X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pages%2Fblog-0010.html-inc;h=4c366da9655f0706e833bbc242ab0e3902d77a9f;hb=1d5d4d44a3acf89f7820195b5016f4ebc4489250;hp=fe4b8d48d37cc0a4205e7c209051f61deb0a418b;hpb=d502f71f4cb7e6073e2629cdba69f20e7001b721;p=sdlgit%2FSDL-Site.git diff --git a/pages/blog-0010.html-inc b/pages/blog-0010.html-inc index fe4b8d4..4c366da 100644 --- a/pages/blog-0010.html-inc +++ b/pages/blog-0010.html-inc @@ -1,6 +1,26 @@

-The beginnings of modular design for SDL Perl +The Build Process of SDL Perl

-
“Do or do not... there is no try.”
--yoda

The design before


The bindings before were all in one huge XS file. This was then exported into the SDL module. This means that the XS file has to handle with macros if any component (e.x SDL_Mixer) is not compiled. Moreover having ever binding in one XS file prevents use to treat C structs as object with only one point of free and malloc. This would be BEGIN and DESTROY in Perl. Also the monolithic design introduces a lot of bugs because we have to use free and malloc all over the place. Lastly SDL monolithic design has the constructor for all structs in both Perl and in XS.

The design we are aiming for

Simple one XS per Module. This would also simplify the Build code.

First Step


We have began with SDL Rect. It is in github master branch now. We are in the progress of making it back compatible. Originally SDL::Rect took named variables as parameters for new(). Now since the constructor is in XS we have only unnamed parameters.


Before


SDL::Rect->new( -x => 0, -y => 0, -width => 0, -height => 0);

After


SDL::Rect->new(0, 0, 0, 0);

Ideally we would like both ways of constructing Rect.
\ No newline at end of file +

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.


+
+

The Build Process


+ Alien::SDL
+
+

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.


+

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.


+

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
+
+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).
+
+

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.


+

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()
+
+
+ Conclusion
+

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.
+

+


+

\ No newline at end of file