Rubymotion and Pointers to Structs

Question

I'm experimenting with cocosmotion, a Rubymotion implementation of Cocos2d. In the tutorial I'm working through, I have a method that takes a struct as an argument. I consulted the Rubymotion and MacRuby docs, but can't figure out how to instantiate a new object based on the struct I need. I think the main issue is that the struct starts with a lowercase letter and Ruby thinks it's a local variable when I try to work with it.

I believe I have the same problem as stated here: https://github.com/MacRuby/MacRuby/issues/121

Is there a solution or workaround?

The struct is defined in Objective-C like so:

 typedef struct _ccTexParams {
         GLuint  minFilter;
         GLuint  magFilter;
         GLuint  wrapS;
         GLuint  wrapT;
 } ccTexParams;

The method I'm trying to call expects a ccTexParams struct.

Here is what I've tried:

            @mysprite = Pointer.new("{ccTexParams=
            {GLUint=GL_LINEAR_MIPMAP_LINEAR}
            {GLUint=GL_LINEAR}
            {GLUint=GL_CLAMP_TO_EDGE}
            {GLUint=GL_CLAMP_TO_EDGE}}", 4)

When I try it this way:

        @mysprite = Pointer.new(:object, 4)

        @mysprite[0] = GL_LINEAR_MIPMAP_LINEAR 
        @mysprite[1] = GL_LINEAR
        @mysprite[2] = GL_CLAMP_TO_EDGE
        @mysprite[3] = GL_CLAMP_TO_EDGE

The runtime error is:

expected instance of Pointer of type `{_ccTexParams=IIII}', got `@' (TypeError)

I also tried:

@mysprite = Pointer.new("_ccTexParams", 4)

        @mysprite[0] = GL_LINEAR_MIPMAP_LINEAR 
        @mysprite[1] = GL_LINEAR
        @mysprite[2] = GL_CLAMP_TO_EDGE
        @mysprite[3] = GL_CLAMP_TO_EDGE

The error:

Can't find pointer description for type `_ccTexParams'

I've also tried to replace it as CcTexParams, _ccTexParams, and just ccTexParams in a bunch of different ways, no versions of it work.

I tried this:

@mysprite = CcTexParams.new
@mysprite.minFilter = GL_LINEAR_MIPMAP_LINEAR 
@mysprite.magFilter = GL_LINEAR
@mysprite.wrapS = GL_CLAMP_TO_EDGE
@mysprite.wrapT = GL_CLAMP_TO_EDGE

RubyMotion complains it expected an instance of Pointer, got '#<CcTexParams minFilter=9987 magFilter=9729 wrapS=33071 wrapT=33071>' (CcTexParams) (TypeError)

I tried just passing [GL_LINEAR_MIPMAP_LINEAR, GL_LINEAR, GL_CLAMP_TO_EDGE, GL_CLAMP_TO_EDGE] directly to the method. It complains that it expected a Pointer but got an Array.

Perhaps I should just rename ccTexParams in the lib to something like CCTexParams? I'm guessing that's not an ideal workaround.

Answer 1

If someone's looking for a solution for this, try Joybox. It's a wrapper for Cocos2D.

Joybox combines the most popular and widely used 2D game engine for iOS, Cocos2D, folds in the amazing Box2D physics engine, and then wraps them up into a clean Ruby API that will make game development faster and more enjoyable for both beginners and experts alike.