Represents an adjustment to apply to an image primitive.
This can be used to compensate for a difference between the bounds of
the images expected by the primitive and the bounds that were actually
drawn in the texture cache.
Instance specific fields for an image primitive. These are
currently stored in a separate array to avoid bloating the
size of PrimitiveInstance. In the future, we should be able
to remove this and store the information inline, by:
(a) Removing opacity collapse / binding support completely.
Once we have general picture caching, we don’t need this.
(b) Change visible_tiles to use Storage in the primitive
scratch buffer. This will reduce the size of the
visible_tiles field here, and save memory allocation
when image tiling is used. I’ve left it as a Vec for
now to reduce the number of changes, and because image
tiling is very rare on real pages.