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.TH INTRO 9
.SH NAME
intro \- introduction to Inferno Tk
.SH DESCRIPTION
This section of the manual provides a reference for the Inferno
Tk implementation,
which is accessed by Limbo programs via
.IR tk (2),
and from
.IR sh (1)
via
.IR sh-tk (1).
.PP
The following pages were derived by Vita Nuova from documentation that is
.IP
Copyright © 1990 The Regents of the University of California
.br
Copyright © 1994-1996 Sun Microsystems, Inc.
.br
See
.IR copyright (9)
for the full copyright notice.
.PP
The format of the pages has changed to follow the format of the rest of
this manual, but more important, the content has been changed
(typically in small ways) to reflect the variant of Tk implemented by
Inferno.
.SS Programming Interface
The interface to Inferno Tk is exclusively through the
.IR tk (2)
module; all the Tk commands described in this section of
the manual are excecuted by passing them as strings to the
.B cmd
function in that module.
The Inferno Tk implementation is based on the Tk 4.0 documentation,
but there are many differences, probably the greatest of which is that
there is no associated Tcl implementation, so almost every
Inferno application using Tk will need to have some Limbo code
associated with it (the
.IR sh-tk (1)
shell module can also fulful this rôle). See ``An Overview of Limbo/Tk''
in Volume 2 for a tutorial-style introduction to the use of Inferno Tk
which summarises the differences from Tk 4.0.
.SS Tk Commands
The command string passed to
.B tk->cmd
may contain one or more Tk commands, separated by semicolons.
A semicolon is not a command separator when it is nested in braces
.RB ( {} )
or brackets
.RB ( [] )
or it is escaped by a backslash
.RB ( \e ).
Each command is divided into
.IR words :
sequences of characters separated by one or more
blanks and tabs.
.PP
There is also a `super quote' convention: at any point in the command
string a single quote mark
.RB ( ' )
means that the entire rest of the string should be treated as one word.
.PP
A word beginning with an opening brace
.RB ( { )
continues until the balancing closing brace
.RB ( } )
is reached. The outer brace characters are stripped. A backslash
can be used to escape a brace in this context. Backslash
characters not used to escape braces are left unchanged.
.PP
A word beginning with an opening bracket
.RB ( [ )
continues until the balancing closing bracket
.RB ( ] )
is reached. The enclosed string is then evaluated as if it
were a command string, and the resulting value
is used as the contents of the word.
.PP
Single commands are executed in order until they are all done
or an error is encountered. By convention, an error is signaled by a
return value starting with an exclamation mark
.RB ( ! ).
The return value from
.B tk->cmd
is the return value of the first error-producing
command or else the return value of the final single command.
.PP
To execute a single command, the first word is examined. It
must either begin with dot
.RB ( . )
in which case it must name an existing widget, which will
interpret the rest of the command according to its type,
or one of the following words, each of which is
documented in a manual page of that name in this section:
.EX
bind focus lower scrollbar
button frame menu see
canvas grab menubutton send
checkbutton grid pack text
cursor image radiobutton update
destroy label raise variable
entry listbox scale
.EE
.SS Widget Options
Each manual page in this section documents the options
that a particular command will accept. A number of options
are common to several of the widgets and are named as
``standard options'' near the beginning of the manual page
for each widget. These options are documented in
.IR options (9).
The types of value required as arguments to options within
Inferno Tk are documented under
.IR types (9).
.SH SEE ALSO
.IR options (9),
.IR types (9),
.IR tk (2),
.IR sh-tk (1),
.IR tkcmd (1),
.IR wmlib (2),
.IR draw-intro (2),
``An Overview of Limbo/Tk'' in Volume 2.
.SH BUGS
The bracket
.RB ( [] )
command interpretation is not applied consistently throughout
the Inferno Tk commands (notably, the argument to
the
.IR send (9)
command will not interpret this correctly).
Moreover, if the string to be substituted is significantly bigger
than the command it was substituting, then it will be truncated.