For Microsoft app's this is often a matter of wrapping a DLL. They have some advice at
http://msdn.microsoft.com/en-us/library/ms801250.aspx
When I used to do printer app's in Smalltalk we did our own C DLL's - I don't know how much life has changed under MS .net The modern Dolphin Smalltalk has an excellent example and there is a DLL kit for VW Smalltalk that can be a help to see the approach if you have not done C or C++. At least we have escaped parallel and serial ports in most of MS-land ... I see this note at
http://www.codeproject.com/KB/dotnet/NET_Printer_Library.aspx
I haven't deployed anything for Mac since about '98 ... Cocoa may have added a higher level for Objective-C.
Linux is more straightforward as I/O specifics was not part of the C language spec - and I/O was the weakpoint of Intel PC design ... and mainframe graphics lessons were ignored in the MS GDI.
Here is a linux HOWTO
http://www.faqs.org/docs/Linux-HOWTO/Printing-HOWTO.html
When I worked on industrial printer app's we were in distributed Smalltalk (CORBA) with any kind of printer you can imagine in any sequence (multiple format printers per single workflow task) - you learn to hate printers or discover that maybe you should have been an actuary ...
Hope you find the DLL stuff in the Curl doc's helpful. An external library project has appeared on sourceforge.
You might want to look at ActiveX as your component approach if this is Windows issue - and in that case there is a good deal of info on the internet and Curl plays well with ActiveX.
If you have used Gtk with another language such as Python, there is a Gtk::Printer to look into.
I don't see handling printers as a Curl language weakness as prior to USB this was just interrupt controllers and the hardware and its drivers. As a web-content language, it is not surprising that we leave printing to the browser or to the ubiquitous Crystal Reports - but as a desktop app for RIA, well, there Curl has a project underway (I suspect). I am following the efforts of another web language, Rebol3, to remain cross-platform + PITL modular + UNICODE at this very moment. Not a simple matter. Unless your language capitulates to DOT net, for example ( and just where is IronPython these days ? ;-)
