--- name: "wayland_server_zwp_linux_dmabuf_feedback_v1_t" section: "3" platform: "linux" package: "waylandpp-dev" version: "1.0.0-6+b2" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/wayland_server_zwp_linux_dmabuf_feedback_v1_t" --- # wayland\_server\_zwp\_linux\_dmabuf\_feedback\_v1\_t(3) dmabuf feedback ## NAME wayland::server::zwp\_linux\_dmabuf\_feedback\_v1\_t - dmabuf feedback ## SYNOPSIS `#include ` Inherits wayland::server::resource\_t. ### Public Member Functions std::function\< void()\> & **on\_destroy** ()\ destroy the feedback object void **done** (bool post=true)\ all feedback has been sent void **format\_table** (int fd, uint32\_t size, bool post=true)\ format and modifier table void **main\_device** (array\_t const &device, bool post=true)\ preferred main device void **tranche\_done** (bool post=true)\ a preference tranche has been sent void **tranche\_target\_device** (array\_t const &device, bool post=true)\ target device void **tranche\_formats** (array\_t const &indices, bool post=true)\ supported buffer format modifier void **tranche\_flags** (zwp\_linux\_dmabuf\_feedback\_v1\_tranche\_flags const &flags, bool post=true)\ tranche flags bool **proxy\_has\_object** () const\ Check whether this wrapper actually wraps an object. void **post\_no\_memory** () const\ uint32\_t **get\_id** () const\ client\_t **get\_client** () const\ unsigned int **get\_version** () const\ std::string **get\_class** ()\ ### Static Public Attributes static constexpr std::uint32\_t **done\_since\_version** = 1\ Minimum protocol version required for the **done** function. static constexpr std::uint32\_t **format\_table\_since\_version** = 1\ Minimum protocol version required for the **format\_table** function. static constexpr std::uint32\_t **main\_device\_since\_version** = 1\ Minimum protocol version required for the **main\_device** function. static constexpr std::uint32\_t **tranche\_done\_since\_version** = 1\ Minimum protocol version required for the **tranche\_done** function. static constexpr std::uint32\_t **tranche\_target\_device\_since\_version** = 1\ Minimum protocol version required for the **tranche\_target\_device** function. static constexpr std::uint32\_t **tranche\_formats\_since\_version** = 1\ Minimum protocol version required for the **tranche\_formats** function. static constexpr std::uint32\_t **tranche\_flags\_since\_version** = 1\ Minimum protocol version required for the **tranche\_flags** function. ## Detailed Description dmabuf feedback This object advertises dmabuf parameters feedback. This includes the preferred devices and the supported formats/modifiers. The parameters are sent once when this object is created and whenever they change. The done event is always sent once after all parameters have been sent. When a single parameter changes, all parameters are re-sent by the compositor. Compositors can re-send the parameters when the current client buffer allocations are sub-optimal. Compositors should not re-send the parameters if re-allocating the buffers would not result in a more optimal configuration. In particular, compositors should avoid sending the exact same parameters multiple times in a row. The tranche\_target\_device and tranche\_modifier events are grouped by tranches of preference. For each tranche, a tranche\_target\_device, one tranche\_flags and one or more tranche\_modifier events are sent, followed by a tranche\_done event finishing the list. The tranches are sent in descending order of preference. All formats and modifiers in the same tranche have the same preference. To send parameters, the compositor sends one main\_device event, tranches (each consisting of one tranche\_target\_device event, one tranche\_flags event, tranche\_modifier events and then a tranche\_done event), then one done event. Definition at line **2096** of file **wayland-server-protocol-unstable.hpp**. ## Member Function Documentation ### void zwp\_linux\_dmabuf\_feedback\_v1\_t::done (bool post = `true`) all feedback has been sent This event is sent after all parameters of a wp\_linux\_dmabuf\_feedback object have been sent. This allows changes to the wp\_linux\_dmabuf\_feedback parameters to be seen as atomic, even if they happen via multiple events. Definition at line **5130** of file **wayland-server-protocol-unstable.cpp**. ### void zwp\_linux\_dmabuf\_feedback\_v1\_t::format\_table (int fd, uint32\_t size, bool post = `true`) format and modifier table **Parameters** *fd* table file descriptor \ *size* table size, in bytes This event provides a file descriptor which can be memory-mapped to access the format and modifier table. The table contains a tightly packed array of consecutive format + modifier pairs. Each pair is 16 bytes wide. It contains a format as a 32-bit unsigned integer, followed by 4 bytes of unused padding, and a modifier as a 64-bit unsigned integer. The native endianness is used. The client must map the file descriptor in read-only private mode. Compositors are not allowed to mutate the table file contents once this event has been sent. Instead, compositors must create a new, separate table file and re-send feedback parameters. Compositors are allowed to store duplicate format + modifier pairs in the table. Definition at line **5135** of file **wayland-server-protocol-unstable.cpp**. ### std::string wayland::server::resource\_t::get\_class ()` [inherited]` Retrieve the interface name (class) of a resource object. **Returns** Interface name of the resource object. ### client\_t wayland::server::resource\_t::get\_client () const` [inherited]` Get the associated client **Returns** the client that owns the resource. ### uint32\_t wayland::server::resource\_t::get\_id () const` [inherited]` Get the internal ID of the resource **Returns** the internal ID of the resource ### unsigned int wayland::server::resource\_t::get\_version () const` [inherited]` Get interface version **Returns** Interface version this resource has been constructed with. ### void zwp\_linux\_dmabuf\_feedback\_v1\_t::main\_device (array\_t const & device, bool post = `true`) preferred main device **Parameters** *device* device dev\_t value This event advertises the main device that the server prefers to use when direct scan-out to the target device isn't possible. The advertised main device may be different for each wp\_linux\_dmabuf\_feedback object, and may change over time. There is exactly one main device. The compositor must send at least one preference tranche with tranche\_target\_device equal to main\_device. Clients need to create buffers that the main device can import and read from, otherwise creating the dmabuf wl\_buffer will fail (see the wp\_linux\_buffer\_params.create and create\_immed requests for details). The main device will also likely be kept active by the compositor, so clients can use it instead of waking up another device for power savings. In general the device is a DRM node. The DRM node type (primary vs. render) is unspecified. Clients must not rely on the compositor sending a particular node type. Clients cannot check two devices for equality by comparing the dev\_t value. If explicit modifiers are not supported and the client performs buffer allocations on a different device than the main device, then the client must force the buffer to have a linear layout. Definition at line **5140** of file **wayland-server-protocol-unstable.cpp**. ### std::function\< void()\> & zwp\_linux\_dmabuf\_feedback\_v1\_t::on\_destroy () destroy the feedback object Using this request a client can tell the server that it is not going to use the wp\_linux\_dmabuf\_feedback object anymore. Definition at line **5124** of file **wayland-server-protocol-unstable.cpp**. ### void wayland::server::resource\_t::post\_no\_memory () const` [inherited]` Post 'not enough memory' error to the client If the compositor has not enough memory to fulfill a certail request of the client, this function can be called to notify the client of this circumstance. ### bool wayland::server::resource\_t::proxy\_has\_object () const` [inherited]` Check whether this wrapper actually wraps an object. **Returns** true if there is an underlying object, false if this wrapper is empty ### void zwp\_linux\_dmabuf\_feedback\_v1\_t::tranche\_done (bool post = `true`) a preference tranche has been sent This event splits tranche\_target\_device and tranche\_modifier events in preference tranches. It is sent after a set of tranche\_target\_device and tranche\_modifier events; it represents the end of a tranche. The next tranche will have a lower preference. Definition at line **5145** of file **wayland-server-protocol-unstable.cpp**. ### void zwp\_linux\_dmabuf\_feedback\_v1\_t::tranche\_flags (zwp\_linux\_dmabuf\_feedback\_v1\_tranche\_flags const & flags, bool post = `true`) tranche flags **Parameters** *flags* tranche flags This event sets tranche-specific flags. The scanout flag is a hint that direct scan-out may be attempted by the compositor on the target device if the client appropriately allocates a buffer. How to allocate a buffer that can be scanned out on the target device is implementation-defined. This event is tied to a preference tranche, see the tranche\_done event. Definition at line **5160** of file **wayland-server-protocol-unstable.cpp**. ### void zwp\_linux\_dmabuf\_feedback\_v1\_t::tranche\_formats (array\_t const & indices, bool post = `true`) supported buffer format modifier **Parameters** *indices* array of 16-bit indexes This event advertises the format + modifier combinations that the compositor supports. It carries an array of indices, each referring to a format + modifier pair in the last received format table (see the format\_table event). Each index is a 16-bit unsigned integer in native endianness. For legacy support, DRM\_FORMAT\_MOD\_INVALID is an allowed modifier. It indicates that the server can support the format with an implicit modifier. When a buffer has DRM\_FORMAT\_MOD\_INVALID as its modifier, it is as if no explicit modifier is specified. The effective modifier will be derived from the dmabuf. A compositor that sends valid modifiers and DRM\_FORMAT\_MOD\_INVALID for a given format supports both explicit modifiers and implicit modifiers. Compositors must not send duplicate format + modifier pairs within the same tranche or across two different tranches with the same target device and flags. This event is tied to a preference tranche, see the tranche\_done event. For the definition of the format and modifier codes, see the wp\_linux\_buffer\_params.create request. Definition at line **5155** of file **wayland-server-protocol-unstable.cpp**. ### void zwp\_linux\_dmabuf\_feedback\_v1\_t::tranche\_target\_device (array\_t const & device, bool post = `true`) target device **Parameters** *device* device dev\_t value This event advertises the target device that the server prefers to use for a buffer created given this tranche. The advertised target device may be different for each preference tranche, and may change over time. There is exactly one target device per tranche. The target device may be a scan-out device, for example if the compositor prefers to directly scan-out a buffer created given this tranche. The target device may be a rendering device, for example if the compositor prefers to texture from said buffer. The client can use this hint to allocate the buffer in a way that makes it accessible from the target device, ideally directly. The buffer must still be accessible from the main device, either through direct import or through a potentially more expensive fallback path. If the buffer can't be directly imported from the main device then clients must be prepared for the compositor changing the tranche priority or making wl\_buffer creation fail (see the wp\_linux\_buffer\_params.create and create\_immed requests for details). If the device is a DRM node, the DRM node type (primary vs. render) is unspecified. Clients must not rely on the compositor sending a particular node type. Clients cannot check two devices for equality by comparing the dev\_t value. This event is tied to a preference tranche, see the tranche\_done event. Definition at line **5150** of file **wayland-server-protocol-unstable.cpp**. ## Member Data Documentation ### constexpr std::uint32\_t wayland::server::zwp\_linux\_dmabuf\_feedback\_v1\_t::done\_since\_version = 1` [static]`, ` [constexpr]` Minimum protocol version required for the **done** function. Definition at line **2143** of file **wayland-server-protocol-unstable.hpp**. ### constexpr std::uint32\_t wayland::server::zwp\_linux\_dmabuf\_feedback\_v1\_t::format\_table\_since\_version = 1` [static]`, ` [constexpr]` Minimum protocol version required for the **format\_table** function. Definition at line **2169** of file **wayland-server-protocol-unstable.hpp**. ### constexpr std::uint32\_t wayland::server::zwp\_linux\_dmabuf\_feedback\_v1\_t::main\_device\_since\_version = 1` [static]`, ` [constexpr]` Minimum protocol version required for the **main\_device** function. Definition at line **2203** of file **wayland-server-protocol-unstable.hpp**. ### constexpr std::uint32\_t wayland::server::zwp\_linux\_dmabuf\_feedback\_v1\_t::tranche\_done\_since\_version = 1` [static]`, ` [constexpr]` Minimum protocol version required for the **tranche\_done** function. Definition at line **2217** of file **wayland-server-protocol-unstable.hpp**. ### constexpr std::uint32\_t wayland::server::zwp\_linux\_dmabuf\_feedback\_v1\_t::tranche\_flags\_since\_version = 1` [static]`, ` [constexpr]` Minimum protocol version required for the **tranche\_flags** function. Definition at line **2308** of file **wayland-server-protocol-unstable.hpp**. ### constexpr std::uint32\_t wayland::server::zwp\_linux\_dmabuf\_feedback\_v1\_t::tranche\_formats\_since\_version = 1` [static]`, ` [constexpr]` Minimum protocol version required for the **tranche\_formats** function. Definition at line **2289** of file **wayland-server-protocol-unstable.hpp**. ### constexpr std::uint32\_t wayland::server::zwp\_linux\_dmabuf\_feedback\_v1\_t::tranche\_target\_device\_since\_version = 1` [static]`, ` [constexpr]` Minimum protocol version required for the **tranche\_target\_device** function. Definition at line **2254** of file **wayland-server-protocol-unstable.hpp**. ## Author Generated automatically by Doxygen for Wayland++ from the source code.