Half-baked API (Camera position)

[Stephen F Northover]

The problem is this:  How is anyone supposed to ever do anything with 
this?  I suppose they call the thing by mistake, get an exception and 
then never call it again.  Then, later on, we come along and fix it.

If the original people ever catch the exception and do something, then 
when we stop throwing the exception, they will be broken. Exceptions are 
API.  I suppose the odds of people catching and exception like this and 
doing something are low but it is a possibility.

I would rather do something sensible with it now as best we can and 
document it.  In the future, if this turns out not to be a good thing, 
we add a new API that gives a better result (ie. intersectedDistance3D() 
or whatever).

Steve


On 2013-10-16 3:37 PM, Pavel Safrata wrote:
> As I've said, we intend to fix it in the future, so the situation 
> should not be impossible. It is mostly used that way in the existing 
> code, but there definitely are precedents for throwing it just 
> temporarily. For instance:
>
> nodeOrientationProperty().getCssMetaData:
>         throw new UnsupportedOperationException("Not supported yet.");
>
> or
>
> MeshView.impl_computeContains():
>         throw new UnsupportedOperationException("Not supported yet.");
> (internal but directly accessible to users via contains())
>
> Pavel
>
> On 16.10.2013 20:10, Stephen F Northover wrote:
>> I took a quick look through JavaFX to find how this exception is 
>> used. It is mostly used to indicate impossible situation.  Is that 
>> the situation we have here?
>>
>> Personally, for me, if we throw the exception, then we will generally 
>> just leave it that way forever.
>>
>> Steve
>>
>> On 2013-10-16 11:22 AM, Pavel Safrata wrote:
>>> On 16.10.2013 17:03, Stephen F Northover wrote:
>>>> Could do something useful with what was there now?  We can always 
>>>> fix this in future by adding another API to govern the 
>>>> interpretation of the value.
>>>
>>> Not much useful. Anyway, any such stuff can be quite easily done by 
>>> reading the intersectedPoint's Z coordinate.
>>>
>>>>
>>>> Throwing the exception indicates that the call is unsupported, but 
>>>> application code can be written to catch the exception and when we 
>>>> implement the API, it can break (I realize that this is unlikely).
>>>
>>> The exception can tell by the message that the operation will be 
>>> supported in the future.
>>>
>>> Pavel
>>>
>>>>
>>>> Steve
>>>>
>>>> On 2013-10-16 10:46 AM, Richard Bair wrote:
>>>>> My quick vote would be throwing the exception, but is like to hear 
>>>>> from Steve and Kevin.
>>>>>
>>>>>> On Oct 16, 2013, at 1:04 AM, Pavel Safrata 
>>>>>> <pavel.safrata at oracle.com> wrote:
>>>>>>
>>>>>> Hello,
>>>>>> it looks like we can't help releasing a not-fully-baked piece of 
>>>>>> API with FX8. We've added bunch of new APIs for 3D and did our 
>>>>>> best to make them work well. Unfortunately, there's been not 
>>>>>> enough time&priority to fine-tune their behavior in 2D world. 
>>>>>> Right now I'm concerned about camera position in scene. It is 
>>>>>> inherent in the 3D perspective camera that it has its specific 
>>>>>> position in world, but the 2D parallel camera as we have it 
>>>>>> projects everything to the XY plane basically by ignoring the Z 
>>>>>> coordinate, so the camera position doesn't matter all that much. 
>>>>>> However, some of the newly added APIs depend on it:
>>>>>>
>>>>>> 1. Near/far clip on camera. This obviously cannot work without 
>>>>>> knowing where the camera is. Right now the parallel camera does 
>>>>>> no clipping though, so I guess we are OK to go with it as a 
>>>>>> "known limitation".
>>>>>>
>>>>>> 2. PickResult on events which reports "intersectedDistance" 
>>>>>> between the camera and the picked point. This is worse because we 
>>>>>> can't just "not support" it - there will be some value and once 
>>>>>> somebody uses it we'll have a backward compatibility issue. The 
>>>>>> state right now is that the camera is (tentatively, by my 
>>>>>> arbitrary decision) at [0, 0, -1] and reports distances from 
>>>>>> there (note that as the camera renders everything, for nodes "in 
>>>>>> front of Z=-1" it reports negative distances). This may change 
>>>>>> when the camera position is properly discussed and specified.
>>>>>>
>>>>>> Note that this post is *not* meant to discuss the camera 
>>>>>> position. Even if we could find the answer quickly (which I 
>>>>>> doubt), it's most probably too late to apply the change for FX8.
>>>>>>
>>>>>> So finally here is my question: do you think it's OK to solve 
>>>>>> this by keeping the current behavior and documenting the 
>>>>>> "intersectedDistance" in a way that for parallel camera the 
>>>>>> numbers are unspecified and subject to change in future versions? 
>>>>>> Or would you prefer something more drastic like throwing an 
>>>>>> UnsupportedOperationException (losing the possibility to compare 
>>>>>> the distances)?
>>>>>>
>>>>>> Thanks,
>>>>>> Pavel
>>>>
>>>
>>
>