[RFC PATCH v1 2/5] apps: cam: sdl_texture: Add single plane generic texture

[Barnabás Pőcze]

Hi


2025. 04. 23. 1:40 keltezéssel, Laurent Pinchart írta:
> Hi Barnabás,
> 
> Thank you for the patch.
> 
> On Mon, Apr 21, 2025 at 05:51:06PM +0200, Barnabás Pőcze wrote:
>> Add the `SDLTexture1Plane` type that can be instantiated with
>> an arbitrary SDL pixel format and that uses `SDL_UpdateTexture()`
>> to update the texture using exactly a single plane.
> 
> You can squash patches 2/5, 3/5 and 4/5 together. The commit message can
> be reworded to explain how SDLTextureYUYV is generalized for later use
> with other 1-plane formats.
> 
>> Signed-off-by: Barnabás Pőcze <barnabas.pocze at ideasonboard.com>
>> ---
>>   src/apps/cam/sdl_texture_1plane.h | 18 ++++++++++++++++++
>>   1 file changed, 18 insertions(+)
>>   create mode 100644 src/apps/cam/sdl_texture_1plane.h
>>
>> diff --git a/src/apps/cam/sdl_texture_1plane.h b/src/apps/cam/sdl_texture_1plane.h
>> new file mode 100644
>> index 000000000..ded35c589
>> --- /dev/null
>> +++ b/src/apps/cam/sdl_texture_1plane.h
>> @@ -0,0 +1,18 @@
>> +#pragma once
>> +
>> +#include <assert.h>
>> +
>> +#include "sdl_texture.h"
>> +
>> +class SDLTexture1Plane final : public SDLTexture
>> +{
>> +public:
>> +	using SDLTexture::SDLTexture;
>> +
>> +	void update(libcamera::Span<const libcamera::Span<const uint8_t>> data) override
>> +	{
>> +		assert(data.size() == 1);
>> +		assert(data[0].size_bytes() == std::size_t(rect_.h * stride_));
>> +		SDL_UpdateTexture(ptr_, nullptr, data[0].data(), stride_);
> 
> No need to pass &rect_ as the second argument, like done by
> SDLTextureYUYV ?

As far as I can see it is only required if only a part of the texture is to be updated,
and if it is `nullptr, then SDL updates the full size of the texture, which is what
is wanted here.

   https://github.com/libsdl-org/SDL/blob/3343cb21473ea454261bc4187393aaec9cc3f28f/src/render/SDL_render.c#L2153


Regards,
Barnabás Pőcze

> 
>> +	}
>> +};
>