Re: [mediacapture-image] Clarify meaning of PTZ constraints presence (#256)

I raised a similar concern when the boolean override was proposed since pan: {} is not different from having the property unconstrained in terms of the SelectSettings algorithm.
The issue was resolved by stating that the presence of the property (even if unconstrained) means that the PTZ capability is being requested.
To me, this was enough to have a meaning that was precise enough to produce an implementation.
In this case
{pan: true} means that PTZ is required and, when not available, gUM() fails with OverconstrainedError if used in the basic set (the set is ignored if used in an advanced set) . The somewhat confusing part is that "pan: true" looks more like an ideal naked value if used in the basic set.
There is one proposal is to treat {pan: true} (and pan:{})  like an ideal value and make it mean "prefer" the PTZ capability, but not require it. This would mean that there is no way to require the PTZ capability, which is the intended result of the proposal.

Option 3 is similar to the current spec, except that has more possibilities. I would interpret it as follows (unless some other explicit meaning is given): 
- pan: {ideal: true} would mean prefer a camera with pan (PTZ) capability
- pan: {exact: true}, would mean require a camera with pan capability (OverconstrainedError if not possible in basic set, or ignore in advanced set)
- pan: {ideal: false}, would  mean prefer a camera without pan capability
- pan: {exact: false}, would mean require a camera without pan capability 
-pan: {ideal: 10} would mean prefer a camera with pan capability and preferably set pan to 10.
-pan: {exact: 10} would mean require a camera with pan capability and set pan to 10. (OverconstrainedError if not possible in basic set, ignore in advanced)

Not sure if the extra complexity of allowing pan to be used this way or in the usual DoubleConstraint way is worth it over using a separate constraint for the PTZ capability.

-- 
GitHub Notification of comment by guidou
Please view or discuss this issue at https://github.com/w3c/mediacapture-image/issues/256#issuecomment-689017348 using your GitHub account


-- 
Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config

Received on Tuesday, 8 September 2020 17:10:27 UTC