tepam(n)         Tcl's Enhanced Procedure and Argument Manager        tepam(n)



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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:

       o      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.

       o      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.

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

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

       o      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).

       o      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).

       o      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.

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

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

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

       o      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

              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(n), tepam::procedure(n)

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




tepam                                0.2.0                            tepam(n)
