Tag: ObjectARX

I’ve received several emails recently from users of my VC Build Hook utility that mention switching the ‘UseVC7Paths’ setting on and off depending on the build configuration they are working on. If you are doing this, you need to change your project structure!

Build configurations in Visual Studio 6 and later are logically attached to the solution, not to an individual project as they were in older Visual Studio versions. What happens is that programmers find it easy to add a new build configuration to an existing ObjectARX wizard created project for targeting a new release of AutoCAD — unfortunately those configurations end up belonging to the entire solution instead of just one project. Since VC Build Hook cannot be set on a per-configuration basis, they end up having to change the project setting depending on which configuration they are building. That’s bad, very bad!

The correct way to handle this situation is to create new projects, not new build configurations. Yes, it’s a bit more work, and it would be nice if Microsoft added an easy way to clone a project, but them’s the breaks. Targeting different AutoCAD releases requires project-level changes, so you must create a new project instead of trying to get by with a new build configuration. You can and should share source code files between the projects, however.

When I create a new multi-target solution that e.g. targets AutoCAD 2000 – AutoCAD 2008, I structure the project files on my hard drive like this:

Solution (.sln file)
ARXProject (ARX module source files)
 +ARXProject.15 (.vcproj file)
 +ARXProject.16 (.vcproj file)
 +ARXProject.17 (.vcproj file)
DBXProject (DBX module source files)
 +DBXProject.15 (.vcproj file)
 +DBXProject.16 (.vcproj file)
 +DBXProject.17 (.vcproj file)

When starting a new project, I first use the wizard to create a default project structure and source code files for the current AutoCAD release. Once I’ve got that set up the way I want (including moving the project file into a subdirectory and modifying the source file paths appropriately, as well as setting the _ACADTARGET preprocessor macro), I clone projects by copying the .vcproj files and editing the copies in a text editor to give them a new GUID, then recreate my solution’s project structure from scratch by dragging and dropping the project files back into the solution and editing them as necessary.

If you need to target multiple AutoCAD releases from a single project, invest the time to set your solution up this way (and follow the other advice on my ARX tips page!), otherwise you will find yourself constantly fighting the system.

With the advent of Visual Studio 2005 and automatically generated manifest files, the topic of when and how to use manifest files comes up occasionally. Since a default ObjectARX wizard generated project in Visual Studio 2005 generates an embedded manifest by default, most people don’t even think about it. Of course that was the whole idea — the manifest would ensure that the correct dependent DLLs get loaded, and voila, no *need* to think about it. One of my programming axioms applies in this case: TANSTAAFL.

The problem is that ObjectARX applications are not in charge. AutoCAD is in charge, and it will decide which VC runtime and MFC runtime DLLs to load. If your ObjectARX application loads a different VC or MFC runtime than the ones AutoCAD is using, you’ll encounter big problems. I’ve always advised disabling the manifest completely (see my ObjectARX Tips page) to avoid such a possibility. Unfortunately, there’s a catch.

The problem is that linking to the ATL80.DLL file isn’t possible by just disabling the manifest and doing nothing more. ATL is now a side-by-side (SxS) assembly, and it no longer lives on the Windows support path, so a standard un-manifested DLL won’t be able to find it. The preferred solution is to link statically to ATL (see Configuration -> General -> ‘Use of ATL’ in VS 2005 project properties) and avoid the problem altogether. If you only have one module that uses ATL, this is always the best solution.

The less desirable solution is to add a *manually-created* manifest that specifies the desired ATL SxS assembly, but ignores the VC and MFC runtime DLLs. You’ll still need to decide whether to make ATL shared or private, and in either case you *must* distribute ATL with your application to ensure that it is available when your application is deployed. You can cheat, and let VS generate your manifest file (instruct it to *not* embed the file), then just edit the resulting .manifest file to remove references to the VC and MFC assemblies. For example, here’s one that I generated (you’ll need to generate your own to ensure that the manifest matches the version you are redistributing):

<?xml version=”1.0″ encoding=”UTF-8″ standalone=”yes”?>
<assembly xmlns=”urn:schemas-microsoft-com:asm.v1″ manifestversion=”1.0″>
<dependency>
<dependentassembly>
<assemblyidentity type=”win32″ name=”Microsoft.VC80.ATL” version=”8.0.50727.762″ processorarchitecture=”x86″ publickeytoken=”1fc8b3b9a1e18e3b”>
</assemblyidentity>
</dependentassembly>
</dependency>
</assembly>

In my work, I’ve had very little need for manifests. The VC optimizer is able to strip the unused portions of statically linked ATL out of your code, leaving a much smaller footprint than the entire assembly would require. This eliminates the need to redistribute ATL with your application, thus reducing the overall potential for deployment issues. Nevertheless, there are exceptions to every rule, and your mileage may vary.

I’ve installed Visual Studio 2005 SP1 and have been busy testing all my projects to make sure they didn’t break. Microsoft did fix at least one of the bugs I reported (the resource editor choked on resource strings that contained an embedded NULL character), but the IDE still crashes fairly consistently if I initiate a large solution build while the Intellisense database is being rebuilt. SP1 also managed to break my VCBuildHook utility, so I’ve uploaded an updated version (2.0.3.0) for use with SP1.

If you’ve been programming with ObjectARX for a while, you already know that each version of the ObjectARX SDK only works with a specific version of Visual Studio. Mazhar Basa touches on the subject in his article Components of ObjectARX Applications. My VCBuildHook utility makes it possible to build for multiple target AutoCAD versions from a single Visual Studio 2005 solution, but this utility still needs the older versions of Visual Studio to be installed on the same system in order to perform its magic.

The problem is, legitimate licenses of older versions of Visual Studio are hard to come by. Back in the Visual Studio .NET 2003 days, you could purchase a new license of VS 2003, then get a free license downgrade from Microsoft that allowed you to install Visual Studio 2002 side by side on the same system. That combination allowed you to target AutoCAD versions as far back as AutoCAD 2004. Unfortunately, Microsoft stopped offering the VS 2002 downgrade license when Visual Studio 2005 began shipping in November of 2006.

The end result is that new ObjectARX programmers are faced with a dilemma if they need to target anything older than AutoCAD 2007. One of the attendees at my “High-Octane ObjectARX” class at AU 2006 reminded me that MSDN (Microsoft Developer Network) members can download older versions of Visual Studio from the MSDN subscriber download center.

I have verified that Visual Studio .NET 2002 (VS 2002) is available for download to MSDN Professional subscribers, but I could not find Visual Studio 6.0, which is required to target AutoCAD 2000 – 2002. Visual Studio 4.2 (required for AutoCAD R14) is available though, so maybe I’m just not looking in the right place.

If you are a professional software developer, whether commercial or in-house, you should consider subscribing to MSDN for various reasons. If you’re an ObjectARX programmer and need to target older versions of AutoCAD, MSDN may be the only way to obtain the older Visual Studio build tools and libraries that you’ll need.