I decided to look into some more books on cross-platform work to see what more professionals were doing in this field. The book Cross-Platform Development in C++:Building Mac OS X, Linx and Windows Applications by Syd Logan, describes some of the techniques used in creating the Mozilla/Netscape browser to multiple platforms, and the challenges involved in creating such a massive project.
The basic theme of the book is abstraction, especially when dealing with low level implementation details, file I/O, threads, byte order, any platform specific code etc. Logan recommends creating factory classes that returns a concrete class implementation of an interface for these types of problems. The code should NOT be sprinkled with #if defines as it makes coding and debugging these things a nightmare as nearly every line could contain one or more #defines. Instead creating an abstract factory for returning the necessary factory and concrete implementation is essential.
In this book Logan share tips and workflow processes that allowed these projects to succeed on multiple platforms. These included having multiple experts on each of the platforms for handling, requiring developers to test on all three major platforms (Windows, Mac OS and the target flavour of Linux) before commiting to the code base. Logan also suggests another requirement is to compile with different compilers, pay attention to warnings and consider whether the native compilers for each operating system are the best approach (whichever compiler makes the most sense). One scheduling requirement was that all functionality worked on all platforms at the same time, this was essential to keeping everything working and preventing features from only being implemented on a given platform (which goes against the application being entirely cross-platform).
The book goes into quite a bit of detail on setting up Makefiles for each of the platforms using Imake and having a cross platform make system. It is also suggested to use a cross platform bug reporting system (Logan uses Bugzilla and Tinderbox since they are other Netscape/Mozilla projects). CVS is used (although Subversion is mentioned) but it is also a requirement to have cross platform tools (while also relying on Cygwin to emulate a lot of Linux tools on Windows).
There are other tips such as consider using the NSPR platform abstraction library (Netscape Portable Runtime Library), being wary of what standards floating point calculations are done, avoiding serialization of binary data (unlss you are using a convention for the data), using the limits.h for any size information (instead of using sizeof), etc.
One particularly good example in the book was related to the floating point representation:
float x = 4.0/5.0;
if (x == 4.0/5.0)
{
printf("Same\n");
}
else
{
printf("Different\n");
}
The above example will print out “Different”, since floating point expressions are evaluated to the greatest precision representation available (in this case double). The example below will print out “Same”.
double x = 4.0/5.0;
if (x == 4.0/5.0)
{
printf("Same\n");
}
else
{
printf("Different\n");
}
The book deals a lot with user interfaces as well (which are often a major issue with portability). Logan goes into some detail of the MVC (Model-View-Controller) paradigm, but also covers wxWidgets http://www.wxwidgets.org/, some of Netscape/Mozilla’s XML-based GUI toolkit XUL https://developer.mozilla.org/En/XUL and his own open source project Trixul http://www.trixul.com/.
Trixul is an interesting project and some of the functionality of a browser (like embedded Javascript to interact with the DOM) are concepts that would be interesting to apply to a game engine, although perhaps in a slightly different way. Serializing in XML for the UI is incredibly valuable, although likely something that individuals will have to write themselves (see my post on XNA Serialization for this). Trixul allows C++ components to be written that can be accessed through a Javascript component manager to extend the functionality, within the SpiderMonkey Javascript engine. I won’t go into too much detail about Trixul here, but if you are interested check out the links (and the book).
All in all, I think this book gives a great insight into the complexities of cross-platform development, especially in working in a large team. I still stand by my post about indie game developers should not initially target multiple platforms: http://gameprogrammertechnicalartist.blogspot.com/2011/08/indie-multi-platform-game-development.html as the amount of effort involved in making this work, the number of experts involved and the time it takes to get just three major platforms to work can be significant. If possible try to use tools that are platform independent, and see about abstracting all platform specific code, test on all systems as you write the code, and realize this is going to take some time.
Best of luck,
Michael Hubbard
https://michaelhubbard.ca