+ /* This function is typically called by redisplay just before
+ outputting the information to the screen. Thus we record a hash
+ of the output to determine whether on-screen is the same as
+ recorded structure. This approach has limitations in there is a
+ good chance that hash values will be different for the same
+ visual appearance. However, we would rather that then the other
+ way round - it simply means that we will get more displays than
+ we might need. We can get better hashing by making the depth
+ negative - currently it will recurse down 5 levels.*/
+ IMAGE_INSTANCE_DISPLAY_HASH (ii) = display_hash;