libcamera::eGL Class Reference

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

Public Member Functions
	eGL (EGLDisplay display)
	Construct an EGL helper.
	~eGL ()
	Destroy the EGL helper.
int	initEGLContext ()
	Initialise the EGL context.
void	resetEGLContext ()
	Destroy 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.
int	compileVertexShader (GLuint &shaderId, std::span< const unsigned char > shaderData, std::span< const std::string > shaderEnv)
	Compile a vertex shader.
int	compileFragmentShader (GLuint &shaderId, std::span< const unsigned char > shaderData, std::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	syncOutput ()
	Synchronise rendering output.
void	flushOutput ()
	Flush the rendering pipeline.
void	assertThread () const
	Assert that the execution is in the right thread.

Static Public Member Functions
static EGLDisplay	probeDisplay ()
	Try to create an EGL display for surfaceless rendering.

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

(

EGLDisplay

display

)

Construct an EGL helper.

Parameters

[in]

display

The EGL display to use

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

~eGL()

libcamera::eGL::~eGL

(

)

Destroy the EGL helper.

An instance must only be destroyed if there is no active EGL context.

See also

resetEGLContext()

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.

assertThread()

libcamera::eGL::assertThread ( ) const

inline

Assert that the execution is in the right thread.

Asserts that the execution is in the thread for which the created EGL context has been made current.

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,
		std::span< const unsigned char >	shaderData,
		std::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,
		std::span< const unsigned char >	shaderData,
		std::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.

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

Each successful invocation must be followed by a call to resetEGLContext().

If a valid EGL context is already present, initialization attempts will be rejected.

Returns

0 on success, or negative error code on failure

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

probeDisplay()

EGLDisplay libcamera::eGL::probeDisplay ( )

static

Try to create an EGL display for surfaceless rendering.

Tries to create an EGL display for surfaceless rendering.

Returns

A EGL display handle if successful, otherwise EGL_NO_DISPLAY

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.

resetEGLContext()

void libcamera::eGL::resetEGLContext

(

)

Destroy the EGL context.

This function destroys the EGL context created by initEGLContext(). If there is no valid EGL context, this function has no effect.

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.

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

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