PDFlib 8 Windows COM/.NET Tutorial

2.3 COM Binding
COM (Component Object Model) 1 is a language-independent standard for interoperable
software components. The COM implementation of PDFlib is built as a DLL based on the
PDFlib core. The wrapper DLL calls the PDFlib core functions and is responsible for communicating
with the underlying COM machinery, registration and type library issues,
and COM exception handling. The PDFlib COM wrapper can technically be characterized
as follows (don’t worry if you are not familiar with all of these terms – they are not required
for using PDFlib):
> PDFlib acts as a Win32 in-process COM server component (also known as an automation
server) without any user interface.
> PDFlib is a »both-threaded« component, i.e., it is treated as both an apartmentthreaded
as well as a free-threaded component. In addition, PDFlib aggregates a freethreaded
marshaller. In simple terms, clients can use the PDFlib object directly (instead
of going through a proxy/stub pair) which boosts performance.
> The PDFlib binary pdflib_com.dll is a self-registering DLL with a type library.
> PDFlib is stateless, i.e., method parameters are used instead of properties.
> PDFlib’s dual interface supports both early and late binding.
> PDFlib supports rich error information.
Note PDFlib is not MTS-aware (Microsoft Transaction Server), although it can be deployed with MTS.
Installing the PDFlib COM edition. PDFlib can be deployed in all environments that
support COM components. We will demonstrate our examples in several environments:
> Visual Basic
> Active Server Pages (ASP) with JScript
> Windows Script Host (WSH) with VBScript
> Borland Delphi
Active Server Pages and Windows Script Host both support JScript and VBScript. Since
the scripts are nearly identical, however, we do not demonstrate all combinations here.
In addition, there are many other COM-aware development environments available –
Microsoft Visual C++, Borland C++ Builder, PowerBuilder, to name but a few. PDFlib also
works in Visual Basic for Applications (VBA).
Installing PDFlib is an easy and straight-forward process. Please note the following:
> If you install on an NTFS partition all PDFlib users must have read permission to the
installation directory, and execute permission to ...\PDFlib 8.0.6\bin\pdflib_com.dll.
> The installer must have write permission to the system registry. Administrator or
Power Users group privileges will usually be sufficient.
The PDFlib MSI installer. PDFlib is available as an MSI package (Microsoft’s Windows
Installer) which supports installation, repair, and uninstall features. To install PDFlib
from the MSI package simply double-click on the .msi file, or right-click on it and choose
install.
If your system does not support MSI (like Windows NT) you can get MSI support for
free from Microsoft.
The installation programs supplied for the PDFlib COM component automatically
takes care of all issues related to using PDFlib with COM. For the sake of completeness,
1. See www.microsoft.com/com for more information about COM
2.3 COM Binding 29