From DWG to XAML (I)

DWG's time singular point

AutoCAD (Auto Computer aided Design) is the first automatic CAD software produced in 1982 by American Autodesk Company, which is used for two-dimensional drawing, detailed drawing, design documents and basic three-dimensional designs. Now it has become a popular drawing tool in the world. CAD technology is not the Autodesk Company's patent, the same CAD application on the computer, is not Autodesk company opened the precedent. Prior to the advent of AutoCAD, there was already a company called Versacad that produced the same software that appeared on the market. Because the VERSACAD is very strong and expensive, so Autodesk in the beginning to choose a smart road, free and open, which allows AutoCAD to quickly spread and upgrade. With the help of the Dongfeng of AutoCAD, DWG file format becomes the standard format of two-dimensional design drawing, this is one of them. The opening of the earlier period has also buried the lead for what happened, this is the second.

But in small parts of the history of the occasional will open a reverse. In the process of AutoCAD development, it gradually turned to the charge, and DWG file became a closed standard! Until today, the Internet still cannot get a complete technical document about a DWG file format version. Autodesk used the influence of AutoCAD to build an empire that, while earning billions of dollars, closed the door to interoperability between DWG format standards and other software systems. We are now just a little hazy thing, for example: The form of the DWG format is based on binary encoding; The DWG format has a self associated compression technique; DWG files can be validated and so on. But it's just that, and there's no detail to it.

At the same time, two development of this huge platform based on AutoCAD has never stopped. AutoLisp and ads have become the early main players. Later, AutoCAD published two development package-objectarx based on C + + language. So far, the two development behaviors based on AutoCAD have been clearly defined for the first time (at least I think so). The flowchart for this development behavior probably looks like left: Objectarx provides the relevant functionality as a class library, and developers can edit two development code in any editor; Compile and link through C + + compiler; Finally, the dynamic link library is generated to load into AutoCAD to implement the function extension. This basic approach is essentially preserved, even if the Objectarx for other languages, such as the C # language, is later. Interoperation becomes partly possible, although not directly implemented. Engineers in the AutoCAD software open the corresponding DWG files, can be expanded through two of development functions, the DWG format content into other systems can be recognized data.

"AutoCAD made a circle on the ground, forcing everyone to put things into this circle."

The pace of the rebels

There is a saying in China, "where there is oppression, there is resistance." Under the pressure of AutoCAD, the first one to rise up is not someone, but an organization. This organization's name is called "Open Design Alliance", referred to as ODA. ODA came with weapons on a dark night of the month, and the weapon was the famous OPENDWG document and Dwgdirect Open Class library. The previous article said that Autodesk initial opening strategy has buried the hidden danger to oneself, this hidden danger is now used by the ODA. Based on the original DWG version, ODA obtained most of the technical details of the DWG format in a way that was similar to cracking. ODA collects a small amount of registration fees to maintain operations, and publishes a dwgdirect-oriented C + + language, Dwgdirectx-oriented ActiveX control, dwgdirect.net-oriented to. NET. ODA commitment, in the face of the version of AutoCAD upgrade, will be the fastest speed to update these class libraries. In fact, it did: Now, the Dwgdirect class library has claimed to support the latest version 2010 of Read and write in DWG/DXF/BDXF format. The behavior of ODA fundamentally shakes the foundation of Autodesk. November 22, 2006 Autodesk filed a lawsuit against Open Design Alliance. The following section is the official statement of the Autodesk Company for the lawsuit:

The ODA software libraries contain technology that falsely identifies customer data files their software as Au todesk-created files. We have the ' right ' to ' control ' of our trademark and ' we depend on ' right ' in informing customers of the source of The files they are introducing in their CAD environments. The ODA interfered with our ability. The ODA failed to respond we reasonable request to stop violating our rights. As a result Autodesk are suing the ODA in order to defend it ability, through TRUSTEDDWG, to assure our customers of the S Ource of customer data files and make sure the origin of the files are not falsely attributed. The ODA ' s latest software libraries mimic trusteddwg and defeat the very of the program. We are relying on trademark laws to protect my ability to inform of the source of customer data files. "

The lawsuit continues, and the trend is unknown, and we can be sure that Autodesk and ODA are living well now. But as system developers, we seem to be more concerned with the potential risks of OPENDWG documentation and Dwgdirect:

The OPENDWG document obtains the details of the DWG format in a way that is approximately cracked. This will bring legal risks to developers who use Dwgdirect.

The OPENDWG document is not a complete description of all the versions of DWG. It supports only to 2004, and partly supports 2007.

Even within a particular version, the OPENDWG document has not yet cracked the meaning of some bytes.