Update: My bad. I was including an alpha value in the color array. Being used to perl sub just ignoring extra args whilst I worked out how to use aplha values in OpenGL. But XS subs aren't like perl subs, and the extra value causes the sub to print it's usage message and fail. :(

I finally got OpenGL built and installed and I'm just starting to play with it and I encountered a Perl problem that I haven't experienced before. I'm trying to call glColor3f() within a subroutine into which I'm passing an array ref containing the rgb values.

  1. My first attempt was: glColor3f( @$ref ); fails!

    But that (and all other failures) bellyaches Usage: OpenGL::glColor3f(red, green, blue) at...

  2. So then I tried hard coding the numbers:glColor3f( 1.0, 0.0, 0.0 ); works!
  3. So then I tried glColor3f( $ref->[ 0 ], $ref->[ 1 ], $ref->[ 2 ] ); works!
  4. Hm! Prototype problem? &glColor3f( @$ref ); Fails!
  5. Then I tried: glColor3f( @{ $ref }[ 0, 1, 2 ] ); works!
  6. Then I tried: glColor3f( map $_, @$ref ); fails!

Quick peruse of the xs source shows: 

void
glColor3f(red, green, blue)
    GLfloat red
    GLfloat green
    GLfloat blue

[download]

Which doesn't clarify what's going on. Can you?

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In reply to XS prototype (or not) problem? by BrowserUk

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