select the variable's data and the second one is a lists  of  attributes  related  to  the
       variable and the entry widget.

       Many  entry  widget  types  are  available:  Beside  the simple generic entries, there are
       different kinds of list and combo boxes available, browsers for existing and new files and
       directories,  check  and  radio  boxes  and buttons, as well as color and font pickers. If
       necessary, additional entry widget types can be defined.

       The attribute list contains pairs of attribute  names  and  attribute  data.  The  primary
       attribute  is -variable used to specify the variable in the calling context into which the
       entered data has to be stored. Another often used attribute is -label that allows adding a
       label  to  the  data  entry  widget. Other attributes are available that allows specifying
       default values, the expected data types, valid data ranges, etc.

       The next example of a more complex argument dialog box provides a good overview about  the
       different available entry widget types and parameter attributes. The example contains also
       some formatting instructions like -frame and -sep which allows  organizing  the  different
       entry widgets in frames and sections:

              set ChoiceList {"Choice 1" "Choice 2" "Choice 3" "Choice 4" "Choice 5" "Choice 6"}

              set Result [tepam::argument_dialogbox \
                 -title "System configuration" \
                 -context test_1 \
                 -frame {-label "Entries"} \
                    -entry {-label Entry1 -variable Entry1} \
                    -entry {-label Entry2 -variable Entry2 -default "my default"} \
                 -frame {-label "Listbox & combobox"} \
                    -listbox {-label "Listbox, single selection" -variable Listbox1 \
                              -choices {1 2 3 4 5 6 7 8} -default 1 -height 3} \
                    -listbox {-label "Listbox, multiple selection" -variable Listbox2
                              -choicevariable ChoiceList -default {"Choice 2" "Choice 3"}
                              -multiple_selection 1 -height 3} \
                    -disjointlistbox {-label "Disjoined listbox" -variable DisJntListbox
                                      -choicevariable ChoiceList \
                                      -default {"Choice 3" "Choice 5"} -height 3} \
                    -combobox {-label "Combobox" -variable Combobox \
                               -choices {1 2 3 4 5 6 7 8} -default 3} \
                 -frame {-label "Checkbox, radiobox and checkbutton"} \
                    -checkbox {-label Checkbox -variable Checkbox
                               -choices {bold italic underline} -choicelabels {Bold Italic Underline} \
                               -default italic} \
                    -radiobox {-label Radiobox -variable Radiobox
                               -choices {bold italic underline} -choicelabels {Bold Italic Underline} \
                               -default underline} \
                    -checkbutton {-label CheckButton -variable Checkbutton -default 1} \
                 -frame {-label "Files & directories"} \
                    -existingfile {-label "Input file" -variable InputFile} \
                    -file {-label "Output file" -variable OutputFile} \
                    -sep {} \
                    -existingdirectory {-label "Input directory" -variable InputDirectory} \
                    -directory {-label "Output irectory" -variable OutputDirectory} \
                 -frame {-label "Colors and fonts"} \
                    -color {-label "Background color" -variable Color -default red} \
                    -sep {} \
                    -font {-label "Font" -variable Font -default {Courier 12 italic}}]
       The  validation  status  is in this case stored inside the Result variable. If the entered
       data are validated, Result will contain 0 and the calling program  can  read  the  entered
       data via the variables that have been specified:

              if {$Result=="cancel"} {
                 puts "Canceled"
              } else {
                 puts "Arguments: "
                 foreach Var {
                    Entry1 Entry2
                    Listbox1 Listbox2 DisJntListbox
                    Combobox Checkbox Radiobox Checkbutton
                    InputFile OutputFile InputDirectory OutputDirectory
                    Color Font
                 } {
                    puts "  $Var: '[set $Var]'"
                 }
              }
              -> Arguments:
                 Entry1: 'Hello, this is a trial'
                 Entry2: 'my default'
                 Listbox1: '1'
                 Listbox2: '{Choice 2} {Choice 3}'
                 DisJntListbox: '{Choice 3} {Choice 5}'
                 Combobox: '3'
                 Checkbox: 'italic'
                 Radiobox: 'underline'
                 Checkbutton: '1'
                 InputFile: 'c:\tepam\in.txt'
                 OutputFile: 'c:\tepam\out.txt'
                 InputDirectory: 'c:\tepam\input'
                 OutputDirectory: 'c:\tepam\output'
                 Color: 'red'
                 Font: 'Courier 12 italic'

SEE ALSO

       tepam::argument_dialogbox(3tcl), tepam::procedure(3tcl)

KEYWORDS

       argument  integrity,  argument  validation,  arguments,  entry mask, parameter entry form,
       procedure, subcommand

CATEGORY

       Procedures, arguments, parameters, options

COPYRIGHT

       Copyright (c) 2009/2010, Andreas Drollinger