--- name: "wayland_presentation_feedback_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_presentation_feedback_t" --- # wayland\_presentation\_feedback\_t(3) presentation time feedback event ## NAME wayland::presentation\_feedback\_t - presentation time feedback event ## SYNOPSIS `#include ` Inherits **wayland::proxy\_t**. ### Public Types enum class **wrapper\_type** { **standard**, **display**, **foreign**, **proxy\_wrapper** }\ ### Public Member Functions std::function\< void(**output\_t**)\> & **on\_sync\_output** ()\ presentation synchronized to this output std::function\< void(uint32\_t, uint32\_t, uint32\_t, uint32\_t, uint32\_t, uint32\_t, **presentation\_feedback\_kind**)\> & **on\_presented** ()\ the content update was displayed std::function\< void()\> & **on\_discarded** ()\ the content update was not displayed uint32\_t **get\_id** () const\ Get the id of a proxy object. std::string **get\_class** () const\ Get the interface name (class) of a proxy object. uint32\_t **get\_version** () const\ Get the protocol object version of a proxy object. **wrapper\_type** **get\_wrapper\_type** () const\ Get the type of a proxy object. void **set\_queue** (**event\_queue\_t** queue)\ Assign a proxy to an event queue. wl\_proxy \* **c\_ptr** () const\ Get a pointer to the underlying C struct. bool **proxy\_has\_object** () const\ Check whether this wrapper actually wraps an object. **operator bool** () const\ Check whether this wrapper actually wraps an object. bool **operator==** (const **proxy\_t** &right) const\ Check whether two wrappers refer to the same object. bool **operator!=** (const **proxy\_t** &right) const\ Check whether two wrappers refer to different objects. void **proxy\_release** ()\ Release the wrapped object (if any), making this an empty wrapper. ## Detailed Description presentation time feedback event A presentation\_feedback object returns an indication that a wl\_surface content update has become visible to the user. One object corresponds to one content update submission (wl\_surface.commit). There are two possible outcomes: the content update is presented to the user, and a presentation timestamp delivered; or, the user did not see the content update because it was superseded or its surface destroyed, and the content update is discarded. Once a presentation\_feedback object has delivered a 'presented' or 'discarded' event it is automatically destroyed. Definition at line **187** of file **wayland-client-protocol-extra.hpp**. ## Member Enumeration Documentation ### enum class wayland::proxy\_t::wrapper\_type` [strong]`, ` [inherited]` Underlying wl\_proxy type and properties of a **proxy\_t** that affect construction, destruction, and event handling **Enumerator** - *standard* *C pointer is a standard type compatible with wl\_proxy\*. Events are dispatched and it is destructed when the* **proxy\_t** *is destructed. User data is set.* - *display* *C pointer is a wl\_display\*. No events are dispatched, wl\_display\_disconnect is called when the* **proxy\_t** *is destructed. User data is set.* - *foreign* *C pointer is a standard type compatible with wl\_proxy\*, but another library owns it and it should not be touched in a way that could affect the operation of the other library. No events are dispatched, wl\_proxy\_destroy is not called when the* **proxy\_t** *is destructed, user data is not touched. Consequently, there is no reference counting for the* **proxy\_t***. Lifetime of such wrappers should preferably be short to minimize the chance that the owning library decides to destroy the wl\_proxy.* - *proxy\_wrapper* *C pointer is a wl\_proxy\* that was constructed with wl\_proxy\_create\_wrapper. No events are dispatched, wl\_proxy\_wrapper\_destroy is called when the* **proxy\_t** *is destroyed. Reference counting is active. A reference to the* **proxy\_t** *creating this proxy wrapper is held to extend its lifetime until after the proxy wrapper is destroyed.* *Definition at line* **116** *of file* **wayland-client.hpp***.* ## Member Function Documentation ### wl\_proxy \* wayland::proxy\_t::c\_ptr () const` [inherited]` *Get a pointer to the underlying C struct.* **Returns** *The underlying wl\_proxy wrapped by this* **proxy\_t** *if it exists, otherwise an exception is thrown* ### std::string wayland::proxy\_t::get\_class () const` [inherited]` *Get the interface name (class) of a proxy object.* **Returns** *The interface name of the object associated with the proxy* ### uint32\_t wayland::proxy\_t::get\_id () const` [inherited]` *Get the id of a proxy object.* **Returns** *The id the object associated with the proxy* ### uint32\_t wayland::proxy\_t::get\_version () const` [inherited]` *Get the protocol object version of a proxy object. Gets the protocol object version of a proxy object, or 0 if the proxy was created with unversioned API.* *A returned value of 0 means that no version information is available, so the caller must make safe assumptions about the object's real version.* **display\_t** *will always return version 0.* **Returns** *The protocol object version of the proxy or 0* ### wrapper\_type wayland::proxy\_t::get\_wrapper\_type () const` [inline]`, ` [inherited]` *Get the type of a proxy object.* *Definition at line* **302** *of file* **wayland-client.hpp***.* ### std::function\< void()\> & presentation\_feedback\_t::on\_discarded () *the content update was not displayed The content update was never displayed to the user.* *Definition at line* **804** *of file* **wayland-client-protocol-extra.cpp***.* ### std::function\< void(uint32\_t, uint32\_t, uint32\_t, uint32\_t, uint32\_t, uint32\_t, presentation\_feedback\_kind)\> & presentation\_feedback\_t::on\_presented () *the content update was displayed* **Parameters** *tv\_sec\_hi high 32 bits of the seconds part of the presentation timestamp* \ *tv\_sec\_lo low 32 bits of the seconds part of the presentation timestamp* \ *tv\_nsec nanoseconds part of the presentation timestamp* \ *refresh nanoseconds till next refresh* \ *seq\_hi high 32 bits of refresh counter* \ *seq\_lo low 32 bits of refresh counter* \ *flags combination of 'kind' values* *The associated content update was displayed to the user at the indicated time (tv\_sec\_hi/lo, tv\_nsec). For the interpretation of the timestamp, see presentation.clock\_id event.* *The timestamp corresponds to the time when the content update turned into light the first time on the surface's main output. Compositors may approximate this from the framebuffer flip completion events from the system, and the latency of the physical display path if known.* *This event is preceded by all related sync\_output events telling which output's refresh cycle the feedback corresponds to, i.e. the main output for the surface. Compositors are recommended to choose the output containing the largest part of the wl\_surface, or keeping the output they previously chose. Having a stable presentation output association helps clients predict future output refreshes (vblank).* *The 'refresh' argument gives the compositor's prediction of how many nanoseconds after tv\_sec, tv\_nsec the very next output refresh may occur. This is to further aid clients in predicting future refreshes, i.e., estimating the timestamps targeting the next few vblanks. If such prediction cannot usefully be done, the argument is zero.* *If the output does not have a constant refresh rate, explicit video mode switches excluded, then the refresh argument must be zero.* *The 64-bit value combined from seq\_hi and seq\_lo is the value of the output's vertical retrace counter when the content update was first scanned out to the display. This value must be compatible with the definition of MSC in GLX\_OML\_sync\_control specification. Note, that if the display path has a non-zero latency, the time instant specified by this counter may differ from the timestamp's.* *If the output does not have a concept of vertical retrace or a refresh cycle, or the output device is self-refreshing without a way to query the refresh count, then the arguments seq\_hi and seq\_lo must be zero.* *Definition at line* **799** *of file* **wayland-client-protocol-extra.cpp***.* ### std::function\< void(output\_t)\> & presentation\_feedback\_t::on\_sync\_output () *presentation synchronized to this output* **Parameters** *output presentation output* *As presentation can be synchronized to only one output at a time, this event tells which output it was. This event is only sent prior to the presented event.* *As clients may bind to the same global wl\_output multiple times, this event is sent for each bound instance that matches the synchronized output. If a client has not bound to the right wl\_output global at all, this event is not sent.* *Definition at line* **794** *of file* **wayland-client-protocol-extra.cpp***.* ### wayland::proxy\_t::operator bool () const` [inherited]` *Check whether this wrapper actually wraps an object.* **Returns** *true if there is an underlying object, false if this wrapper is empty* ### bool wayland::proxy\_t::operator!= (const proxy\_t & right) const` [inherited]` *Check whether two wrappers refer to different objects.* ### bool wayland::proxy\_t::operator== (const proxy\_t & right) const` [inherited]` *Check whether two wrappers refer to the same object.* ### bool wayland::proxy\_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 wayland::proxy\_t::proxy\_release ()` [inherited]` *Release the wrapped object (if any), making this an empty wrapper. Note that* **display\_t** *instances cannot be released this way. Attempts to do so are ignored.* **Examples** **foreign\_display.cpp***.* ### void wayland::proxy\_t::set\_queue (event\_queue\_t queue)` [inherited]` *Assign a proxy to an event queue.* **Parameters** *queue The event queue that will handle this proxy* *Assign proxy to event queue. Events coming from proxy will be queued in queue instead of the display's main queue.* *See also:* **display\_t::dispatch\_queue()***.* **Examples** **proxy\_wrapper.cpp***.* ## Author *Generated automatically by Doxygen for Wayland++ from the source code.*