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Article contents:== Outdated egg! This is an egg for CHICKEN 3, the unsupported old release. You're almost certainly looking for [[/eggref/4/sdl|the CHICKEN 4 version of this egg]], if it exists. If it does not exist, there may be equivalent functionality provided by another egg; have a look at the [[https://wiki.call-cc.org/chicken-projects/egg-index-4.html|egg index]]. Otherwise, please consider porting this egg to the current version of CHICKEN. [[tags: egg]] == sdl [[toc:]] === Description This is a Chicken extension for basic SDL support. === Author Tony Garnock-Jones <tonyg@kcbbs.gen.nz> === Requirements [[syntax-case]] === Download [[http://code.call-cc.org/legacy-eggs/3/sdl.egg|sdl.egg]] === Documentation ==== Naming conventions I've tried to follow guile-sdl here. From the guile-sdl infopages: > As with standard guile naming conventions, all names are converted to > lower-case, and underscores are replaced with hyphens. Functions that > modify one or more arguments have an exclamation point (`{{!}}') appended, > and functions which ask a question and return a boolean value have a > question mark (`{{?}}') appended. Regarding flags, enums and constants: I differ from guile-sdl here - where guile-sdl exposes these as symbols, with functions for converting to and from numeric values, this library exposes a number of variables bound to numbers. To combine flags, use {{(+)}}. For instance: <enscript highlight=scheme> (define s (sdl-set-video-mode 640 480 0 (+ SDL_HWSURFACE SDL_HWPALETTE SDL_DOUBLEBUF))) </enscript> Note also that I differ from guile-sdl in the case of flag, enum and constant definitions. Since Chicken is now case-sensitive by default, I've made this extension retain the case of the C preprocessor definitions. The reason I am recommending {{(+)}} over {{(bitwise-ior)}} here is that some of the flags do not fit in an immediate small integer, and must be represented as inexact numbers. Unfortunately, {{bitwise-ior}} only works properly when applied to immediate small integers, so there is a tradeoff to be made: use {{(bitwise-ior)}} where you are ''sure'' all the flags will fit in immediate integers, and use {{(+)}} otherwise, bearing in mind the fact that {{(bitwise-ior)}} gives an answer much more in the spirit of a bit set definition: if a flag is already set, {{(bitwise-ior)}} will not set it twice, where {{(+)}} will happily screw up the result completely. ==== Garbage Collection Currently, some datastructures ({{SDL_Surface}} and {{TTF_Font}}) require manual deallocation. Use {{(sdl-free-surface)}} and {{(ttf-close-font)}}, respectively. Future versions of this library may implement automatic reclamation of unused {{SDL_Surface}} and/or {{TTF_Font}} structures. ==== Timers It is problematic supporting {{SDL_AddTimer}} and {{SDL_RemoveTimer}} from chicken, since they a) are implemented using {{setitimer}}(2) and b) involve callbacks from C to Scheme. Each would be fine on its own, but taken together they interfere with the main Scheme thread. As it happens, the {{SDL_WaitEvent}} function is implemented in terms of polling (!) for events, with a short delay if none present themselves - the usual pragmatic tradeoff for event-based systems on Unix-like machines - and so we will be doing no worse if we do a similar thing ourselves. Hence, I've written a Scheme-based timer library which integrates with SDL's event loop, calling {{SDL_Delay(10)}} when there's no work, just like {{SDL_WaitEvent}}. ==== SDL_Init / sdl-init on MacOS X {{sdl-init}} does not work on MacOS X when called from a dynamically-loaded extension. Something internal to Quartz seems to get confused. (Chances are it's the redefinition of {{main()}} in {{SDL_main.h}}, which implies there will be problems on Windows as well.) You must call {{SDL_Init}} ''directly'' from your main program - if your main program is written in Scheme, you need to say something like <enscript highlight=scheme> (declare (foreign-declare "#include &lt;SDL.h&gt;\n")) (foreign-code "SDL_Init(SDL_INIT_EVERYTHING);") </enscript> and then compile that part of the code, linking it against {{libSDL}} directly. For convenience, this extension includes a program called {{sdl-csi}} which calls {{SDL_Init}} and then enters a version of the Chicken read-eval-print-loop, which can be used for interpreted/interactive use of the SDL bindings. The {{sdl-csi}} program is installed into the chicken program directory by {{chicken-setup}}. Calls to SDL should be initiated via sdl#, e.g. sdl#sdl-set-video-mode 320 240 8 0). Note that all this special handling of {{sdl-init}} is only required on MacOS X - other platforms (I've tried Debian linux on x86) have no difficulty with invoking {{sdl-init}} as a normal library procedure. ==== For more information Consult the [[http://www.libsdl.org/|libsdl C library]] documentation for the precise usage of each function, structure, and variable. You can find the C library documentation here: [[http://www.libsdl.org/intro/toc.html]] === Warning THIS IS ALPHA CODE. Only some of the features have been tested. The interfaces are likely to change in the future. Not all of SDL is supported. BE WARNED! See especially the lack of warranty in the LGPL! === Changelog * v0.4.51117.6 Added {{sdl-gl-swap-buffers}}, {{sdl-gl-set-attribute}} and {{sdl-gl-get-attribute}}, suggested by Koen Weddepohl * v0.4.51117.5 Another attempt at mingw porting * v0.4.51117.4 Modified sdl.scm to include proper headers for windows [reported by Jong-Hyouk Yun] * v0.4.51117.3 Added a few missing functions * v0.4.51117.2 A few missing functions added for joystick support * v0.4.51117.1 Joystick-support by Achernar Alpha Eridani * v0.4.51117.0 === License This library is licensed under the LGPL, the same license as SDL itself. See the file "COPYING" in the provided archive. Description of your changes:

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