how to declare a pointer

[Simon]

I'm a js newbie trying to use some very simple js to call an ActiveX
object's methods.
I need to use a pointer to call an embedded ActiveX object's method to
receive a number.
As I understand it, js is typeless so how can I get a variable to be a
pointer type?
Passing var i as the parameter gets an undefined value in return.

Thanks IA, Simon

[Michael Winter]

On Sun, 4 Apr 2004 19:35:24 +0000 (UTC), Simon
<si****************@btinternet.please.com> wrote:

I'm a js newbie trying to use some very simple js to call an ActiveX
object's methods.
I need to use a pointer to call an embedded ActiveX object's method to
receive a number.
As I understand it, js is typeless so how can I get a variable to be a
pointer type?
Passing var i as the parameter gets an undefined value in return.

JavaScript doesn't have pointers[1]. The closest thing is references, but
they only exist for passing objects and arrays as function parameters.
Primitive types (booleans, string, numbers) are always passed by value.

Without pointing to the documentation for this ActiveX object, or
describing it in more detail, there isn't much help anyone can provide.

Mike
[1] Microsoft's DHTML Reference documentation talks about them all the
time, but there's a lot of mistakes in those pages, and using the word
"pointer" is one of them.

--
Michael Winter
M.******@blueyonder.co.invalid (replace ".invalid" with ".uk" to reply)

[Simon]

>

JavaScript doesn't have pointers[1]. The closest thing is references, but
they only exist for passing objects and arrays as function parameters.
Primitive types (booleans, string, numbers) are always passed by value.

Without pointing to the documentation for this ActiveX object, or
describing it in more detail, there isn't much help anyone can provide.

Mike,

The ActiveX object is one of my own so I can change the parameters as
necessary. Currently it has a function that takes 2 paramters, one in is a
WideString (in) and the other is a Variant pointer (out). It was written
purely as an exercise to see if I can get a returned variable in javascript.
The ActiveX limitation is that 'out' type parameters must be pointers.
It may work if I can pass a variable by reference as a reference is an
address of the variable much like a pointer? Is there a way to reference a
variable in js or does it happen automatically when the variable is passed
to a function?

Thanks, Simon

[Michael Winter]

On Mon, 5 Apr 2004 08:11:04 +0000 (UTC), Simon
<si****************@btinternet.please.com> wrote:

[snip]

The ActiveX object is one of my own so I can change the parameters as
necessary. Currently it has a function that takes 2 paramters, one in is
a WideString (in) and the other is a Variant pointer (out). It was
written purely as an exercise to see if I can get a returned variable in
javascript.
It would probably be best to use a return value, rather than attempting to
pass by reference.
The ActiveX limitation is that 'out' type parameters must be pointers.
It may work if I can pass a variable by reference as a reference is an
address of the variable much like a pointer?
There is no concept of "addresses" in JavaScript.
Is there a way to reference a variable in js or does it happen
automatically when the variable is passed to a function?

References are always used with objects and arrays, whether a function
call is involved or not. However, they are only used with objects and
arrays. You can't specify how a variable is passed during a call.

Mike

--
Michael Winter
M.******@blueyonder.co.invalid (replace ".invalid" with ".uk" to reply)

[Simon]

> It would probably be best to use a return value, rather than attempting to

pass by reference.
Functions of automation interfaces mush have a return type of HResult (a
least that is what my IDE tells me), so I cannot emply this strategy.
References are always used with objects and arrays, whether a function
call is involved or not. However, they are only used with objects and
arrays. You can't specify how a variable is passed during a call.

Looks like it won't work then. Thanks for your help.

[Dag Sunde]

"Simon" <si****************@btinternet.please.com> wrote in message
news:c4**********@titan.btinternet.com...

It would probably be best to use a return value, rather than attempting to pass by reference.

Functions of automation interfaces mush have a return type of HResult (a
least that is what my IDE tells me), so I cannot emply this strategy.

References are always used with objects and arrays, whether a function
call is involved or not. However, they are only used with objects and
arrays. You can't specify how a variable is passed during a call.

Looks like it won't work then. Thanks for your help.

Do I understand you corredtly, when I sat that you have made a (visible)
ActiveX component that you display on a web-bage like this:

<object
classid="clsid:E217D189-AEA5-4F62-A044-A716C202474B"
id="activeX">
</object>

....and that you want to access some (public) value or call a method in
that activeX component from JavaScript on the same page?

like this(?):

<script type="text/javascript">
function Test()
{
var myObj = document.getElementById("activeX")
alert(myObj.getValue());
}
</script>

If so, that is quite possible, and JavaScript can call any public method,
and access any public member of the activeX control. And functions are
*not* limited to the HResult type!

--
Dag.

[Simon]

>

Do I understand you corredtly, when I sat that you have made a (visible)
ActiveX component that you display on a web-bage like this:

<object
classid="clsid:E217D189-AEA5-4F62-A044-A716C202474B"
id="activeX">
</object>

Yep
...and that you want to access some (public) value or call a method in
that activeX component from JavaScript on the same page?

like this(?):

<script type="text/javascript">
function Test()
{
var myObj = document.getElementById("activeX")
alert(myObj.getValue());
}
</script>
Near enough, yes.

If so, that is quite possible, and JavaScript can call any public method,
and access any public member of the activeX control. And functions are
*not* limited to the HResult type!

The return of an automation interface method is limited to HResult in
Delphi, I don't know why.

I have no problem getting and setting properties and I have no problem
calling methods. The issue is getting a return (out) parameter from the
method.

eg. Method = AddText(in Text: BSTR; out Index: long * )

I can call the above method and it will execute, but I cannot get the out
parameter.
In Delphi the out parameters must be pointer types.

Any ideas?

Simon

[Dag Sunde]

"Simon" <si****************@btinternet.please.com> wrote in message
news:c4**********@hercules.btinternet.com...
<snipped />

The return of an automation interface method is limited to HResult in
Delphi, I don't know why.

I have no problem getting and setting properties and I have no problem
calling methods. The issue is getting a return (out) parameter from the
method.

eg. Method = AddText(in Text: BSTR; out Index: long * )

I can call the above method and it will execute, but I cannot get the out
parameter.
In Delphi the out parameters must be pointer types.

Any ideas?

Let's clear up a couple of things first...

The HRESULT return type of an automation interface does not have
anything to do with your parameters of return value, but is the result
of the automation process (ie. success/error code).

The Delphi help file say that:
"If a parameter type is specified as a Pointer type, the Type Library
editor usually translates that type into a variable parameter. When the
type library is saved, the variable parameter's associated ElemDesc's
IDL flags are marked IDL_FIN or IDL_FOUT."

// ---------- copied from Delphi help...----------------
DevGuide: Developing COM-based applications
Valid types

Topic Groups See Also

In the Type Library editor, you use different type identifiers, depending on
whether you are working in IDL or Delphi. Specify the language you want to
use in the Environment options dialog.

The following types are valid in a type library for COM development. The
Automation compatible column specifies whether the type can be used by an
interface that has its Automation or Dispinterface flag checked. These are
the types that COM can marshal via the type library automatically.

Delphi type IDL type variant type Automation compatible Description
Smallint short VT_I2 Yes 2-byte signed integer
Integer long VT_I4 Yes 4-byte signed integer
Single single VT_R4 Yes 4-byte real
Double double VT_R8 Yes 8-byte real
Currency CURRENCY VT_CY Yes currency
TDateTime DATE VT_DATE Yes date
WideString BSTR VT_BSTR Yes binary string
IDispatch IDispatch VT_DISPATCH Yes pointer to IDispatch interface
SCODE SCODE VT_ERROR Yes Ole Error Code
WordBool VARIANT_BOOL VT_BOOL Yes True = -1, False = 0
OleVariant VARIANT VT_VARIANT Yes Ole Variant
IUnknown IUnknown VT_UNKNOWN Yes pointer to IUnknown interface
Shortint byte VT_I1 No 1 byte signed integer
Byte unsigned char VT_UI1 Yes 1 byte unsigned integer
Word unsigned short VT_UI2 Yes* 2 byte unsigned integer
LongWord unsigned long VT_UI4 Yes* 4 byte unsigned integer
Int64 __int64 VT_I8 No 8 byte signed integer
Largeuint uint64 VT_UI8 No 8 byte unsigned integer
SYSINT int VT_INT Yes* system dependent integer (Win32=Integer)
SYSUINT unsigned int VT_UINT Yes* system dependent unsigned integer
HResult HRESULT VT_HRESULT No 32 bit error code
Pointer VT_PTR -> VT_VOID No untyped pointer
SafeArray SAFEARRAY VT_SAFEARRAY No OLE Safe Array
PChar LPSTR VT_LPSTR No pointer to Char
PWideChar LPWSTR VT_LPWSTR No pointer to WideChar
* Word, LongWord, SYSINT, and SYSUINT may be Automation-compatible with some
applications.
See safe arrays for more information about the SAFEARRAY Variant type.

Note

The Byte (VT_UI1) is Automation-compatible, but is not allowed in a Variant
or OleVariant since many Automation servers do not handle this value
correctly.
Besides these IDL types, any interfaces and types defined in the library or
defined in referenced libraries can be used in a type library definition.
The Type Library editor stores type information in the generated type
library (.TLB) file in binary form.
If a parameter type is specified as a Pointer type, the Type Library editor
usually translates that type into a variable parameter. When the type
library is saved, the variable parameter's associated ElemDesc's IDL flags
are marked IDL_FIN or IDL_FOUT.

Often, ElemDesc IDL flags are not marked by IDL_FIN or IDL_FOUT when the
type is preceded with a Pointer. Or, in the case of dispinterfaces, IDL
flags are not typically used. In these cases, you may see a comment next to
the variable identifier such as {IDL_None} or {IDL_In}. These comments are
used when saving a type library to correctly mark the IDL flags.

--
Dag.

[Simon]

<snipped>

Let's clear up a couple of things first...

The HRESULT return type of an automation interface does not have
anything to do with your parameters of return value, but is the result
of the automation process (ie. success/error code).

Ok.
The Delphi help file say that:

<snipped>

Yes.

So back to my original question - how can I use an IDL_FOUT parameter in
javascipt?

Activex:
eg. Method = AddText(in Text: BSTR; out Index: long * )

Js:
var i;
i = 0;
activeX.Method('hello', i);
//i still = 0

Thanks, Simon

[Dag Sunde]

"Simon" <si****************@btinternet.please.com> wrote in message
news:c5*********@hercules.btinternet.com...

<snipped>

Let's clear up a couple of things first...

The HRESULT return type of an automation interface does not have
anything to do with your parameters of return value, but is the result
of the automation process (ie. success/error code).

Ok.

The Delphi help file say that:

<snipped>

Yes.

So back to my original question - how can I use an IDL_FOUT parameter in
javascipt?

Activex:
eg. Method = AddText(in Text: BSTR; out Index: long * )

Js:
var i;
i = 0;
activeX.Method('hello', i);
//i still = 0

Have you tried declaring it like:

HRESULT = _stdcall AddText([in] BSTR Text, [out, retval] long * Index);
(in the "View -> Type Library" menu...)

and use it like:

var i = activeX.method('hello');

???

--
Dag.

[Simon]

>

Have you tried declaring it like:

HRESULT = _stdcall AddText([in] BSTR Text, [out, retval] long * Index); (in the "View -> Type Library" menu...)

and use it like:

var i = activeX.method('hello');

???

--
Dag.

I tried that and it works with the out param set as the retval.
Thanks Dag.