[libcamera-devel] [PATCH v5 0/3] Python bindings

[Tomi Valkeinen]

On 17/03/2022 11:55, Tomi Valkeinen wrote:
> On 17/03/2022 11:44, David Plowman wrote:
>> Hi everyone
>>
>> Thanks for the update!
>>
>> On Mon, 14 Mar 2022 at 15:46, Tomi Valkeinen
>> <tomi.valkeinen at ideasonboard.com> wrote:
>>>
>>> Hi,
>>>
>>> This is v5 of the series. The changes to v4:
>>>
>>> - Changed to pybind11 'smart_holders' branch which allows us to drop the
>>>    HACK for Camera public destructor
>>> - Changed Request.set_control() so that we can drop the HACK for
>>>    exposing Camera from Request
>>> - Moved Python enum defs to a separate file for clarity
>>> - "Forward" declare Python classes to fix docstring issues.
>>>
>>> The set_control change breaks the current users of that function.
>>> Previously you could do this:
>>>
>>> req.set_control("Brightness", 1)
>>>
>>> Now you need to do:
>>>
>>> cid = camera.find_control("Brightness")
>>> req.set_control(cid, 1)
>>>
>>
>> I see the need for this, and I guess it's fine - obviously we'll hide
>> that under our Picamera2 API as we wouldn't want our users to have to
>> do that!

I think the core question is whether a Request is tied to a Camera. I 
thought it is, as it is created from the Camera. And if that's the case, 
I don't see why the Camera cannot be exposed from the Request.

Maybe Laurent can explain the reasons why not to expose it.

> Yes, it's not very nice. Then again, having to do a string search every 
> time we call set_control is not good either, at least if we can avoid it 
> (and we can, as above). But I agree that in a higher level API things 
> should be easy. Of course, it would be nice to have both versions even 
> in this low level API, but... if Request doesn't expose camera, I don't 
> think we can do it in a simple way.

Note that there are multiple ways to approach this. E.g.:

req.set_control(camera.controls["Brightness"], 1)

or:

req.set_control(camera.controls.Brightness, 1)

or even (although this could perhaps conflict too easily):

req.set_control(camera.Brightness, 1)

Or we could go the other way:

camera.set_control(req, "Brightness", 1)

or:

camera.controls.Brightness.set(req, 1)

  Tomi