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-Migrating Sol's Tutorial of SDL to SDL_Perl +The Build Process of SDL Perl

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If I have seen further it is only by standing on the shoulders of giants. --Newton



Sol's Tutorials


When I was struggling with SDL C a while ago, someone recommended Sol's Tutorial to me. It had not only help me understand video in SDL, but I believe my code has improved using Sol's code style. I would like to pass these along to fellow SDL_Perl users too. So here is the Ch 02 code of Sol's Tutorial in SDL_Perl. It will be getting more and more Perly as our team hacks on it. There is more to come!


To use this code you need the new Redesigned SDL_Perl Library


Getting SDL Dependencies


Only If you are on Linux (debian/ubuntu) you need the following dependencies:

$ sudo apt-get install libsdl-net1.2-dev libsdl-mixer1.2-dev libsmpeg-dev libsdl1.2-dev libsdl-image1.2-dev libsdl-ttf2.0-dev

On Windows we recommend using Strawberry Perl. It comes with SDL-1.2.13 header files and libs included.

Both Windows and Linux needs to install Alien::SDL

$ cpan Alien::SDL
** Add sudo to this for Linux

Getting Bleeding SDL


The bleeding SDL is on github. Click download on this site .

Extract it and cd into the folder run 
$ cpan .
** The dot is needed
** in Linux you may need to do sudo

Then you can run this script by doing

$ perl examples/sols/ch02.pl
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A while ago I had a long chat with mst on why SDL uses Module::Build rather then Make. I told him it is a simple matter of code inertia. The existing Module::Build system has worked well for us so far. Never the less, he convinced me that switching to Make will improve debugging the Build system. But to be able to switch we will need to completely replace the Build system. I am not prepared to do that so I will just present the requirements so mst or someone else can at least attempt to switch.


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The Build Process


+ Alien::SDL
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SDL Perl depends on a few C libraries for a complete install. This is handled by Alien::SDL. First we look for existing SDL libraries and dependencies by doing a File::Find for headers. If these headers are found we present and option for the user to use those. We then store these locations in Alien::SDL->config options 'cflags', 'prefix' and 'libs'. If we do not have libraries available even for a minimum SDL installed ( SDL.h is not found). We provide several platform specific options.


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For windows we have a simpler process. We download prebuilt binaries ( and checksum ) based on the user's selection and just copy them in to the right location. Again the 'prefix', 'cflags', and 'libs' is saved in Alien::SDL->config.


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For *nix/MacOSX we download sources and attempt to compile them. To be able to do this we download several other dependencies like libpng, jpeg and pango. You can see how we do this using hashes here. During the compile process we also apply patches as needed for the sources. Once this is done we can head to SDL Build.PL


+ SDL Perl dependency resolution
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+SDL's Build is responsible for linking the right libraries to the correct XS. If libraries are missing it will disable the component (not put it in SDL->config).
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For example to build Image.xs we require libsdl, libsdl_image and lib[jpg|png|tiff]. So we would check for these headers in the prefix provided by Alien::SDL->config. If they are not provided we will disable the SDL::Image module.


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More over the availability of each library is specified as a -DMACRO to the gcc compiler. This way we can prevent XS failures due to missing libraries using #DEFINES. Here the SDL_image macro is defined and used. The availability of the module is then available from SDL::Config->has()
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+ Conclusion
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This is a high level overview of our Build process, because frankly I hate traumatizing my brain with this again. Credits have to go to FROGGS and kmx for helping with this Build scheme. Hopefully my post have helped people at the very least appreciate the problem scope of this Build system. That said I believe a fresh written build system, with these requirements in mind, will be more then welcome.
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