Programming

I have updated the automatic lisp loader modules (LspLoad.zip on my freebies page) to support BricsCAD V17 and ZWCAD 2017. Note that the source code for LspLoad is also available.

I’ve updated QuirkyPolyline and added support for Bricscad 14 – 15 and ZWCAD+ 2014 – 2015. The new QuirkyPolyline download is available on the ObjectARX freebies page. Share ThisTweetFacebookLinkedInTumblrStumbleDiggDelicious

Rumors about the death of AutoLISP have been floating around for many years, but fear not, those rumors are greatly exaggerated. Bricscad and ZWCAD both have excellent support for lisp plugins, so well-written lisp code is truly cross-platform and enjoys a large and growing audience. Unlike other languages, the vast majority of lisp code works unmodified on any hardware architecture, in any version of Windows, and inside any host application that supports it, including AutoCAD versions released more than a decade ago. On top of that, OpenDCL gives lisp developers the power of a modern event-driven user interface that can put their lisp plugins on the same playing field as plugins written in any other language. This is a powerful combination, and given lisp’s low entry cost, it is not surprising to see lisp continuing to enjoy strong support in the developer community. ...

One of the cardinal rules of C++ exception handling is “don’t catch what you can’t handle”. Of course there are always, er, exceptions to the rule, but the basic principle always holds. The consequences of violating the rule are less severe in the .NET world, but even there it’s a good rule of thumb. ...

I have updated the automatic lisp loader modules (LspLoad.zip on my freebies page) to support Bricscad V14 and ZWCAD+ 2014. Note that the source code for Lspload is also available.

The automatic lisp loader modules (LspLoad.zip on my freebies page) have been updated to add support for AutoCAD 2014 and Bricscad 13 64-bit. The modules are now digitally signed so that AutoCAD 2014 loads them quietly.

Creating and calling functions is one of the most fundamental tasks in C++ programming. The function declaration serves as the primary description of a function’s interface - or contract - with callers, thereby making it the most important piece of code documentation. A good function declaration should convey as much information as possible. I’m sure an entire book could be written on the topic of function interface design, but I’ll just touch briefly on a few factors to consider when designing a function’s interface. ...

Let’s say you have an ObjectARX module with an implicit dependency on another DLL. Your installer puts both your ARX module and the dependent DLL into a private application folder. Windows must be able to resolve the implicit DLL dependency at load time, otherwise it will fail to load your ARX module. Alas, Windows will not automatically search for the dependent DLL in your application folder, even though your ARX module is located there. Therefore your ARX module won’t load because the dependent DLL cannot be resolved. ...

In AutoCAD, the AcDbCurve class defines a general parametrized curve. On a parametrized curve, points in space are mapped to real numbers (parameters) by an arbitrary function F(p) for values of p from the curve start parameter to the curve end parameter. Defining a curve this way simplifies working with complex 3D curves because one can work in the curve’s one dimensional “parameter space” instead of the more complex three dimensional cartesian space. ...

I’ve written before about RoboCache, a command line utility I wrote for managing the offline files cache in Windows Vista, Windows 7, and now Windows 8. After using the utility internally for a few years, I decided that I might as well clean it up and make it available to the rest of you. RoboCache is now available at the ManuSoft web site. There is a shareware version available, and you can purchase the registered version at the ManuSoft store (cost is 25 USD for a single user license). ...

I often encounter cases in ObjectARX programming where numerous boolean flags need to be persisted as part of an AutoCAD database object. For filing and for passing around to other functions, it’s most efficient to package those bit flags into a single unsigned integer. Below is an example that demonstrates how to use a union inside a containing class that can be simultaneously used as either a single unsigned integer or as individual booleans. ...

A lot of you are guilty of not checking return values from API function calls. I’ll bet you have a good excuse, like “it’s a lot of extra typing for no reason”, or “that function should never return an error code”. ...