Ruby c extension and Sketchup Objects

Marc477

I created a ruby c extension and I know how to use primitive types (int arrays...) as parameter in the functions I created in c.

But is there any way to use a Sketchup object in a parameter? (like an entity) How can I decode the VALUE on the c side? Do I need a struct that fits the EXACT implementation of the object? Can I find that implementation?

Thank you

Marc477

Ok I found a way to achieve that. Here is an exemple with the Sketchup class Geom::Point3d

static VALUE AddOne( VALUE self, VALUE p1 )
{
    VALUE point;
    VALUE rbGeom, rbPoint3d;
    float x,y,z;
    
    //Convert to c float
    x = NUM2DBL(rb_funcall( p1, rb_intern( "x" ), 0 )) + 1;
    y = NUM2DBL(rb_funcall( p1, rb_intern( "y" ), 0 )) + 1;
    z = NUM2DBL(rb_funcall( p1, rb_intern( "z" ), 0 )) + 1;
    
    //Convert back to ruby VALUE
    rbGeom = rb_define_module( "Geom" );
    rbPoint3d = rb_define_class_under( rbGeom, "Point3d", rb_cObject );
    point = rb_funcall( rbPoint3d, rb_intern( "new" ), 3, rb_float_new(x), rb_float_new(y), rb_float_new(z) );
    return point;
}

This code takes a Point3d as parameter, adds one to each value and return the resulting Sketchup ruby object.

tt_su

You might want to make sure the user passed a Point3d object to your function.

Chris Lalancette got a nice series that digs into creating Ruby C Extensions:
http://clalance.blogspot.no/2011/01/writing-ruby-extensions-in-c-part-1.html

We recently released Ruby C++ Extension examples that include Visual Studio and Xcode projects as well as the exact binaries we use for SketchUp:
https://github.com/SketchUp/ruby-c-extension-examples

Anton_S

I find this point conversion useful, along with SketchUp Ruby C Extension / src / Example - Basics / SXBasics.c by Thom, which demonstrates conversion from SU Point3d to C.

@tt_su said:

You might want to make sure the user passed a Point3d object to your function.

Is there a way to check if passed item is a Point3d object?

Edit: I think it really doesn't matter because user may also pass their custom point3d classes or just an array. The rb_funcall( v_point, rb_intern("x"), 0 ) should do the job and raise an error if v_point doesn't respond to .x method.

Anton_S

Also, is SketchUp Length class handled well when it comes to converting it using NUM2DBL, or I should first convert it to float before passing to a c extension?

thomthom

@anton_s said:

@tt_su said:

You might want to make sure the user passed a Point3d object to your function.

Is there a way to check if passed item is a Point3d object?

Get a reference tot he Geom::Point3d class and invoke a call to is_a? or kind_of?.

thomthom

@anton_s said:

Also, is SketchUp Length class handled well when it comes to converting it using NUM2DBL, or I should first convert it to float before passing to a c extension?

Yes. Prior to SU2015 Length was hacked to be a subclass of Float. Now - that's not really possible in Ruby, but it was still done.
In 64bit Ruby that broke and we had to change it, it is now a Numeric which forwards to Float. Because of duck typing NUM2DBL should work.

Anton_S

Thank you Thom.