Alacron FAST-UXGA, Technical Product Manual, Page: 21 / 28

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ALACRON’S STRETCH/NEXPERIA OCX
Many of the Alacron Stretch applications are based on an ActiveX Control (OCX). The control
masks the details of using ALRT to load and communicate with a processor. The interface is
based on a callback scheme which provides information to the user, and an interface definition
which performs all the functions provided by the ALRT runtime environment.
The OCX does not provide support for abstractions such as images and ring buffers it only
provides a thin layer over the ALRT driver and drive library, while simplifying their use. In
addition it does not provide support for the old legacy interfaces, which do not perform well in
any case, and to a degree can not be supported due to the way the Stretch provides access to
its memory.
If you do not know what an OCX is, the short definition is it is a component object (Com
Object), which supports a number of standard interfaces required for it to be instantiated into a
host program in a standard control site in an application.
The StretchBoard.OCX is implemented with Microsoft ATL.
One possible drawback of the OCX is it does not use 'standard' events to signal events to the
user. It uses a callback which is higher performance, but will not work with older versions of
Visual Basic.
The OCX was not created for Visual Basic users and does not have a lot of testing time in that
local. It is used by Alacron in C++ applications.
I
NTERFACES
IS
TRETCH
B
OARD
The definition of the interface is:
[
object,
uuid(D5D4FE04-5254-430E-9E19-03313AF769A6),
dual,
helpstring("IStretchBoard Interface"),
pointer_default(unique)
]
__interface IStretchBoard : public IDispatch
{
[propput, bindable, requestedit, id(DISPID_VALID)]
HRESULT Valid([in]VARIANT_BOOL vbool);
[propget, bindable, requestedit, id(DISPID_VALID)]
HRESULT Valid([out, retval]VARIANT_BOOL* pbool);
[propput, bindable, requestedit, id(DISPID_READYSTATE)]
HRESULT ReadyState([in] long state);
[propget, bindable, requestedit, id(DISPID_READYSTATE)]
HRESULT ReadyState([out, retval] long * pstate);
[propget, id( 1), helpstring("property pid")]
HRESULT pid ([out, retval] LONG* pVal);
[propget, id( 2), helpstring("property rval")]