class Gdk::DmabufTextureBuilder

Overview

Constructs Gdk::Texture objects from DMA buffers.

DMA buffers are commonly called dma-bufs.

DMA buffers are a feature of the Linux kernel to enable efficient buffer and memory sharing between hardware such as codecs, GPUs, displays, cameras and the kernel drivers controlling them. For example, a decoder may want its output to be directly shared with the display server for rendering without a copy.

Any device driver which participates in DMA buffer sharing, can do so as either the exporter or importer of buffers (or both).

The memory that is shared via DMA buffers is usually stored in non-system memory (maybe in device's local memory or something else not directly accessible by the CPU), and accessing this memory from the CPU may have higher-than-usual overhead.

In particular for graphics data, it is not uncommon that data consists of multiple separate blocks of memory, for example one block for each of the red, green and blue channels. These blocks are called planes. DMA buffers can have up to four planes. Even if the memory is a single block, the data can be organized in multiple planes, by specifying offsets from the beginning of the data.

DMA buffers are exposed to user-space as file descriptors allowing to pass them between processes. If a DMA buffer has multiple planes, there is one file descriptor per plane.

The format of the data (for graphics data, essentially its colorspace) is described by a 32-bit integer. These format identifiers are defined in the header file drm_fourcc.h and commonly referred to as fourcc values, since they are identified by 4 ASCII characters. Additionally, each DMA buffer has a modifier, which is a 64-bit integer that describes driver-specific details of the memory layout, such as tiling or compression.

For historical reasons, some producers of dma-bufs don't provide an explicit modifier, but instead return DMA_FORMAT_MOD_INVALID to indicate that their modifier is implicit. GTK tries to accommodate this situation by accepting DMA_FORMAT_MOD_INVALID as modifier.

The operation of Gdk::DmabufTextureBuilder is quite simple: Create a texture builder, set all the necessary properties, and then call Gdk::DmabufTextureBuilder#build to create the new texture.

The required properties for a dma-buf texture are

Gdk::DmabufTextureBuilder can be used for quick one-shot construction of textures as well as kept around and reused to construct multiple textures.

For further information, see

Defined in:

lib/gi-crystal/src/auto/gdk-4.0/dmabuf_texture_builder.cr

Constructors

Class Method Summary

Instance Method Summary

Instance methods inherited from class GObject::Object

==(other : self) ==, bind_property(source_property : String, target : GObject::Object, target_property : String, flags : GObject::BindingFlags) : GObject::Binding bind_property, bind_property_full(source_property : String, target : GObject::Object, target_property : String, flags : GObject::BindingFlags, transform_to : GObject::Closure, transform_from : GObject::Closure) : GObject::Binding bind_property_full, data(key : String) : Pointer(Void) | Nil data, finalize finalize, freeze_notify : Nil freeze_notify, getv(names : Enumerable(String), values : Enumerable(_)) : Nil getv, hash(hasher) hash, notify(property_name : String) : Nil notify, notify_by_pspec(pspec : GObject::ParamSpec) : Nil notify_by_pspec, notify_signal notify_signal, property(property_name : String, value : _) : Nil property, qdata(quark : UInt32) : Pointer(Void) | Nil qdata, ref_count : UInt32 ref_count, run_dispose : Nil run_dispose, set_data(key : String, data : Pointer(Void) | Nil) : Nil set_data, set_property(property_name : String, value : _) : Nil set_property, steal_data(key : String) : Pointer(Void) | Nil steal_data, steal_qdata(quark : UInt32) : Pointer(Void) | Nil steal_qdata, thaw_notify : Nil thaw_notify, to_unsafe : Pointer(Void) to_unsafe, watch_closure(closure : GObject::Closure) : Nil watch_closure

Constructor methods inherited from class GObject::Object

cast(obj : GObject::Object) : self cast, new(pointer : Pointer(Void), transfer : GICrystal::Transfer)
new new, newv(object_type : UInt64, parameters : Enumerable(GObject::Parameter)) : self newv

Class methods inherited from class GObject::Object

cast?(obj : GObject::Object) : self | Nil cast?, compat_control(what : UInt64, data : Pointer(Void) | Nil) : UInt64 compat_control, g_type : UInt64 g_type, interface_find_property(g_iface : GObject::TypeInterface, property_name : String) : GObject::ParamSpec interface_find_property, interface_list_properties(g_iface : GObject::TypeInterface) : Enumerable(GObject::ParamSpec) interface_list_properties

Macros inherited from class GObject::Object

previous_vfunc(*args) previous_vfunc, previous_vfunc!(*args) previous_vfunc!, signal(signature) signal

Constructor Detail

def self.new : self #

Creates a new texture builder.


def self.new(*, color_state : Gdk::ColorState | Nil = nil, display : Gdk::Display | Nil = nil, fourcc : UInt32 | Nil = nil, height : UInt32 | Nil = nil, modifier : UInt64 | Nil = nil, n_planes : UInt32 | Nil = nil, premultiplied : Bool | Nil = nil, update_region : Cairo::Region | Nil = nil, update_texture : Gdk::Texture | Nil = nil, width : UInt32 | Nil = nil) #

Class Method Detail

def self.g_type : UInt64 #

Returns the type id (GType) registered in GLib type system.


Instance Method Detail

def ==(other : self) #
Description copied from class Reference

Returns true if this reference is the same as other. Invokes same?.


def build(destroy : GLib::DestroyNotify | Nil, data : Pointer(Void) | Nil) : Gdk::Texture | Nil #

Builds a new Gdk::Texture with the values set up in the builder.

It is a programming error to call this function if any mandatory property has not been set.

Not all formats defined in the drm_fourcc.h header are supported. You can use Gdk::Display#dmabuf_formats to get a list of supported formats. If the format is not supported by GTK, nil will be returned and error will be set.

The destroy function gets called when the returned texture gets released.

It is the responsibility of the caller to keep the file descriptors for the planes open until the created texture is no longer used, and close them afterwards (possibly using the destroy notify).

It is possible to call this function multiple times to create multiple textures, possibly with changing properties in between.


def color_state : Gdk::ColorState | Nil #

Gets the color state previously set via gdk_dmabuf_texture_builder_set_color_state().


def color_state=(color_state : Gdk::ColorState | Nil) : Nil #

Sets the color state for the texture.

By default, the colorstate is NULL. In that case, GTK will choose the correct colorstate based on the format. If you don't know what colorstates are, this is probably the right thing.


def display : Gdk::Display #

Returns the display that this texture builder is associated with.


def display=(display : Gdk::Display) : Nil #

Sets the display that this texture builder is associated with.

The display is used to determine the supported dma-buf formats.


def display=(value : Gdk::Display | Nil) : Gdk::Display | Nil #

def fd(plane : UInt32) : Int32 #

Gets the file descriptor for a plane.


def fourcc : UInt32 #

Gets the format previously set via gdk_dmabuf_texture_builder_set_fourcc() or 0 if the format wasn't set.

The format is specified as a fourcc code.


def fourcc=(fourcc : UInt32) : Nil #

Sets the format of the texture.

The format is specified as a fourcc code.

The format must be set before calling Gdk::DmabufTextureBuilder#build.


def hash(hasher) #
Description copied from class Reference

See Object#hash(hasher)


def height : UInt32 #

Gets the height previously set via gdk_dmabuf_texture_builder_set_height() or 0 if the height wasn't set.


def height=(height : UInt32) : Nil #

Sets the height of the texture.

The height must be set before calling Gdk::DmabufTextureBuilder#build.


def modifier : UInt64 #

Gets the modifier value.


def modifier=(modifier : UInt64) : Nil #

Sets the modifier.


def n_planes : UInt32 #

Gets the number of planes.


def n_planes=(n_planes : UInt32) : Nil #

Sets the number of planes of the texture.


def offset(plane : UInt32) : UInt32 #

Gets the offset value for a plane.


def premultiplied : Bool #

Whether the data is premultiplied.


def premultiplied=(premultiplied : Bool) : Nil #

Sets whether the data is premultiplied.

Unless otherwise specified, all formats including alpha channels are assumed to be premultiplied.


def premultiplied? : Bool #

def set_fd(plane : UInt32, fd : Int32) : Nil #

Sets the file descriptor for a plane.


def set_offset(plane : UInt32, offset : UInt32) : Nil #

Sets the offset for a plane.


def set_stride(plane : UInt32, stride : UInt32) : Nil #

Sets the stride for a plane.

The stride must be set for all planes before calling Gdk::DmabufTextureBuilder#build.


def stride(plane : UInt32) : UInt32 #

Gets the stride value for a plane.


def update_region : Cairo::Region | Nil #

Gets the region previously set via gdk_dmabuf_texture_builder_set_update_region() or nil if none was set.


def update_region=(region : Cairo::Region | Nil) : Nil #

Sets the region to be updated by this texture. Together with [property@Gdk.DmabufTextureBuilder:update-texture] this describes an update of a previous texture.

When rendering animations of large textures, it is possible that consecutive textures are only updating contents in parts of the texture. It is then possible to describe this update via these two properties, so that GTK can avoid rerendering parts that did not change.

An example would be a screen recording where only the mouse pointer moves.


def update_texture : Gdk::Texture | Nil #

Gets the texture previously set via gdk_dmabuf_texture_builder_set_update_texture() or nil if none was set.


def update_texture=(texture : Gdk::Texture | Nil) : Nil #

Sets the texture to be updated by this texture. See Gdk::DmabufTextureBuilder#update_region= for an explanation.


def width : UInt32 #

Gets the width previously set via gdk_dmabuf_texture_builder_set_width() or 0 if the width wasn't set.


def width=(width : UInt32) : Nil #

Sets the width of the texture.

The width must be set before calling Gdk::DmabufTextureBuilder#build.