[libcamera-devel] [PATCH v2 1/2] libcamera: control: initialise control info to ControlTypeNone by default

[David Plowman]

Hi Christian

I have a question about this because it's causing my Python code to
break. Not in any major way, we just need to decide what we want to do
about it.

The problem is that you can no longer fetch the default value for a
control, it causes a runtime error. The code in question is here:
https://git.linuxtv.org/libcamera.git/tree/src/py/libcamera/py_helpers.cpp#n57

There are a number of straightforward solutions, such as returning
"py::none()", for example. Does that sound like a reasonable thing to
do?

Thanks!
David

On Tue, 30 Aug 2022 at 21:21, Christian Rauch via libcamera-devel
<libcamera-devel at lists.libcamera.org> wrote:
>
> The default ControlInfo constructor allows to partially initialised the
> min/max/def values. Uninitialised values are assigned to 0 by default. This
> implicit initialisation makes it impossible to distinguish between and
> uninitialised and an explicitly 0-initialised ControlValue.
>
> Default construct the ControlValue in the ControlInfo default contructor to
> explicitly represent uninitialised values by the ControlTypeNone type.
>
> Signed-off-by: Christian Rauch <Rauch.Christian at gmx.de>
> ---
>  include/libcamera/controls.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h
> index ebc168fc..38d0a3e8 100644
> --- a/include/libcamera/controls.h
> +++ b/include/libcamera/controls.h
> @@ -268,9 +268,9 @@ private:
>  class ControlInfo
>  {
>  public:
> -       explicit ControlInfo(const ControlValue &min = 0,
> -                            const ControlValue &max = 0,
> -                            const ControlValue &def = 0);
> +       explicit ControlInfo(const ControlValue &min = {},
> +                            const ControlValue &max = {},
> +                            const ControlValue &def = {});
>         explicit ControlInfo(Span<const ControlValue> values,
>                              const ControlValue &def = {});
>         explicit ControlInfo(std::set<bool> values, bool def);
> --
> 2.34.1
>