pTk(3) User Contributed Perl Documentation pTk(3)
NAME
Tk2portableTk - how to make your Tk source portable to other
interpreted languages.
Author
Ilya Zakharevich <ilya@math.ohio-state.edu> has contributed most of
this document. Many thanks.
DESCRIPTION
PortableTk is an attempt to make Tk useful from other languages.
Currently tk4.0 runs under Perl using this approach. Below, Lang is the
notation for an external language to which PortableTk glues Tk code.
The main problem with using the code developed for TCL with different
languages is the absence of data types: almost anything is "char*". It
makes automatic translation hopeless. However, if you "typedef" several
new symbols to be "char*", you can still use your code in TCL, and it
will make the automatic translation possible.
Another problem with the approach that "everything is a string" is
impossibility to have a result that says "NotApplicable" without
setting an error. Thus different Tk command return different string
values that mean "error happened", like "", " " or "??". Other
languages can be more flexible, so in portableTk you should inform the
compiler that what you want to return means "error" (see "Setting
variables").
Currently PortableTk uses several different approachs to simplify
translation: several TCL functions that are especially dangerous to use
are undefined, so you can easily find places that need to be updated to
use Language-independent functions based on compiler warnings.
Eventually a way to use these Language-independent functions under
proper TCL will be also provided. The end of this document provides a
starting point for such a project.
Structure of pTk, porting your code
pTk, that is a port of Tk, is very special with respect to porting of
other code to portableTk. The problem is that currently there is very
little hope to merge the modifications back into Tk, so a special
strategy is needed to maintain this port. Do not use this strategy to
port your own code.
pTk is produced from Tk via a two-step process: first, some manual
editing (the result is in the subdirectory "mTk"), and second,
automatic conversion by the "munge" script (written in Perl). Thus the
subdirectory "pTk/mTk" contains code with minimal possible difference
from the virgin Tk code, so it is easier to merge(1) the differences
between Tk versions into modified code.
It looks like the strategy for a portable code should be exactly
opposite: starting from TCL-based code, apply "munge", and then hand-
edit the resulting code. Probably it is also possible to target your
code to portableTk from scratch, since this will make it possible to
run it under a lot of Languages.
The only reason anyone would like to look into contents of "pTk/mTk"
directory is to find out which constructs are not supported by "munge".
On the other hand, "pTk" directory contains code that is conformant to
portableTk, so you can look there to find example code.
"munge" is the script that converts most common Tk constructs to their
"portableTk" equivalent. For your code to qualify, you should follow Tk
conventions on indentation and names of variables, in particular, the
array of arguments for the "...CmdProc" should be called "argv".
For details on what "munge" can do, see "Translation of some TCL
functions".
PortableTk API
Checking what you are running under
PortableTk provides a symbol "????". If this symbol is defined, your
source is compiled with it.
New types of configuration options
PortableTk defines several new types of configuration options:
TK_CONFIG_CALLBACK
TK_CONFIG_LANGARG
TK_CONFIG_SCALARVAR
TK_CONFIG_HASHVAR
TK_CONFIG_ARRAYVAR
TK_CONFIG_IMAGE
You should use them instead of TK_CONFIG_STRING whenever appropriate.
This allows your application to receive a direct representation of the
corresponding resource instead of the string representation, if this is
possible under given language.
???? It looks like "TK_CONFIG_IMAGE" and "TK_CONFIG_SCALARVAR" set
variables of type "char*".
Language data
The following data types are defined:
"Tcl_Obj *"
is the main datatype of the language. This is a type that your C
function gets pointers to for arguments when the corresponding Lang
function is called. The corresponding config type is
"TK_CONFIG_LANGARG".
This is also a type that keeps information about contents of Lang
variable.
"Var"
Is a substitute for a "char *" that contains name of variable. In
Lang it is an object that contains reference to another Lang
variable.
"LangResultSave"
????
"LangCallback"
"LangCallback*" a substitute for a "char *" that contains command
to call. The corresponding config type is "TK_CONFIG_CALLBACK".
"LangFreeProc"
It is the type that the "Lang_SplitList" sets. Before you call it,
declare
Args *args;
LangFreeProc *freeProc = NULL;
...
code = Lang_SplitList(interp, value,
&argc, &args, &freeProc);
After you use the split values, call
if (args != NULL && freeProc) (*freeProc)(argc,args);
It is not guaranteed that the "args" can survive deletion of
"value".
Conversion
The following macros and functions are used for conversion between
strings and the additional types:
LangCallback * LangMakeCallback(Tcl_Obj *)
Tcl_Obj * LangCallbackArg(LangCallback *)
char * LangString(Tcl_Obj *)
After you use the result of LangCallbackArg(), you should free it with
"freeProc" "LANG_DYNAMIC" (it is not guaranteed that any change of
"Tcl_Obj *" will not be reflected in <LangCallback>, so you cannot do
LangSet...() in between, and you should reset it to "NULL" if you want
to do any further assignments to this "Tcl_Obj *").
The following function returns the "Tcl_Obj *" that is a reference to
"Var":
Tcl_Obj * LangVarArg(Var)
???? It is very anti-intuitive, I hope the name is changed.
int LangCmpCallback(LangCallback *a,Tcl_Obj * b)
(currently only a stub), and, at last,
LangCallback * LangCopyCallback(LangCallback *)
Callbacks
Above we have seen the new datatype "LangCallback" and the
corresponding Config option "TK_CONFIG_CALLBACK". The following
functions are provided for manipulation of "LangCallback"s:
void LangFreeCallback(LangCallback *)
int LangDoCallback(Tcl_Interp *,LangCallback *,
int result,int argc, char *format,...)
The argument "format" of "LangDoCallback" should contain a string that
is suitable for "sprintf" with optional arguments of "LangDoCallback".
"result" should be false if result of callback is not needed.
int LangMethodCall(Tcl_Interp *,Tcl_Obj *,char *method,
int result,int argc,...)
????
Conceptually, "LangCallback*" is a substitute for ubiquitous "char *"
in TCL. So you should use "LangFreeCallback" instead of "ckfree" or
"free" if appropriate.
Setting variables
void LangFreeArg (Tcl_Obj *, Tcl_FreeProc *freeProc)
Tcl_Obj * LangCopyArg (Tcl_Obj *);
void Tcl_AppendArg (Tcl_Interp *interp, Tcl_Obj *)
void LangSetString(Tcl_Obj * *, char *s)
void LangSetDefault(Tcl_Obj * *, char *s)
These two are equivalent unless s is an empty string. In this case
"LangSetDefault" behaves like "LangSetString" with "s==NULL", i.e., it
sets the current value of the Lang variable to be false.
void LangSetInt(Tcl_Obj * *,int)
void LangSetDouble(Tcl_Obj * *,double)
The Lang functions separate uninitialized and initialized data
comparing data with "NULL". So the declaration for an "Tcl_Obj *"
should look like
Tcl_Obj * arg = NULL;
if you want to use this "arg" with the above functions. After you are
done, you should use "LangFreeArg" with "TCL_DYNAMIC" as "freeProc".
Language functions
Use
"int LangNull(Tcl_Obj *)"
to check that an object is false;
"int LangStringMatch(char *string, Tcl_Obj * match)"
????
"void LangExit(int)"
to make a proper shutdown;
"int LangEval(Tcl_Interp *interp, char *cmd, int global)"
to call Lang "eval";
"void Lang_SetErrorCode(Tcl_Interp *interp,char *code)"
"char *Lang_GetErrorCode(Tcl_Interp *interp)"
"char *Lang_GetErrorInfo(Tcl_Interp *interp)"
"void LangCloseHandler(Tcl_Interp *interp,Tcl_Obj * arg,FILE
*f,Lang_FileCloseProc *proc)"
currently stubs only;
"int LangSaveVar(Tcl_Interp *,Tcl_Obj * arg,Var *varPtr,int type)"
to save the structure "arg" into Lang variable *varPtr;
"void LangFreeVar(Var var)"
to free the result;
"int LangEventCallback(Tcl_Interp *,LangCallback *,XEvent *,KeySym)"
????
"int LangEventHook(int flags)"
"void LangBadFile(int fd)"
"int LangCmpConfig(char *spec, char *arg, size_t length)"
unsupported????;
"void Tcl_AppendArg (Tcl_Interp *interp, Tcl_Obj *)"
Another useful construction is
Tcl_Obj * variable = LangFindVar(interp, Tk_Window tkwin, char *name);
After using the above function, you should call
LangFreeVar(Var variable);
???? Note discrepancy in types!
If you want to find the value of a variable (of type "Tcl_Obj *") given
the variable name, use "Tcl_GetVar(interp, varName, flags)". If you are
interested in the string value of this variable, use
"LangString(Tcl_GetVar(...))".
To get a C array of "Tcl_Obj *" of length "n", use
Tcl_Obj * *args = LangAllocVec(n);
...
LangFreeVec(n,args);
You can set the values of the "Tcl_Obj *"s using "LangSet..."
functions, and get string value using "LangString".
If you want to merge an array of "Tcl_Obj *"s into one "Tcl_Obj *"
(that will be an array variable), use
result = Tcl_Merge(listLength, list);
Translation of some TCL functions
We mark items that can be dealt with by "munge" by Autoconverted.
"Tcl_AppendResult"
does not take "(char*)NULL", but "NULL" as delimiter.
Autoconverted.
"Tcl_CreateCommand", "Tcl_DeleteCommand"
"Tk_CreateWidget", "Tk_DeleteWidget", the second argument is the
window itself, not the pathname. Autoconverted.
"sprintf(interp->result, "%d %d %d %d",...)"
"Tcl_IntResults(interp,4,0,...)". Autoconverted.
"interp->result = "1";"
"Tcl_SetResult(interp,"1", TCL_STATIC)". Autoconverted.
Reading "interp->result"
"Tcl_GetResult(interp)". Autoconverted.
"interp->result = Tk_PathName(textPtr->tkwin);"
"Tk_WidgetResult(interp,textPtr->tkwin)". Autoconverted.
Sequence "Tcl_PrintDouble, Tcl_PrintDouble, ..., Tcl_AppendResult"
Use a single command
void Tcl_DoubleResults(Tcl_Interp *interp, int append,
int argc,...);
"append" governs whether it is required to clear the result first.
A similar command for "int" arguments is "Tcl_IntResults".
"Tcl_SplitList"
Use "Lang_SplitList" (see the description above).
Translation back to TCL
To use your portableTk program with TCL, put
#include "ptcl.h"
before inclusion of "tk.h", and link the resulting code with
"ptclGlue.c".
These files currently implement the following:
Additional config types:
TK_CONFIG_CALLBACK
TK_CONFIG_LANGARG
TK_CONFIG_SCALARVAR
TK_CONFIG_HASHVAR
TK_CONFIG_ARRAYVAR
TK_CONFIG_IMAGE
Types:
Var, Tcl_Obj *, LangCallback, LangFreeProc.
Functions and macros:
Lang_SplitList, LangString, LangSetString, LangSetDefault,
LangSetInt, LangSetDouble Tcl_ArgResult, LangCallbackArg,
LangSaveVar, LangFreeVar,
LangFreeSplitProc, LangFreeArg, Tcl_DoubleResults, Tcl_IntResults,
LangDoCallback, Tk_WidgetResult, Tcl_CreateCommand,
Tcl_DeleteCommand, Tcl_GetResult.
Current implementation contains enough to make it possible to compile
"mTk/tkText*.[ch]" with the virgin Tk.
New types of events ????
PortableTk defines following new types of events:
TK_EVENTTYPE_NONE
TK_EVENTTYPE_STRING
TK_EVENTTYPE_NUMBER
TK_EVENTTYPE_WINDOW
TK_EVENTTYPE_ATOM
TK_EVENTTYPE_DISPLAY
TK_EVENTTYPE_DATA
and a function
char * Tk_EventInfo(int letter,
Tk_Window tkwin, XEvent *eventPtr,
KeySym keySym, int *numPtr, int *isNum, int *type,
int num_size, char *numStorage)
Checking for trouble
If you start with working TCL code, you can start convertion using the
above hints. Good indication that you are doing is OK is absence of
"sprintf" and "sscanf" in your code (at least in the part that is
working with interpreter).
Additional API
What is described here is not included into base portableTk
distribution. Currently it is coded in TCL and as Perl macros (core is
coded as functions, so theoretically you can use the same object files
with different interpreted languages).
"ListFactory"
Dynamic arrays in TCL are used for two different purposes: to construct
strings, and to construct lists. These two usages will have separate
interfaces in other languages (since list is a different type from a
string), so you should use a different interface in your code.
The type for construction of dynamic lists is "ListFactory". The API
below is a counterpart of the API for construction of dynamic lists in
TCL:
void ListFactoryInit(ListFactory *)
void ListFactoryFinish(ListFactory *)
void ListFactoryFree(ListFactory *)
Tcl_Obj * * ListFactoryArg(ListFactory *)
void ListFactoryAppend(ListFactory *, Tcl_Obj * *arg)
void ListFactoryAppendCopy(ListFactory *, Tcl_Obj * *arg)
ListFactory * ListFactoryNewLevel(ListFactory *)
ListFactory * ListFactoryEndLevel(ListFactory *)
void ListFactoryResult(Tcl_Interp *, ListFactory *)
The difference is that a call to "ListFactoryFinish" should precede the
actual usage of the value of "ListFactory", and there are two different
ways to append an "Tcl_Obj *" to a "ListFactory":
ListFactoryAppendCopy() guarantees that the value of "arg" is copied to
the list, but ListFactoryAppend() may append to the list a reference to
the current value of "arg". If you are not going to change the value of
"arg" after appending, the call to ListFactoryAppend may be quicker.
As in TCL, the call to ListFactoryFree() does not free the
"ListFactory", only the objects it references.
The functions ListFactoryNewLevel() and ListFactoryEndLevel() return a
pointer to a "ListFactory" to fill. The argument of
ListFactoryEndLevel() cannot be used after a call to this function.
DStrings
Production of strings are still supported in portableTk.
Accessing "Tcl_Obj *"s
The following functions for getting a value of an "Tcl_Obj *" may be
provided:
double LangDouble(Tcl_Obj *)
int LangInt(Tcl_Obj *)
long LangLong(Tcl_Obj *)
int LangIsList(Tcl_Obj * arg)
The function LangIsList() is supported only partially under TCL, since
there is no data types. It checks whether there is a space inside the
string "arg".
Assigning numbers to "Tcl_Obj *"s
While LangSetDouble() and LangSetInt() are supported ways to assign
numbers to assign an integer value to a variable, for the sake of
efficiency under TCL it is supposed that the destination of these
commands was massaged before the call so it contains a long enough
string to sprintf() the numbers inside it. If you are going to
immediately use the resulting "Tcl_Obj *", the best way to do this is
to declare a buffer in the beginning of a block by
dArgBuffer;
and assign this buffer to the "Tcl_Obj *" by
void LangSetDefaultBuffer(Tcl_Obj * *)
You can also create the buffer(s) manually and assign them using
void LangSetBuffer(Tcl_Obj * *, char *)
This is the only choice if you need to assign numeric values to several
"Tcl_Obj *"s simultaneously. The advantage of the first approach is
that the above declarations can be made "nop"s in different languages.
Note that if you apply "LangSetDefaultBuffer" to an "Tcl_Obj *" that
contains some value, you can create a leak if you do not free that
"Tcl_Obj *" first. This is a non-problem in real languages, but can be
a trouble in "TCL", unless you use only the above API.
Creating new "Tcl_Obj *"s
The API for creating a new "Tcl_Obj *" is
void LangNewArg(Tcl_Obj * *, LangFreeProc *)
The API for creating a new "Tcl_Obj *" is absent. Just initialize
"Tcl_Obj *" to be "NULL", and apply one of "LangSet..." methods.
After you use this "Tcl_Obj *", it should be freed thusly:
"LangFreeArg(arg, freeProc)".
Evaluating a list
Use
int LangArgEval(Tcl_Interp *, Tcl_Obj * arg)
Here "arg" should be a list to evaluate, in particular, the first
element should be a "LangCallback" massaged to be an "Tcl_Obj *". The
arguments can be send to the subroutine by reference or by value in
different languages.
Getting result as "Tcl_Obj *"
Use "Tcl_ArgResult". It is not guaranteed that result survives this
operation, so the "Tcl_Obj *" you get should be the only mean to access
the data from this moment on. After you use this "Tcl_Obj *", you
should free it with "freeProc" "LANG_DYNAMIC" (you can do LangSet...()
in between).
perl v5.18.0 2010-05-29 pTk(3)
perl-Tk 804.030_502 - Generated Sat Aug 17 18:10:21 CDT 2013