Re: From seq[] to C array, the safest way...

[b3liever]

It's not a hack I don't know where it is documented but for this code:
    
    
    proc setDash*(cr: Context, dashes: openarray[float64], offset: float64) 
{.importc: "cairo_set_dash".}
    var
      dashes = @[
        50.0,  # ink
        10.0,  # skip
        10.0,  # ink
        10.0   # skip
      ]
      offset = -50.0
    
    ctx.setDash(dashes, offset)
    
    
    Run

compiler turns it into: 
    
    
    dl(ctx, dashes.p->data, dashes.len, offset);
    
    
    Run

Also works correctly when dashes is an array. so for me it's the safest choice.