Empty itemType → loading state (backdrop visible, glyph hidden). Non-empty itemType → placeholder fallback state (backdrop + tinted glyph).

Resize the backdrop and glyph to track the parent's declared dimensions. Glyph uses scaleToFit (declared in XML) so the 256×256 placeholder PNG renders centered at the smaller of width/height, preserving aspect ratio. setFields batches the two writes per child, halving the field-write count.