| TclInterface {tcltk} | R Documentation |
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.
win |
a window structure |
x |
an object |
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 |
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 a text string.
.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 -
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 the function will exist at that 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 subwindows 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 subwindow of a given
parent window.
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 sie 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.
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", or "integer". Conversely, such vectors can be
converted using as.tclObj. The object behind a Tcl variable
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.
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.
Strings containing unbalanced braces are currently not handled well in many circumstances.
TkWidgets,
TkCommands,
TkWidgetcmds.
capabilities("tcltk"
## Not run:
## These cannot be run by example() but should be OK when pasted
## into an interactive R session with the tcltk package loaded
.Tcl("format \"%s\n\" \"Hello, World!\"")
f <- function()"HI!"
.Tcl.callback(f)
.Tcl.args(text="Push!", command=f) # NB: Different address
xyzzy <- tclVar(7913)
tclvalue(xyzzy)
tclvalue(xyzzy) <- "foo"
as.character(xyzzy)
tkcmd("set", as.character(xyzzy))
top <- tktoplevel() # a Tk widget, see Tk-widgets
ls(envir=top$env, all=TRUE)
ls(envir=.TkRoot$env, all=TRUE)# .Tcl.args put a callback ref in here
## End(Not run)