The Heart of the Engine
The engine was based on Directx 7 and used the Win32 API for OS dependant tasks. On iOS and Android obviously the DirectX and Win32 APIs doesn’t exist. Trawling through the source code, we realised that we were facing the prospect of re-writing several major subsystems:
- Window Management
- Event Handling
- Interfacing with the Audio Device
- Displaying images/graphics via OpenGL
- Loading Textures, Sound, Music
- File Handling
And so on.
This was pretty much looking like a total engine re-write. Not wanting to do that, we looked for low level libraries to do most of these things for us.
Having the source code for the library was an important requirement.
If you don’t possess the source code to your engine then your game is effectively controlled by the engine developer. Whether your game will be available on a platform is a decision in the hands of engine developer, not yours. It gets even worse if middleware is thrown in the mix.
Sometimes this is not an issue, when the engine is already ported to all the platforms you need. At other times it can be a real showstopper.
We evaluated a lot of 3rd party libraries for this, and eventually decided on SDL. This was probably before Valve had decided to port Steam to Linux. At least it wasn’t known to us that something like this is in the offing. SDL1.3 at the time was still alpha, and not ready for prime time. It also seemed that development work on SDL was faltering.
However, SDL supported iOS, and with a little work, Android. It was also open source, under zlib license. Further, we felt that if there were any issues remaining, it would be relatively easy to fix them given that we had access to the code.
But the real reason we liked SDL (and rejected the other libraries) was the elegance of the API. SDL has one of the best designed 2D APIs we have seen. The transition from SDL1.2 to SDL 2 has hurt the elegance of the API a bit, but only a little.
This turned out to be a good decision. It proved to be relatively easy to replace the PopCap Framework internals with SDL. Despite its beta nature, we had no SDL related crashes. There were some minor issues, but those were easily fixed. The development on SDL suddenly picked up, and we later learnt that valve was behind this. It turned out that steam on linux was using SDL.
It was a great moment when the first of the engine demos started working on windows! Everything in the demo looked exactly as before, but underneath the hood everything had changed! The demos, intended as a tutorials for the first time users, also served as test cases for us. In a matter of days we made all the demos work.