getImageTextureKey

Texture cache key for the shape's pixels, or null when it must stay on the DOM overlay.

The GPU path only covers the plain case. The engine maps uv 0..1 over the shape's local geometry bounds, so a crop window or a flip would need the quad to carry its own uvs; until the bridge does, cropped and flipped images (and anything without a decoded source) are drawn by component.

Assets are treated as immutable, so the key is the asset id: replacing an asset's src in place keeps the cached texture.