libcamera::eGL Class Reference

Helper class for managing OpenGL ES operations. More...

Public Member Functions
	eGL ()
	Construct an EGL helper.
	~eGL ()
	Destroy the EGL helper.
int	initEGLContext ()
	Initialise the EGL context.
int	createInputDMABufTexture2D (eGLImage &eglImage, int fd)
	Create an input DMA-BUF backed texture.
int	createOutputDMABufTexture2D (eGLImage &eglImage, int fd)
	Create an output DMA-BUF backed texture.
void	createTexture2D (eGLImage &eglImage, void *data)
	Create a 2D texture from a memory buffer.
void	updateTexture2D (eGLImage &eglImage, void *data)
	Update a 2D texture already created.
void	createOutputTexture2D (eGLImage &eglImage)
	Create a 2D texture attached to an FBO for render-to-texture.
int	attachTextureToFBO (eGLImage &eglImage)
	Attach a texture to a frame-buffer-object.
void	activateBindTexture (eGLImage &eglImage)
	Activate a texture unit and bind a texture to that unit.
void	pushEnv (std::vector< std::string > &shaderEnv, const char *str)
	Add a preprocessor definition to shader environment.
void	makeCurrent ()
	Make the EGL context current for the calling thread.
int	compileVertexShader (GLuint &shaderId, Span< const unsigned char > shaderData, Span< const std::string > shaderEnv)
	Compile a vertex shader.
int	compileFragmentShader (GLuint &shaderId, Span< const unsigned char > shaderData, Span< const std::string > shaderEnv)
	Compile a fragment shader.
int	linkProgram (GLuint &programId, GLuint fragmentshaderId, GLuint vertexshaderId)
	Link a shader program.
void	dumpShaderSource (GLuint shaderId)
	Dump shader source code to the log.
void	useProgram (GLuint programId)
	Activate a shader program for rendering.
void	deleteProgram (GLuint programId)
	Delete a shader program.
void	syncOutput ()
	Synchronise rendering output.
void	flushOutput ()
	Flush the rendering pipeline.

Static Public Member Functions
static bool	isAvailable ()
	Probe whether EGL surfaceless rendering is available.

Detailed Description

Helper class for managing OpenGL ES operations.

It provides:

• EGL context setup and management
• Extension function pointer retrieval
• Shader compilation and program linking
• DMA-BUF texture creation and management
• Synchronisation primitives

This class is designed to work with zero-copy buffers via DMA-BUF file descriptors.

Constructor & Destructor Documentation

eGL()

libcamera::eGL::eGL

(

)

Construct an EGL helper.

Creates an eGL instance with uninitialised context. Call initEGLContext() to set up the EGL display, context, and load extension functions.

~eGL()

libcamera::eGL::~eGL

(

)

Destroy the EGL helper.

Destroys the EGL context and surface if they were successfully created.

Member Function Documentation

activateBindTexture()

void libcamera::eGL::activateBindTexture

(

eGLImage &

eglImage

)

Activate a texture unit and bind a texture to that unit.

Parameters

[in,out]

eglImage

EGL image containing data related to unit and texture id

When we create a texture we will bind a texture unit and texture id so we can set filters. For the case where a texture already exists though we need to activate and bind an existing texture. This helper function facilitates both cases.

attachTextureToFBO()

int libcamera::eGL::attachTextureToFBO

(

eGLImage &

eglImage

)

Attach a texture to a frame-buffer-object.

Parameters

[in,out]

eglImage

EGL image containing texture to attach to FBO

Helper function to make attachment of texture to FBO easy to reuse.

Returns

0 on success, or -ENODEV on failure

compileFragmentShader()

int libcamera::eGL::compileFragmentShader	(	GLuint &	shaderId,
		Span< const unsigned char >	shaderData,
		Span< const std::string >	shaderEnv )

Compile a fragment shader.

Parameters

[out]	shaderId	OpenGL shader object ID
[in]	shaderData	Shader source code
[in]	shaderEnv	Span of preprocessor definitions to prepend

Compiles a fragment shader from source code with optional preprocessor definitions. On compilation failure, logs the shader info log.

Returns

0 on success, or -EINVAL on compilation failure

compileVertexShader()

int libcamera::eGL::compileVertexShader	(	GLuint &	shaderId,
		Span< const unsigned char >	shaderData,
		Span< const std::string >	shaderEnv )

Compile a vertex shader.

Parameters

[out]	shaderId	OpenGL shader object ID
[in]	shaderData	Shader source code
[in]	shaderEnv	Span of preprocessor definitions to prepend

Compiles a vertex shader from source code with optional preprocessor definitions. On compilation failure, logs the shader info log.

Returns

0 on success, or -EINVAL on compilation failure

createInputDMABufTexture2D()

int libcamera::eGL::createInputDMABufTexture2D	(	eGLImage &	eglImage,
		int	fd )

Create an input DMA-BUF backed texture.

Parameters

[in,out]	eglImage	EGL image to associate with the DMA-BUF
[in]	fd	DMA-BUF file descriptor

Creates an EGL image from a DMA-BUF file descriptor and binds it to a 2D texture for use as an input texture in shaders. The texture is configured with nearest filtering and clamp-to-edge wrapping.

Returns

0 on success, or -ENODEV on failure

createOutputDMABufTexture2D()

int libcamera::eGL::createOutputDMABufTexture2D	(	eGLImage &	eglImage,
		int	fd )

Create an output DMA-BUF backed texture.

Parameters

[in,out]	eglImage	EGL image to associate with the DMA-BUF
[in]	fd	DMA-BUF file descriptor

Creates an EGL image from a DMA-BUF file descriptor and binds it to a 2D texture, then attaches it to a framebuffer object for use as a render target. This enables zero-copy rendering directly to the DMA-BUF.

Returns

0 on success, or -ENODEV on failure

createOutputTexture2D()

void libcamera::eGL::createOutputTexture2D

(

eGLImage &

eglImage

)

Create a 2D texture attached to an FBO for render-to-texture.

Parameters

[in,out]

eglImage

EGL image to associate with the texture

Creates a 2D texture in VRAM. Subsequetly attach the texture to the texture unit specified in the eGLImage object.

createTexture2D()

void libcamera::eGL::createTexture2D	(	eGLImage &	eglImage,
		void *	data )

Create a 2D texture from a memory buffer.

Parameters

[in,out]	eglImage	EGL image to associate with the texture
[in]	data	Pointer to pixel data, or nullptr for uninitialised texture

Creates a 2D texture from a CPU-accessible memory buffer. The texture is configured with nearest filtering and clamp-to-edge wrapping. This is useful for uploading static data like lookup tables or uniform color matrices to the GPU.

deleteProgram()

void libcamera::eGL::deleteProgram

(

GLuint

programId

)

Delete a shader program.

Parameters

[in]

programId

OpenGL program object ID

Deletes a shader program and frees associated resources. The program must not be currently in use.

dumpShaderSource()

void libcamera::eGL::dumpShaderSource

(

GLuint

shaderId

)

Dump shader source code to the log.

Parameters

[in]

shaderId

OpenGL shader object ID

Retrieves and logs the complete source code of a compiled shader. Useful for debugging shader compilation issues.

flushOutput()

void libcamera::eGL::flushOutput

(

)

Flush the rendering pipeline.

Calls glFlush().

initEGLContext()

int libcamera::eGL::initEGLContext

(

)

Initialise the EGL context.

Sets up the EGL display, creates an OpenGL ES 2.0 context, and retrieves function pointers for required extensions including:

• eglCreateImageKHR / eglDestroyImageKHR
• glEGLImageTargetTexture2DOES

Returns

0 on success, or -ENODEV on failure

isAvailable()

bool libcamera::eGL::isAvailable ( )

static

Probe whether EGL surfaceless rendering is available.

Checks if an EGL surfaceless display can be obtained and initialised. The display is immediately terminated so that no resources are leaked.

Returns

True if EGL surfaceless rendering is available, false otherwise

linkProgram()

int libcamera::eGL::linkProgram	(	GLuint &	programId,
		GLuint	vertexshaderId,
		GLuint	fragmentshaderId )

Link a shader program.

Parameters

[out]	programId	OpenGL program object ID
[in]	fragmentshaderId	Compiled fragment shader ID
[in]	vertexshaderId	Compiled vertex shader ID

Links vertex and fragment shaders into an executable shader program. On link failure, logs the program info log and deletes the program.

Returns

0 on success, or -ENODEV on link failure

makeCurrent()

void libcamera::eGL::makeCurrent

(

)

Make the EGL context current for the calling thread.

Binds the EGL context to the current thread, allowing OpenGL ES operations to be performed. Must be called from the thread that will perform rendering operations.

pushEnv()

void libcamera::eGL::pushEnv	(	std::vector< std::string > &	shaderEnv,
		const char *	str )

Add a preprocessor definition to shader environment.

Parameters

[in,out]	shaderEnv	Vector of shader environment strings
[in]	str	Preprocessor definition string (e.g., "#define APPLY_RGB_PARAMETERS")

Appends a preprocessor definition to the shader environment vector. These definitions are prepended to shader source code during compilation.

syncOutput()

void libcamera::eGL::syncOutput

(

)

Synchronise rendering output.

Sychronise here. Calls glFinish() right now.

updateTexture2D()

void libcamera::eGL::updateTexture2D	(	eGLImage &	eglImage,
		void *	data )

Update a 2D texture already created.

Parameters

[in,out]	eglImage	EGL image to associate with the texture
	[data]	Data to update the texture with

Updates a 2D texture in VRAM.

useProgram()

void libcamera::eGL::useProgram

(

GLuint

programId

)

Activate a shader program for rendering.

Parameters

[in]

programId

OpenGL program object ID

Sets the specified program as the current rendering program. All subsequent draw calls will use this program's shaders.

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The documentation for this class was generated from the following files:

• include/libcamera/internal/egl.h
• src/libcamera/egl.cpp