Re: [RFC PATCH 6/9] ui/gtk: Add a new parameter to assign connectors/monitors to GFX VCs

[Markus Armbruster <armbru@redhat.com>]

"Kim, Dongwon" <dongwon.kim@intel.com> writes:

> On 7/10/2023 11:36 PM, Markus Armbruster wrote:
>> "Kim, Dongwon" <dongwon.kim@intel.com> writes:
>>
>>> On 7/9/2023 11:05 PM, Markus Armbruster wrote:
>>>> "Kim, Dongwon" <dongwon.kim@intel.com> writes:
>>>>
>>>>> On 7/7/2023 7:07 AM, Markus Armbruster wrote:

[...]

>>>>>> Old question not yet answered: Using a list for the mapping means the
>>>>>> mapping must be dense, e.g. I can't map #0 and #2 but not #1.  Is this
>>>>>> what we want?
>>>>>
>>>>> No, it doesn't have to be dense. In your example, you can just leave the place for VC1 blank. For example, you could do connectors.0=DP-1,connectors.2=HDMI-1. But in this case, VC1 won't be activated and stay as disconnected from guest's perspective. I think this info is also needed in v2.
>>>>
>>>> Have you tried this?  I believe it'll fail with something like
>>>> "Parameter 'connectors.1' missing".
>>>
>>> Just tested it. Yeah you are correct. I think I had a bad assumption. Let me take a look to see if I can make it work as I assumed.
>>
>> If sparse mappings make sense, we should provide for them, I think.
>>
>> An array like '*connectors': ['str'] maps from integers 0, 1, ...  It
>> can't do sparse (you can't omit integers in the middle).
>
> Yeah, I understand this now. Despite of my initial intention was different, I am wondering if we don't allow the sparse mapping in this implementation. Any thought on that?

Repeating myself: if sparse mappings make sense, we should provide for
them, I think.

So, do they make sense?  Or asked differently, could a user conceivably
want to *not* place a VC?

> The V2 patch is with that change in the description. Another thing I think is to change QAPI design little bit to make it fill the element with null (0) if it's not given. Would this be a feasible option?

A 'str' cannot be NULL.  In fact, no QAPI type can be null, except for
'null' (which is always NULL), alternates with a 'null' branch, and
pointer-valued optionals (which are null when absent).

>> Instead of omitting them, we could map them to null: '*connectors':
>> ['StrOrNull'].  JSON input looks like [null, "HDMI-A-0"].  Since dotted
>> key syntax does not support null at this time, you'd have to use JSON.
>>
>> Only an object can do sparse.  However, the QAPI schema language can't
>> express "object where the keys are integers and the values are strings".
>> We'd have to use 'any', and check everything manually.
>>
>> Hmm.  Thoughts?
>>
>>>>>> [...]