| TclInterface {tcltk} | R Documentation |
Low-level Tcl/Tk Interface
Description
These functions and variables provide the basic glue between R and the
Tcl interpreter and Tk GUI toolkit. Tk
windows may be represented via R objects. Tcl variables can be accessed
via objects of class tclVar and the C level interface to Tcl
objects is accessed via objects of class tclObj.
Usage
.Tcl(...)
.Tcl.objv(objv)
.Tcl.args(...)
.Tcl.args.objv(...)
.Tcl.callback(...)
.Tk.ID(win)
.Tk.newwin(ID)
.Tk.subwin(parent)
.TkRoot
.TkUp
tkdestroy(win)
is.tkwin(x)
tclvalue(x)
tclvalue(x) <- value
tclVar(init = "")
## S3 method for class 'tclVar'
as.character(x, ...)
## S3 method for class 'tclVar'
tclvalue(x)
## S3 replacement method for class 'tclVar'
tclvalue(x) <- value
tclArray()
## S3 method for class 'tclArray'
x[[...]]
## S3 replacement method for class 'tclArray'
x[[...]] <- value
## S3 method for class 'tclArray'
x$i
## S3 replacement method for class 'tclArray'
x$i <- value
## S3 method for class 'tclArray'
names(x)
## S3 method for class 'tclArray'
length(x)
tclObj(x)
tclObj(x) <- value
## S3 method for class 'tclVar'
tclObj(x)
## S3 replacement method for class 'tclVar'
tclObj(x) <- value
as.tclObj(x, drop = FALSE)
is.tclObj(x)
## S3 method for class 'tclObj'
as.character(x, ...)
## S3 method for class 'tclObj'
as.integer(x, ...)
## S3 method for class 'tclObj'
as.double(x, ...)
## S3 method for class 'tclObj'
as.logical(x, ...)
## S3 method for class 'tclObj'
as.raw(x, ...)
## S3 method for class 'tclObj'
tclvalue(x)
## Default S3 method:
tclvalue(x)
## Default S3 replacement method:
tclvalue(x) <- value
addTclPath(path = ".")
tclRequire(package, warn = TRUE)
tclVersion()
Arguments
objv |
a named vector of Tcl objects |
win |
a window structure |
x |
an object |
i |
character or (unquoted) name |
drop |
logical. Indicates whether a single-element vector should be made into a simple Tcl object or a list of length one |
value |
For |
ID |
a window ID |
parent |
a window which becomes the parent of the resulting window |
path |
path to a directory containing Tcl packages |
package |
a Tcl package name |
warn |
logical. Warn if not found? |
... |
Additional arguments. See below. |
init |
initialization value |
Details
Many of these functions are not intended for general use but are used
internally by the commands that create and manipulate Tk widgets and
Tcl objects. At the lowest level .Tcl sends a command as a text
string to the Tcl interpreter and returns the result as an object of
class tclObj (see below). A newer variant .Tcl.objv
accepts arguments in the form of a named list of tclObj
objects.
.Tcl.args converts an R argument list of tag = value pairs
to the Tcl -option value style, thus
enabling a simple translation between the two languages. To send a
value with no preceding option flag to Tcl, just use an untagged
argument. In the rare case one needs an option with no subsequent
value tag = NULL can be used. Most values are just converted to
character mode and inserted in the command string, but window objects
are passed using their ID string, and callbacks are passed via the
result of .Tcl.callback. Tags are converted to option flags
simply by prepending a -
.Tcl.args.objv serves a similar purpose as .Tcl.args but
produces a list of tclObj objects suitable for passing to
.Tcl.objv. The names of the list are converted to Tcl option
style internally by .Tcl.objv.
Callbacks can be either atomic callbacks handled by
.Tcl.callback or expressions. An expression is treated as a
list of atomic callbacks, with the following exceptions: if an
element is a name, it is first evaluated in the callers frame, and
likewise if it is an explicit function definition; the break
expression is translated directly to the Tcl counterpart.
.Tcl.callback converts R functions and unevaluated calls to
Tcl command strings. The argument must be either a function closure
or an object of mode "call" followed by an environment. The
return value in the first case is of the form R_call
0x408b94d4 in which the hexadecimal number is the memory address of
the function. In the second case it will be of the form
R_call_lang 0x8a95904 0x819bfd0. For expressions, a sequence
of similar items is generated, separated by
semicolons. .Tcl.args takes special precautions to ensure
that functions or calls will continue to exist at the specified
address by assigning the
callback into the relevant window environment (see below).
Tk windows are represented as objects of class tkwin which are
lists containing a ID field and an env field which is
an R environments, enclosed in the global environment. The value of
the ID field is identical to the Tk window name. The env
environment contains a parent variable and a num.subwin
variable. If the window obtains sub-windows and callbacks, they are
added as variables to the environment. .TkRoot is the top
window with ID "."; this window is not displayed in order to avoid
ill effects of closing it via window manager controls. The
parent variable is undefined for .TkRoot.
.Tk.ID extracts the ID of a window,
.Tk.newwin creates a new window environment with a given ID and
.Tk.subwin creates a new window which is a sub-window of a given
parent window.
.TkUp is a logical flag to indicate whether the Tk widget
system is active; if FALSE, only the Tcl interpreter is available.
tkdestroy destroys a window and also removes the reference to a
window from its parent.
is.tkwin can be used to test whether a given object is a window
environment.
tclVar creates a new Tcl variable and initializes it to
init. An R object of class tclVar is created to
represent it. Using as.character on the object returns the Tcl
variable name. Accessing the Tcl variable from R is done using the
tclvalue function, which can also occur on the left-hand side of
assignments. If tclvalue is passed an argument which is not a
tclVar object, then it will assume that it is a character string
explicitly naming global Tcl variable. Tcl variables created by
tclVar are uniquely named and automatically unset by the
garbage collector when the representing object is no longer in use.
tclArray creates a new Tcl array and initializes it to the empty
array. An R object of class tclArray and inheriting from class
tclVar is created to represent it. You can access elements of
the Tcl array using indexing with [[ or $, which also
allow replacement forms. Notice that Tcl arrays are associative by
nature and hence unordered; indexing with a numeric index i
refers to the element with the name
as.character(i). Multiple indices are pasted together separated
by commas to form a single name. You can query the
length and the set of names in an array using methods for
length and names, respectively; these cannot
meaningfully be set so assignment forms exist only to print an error
message.
It is possible to access Tcl's ‘dual-ported’ objects directly,
thus avoiding parsing and deparsing of their string representation.
This works by using objects of class tclObj. The string
representation of such objects can be extracted (but not set) using
tclvalue and conversion to vectors of mode "character",
"double", "integer", "logical", and "raw"
is performed using the standard coercion functions as.character,
etc. Conversely, such
vectors can be converted using as.tclObj. There is an
ambiguity as to what should happen for length one vectors, controlled
by the drop argument; there are cases where the distinction
matters to Tcl, although mostly it treats them equivalently. Notice
that tclvalue and as.character differ on an object whose
string representation has embedded spaces, the former is sometimes to
be preferred, in particular when applied to the result of
tclread, tkgetOpenFile, and similar functions. The
as.raw method returns a raw vector or a list of raw vectors and
can be used to return binary data from Tcl.
The object behind a tclVar object is extracted using
tclObj(x) which also allows an assignment form, in which the
right hand side of the assignment is automatically converted using
as.tclObj. There is a print method for tclObj objects;
it prints ‘<Tcl>’ followed by the string representation of the
object. Notice that as.character on a tclVar object is
the name of the corresponding Tcl variable and not the value.
Tcl packages can be loaded with tclRequire; it may be necessary
to add the directory where they are found to the Tcl search path with
addTclPath. The return value is a class "tclObj" object
if it succeeds, or FALSE if it fails (when a warning is
issued). To see the current search path as an R character vector,
use:
strsplit(tclvalue('auto_path'), " ")[[1]]
The Tcl version (including patch level) is returned as a character
string (such as "8.6.3").
Note
Strings containing unbalanced braces are currently not handled well in many circumstances.
See Also
TkWidgets,
TkCommands,
TkWidgetcmds.
capabilities("tcltk") to see if Tcl/Tk support was
compiled into this build of R.
Examples
tclVersion()
.Tcl("format \"%s\n\" \"Hello, World!\"")
f <- function() cat("HI!\n")
.Tcl.callback(f)
.Tcl.args(text = "Push!", command = f) # NB: Different address
xyzzy <- tclVar(7913)
tclvalue(xyzzy)
tclvalue(xyzzy) <- "foo"
as.character(xyzzy)
tcl("set", as.character(xyzzy))
## Not run:
## These cannot be run by example() but should be OK when pasted
## into an interactive R session with the tcltk package loaded
top <- tktoplevel() # a Tk widget, see Tk-widgets
ls(envir = top$env, all.names = TRUE)
## End(Not run)
ls(envir = .TkRoot$env, all.names = TRUE) # .Tcl.args put a callback ref in here