Ordering or preference for multiple file references

[deboer-tim]

One nit I noticed while implementing the light/dark file reference tags (#227): let's say you're configuring a contest and you have a light and a dark image, but you want a specific one of them to be used by clients that don't specify a tag. e.g. maybe the light one has a border that works better against random backgrounds. Currently, there's no way to ensure that the light image comes 'first' or is picked up by clients that don't check for tags, even if you try something like providing a third untagged image. The Contest API server could serve them in any order and you don't know how clients will pick them anyway.

Prior to this I've heard of clients that always take the first image regardless of sizes available and ordering of them, so this is somewhat an existing issue.

I don't think we can or should create rules here, but maybe we can list a best practice about how a server should order file references?

[niemela]

Prior to this I've heard of clients that always take the first image regardless of sizes available and ordering of them, so this is somewhat an existing issue.

This feels a little bit like a case of "bad implementations will get bad results".

I don't think we can or should create rules here, but maybe we can list a best practice about how a server should order file references?

The only think I can think of is to say that servers should list the most generically recommended version (i.e. the least specialized?) first. Basically what we would be saying is "look, some client will just pick the first one, so put whatever you think a client that doesn't look at any of the metadata should probably pick". So, the most "reasonably" sized (large, but no too large), most normal (light over dark?) version of the an image should be first?

I don't love this at all... but I definitely see your point.

[deboer-tim]

Prior to this I've heard of clients that always take the first image regardless of sizes available and ordering of them, so this is somewhat an existing issue.

This feels a little bit like a case of "bad implementations will get bad results".

I don't think we can or should create rules here, but maybe we can list a best practice about how a server should order file references?

The only think I can think of is to say that servers should list the most generically recommended version (i.e. the least specialized?) first. Basically what we would be saying is "look, some client will just pick the first one, so put whatever you think a client that doesn't look at any of the metadata should probably pick". So, the most "reasonably" sized (large, but no too large), most normal (light over dark?) version of the an image should be first?

I don't love this at all... but I definitely see your point.

I agree with all your points too. 'When in doubt, pick the first' is maybe the best we can do, but I still don't know how someone with a light and dark logo correctly filenamed can also suggest to the server which might be first, e.g. do they provide an untagged version, an extra tag, or do they have to provide the json list. 🤷🏼‍♂️

[niemela]

IMO there are two obvious options:

1. make the "if you can't bother, just pick the first" explicit, so that servers can make sure that the first is not a terrible choice. Advantage is that this is dead simple for clients, and not too terrible for servers. Disadvantage is that this encourages not bothering.
2. add a special "default" variant that there can be only one of and that is required when there is more than one thing. The recommendation now becomes "if you can't bother, just pick the default". Advantage is that it's more obvious from just reading the API or feed, and that it encourages (well, kinda requires) clients to look at the variant. Disadvantage is that it's less simple to clients and doesn't actually solve the problem with clients that can't bother, at all.

I think I prefer option 1.... (but I still don't like it 😄)

[deboer-tim]

IMHO there often is no global default or 'best', e.g. my scoreboards will pick small logos because they load faster, but may pick different options based on screen resolution. So, I don't want to let clients off the hook and maybe we should put the worst image first to discourage this 😁. But yeah, I don't like option 2 either.

I am mostly trying to figure out how clients who don't understand light/dark yet - or whatever the next tags will be - should pick when there are two 'equivalent' images. For this option 1 would be fine, we just need a mild statement somewhere about ordering.

But to be really specific, take an example like this:

organizations/tudelft/logo.dark.png
organizations/tudelft/logo.light.png

The person who created these likely knows which one generally works better on any background (i.e. which logo they would have used before variants were supported), but there's nothing in the filenames for the server to implement either option. Today it's likely that different servers expose these in different orders, and it's not clear to me whether the author should have also created a logo.png, modified one of the filenames (if so how?), or something else.