apps: cam: sdl_texture: Add SDLTexture1Plane

`SDLTextureYUYV` uses `SDL_PIXELFORMAT_YUY2`, which is a single plane
format. To support other single plane formats, replace `SDLTextureYUYV`
with `SDLTexture1Plane` that can be instantiated with an arbitrary SDL
pixel format and that uses `SDL_UpdateTexture()` to update the texture
using exactly a single plane.

Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/apps/cam/meson.build

@@ -34,6 +34,7 @@ if libsdl2.found()
     cam_sources += files([
         'sdl_sink.cpp',
         'sdl_texture.cpp',
+        'sdl_texture_1plane.cpp',
         'sdl_texture_yuv.cpp',
     ])
 

src/apps/cam/sdl_sink.cpp

@@ -22,6 +22,7 @@
 #include "../common/event_loop.h"
 #include "../common/image.h"
 
+#include "sdl_texture_1plane.h"
 #ifdef HAVE_LIBJPEG
 #include "sdl_texture_mjpg.h"
 #endif
@@ -74,7 +75,7 @@ int SDLSink::configure(const libcamera::CameraConfiguration &config)
 		break;
 #endif
 	case libcamera::formats::YUYV:
-		texture_ = std::make_unique<SDLTextureYUYV>(rect_, cfg.stride);
+		texture_ = std::make_unique<SDLTexture1Plane>(rect_, SDL_PIXELFORMAT_YUY2, cfg.stride);
 		break;
 	default:
 		std::cerr << "Unsupported pixel format "

src/apps/cam/sdl_texture_1plane.cpp

@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2025, Ideas on Board Oy
+ *
+ * SDL single plane textures
+ */
+
+#include "sdl_texture_1plane.h"
+
+#include <assert.h>
+
+void SDLTexture1Plane::update(libcamera::Span<const libcamera::Span<const uint8_t>> data)
+{
+	assert(data.size() == 1);
+	assert(data[0].size_bytes() == std::size_t(rect_.h) * std::size_t(stride_));
+	SDL_UpdateTexture(ptr_, nullptr, data[0].data(), stride_);
+}

src/apps/cam/sdl_texture_1plane.h

@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2025, Ideas on Board Oy
+ *
+ * SDL single plane textures
+ */
+
+#pragma once
+
+#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;
+};

src/apps/cam/sdl_texture_yuv.cpp

@@ -21,13 +21,3 @@ void SDLTextureNV12::update(libcamera::Span<const libcamera::Span<const uint8_t>
 			    data[1].data(), stride_);
 }
 #endif
-
-SDLTextureYUYV::SDLTextureYUYV(const SDL_Rect &rect, unsigned int stride)
-	: SDLTexture(rect, SDL_PIXELFORMAT_YUY2, stride)
-{
-}
-
-void SDLTextureYUYV::update(libcamera::Span<const libcamera::Span<const uint8_t>> data)
-{
-	SDL_UpdateTexture(ptr_, nullptr, data[0].data(), stride_);
-}

src/apps/cam/sdl_texture_yuv.h

@@ -17,10 +17,3 @@ public:
 	void update(libcamera::Span<const libcamera::Span<const uint8_t>> data) override;
 };
 #endif
-
-class SDLTextureYUYV : public SDLTexture
-{
-public:
-	SDLTextureYUYV(const SDL_Rect &rect, unsigned int stride);
-	void update(libcamera::Span<const libcamera::Span<const uint8_t>> data) override;
-};