Very good question. Modern software programming builds on layers and layers of software, some of it in the OS, others in libraries or classes that are common to most development environments, and still others in 3rd party purchased software. The latter rarely comes with source code, and even if it did, porting it to a new platform might be painful. On top of all this sits the application code contributed by the developer in question - which is the only source code he normally sees.
Fortunately, the Willows people no doubt encountered the problem of unavailable source code many times over, because they do a lot to help. In a search of Willows on-line documentation, I found the following:
"Another unique facility allows the inter-mixing of source and binary modules within an application. Flexible tools let developers combine source code and existing 16-bit binary objects, i.e., DLLs, VBXs, drivers (DRV) and custom controls, to achieve the native performance of a source port while taking advantage of third-party component technology. Applications can load resource files, bitmaps, icons, etc. from existing DLLs without modification. This layer translates the Windows API requests to the native TWIN Library API to allow a non-native application to achieve native performance. This feature lets developers bring their applications to market faster by not having to wait for source ports of all components of an application."
In addition, Willows RT and The Willows Toolkit support MFC. This means that Microsoft Foundation Classes (MFC) can be fully utilized as well. Most of the window interface GUI part of a Win32 application would be constructed using MFC.
Finally, an important area where applications make use of 3rd party software is in establishing some kind of connectivity. This aspect of an embedded application would almost always be handled using substituted VxWorks or 3rd party libraries that layer directly on top of VxWorks, rather than the libraries used in the original Windows application. This is possible since the Willows (Win32 API) software can be mixed and matched with native VxWorks software and libraries.
There will still be applications that stubbornly refuse to succumb to a straightforward port due to missing source code for a component, and will require effort to either replace the component or have the it re-compiled for the target platform. But Willows supports lots of different ways to get the job done.
Allen |
