Finally, after beginning soon after the game’s Windows release on Steam, and well over a month after I initially wrote my first post about this topic, I’m finally done with porting Gemstone Keeper to Linux (for the most part) and ready to write about what I’ve learned from porting it over. Since both the Framework and Level Generator have been ported, getting the whole game to compile and run wasn’t as confusing as the last two, but that didn’t stop it being tedious.
Last time on Quest to Linux, I went through porting the Vigilante Game Framework to Linux, but the quest isn’t over yet. The next big task is porting Gemstone Keeper’s level generator and editor, the GenLevelTools, since I need to be able to get the caverns from somewhere.
GenLevelTools, aka the Procedural Level Editor, is a tool/library set that enables proceudrally generated grid-based levels to be modified and previewed in a level and used in games, while independent from any specific game engine or renderer. It was originally developed for my University Thesis on Procedural Level Generation and I later did a talk about it at the International Roguelike Developer Conference in Nottingham. The library is written in C++, so language specific quirks like forward slashes and for loops apply, so the main challenge this time around is the level editor, which uses Allegro 5 as well as the GUI library GWEN.
Allegro 5 is a C framework, although you can still use it for C++. Fortunately like SFML, it’s easy to set up for Linux since it’s part of one of Ubuntu’s repositiories. GWEN is a GUI library that was developed by Garry Newman (of Garry’s Mod). It was the easiest to set up for Windows but I had a few problems with the Linux version, as the gmake scripts rely on finding certain libraries and ending the entire scripts if those libraries cannot be found. This is different from running the scripts for Windows, which create Visual Studio projects that you can apply the libraries yourself. After tweaking the scripts and the source files a bit, I managed to get the GWEN and GWEN Allegro Renderer to build.
Aside from the main changes that I mentioned in the last post (using correct slashes, for loops) there weren’t that many changes I needed to make. I did have to add a lot more include statements, since despite being standard library stuff, GCC doesn’t immediately know what functions like memset, modf, floorf or ceilf among others off the bat, unlike Microsoft Visual Studio. After all these changes the library was able to compile smoothly. To make absolutely sure that it works within Linux, I wanted to build and run the editor, hence why I wanted to set up Allegro and GWEN. I managed to compile it with little effort, but something went wrong…
The editor crashed almost immediately, and the only reason I was able to show the following above was because I tried running the editor without the GWEN GUI rendering in the scene. It didn’t help that Code::Blocks debugger wasn’t working initially, and the closest I got as an error was below.
Fortunately I was able to configure Code::Blocks debugger to work, and was able to find the route cause of the crash being from the GWEN Allegro Renderer being unable to load the font, which is odd because the font I used (Lucida Sans) was able to load fine in my editor code, but fortunately GWEN provides an open source font (Open Sans) that runs just fine. So now with the GUI render up and running, I can test the editor!
I’ve been able to compile the library as both a binary and static build, as well as the editor. I could also compile the unit testing and C# wrapper for it too, but since I mainly wanted to get this done for Gemstone Keeper, I’ll leave it like this for now. Time for the main course!
So with Gemstone Keeper on Steam for Windows only, I thought I’d try my hand at getting a game to build to Linux the proper way. This series of posts will hopefully document each part of porting Gemstone Keeper to run on Linux.
The last time I made a game with Linux support was Secret of Escape, which used the Node-webkit to run HTML5 games to desktop applications. Node-Webkit essentially was a separate, precompiled application that functioned like a limited web-browser using the Chromium engine, all Construct2 did was build a HTML5 game and structured it in a file structure that made the application run the game. This way, porting the game to Windows, Mac and Linux took very little effort. This essentially means that developing for Linux was a completely new thing for me before releasing Gemstone Keeper.
The first stage was porting the Vigilante Game Framework. This is the underlaying C++ framework that uses SFML to develop games with state management, collision, visual effects and audio effects among others. It was partially inspired by HaxeFlixel, although with some of my own approaches that rely on C++ and SFML, as well as my own features (such as circle collision, multipass post process effects and a custom text renderer). Getting this to work on Linux would help me with setting up SFML and having a good idea of how Linux development worked.
Surprisingly, getting the framework to build on Linux ended up being the easiest part, because someone else already did it! I posted the framework to GitHub, and passed around the GitHub page to Twitter and Reddit, and SirFrankalot on the /r/gamedev subreddit was able to fork it and get it to work in Linux, and provided both written notes and a pull request to carry his changes over! The details can be found here, but these are the main points I wanted to get across:
- Using Correct Slashes: When using Windows Explorer and Visual Studio, folders or directories will usually be represented with a backwards slash (\). If you are only developing on Windows, this wouldn’t be a problem. However Linux and Mac both always use a forward slash (/), so for portability you should use that. Using forward slashes also has the advantage of not having to deal with escape sequences, since programming languages use a backwards slash (such as \n, \t and \\).
- For-Loops: These kinds of loops are good for looping a specific number of times using a defined iterator. If that iterator is a list of object or variables, you use a foreach loop, assuming your programming language of choice has that. When using Visual Studio, I found there is a foreach loop in the form of for each (type x in y) where x is a reference to an object in the list, and y is a container like an array or vector. Turns out this way is purely a Visual Studio extension, and the portable foreach loop is for (type x : y).
- XInput: Microsoft XInput is the API used for Xbox 360 and Xbox One controller, which means that it’s works for Windows only, at least that’s what you would assume. Linux has both libudev and linux/joystick.h, which allows some Linux OSes to access XInput functionality. This would mean a complete rewrite, so SirFrankalot simply made all XInputDevice functions return false. I later found someone wrote a Gamepad API was maintained long enough to allow Xinput Controllers to work on Windows and Linux using the same functions. I’ve since added this on as an optional feature that can be set using a preprocessor.
Next was using an IDE, I decided to use Code::Blocks because I have used it before, although it’s still much of a change of Visual Studio. Not to mention I was using a virtual machine, a VirtualBox with Linux Mint 18.1, and for whatever reason my configuration causes it to crash with no warnings. I also had to set up a load of dependancies, although using the terminal to get them is much easier than browsing for libraries online.
In the end I managed to build the SFML tutorial code and a few moments later, VFrame could compile! Aside from some small issues with 3D graphics, it was running almost just like it did on Windows!
Next time, it’ll be my ramblings as I port over the library that makes Gemstone Keeper’s caverns large and random, the GenLevelTools!
To celebrate my birthday, I’ve decided that from this day forth, my stealth game Secret of Escape will now be available to download FREE of charge. You can now get the game from either IndieGameStand or Itch.io if you want to download it and enjoy it as much as you want. I haven’t been able to change the price on Desura because it won’t let me set a price below $1.99, but since Desura’s bankruptcy I doubt anyone will use it.
So the Midsummer Jam Week is over, and my entry (Secret of Escape) is now online, now with its own page on the site and a video trailer!
Let me say I had a great time on this jam, especially posting my progress along the way. If I get enough of a good reception, I will continue work on it to make it bigger and better!
Let me show you some other entries that I enjoyed from the games jam (click on images to go to their pages):
Check out all of the games submitted here.
I hope to enter another games jam very soon, so make sure you follow me to know more.