Add attachment dynamicaly into spine : Canvas + WebGL

spine_attachment.dart

  /// create an empty BitmapData of the desired Label size
  _spinLabelData = new BitmapData(120, 60, true, 0x00000000);
  /// create a Label of the same bounding size with the correct style and text
  _spinLabel = new Label(_spinLabelData.width, _spinLabelData.height)
    ..text = spinTranslation
    ..style = getDefaultStyle()
    ..align = Align.center
    ..x = _spinLabelData.width/2
    ..y = _spinLabelData.height/2;
  /// create a "out of scope" container to render the label correctly
  _spinLabelContainer = new Sprite();
  _spinLabelContainer.addChild(_spinLabel);
  /// draw the container ( containing the label) in the bitmap data
  _spinLabelData.draw(_spinLabelContainer);

  /// name of the slot element in spine
  /// + name of the new attachment we will create
  String name = 'spin_texte';
  /// create new Attachment
  /// scaleX and ScaleY = 1.5 are necessary to compensate the 2/3 scale of the SkeletonAnimation object
  RegionAttachment attachment = new RegionAttachment(name, _spinLabelData)
    ..width = _spinLabelData.width
    ..height = _spinLabelData.height
    ..scaleX = 1.5
    ..scaleY = 1.5
    ..updateUVs()
    ..updateOffset();
  /// find index of the slot that will contain our attachment
  int slotIndex = assets.skeleton.findSlotIndex(name);
  /// add our attachment in the first skin of the spine
  /// !! may not work if more than 1 skin
  assets.skeleton
    ..findSlot(name).attachmentName = name
    ..skins.first.addAttachment(slotIndex, name, attachment);


  /// create and addChild the skeleton animation
  _spineAnim = new SkeletonAnimation(assets.skeleton)
    ..scaleX = 2 / 3
    ..scaleY = 2 / 3;
  addChild(_spineAnim);