internal/restorable/image.go
func (i *Image) makeStale() {
	i.basePixels = nil
	i.drawTrianglesHistory = nil
	i.stale = true

	// Don't have to call makeStale recursively here.
	// Restoring is done after topological sorting is done.
	// If an image depends on another stale image, this means that
	// the former image can be restored from the latest state of the latter image.
}
func (i *Image) makeStale() {
	i.basePixels = nil
	i.drawTrianglesHistory = nil
	i.stale = true

	// Don't have to call makeStale recursively here.
	// Restoring is done after topological sorting is done.
	// If an image depends on another stale image, this means that
	// the former image can be restored from the latest state of the latter image.
}
// makeStale makes the image stale.