---
name: "wayland_touch_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_touch_t"
---

# wayland\_touch\_t(3)

touchscreen input device

## NAME

wayland::touch\_t - touchscreen input device

## SYNOPSIS

`#include <wayland-client-protocol.hpp>`

Inherits **wayland::proxy\_t**.

### Public Types

enum class **wrapper\_type** { **standard**, **display**, **foreign**, **proxy\_wrapper** }\

### Public Member Functions

void **release** ()\
 release the touch object  bool **can\_release** () const\
 Check whether the **release** function is available with the currently bound version of the protocol.  std::function\< void(uint32\_t, uint32\_t, **surface\_t**, int32\_t, double, double)\> & **on\_down** ()\
 touch down event and beginning of a touch sequence  std::function\< void(uint32\_t, uint32\_t, int32\_t)\> & **on\_up** ()\
 end of a touch event sequence  std::function\< void(uint32\_t, int32\_t, double, double)\> & **on\_motion** ()\
 update of touch point coordinates  std::function\< void()\> & **on\_frame** ()\
 end of touch frame event  std::function\< void()\> & **on\_cancel** ()\
 touch session cancelled  std::function\< void(int32\_t, double, double)\> & **on\_shape** ()\
 update shape of touch point  std::function\< void(int32\_t, double)\> & **on\_orientation** ()\
 update orientation of touch point  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.

### Static Public Attributes

static constexpr std::uint32\_t **release\_since\_version** = 3\
 Minimum protocol version required for the **release** function.

## Detailed Description

touchscreen input device

The wl\_touch interface represents a touchscreen associated with a seat.

Touch interactions can consist of one or more contacts. For each contact, a series of events is generated, starting with a down event, followed by zero or more motion events, and ending with an up event. Events relating to the same contact point can be identified by the ID of the sequence.

Definition at line **3297** of file **wayland-client-protocol.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*

### bool touch\_t::can\_release () const

*Check whether the* **release** *function is available with the currently bound version of the protocol.*

*Definition at line* **3243** *of file* **wayland-client-protocol.cpp***.*

### 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()\> & touch\_t::on\_cancel ()

*touch session cancelled Sent if the compositor decides the touch stream is a global gesture. No further events are sent to the clients from that particular gesture. Touch cancellation applies to all touch points currently active on this client's surface. The client is responsible for finalizing the touch points, future touch points on this surface may reuse the touch point ID.*

*Definition at line* **3269** *of file* **wayland-client-protocol.cpp***.*

### std::function\< void(uint32\_t, uint32\_t, surface\_t, int32\_t, double, double)\> & touch\_t::on\_down ()

*touch down event and beginning of a touch sequence*

**Parameters**

*serial serial number of the touch down event* \
 *time timestamp with millisecond granularity* \
 *surface surface touched* \
 *id the unique ID of this touch point* \
 *x surface-local x coordinate* \
 *y surface-local y coordinate*

*A new touch point has appeared on the surface. This touch point is assigned a unique ID. Future events from this touch point reference this ID. The ID ceases to be valid after a touch up event and may be reused in the future.*

*Definition at line* **3249** *of file* **wayland-client-protocol.cpp***.*

### std::function\< void()\> & touch\_t::on\_frame ()

*end of touch frame event Indicates the end of a set of events that logically belong together. A client is expected to accumulate the data in all events within the frame before proceeding.*

*A wl\_touch.frame terminates at least one event but otherwise no guarantee is provided about the set of events within a frame. A client must assume that any state not updated in a frame is unchanged from the previously known state.*

*Definition at line* **3264** *of file* **wayland-client-protocol.cpp***.*

### std::function\< void(uint32\_t, int32\_t, double, double)\> & touch\_t::on\_motion ()

*update of touch point coordinates*

**Parameters**

*time timestamp with millisecond granularity* \
 *id the unique ID of this touch point* \
 *x surface-local x coordinate* \
 *y surface-local y coordinate*

*A touch point has changed coordinates.*

*Definition at line* **3259** *of file* **wayland-client-protocol.cpp***.*

### std::function\< void(int32\_t, double)\> & touch\_t::on\_orientation ()

*update orientation of touch point*

**Parameters**

*id the unique ID of this touch point* \
 *orientation angle between major axis and positive surface y-axis in degrees*

*Sent when a touchpoint has changed its orientation.*

*This event does not occur on its own. It is sent before a wl\_touch.frame event and carries the new shape information for any previously reported, or new touch points of that frame.*

*Other events describing the touch point such as wl\_touch.down, wl\_touch.motion or wl\_touch.shape may be sent within the same wl\_touch.frame. A client should treat these events as a single logical touch point update. The order of wl\_touch.shape, wl\_touch.orientation and wl\_touch.motion is not guaranteed. A wl\_touch.down event is guaranteed to occur before the first wl\_touch.orientation event for this touch ID but both events may occur within the same wl\_touch.frame.*

*The orientation describes the clockwise angle of a touchpoint's major axis to the positive surface y-axis and is normalized to the -180 to +180 degree range. The granularity of orientation depends on the touch device, some devices only support binary rotation values between 0 and 90 degrees.*

*This event is only sent by the compositor if the touch device supports orientation reports.*

*Definition at line* **3279** *of file* **wayland-client-protocol.cpp***.*

### std::function\< void(int32\_t, double, double)\> & touch\_t::on\_shape ()

*update shape of touch point*

**Parameters**

*id the unique ID of this touch point* \
 *major length of the major axis in surface-local coordinates* \
 *minor length of the minor axis in surface-local coordinates*

*Sent when a touchpoint has changed its shape.*

*This event does not occur on its own. It is sent before a wl\_touch.frame event and carries the new shape information for any previously reported, or new touch points of that frame.*

*Other events describing the touch point such as wl\_touch.down, wl\_touch.motion or wl\_touch.orientation may be sent within the same wl\_touch.frame. A client should treat these events as a single logical touch point update. The order of wl\_touch.shape, wl\_touch.orientation and wl\_touch.motion is not guaranteed. A wl\_touch.down event is guaranteed to occur before the first wl\_touch.shape event for this touch ID but both events may occur within the same wl\_touch.frame.*

*A touchpoint shape is approximated by an ellipse through the major and minor axis length. The major axis length describes the longer diameter of the ellipse, while the minor axis length describes the shorter diameter. Major and minor are orthogonal and both are specified in surface-local coordinates. The center of the ellipse is always at the touchpoint location as reported by wl\_touch.down or wl\_touch.move.*

*This event is only sent by the compositor if the touch device supports shape reports. The client has to make reasonable assumptions about the shape if it did not receive this event.*

*Definition at line* **3274** *of file* **wayland-client-protocol.cpp***.*

### std::function\< void(uint32\_t, uint32\_t, int32\_t)\> & touch\_t::on\_up ()

*end of a touch event sequence*

**Parameters**

*serial serial number of the touch up event* \
 *time timestamp with millisecond granularity* \
 *id the unique ID of this touch point*

*The touch point has disappeared. No further events will be sent for this touch point and the touch point's ID is released and may be reused in a future touch down event.*

*Definition at line* **3254** *of file* **wayland-client-protocol.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 touch\_t::release ()

*release the touch object*

*Definition at line* **3238** *of file* **wayland-client-protocol.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***.*

## Member Data Documentation

### constexpr std::uint32\_t wayland::touch\_t::release\_since\_version = 3` [static]`, ` [constexpr]`

*Minimum protocol version required for the* **release** *function.*

*Definition at line* **3333** *of file* **wayland-client-protocol.hpp***.*

## Author

*Generated automatically by Doxygen for Wayland++ from the source code.*