Партнёры:
Хостинг:
_________________________________________________________________
NAME
Tcl_LinkVar, Tcl_UnlinkVar, Tcl_UpdateLinkedVar - link Tcl
variable to C variable
SYNOPSIS
#include <tcl.h>
int
Tcl_LinkVar(interp, varName, addr, type)
Tcl_UnlinkVar(interp, varName)
Tcl_UpdateLinkedVar(interp, varName)
ARGUMENTS
Tcl_Interp *interp (in) Interpreter that contains
varName. Also used by
Tcl_LinkVar to return
error messages.
char *varName (in) Name of global variable.
Must be in writable
memory: Tcl may make tem-
porary modifications to it
while parsing the variable
name.
char *addr (in) Address of C variable that
is to be linked to var-
Name.
int type (in) Type of C variable. Must
be one of TCL_LINK_INT,
TCL_LINK_DOUBLE,
TCL_LINK_BOOLEAN, or
TCL_LINK_STRING, option-
ally OR'ed with
TCL_LINK_READ_ONLY to make
Tcl variable read-only.
_________________________________________________________________
DESCRIPTION
Tcl_LinkVar uses variable traces to keep the Tcl variable
named by varName in sync with the C variable at the address
given by addr. Whenever the Tcl variable is read the value
of the C variable will be returned, and whenever the Tcl
variable is written the C variable will be updated to have
the same value. Tcl_LinkVar normally returns TCL_OK; if an
error occurs while setting up the link (e.g. because varName
is the name of array) then TCL_ERROR is returned and the
interpreter's result contains an error message.
The type argument specifies the type of the C variable, and
must have one of the following values, optionally OR'ed with
TCL_LINK_READ_ONLY:
TCL_LINK_INT
The C variable is of type int. Any value written into
the Tcl variable must have a proper integer form
acceptable to Tcl_GetInt; attempts to write non-
integer values into varName will be rejected with Tcl
errors.
TCL_LINK_DOUBLE
The C variable is of type double. Any value written
into the Tcl variable must have a proper real form
acceptable to Tcl_GetDouble; attempts to write non-
real values into varName will be rejected with Tcl
errors.
TCL_LINK_BOOLEAN
The C variable is of type int. If its value is zero
then it will read from Tcl as ``0''; otherwise it will
read from Tcl as ``1''. Whenever varName is modified,
the C variable will be set to a 0 or 1 value. Any
value written into the Tcl variable must have a proper
boolean form acceptable to Tcl_GetBoolean; attempts to
write non-boolean values into varName will be rejected
with Tcl errors.
TCL_LINK_STRING
The C variable is of type char *. If its value is not |
null then it must be a pointer to a string allocated |
with Tcl_Alloc. Whenever the Tcl variable is modified
the current C string will be freed and new memory will
be allocated to hold a copy of the variable's new
value. If the C variable contains a null pointer then
the Tcl variable will read as ``NULL''.
If the TCL_LINK_READ_ONLY flag is present in type then the
variable will be read-only from Tcl, so that its value can
only be changed by modifying the C variable. Attempts to
write the variable from Tcl will be rejected with errors.
Tcl_UnlinkVar removes the link previously set up for the
variable given by varName. If there does not exist a link
for varName then the procedure has no effect.
Tcl_UpdateLinkedVar may be invoked after the C variable has
changed to force the Tcl variable to be updated immediately.
In many cases this procedure is not needed, since any
attempt to read the Tcl variable will return the latest
value of the C variable. However, if a trace has been set
on the Tcl variable (such as a Tk widget that wishes to
display the value of the variable), the trace will not
trigger when the C variable has changed.
Tcl_UpdateLinkedVar ensures that any traces on the Tcl vari-
able are invoked.
KEYWORDS
boolean, integer, link, read-only, real, string, traces,
variable
|
Закладки на сайте Проследить за страницей |
Created 1996-2024 by Maxim Chirkov Добавить, Поддержать, Вебмастеру |