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Errata to my Digital Dragons 2013 talk: http://www.slideshare.net/LeszekGodlewski/linuxgames
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Linux as a gaming platformIdeology aside
14-07-2013
Leszek GodlewskiGeneralist [email protected]
www.thefarm51.com
ERRATA
2I stand corrected!
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On April 19, 2013 I gave a talk on game development for Linux at the Digital Dragons European Games Festival. In it, I made a couple of mistakes and omissions that I hereby would like to correct.
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3What if SDL doesn't cut it?
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Despite its awesomeness, SDL has its shortcomings● No explicit GLX/WGL context data sharing
and no direct context access→ no threaded rendering ☹
(hit this corner while porting Painkiller HD)● No 3D positioning or DSP support in the
stock SDL audio subsystem- Partially remedied by SDL_mixer
But we need those! Now what?!Original slide 24
4What if SDL doesn't cut it?
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Despite its awesomeness, SDL has its shortcomings● No explicit GLX/WGL context data sharing
and no direct context access→ no threaded rendering ☹
(hit this corner while porting Painkiller HD)● No 3D positioning or DSP support in the
stock SDL audio subsystem- Partially remedied by SDL_mixer
But we need those! Now what?!Original slide 24
5OpenGL context sharing in SDL2
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It actually is possible!
● Just undocumented... ☹ Only mention I could find in Google is the May 2012 commit that introduces the feature
● Needs an SDL OpenGL attribute set before window creation:SDL_GL_SetAttribute( SDL_GL_SHARE_WITH_CURRENT_CONTEXT, 1);
● Voila - all contexts created from now on with SDL_GL_CreateContext() will share data with the currently bound context (buffers, shaders etc.)!
6OpenGL context sharing in SDL2
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I re-read the Valve slides about porting their games to Linux, and noticed their renderer is multithreaded. I knew from elsewhere they are using SDL2, so I thought I should check the source code, not just the SDL2 documentation.
As soon as I found out about my mistake, I rewrote the Painkiller Hell & Damnation client code to use SDL2, too. ☺
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7Joystick/gamepad API
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● Not part of X11 input event framework● Kernel block devices- Created as /dev/input/js*-Hotplug events via libudev (also in Steam
Linux Runtime)-Handled via open() and ioctl()-Detailed documentation in the kernel
http://kernel.org/doc/Documentation/input/joystick-api.txt
Original slide 28
Well, yeah,
Well, yeah, but...
but...
8SDL2 joystick and controller APIs
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Why hurt yourself with the low-level kernel joystick interface and libudev?
9SDL2 joystick and controller APIs
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Joystick API● Support for axes, buttons, hats and trackballs● State polling or events● Hotplugging● Force feedback via the haptic SDL2 subsystem
10 SDL2 joystick and controller APIs
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Game controller API● Built on top of the joystick API● Maps any joystick/gamepad input to a layout
modelled after the Xbox 360 controller● Built by Valve with Steam Big Picture in mind● Bindings may be imported/exported via strings● Popular controllers have built-in mappings
● API very similar to the regular joystick API, but buttons and axes are identified by enumerations● SDL_GameControllerAxis● SDL_GameControllerButton
11 Where do I put the files?
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● Windows-Game data and binaries: C:\Program Files-User data: %APPDATA%, Documents...-AoS-like organization
● Linux (conventional)-Game binaries: /usr/bin/, /usr/games/-Game data: /usr/share/games/-User data: $HOME/.config/
($XDG_CONFIG_HOME environment variable)
- SoA-like organization- Filesystem Hierarchy Standard
Original slide 42
Well, yeah,
Well, yeah, but...
but...
12 Where do I put the files?
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● FHS mainly concerns distro packages● Proprietary software often installs into
/opt/<package name>/(“Add-on application software packages”)
● Proprietary software also often installs “wherever”
● Steam games live in ~/.steam/steam/SteamApps/
● Just put game data and binaries in one place, and save user data to ~/.config/
Original slide 43
Well, yeah,
Well, yeah, but...
but...
13 $XDG_CONFIG_HOME and friends
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● Actually, $XDG_CONFIG_HOME (a.k.a. $HOME/.config) is a for textual configuration files
● User data, which is a more accurate description for savegames, DLC etc., goes into $XDG_DATA_HOME (defaults to $HOME/.local/share)
● All of this is regulated by a FreeDesktop.org standard:http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
14 Summary
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That's all, folks, for now. Sorry for not getting this errata out earlier – at The Farm 51 we're very busy finishing Deadfall Adventures. What do you think, should it be coming to Linux as well? ☺
If you spot any more mistakes, feel free to shoot me an email.
Many thanks to Michael Larabel at Phoronix for blowing up my Slideshare with all the traffic from their news story. ☺
Keep on playing, Linux gamers!
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Thank you!
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