[libcamera-devel] [PATCH v3 00/17] Python bindings event handling

[Laurent Pinchart]

Hi Tomi,

On Fri, Jul 01, 2022 at 11:45:04AM +0300, Tomi Valkeinen wrote:
> Hi,
> 
> v3 introduces an alternative new event system compared to the v2. I like
> this one much better. It's much simpler and more understandable.
> 
> The series has been re-arranged a bit so that up to, and including, the
> "py: Switch to non-blocking eventfd" patch, there are no API changes.
> Except a small thing, the change to non-blocking. Afaik this should not
> cause breakage in picamera2. These can be merged after reviews.
> 
> Then we break the API with the use of exceptions instead of return
> codes. And continue by adding the new API for the events, but keeping
> the deprecated get_ready_requests.
> 
> One particular thing I want to mention about the new event system is
> that most of the events are always subscribed, so the user will e.g. get
> CameraAdded event without specifically subscribing to it. The only
> exception is the BufferCompleted event, and I had no other reason for
> this than I just thought it's rarely used (?), we get it every frame,
> and thus making it opt-in reduces the extra overhead. But I really have
> no idea if it's really rarely used, and if the overhead is even
> noticeable.
> 
> I first tried with a full opt-in approach, but I'm not sure what would
> be a good API for that. I tried with a setEvents(event_mask) but that's
> not very nice to use. We could perhaps have a container struct with a
> bool for each event type, so that you'd do something like:
> 
> cm.enabled_events.buffer_completed = True
> cm.enabled_events.camera_added = True
> 
> Or we could add a parameter to camera.start() to define which events the
> user is interested in (but this wouldn't cover Camera Added/Removed).

How about enableEvents() and disableEvents() methods that take a bitmask
of events to enable or disable ?

> Tomi Valkeinen (17):
>   py: cam.py: Fix multi camera capture without -C
>   py: Add Python logging category
>   py: Move ControlValue helpers to py_helpers.cpp
>   py: cam.py: Remove todo comment
>   py: Create PyCameraManager
>   py: Use UniqueFD
>   py: Set EFD_CLOEXEC on eventfd to avoid fd leaking
>   py: Use libcamera's Mutex classes
>   py: Switch to non-blocking eventfd
>   py: Use exceptions instead of returning error codes
>   py: New event handling
>   py: cam.py: Use new events support
>   py: unittests.py: Use new events support
>   py: simple-capture.py: Use new events support
>   py: simple-continuous-capture.py: Use new events support
>   py: simple-cam.py: Use new events support
>   py: Add hotplug-monitor.py
> 
>  src/py/cam/cam.py                            |  55 ++--
>  src/py/examples/hotplug-monitor.py           |  39 +++
>  src/py/examples/simple-cam.py                |  31 +-
>  src/py/examples/simple-capture.py            |  41 +--
>  src/py/examples/simple-continuous-capture.py |  37 +--
>  src/py/libcamera/meson.build                 |   2 +
>  src/py/libcamera/py_camera_manager.cpp       | 286 ++++++++++++++++++
>  src/py/libcamera/py_camera_manager.h         |  95 ++++++
>  src/py/libcamera/py_helpers.cpp              |  97 ++++++
>  src/py/libcamera/py_helpers.h                |  13 +
>  src/py/libcamera/py_main.cpp                 | 297 +++++++------------
>  src/py/libcamera/py_main.h                   |  14 +
>  test/py/unittests.py                         |  93 +++---
>  13 files changed, 781 insertions(+), 319 deletions(-)
>  create mode 100644 src/py/examples/hotplug-monitor.py
>  create mode 100644 src/py/libcamera/py_camera_manager.cpp
>  create mode 100644 src/py/libcamera/py_camera_manager.h
>  create mode 100644 src/py/libcamera/py_helpers.cpp
>  create mode 100644 src/py/libcamera/py_helpers.h
>  create mode 100644 src/py/libcamera/py_main.h

-- 
Regards,

Laurent Pinchart