vmpstr@, do you have any thoughts on this? We could simply move pre-decoding and locking of checkerable images to use the decode service but that would mean that the upload would happen only when these tiles come within the prepaint region.

Yeah I think moving the predecode images to use the service is worth pursuing. You're right that we'll need better scheduling. We could do something similar to checker imaging tracker for this.

Since we now have a prioritized queue for images given to the tracker, the scheduling there should work fine. The tracker would just need an additional bit for which images are pre-decodes so it doesn't request an impl-side invalidation for them, but keeps them locked.

Checkerable pre-decodes go to the image worker now, similar to all other image decodes. I think there is one area of optimization here. Since we know that these images may have never been used for raster, we can avoid create a pending tree invalidation for them and just pass the ref for the decode from the checker image tracking to the ImageController which keeps refs for other predecode images.