BrightScript vs XML: Scenography

When i wrote the above SG "format" in B/S, i was trying to stay as close to XML as possible. So while better than XML, it's not exactly how a developer is inclined to write structures. But in my defense that format has a 1:1 mapping to XML, is non-ambiguous and i was planning of writing converter utility function, to build SG tree from it. Alas, the title "BrightScript/XML Markup Equivalence" i have seen turned out to be a ruse - there is no way (yet) to dynamically declare a new component type or add/change functions to it.

Now, if Roku's SG were properly supported by BrightScript, i should be able to do something like this instead (look ma, no xml!):

mg_ex = createObject("roSgNode", "Group")

mg_ex.createChild("MaskGroup", {id: "exampleMaskGroup", 
    maskuri: "pkg:/images/GradientLinear.png", masksize: [512, 288], maskOffset: [0, 0]
    children: [ 
      createObject("roSgNode", "Poster", {uri: "pkg:/images/dialogpg.jpg", width: 512, height: 288}) 
    ]
})

mga = createObject("roSgNode", "Animation", {id: "MaskGroupAnimation", 
    duration: 3, easeFunction: "linear", repeat: true
    children: [ 
      createObject("roSgNode", "Vector2DFieldInterpolator", {id: "interpolator", 
        fieldToInterp: "exampleMaskGroup.maskOffset", 
        key: [0.0, 0.50, 1.0], keyValue: [[512,0], [-512,0], [512,0]] 
      }) 
    ]
})
mg_ex.appendChild(mga)
mga.control = "start"

Much better but still tad tedious, since there is createObject() within createObject() or the use temp variables. But notice how "the need" to sub-class and write an initializer vanished naturally.

We can do better too, describe the object like so:

MaskGroupExample = { type: "Group"

  init: function()
      maskgroupanimation = m.top.findNode("MaskGroupAnimation")
      maskgroupanimation.control = "start"
  end function
  
  children: [
    { type: "MaskGroup", id: "exampleMaskGroup", 
      maskuri: "pkg:/images/GradientLinear.png", masksize: [512, 288], maskOffset: [0, 0]
      children: [ 
        { type: "Poster", uri: "pkg:/images/dialogpg.jpg", width: 512, height: 288}
      ]
    }
    
    { type: "Animation", id: "MaskGroupAnimation", 
      duration: 3, easeFunction: "linear", repeat: true
      children: [ 
        { type: "Vector2DFieldInterpolator", id: "interpolator", 
          fieldToInterp: "exampleMaskGroup.maskOffset", 
          key: [0.0, 0.50, 1.0], keyValue: [[512,0], [-512,0], [512,0]] 
        }
      ]
    }
  ]
}

So that's ust a roAA, what do we do with it? Well, in a perfect world i should be able to create the node by calling

mg_ex = createObject("roSgNode", MaskGroupExample)

i.e. passing roAA as argument (instead of string) would be walked by the sgNode constructor, creating all nested nodes. In the mean time though - till the cows come home - it's trivial for us to write own B/S utility function that does the same by walking the tree and createObject() the nested levels.