[MacRuby-devel] Some OpenGL sample code

[Michael Johnston]

The first thing I did to learn Macruby was to port the Ruby Rocks  
tutorial (http://www.rubycocoa.com/ruby-rocks). It is here if anyone  
is interested: http://www.lastobelus.com/uncategorized/ruby-rocks-ported-to-macruby 
  (I kept playing for a while after finishing the tutorial, so my  
version has more code than the tutorial does). Feel free to put this  
on the samples page as well.

Cheerio,

Michael Johnston
lastobelus at mac.com




On 18-Dec-09, at 2:41 PM, Laurent Sansonetti wrote:

> Bonjour Julien,
>
> On Dec 18, 2009, at 4:54 AM, Julien Jassaud wrote:
>
>> Hello to everyone,
>>
>> I tried to port two OpenGL sample code examples from the ADC in  
>> MacRuby ( and plan to port some more ). You can find both projects  
>> here : http://github.com/sojastar
>
> Awesome! I would love to ship these as part of the MacRuby samples  
> once they are completed :)
>
>> Both kind of work but have problems I can't find solutions to so I  
>> turn to the list for a little help.
>>
>>
>> One of the examples ( MacRuby-BoingX ) randomly crashes, either on  
>> launch or exit, about one time out of five. When launching the  
>> application from XCode, I get :
>>
>> Program received signal:  “EXC_BAD_ACCESS”.
>>
>> which suggests a memory access error. It is not unlikely since the  
>> OpenGL functions use a lot of pointers. I am trying to use DTrace  
>> to identify the problem but it is very new territory for me. I  
>> wrote a script returning the name of the last function called. I  
>> get a different result for every crash. I imagine part of my data  
>> ( most often, the vertex data ) must be corrupted, and maybe from  
>> the various pointer operations I have to do to use OpenGL. Has  
>> anyone any suggestion on how I could troubleshoot such a problem ?
>
> I would start by getting the full backtrace from the debugger and  
> examine it. Most of the time it is easy to find what's wrong.
>
> Could you enter "thread apply all bt" into the debugger shell and  
> paste us the result?
>
> If the crash is random there is a possibility that it might be  
> related to garbage collection. A good way to know for sure is to  
> disable it, by setting the GC_DISABLE environment variable to any  
> value before starting the application.
>
>> The problem with the second example is directly related to  
>> pointers. The function CGLQueryRendererInfo function expects a  
>> pointer to a CGLRendererInfoObj object as its second argument.  
>> After the call, the pointer points to a valid CGLRendererInfoObj  
>> object. So I did something like this :
>>
>> renderer_info	= Pointer.new_with_type("^{_CGLRendererInfoObj}")
>> renderer_error	= CGLQueryRendererInfo(display_mask, renderer_info,  
>> renderer_count)
>>
>> and get :
>>
>> expected instance of Pointer of type `^{_CGLRendererInfoObject}',  
>> got `^{_CGLRendererInfoObj}' (TypeError)
>>
>> If I change the pointer type to '^{_CGLRendererInfoObject}',  
>> CGLQueryRendererInfo doesn't complain anymore, but all other  
>> following functions using the CGLRendererInfoObj do. Could this be  
>> a bridge support problem ? As anyone who has a better background in  
>> Cocoa any idea ? I know some things should be done in bundles but,  
>> for sample code, I thought it would be good to try to go Ruby all  
>> the way.
>
> I'm not familiar with OpenGL but it might be a BridgeSupport  
> problem... What other functions using the CGLRendererInfoObj are  
> failing? It might be good to reduce this problem to a small script  
> (even if it can be hard, because of OpenGL).
>
> Laurent
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