[PATCH v1 5/6] Documentation: guides: pipeline-handler: Simplify format collection

[Kieran Bingham]

Quoting Barnabás Pőcze (2024-12-09 17:48:05)
> I believe a simple range based for loop is easier to understand
> here than `std::transform()`. Furthermore, using a for loop enables
> the easy filtering of invalid pixel formats.
> 

I agree, I find the std::transform() difficult to interpret.

I prefer this - but it probably needs to be tested in the vivid pipeline
handler and updated on that tree too to keep these consistent.

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>


> Signed-off-by: Barnabás Pőcze <barnabas.pocze at ideasonboard.com>
> ---
>  Documentation/guides/pipeline-handler.rst | 18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/Documentation/guides/pipeline-handler.rst b/Documentation/guides/pipeline-handler.rst
> index b65145e3a..a798733db 100644
> --- a/Documentation/guides/pipeline-handler.rst
> +++ b/Documentation/guides/pipeline-handler.rst
> @@ -827,9 +827,7 @@ To generate a ``StreamConfiguration``, you need a list of pixel formats and
>  frame sizes which are supported as outputs of the stream. You can fetch a map of
>  the ``V4LPixelFormat`` and ``SizeRange`` supported by the underlying output
>  device, but the pipeline handler needs to convert this to a
> -``libcamera::PixelFormat`` type to pass to applications. We do this here using
> -``std::transform`` to convert the formats and populate a new ``PixelFormat`` map
> -as shown below.
> +``libcamera::PixelFormat`` type to pass to applications.
>  
>  Continue adding the following code example to our ``generateConfiguration``
>  implementation.
> @@ -839,14 +837,12 @@ implementation.
>     std::map<V4L2PixelFormat, std::vector<SizeRange>> v4l2Formats =
>             data->video_->formats();
>     std::map<PixelFormat, std::vector<SizeRange>> deviceFormats;
> -   std::transform(v4l2Formats.begin(), v4l2Formats.end(),
> -          std::inserter(deviceFormats, deviceFormats.begin()),
> -          [&](const decltype(v4l2Formats)::value_type &format) {
> -              return decltype(deviceFormats)::value_type{
> -                  format.first.toPixelFormat(),
> -                  format.second
> -              };
> -          });
> +
> +   for (auto &[v4l2PixelFormat, sizes] : v4l2Formats) {
> +           PixelFormat pixelFormat = v4l2PixelFormat.toPixelFormat();
> +           if (pixelFormat.isValid())
> +                   deviceFormats.try_emplace(pixelFormat, std::move(sizes));
> +   }
>  
>  The `StreamFormats`_ class holds information about the pixel formats and frame
>  sizes that a stream can support. The class groups size information by the pixel
> -- 
> 2.47.1
>