gtkmm: Gdk::Device Class Reference

gtkmm 4.8.0

Public Member Functions | Static Public Member Functions | Protected Member Functions | Related Functions | List of all members
Gdk::Device Class Reference

A Gdk::Device instance contains a detailed description of an extended input device. More...

`#include <gdkmm/device.h>`

Inheritance diagram for Gdk::Device:
[legend]

## Public Member Functions
| Device (Device && src) noexcept
Device & | operator= (Device && src) noexcept
| ~Device () noexcept override
GdkDevice * | gobj ()
| Provides access to the underlying C GObject. More...
const GdkDevice * | gobj () const
| Provides access to the underlying C GObject. More...
GdkDevice * | gobj_copy ()
| Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs. More...
Glib::ustring | get_name () const
| The name of the device, suitable for showing in a user interface. More...
bool | get_has_cursor () const
| Determines whether the pointer follows device motion. More...
InputSource | get_source () const
| Determines the type of the device. More...
Glib::RefPtr< Display > | get_display ()
| Returns the `Gdk::Display` to which device pertains. More...
Glib::RefPtr< const Display > | get_display () const
| Returns the `Gdk::Display` to which device pertains. More...
Glib::RefPtr< Surface > | get_surface_at_position (double & win_x, double & win_y)
| Obtains the surface underneath device, returning the location of the device in win_x and win_y. More...
Glib::RefPtr< const Surface > | get_surface_at_position (double & win_x, double & win_y) const
| Obtains the surface underneath device, returning the location of the device in win_x and win_y. More...
Glib::RefPtr< Surface > | get_surface_at_position ()
| Obtains the surface underneath the device. More...
Glib::RefPtr< const Surface > | get_surface_at_position () const
| Obtains the surface underneath the device. More...
Glib::ustring | get_vendor_id () const
| Returns the vendor ID of this device. More...
Glib::ustring | get_product_id ()
| Returns the product ID of this device. More...
Glib::RefPtr< Seat > | get_seat ()
| Returns the `Gdk::Seat` the device belongs to. More...
Glib::RefPtr< const Seat > | get_seat () const
| Returns the `Gdk::Seat` the device belongs to. More...
guint | get_num_touches () const
| Retrieves the number of touch points associated to device. More...
Glib::RefPtr< DeviceTool > | get_device_tool ()
| Retrieves the current tool for device. More...
Glib::RefPtr< const DeviceTool > | get_device_tool () const
| Retrieves the current tool for device. More...
bool | get_caps_lock_state () const
| Retrieves whether the Caps Lock modifier of the keyboard is locked. More...
bool | get_num_lock_state () const
| Retrieves whether the Num Lock modifier of the keyboard is locked. More...
bool | get_scroll_lock_state () const
| Retrieves whether the Scroll Lock modifier of the keyboard is locked. More...
ModifierType | get_modifier_state () const
| Retrieves the current modifier state of the keyboard. More...
Pango::Direction | get_direction () const
| Returns the direction of effective layout of the keyboard. More...
bool | has_bidi_layouts () const
| Determines if layouts for both right-to-left and left-to-right languages are in use on the keyboard. More...
guint32 | get_timestamp () const
| Returns the timestamp of the last activity for this device. More...
bool | has_device_pad () const
| Checks if this Device instance is a DeviceWithPad. More...
Glib::RefPtr< DeviceWithPad > | device_with_pad_cast ()
| Casts this Device instance to a DeviceWithPad, if possible. More...
Glib::RefPtr< const DeviceWithPad > | device_with_pad_cast () const
| Casts this Device instance to a DeviceWithPad, if possible. More...
Glib::SignalProxy< void()> | signal_changed ()
Glib::SignalProxy< void(const Glib::RefPtr< DeviceTool > &)> | signal_tool_changed ()
Glib::PropertyProxy_ReadOnly< Glib::RefPtr< Display > > | property_display () const
| The `Gdk::Display` the `Gdk::Device` pertains to. More...
Glib::PropertyProxy_ReadOnly< Glib::ustring > | property_name () const
| The device name. More...
Glib::PropertyProxy_ReadOnly< InputSource > | property_source () const
| Source type for the device. More...
Glib::PropertyProxy_ReadOnly< bool > | property_has_cursor () const
| Whether the device is represented by a cursor on the screen. More...
Glib::PropertyProxy_ReadOnly< guint > | property_n_axes () const
| Number of axes in the device. More...
Glib::PropertyProxy_ReadOnly< Glib::ustring > | property_vendor_id () const
| Vendor ID of this device. More...
Glib::PropertyProxy_ReadOnly< Glib::ustring > | property_product_id () const
| Product ID of this device. More...
Glib::PropertyProxy< Glib::RefPtr< Seat > > | property_seat ()
| `Gdk::Seat` of this device. More...
Glib::PropertyProxy_ReadOnly< Glib::RefPtr< Seat > > | property_seat () const
| `Gdk::Seat` of this device. More...
Glib::PropertyProxy_ReadOnly< guint > | property_num_touches () const
| The maximal number of concurrent touches on a touch device. More...
Glib::PropertyProxy_ReadOnly< Glib::RefPtr< DeviceTool > > | property_tool () const
| The `Gdk::DeviceTool` that is currently used with this device. More...
Glib::PropertyProxy_ReadOnly< Pango::Direction > | property_direction () const
| The direction of the current layout. More...
Glib::PropertyProxy_ReadOnly< bool > | property_has_bidi_layouts () const
| Whether the device has both right-to-left and left-to-right layouts. More...
Glib::PropertyProxy_ReadOnly< bool > | property_caps_lock_state () const
| Whether Caps Lock is on. More...
Glib::PropertyProxy_ReadOnly< bool > | property_num_lock_state () const
| Whether Num Lock is on. More...
Glib::PropertyProxy_ReadOnly< bool > | property_scroll_lock_state () const
| Whether Scroll Lock is on. More...
Glib::PropertyProxy_ReadOnly< ModifierType > | property_modifier_state () const
| The current modifier state of the device. More...
Public Member Functions inherited from Glib::Object
| Object (const Object &)=delete
Object & | operator= (const Object &)=delete
| Object (Object &&src) noexcept
Object & | operator= (Object &&src) noexcept
void * | get_data (const QueryQuark &key)
void | set_data (const Quark &key, void *data)
void | set_data (const Quark &key, void *data, DestroyNotify notify)
void | remove_data (const QueryQuark &quark)
void * | steal_data (const QueryQuark &quark)
Glib::RefPtr< Glib::Object > | wrap (GObject *object, bool take_copy=false)
Public Member Functions inherited from Glib::ObjectBase
| ObjectBase (const ObjectBase &)=delete
ObjectBase & | operator= (const ObjectBase &)=delete
void | set_property_value (const Glib::ustring &property_name, const Glib::ValueBase &value)
void | get_property_value (const Glib::ustring &property_name, Glib::ValueBase &value) const
void | set_property (const Glib::ustring &property_name, const PropertyType &value)
void | get_property (const Glib::ustring &property_name, PropertyType &value) const
PropertyType | get_property (const Glib::ustring &property_name) const
sigc::connection | connect_property_changed (const Glib::ustring &property_name, const sigc::slot< void()> &slot)
sigc::connection | connect_property_changed (const Glib::ustring &property_name, sigc::slot< void()> &&slot)
void | freeze_notify ()
void | thaw_notify ()
virtual void | reference () const
virtual void | unreference () const
GObject * | gobj ()
const GObject * | gobj () const
GObject * | gobj_copy () const

## Static Public Member Functions
static GType | get_type ()
| Get the GType for this class, for use with the underlying GObject type system. More...

## Protected Member Functions
| Device ()
Protected Member Functions inherited from Glib::Object
| Object ()
| Object (const Glib::ConstructParams &construct_params)
| Object (GObject *castitem)
| ~Object () noexcept override
Protected Member Functions inherited from Glib::ObjectBase
| ObjectBase ()
| ObjectBase (const char *custom_type_name)
| ObjectBase (const std::type_info &custom_type_info)
| ObjectBase (ObjectBase &&src) noexcept
ObjectBase & | operator= (ObjectBase &&src) noexcept
virtual | ~ObjectBase () noexcept=0
void | initialize (GObject *castitem)
void | initialize_move (GObject *castitem, Glib::ObjectBase *previous_wrapper)

## Related Functions
(Note that these are not member functions.)
Glib::RefPtr< Gdk::Device > | wrap (GdkDevice * object, bool take_copy=false)
| A Glib::wrap() method for this object. More...

## Additional Inherited Members
Public Types inherited from Glib::Object
typedef void(*)(gpointer data | DestroyNotify)

## Detailed Description

A Gdk::Device instance contains a detailed description of an extended input device.

## Constructor & Destructor Documentation

## ◆ Device() [1/2]

Gdk::Device::Device | ( | Device && | src | ) |
| noexcept

## ◆ ~Device()

Gdk::Device::~Device | ( |  | ) |
| overridenoexcept

## ◆ Device() [2/2]

Gdk::Device::Device | ( |  | ) |
| protected

## Member Function Documentation

## ◆ device_with_pad_cast() [1/2]

Glib::RefPtr< DeviceWithPad > Gdk::Device::device_with_pad_cast | ( |  | ) |

Casts this Device instance to a DeviceWithPad, if possible.

Returns
  A DeviceWithPad pointer, or an empty Glib::RefPtr if this Device can't be dynamic_cast to a DeviceWithPad.

Since gtkmm 3.96:

## ◆ device_with_pad_cast() [2/2]

Glib::RefPtr< const DeviceWithPad > Gdk::Device::device_with_pad_cast | ( |  | ) | const

Casts this Device instance to a DeviceWithPad, if possible.

Returns
  A DeviceWithPad pointer, or an empty Glib::RefPtr if this Device can't be dynamic_cast to a DeviceWithPad.

Since gtkmm 3.96:

## ◆ get_caps_lock_state()

bool Gdk::Device::get_caps_lock_state | ( |  | ) | const

Retrieves whether the Caps Lock modifier of the keyboard is locked.

This is only relevant for keyboard devices.

Returns
  `true` if Caps Lock is on for device.

## ◆ get_device_tool() [1/2]

Glib::RefPtr< DeviceTool > Gdk::Device::get_device_tool | ( |  | ) |

Retrieves the current tool for device.

Returns
  The `Gdk::DeviceTool`.

## ◆ get_device_tool() [2/2]

Glib::RefPtr< const DeviceTool > Gdk::Device::get_device_tool | ( |  | ) | const

Retrieves the current tool for device.

Returns
  The `Gdk::DeviceTool`.

## ◆ get_direction()

Pango::Direction Gdk::Device::get_direction | ( |  | ) | const

Returns the direction of effective layout of the keyboard.

This is only relevant for keyboard devices.

The direction of a layout is the direction of the majority of its symbols. See pango_unichar_direction().

Returns
  Pango::Direction::LTR or Pango::Direction::RTL if it can determine the direction. Pango::Direction::NEUTRAL otherwise.

## ◆ get_display() [1/2]

Glib::RefPtr< Display > Gdk::Device::get_display | ( |  | ) |

Returns the `Gdk::Display` to which device pertains.

Returns
  A `Gdk::Display`.

## ◆ get_display() [2/2]

Glib::RefPtr< const Display > Gdk::Device::get_display | ( |  | ) | const

Returns the `Gdk::Display` to which device pertains.

Returns
  A `Gdk::Display`.

## ◆ get_has_cursor()

bool Gdk::Device::get_has_cursor | ( |  | ) | const

Determines whether the pointer follows device motion.

This is not meaningful for keyboard devices, which don't have a pointer.

Returns
  `true` if the pointer follows device motion.

## ◆ get_modifier_state()

ModifierType Gdk::Device::get_modifier_state | ( |  | ) | const

Retrieves the current modifier state of the keyboard.

This is only relevant for keyboard devices.

Returns
  The current modifier state.

## ◆ get_name()

Glib::ustring Gdk::Device::get_name | ( |  | ) | const

The name of the device, suitable for showing in a user interface.

Returns
  A name.

## ◆ get_num_lock_state()

bool Gdk::Device::get_num_lock_state | ( |  | ) | const

Retrieves whether the Num Lock modifier of the keyboard is locked.

This is only relevant for keyboard devices.

Returns
  `true` if Num Lock is on for device.

## ◆ get_num_touches()

guint Gdk::Device::get_num_touches | ( |  | ) | const

Retrieves the number of touch points associated to device.

Returns
  The number of touch points.

## ◆ get_product_id()

Glib::ustring Gdk::Device::get_product_id | ( |  | ) |

Returns the product ID of this device.

This ID is retrieved from the device, and does not change. See get_vendor_id() for more information.

Returns
  The product ID.

## ◆ get_scroll_lock_state()

bool Gdk::Device::get_scroll_lock_state | ( |  | ) | const

Retrieves whether the Scroll Lock modifier of the keyboard is locked.

This is only relevant for keyboard devices.

Returns
  `true` if Scroll Lock is on for device.

## ◆ get_seat() [1/2]

Glib::RefPtr< Seat > Gdk::Device::get_seat | ( |  | ) |

Returns the `Gdk::Seat` the device belongs to.

Returns
  A `Gdk::Seat`.

## ◆ get_seat() [2/2]

Glib::RefPtr< const Seat > Gdk::Device::get_seat | ( |  | ) | const

Returns the `Gdk::Seat` the device belongs to.

Returns
  A `Gdk::Seat`.

## ◆ get_source()

InputSource Gdk::Device::get_source | ( |  | ) | const

Determines the type of the device.

Returns
  A `Gdk::InputSource`.

## ◆ get_surface_at_position() [1/4]

Glib::RefPtr< Surface > Gdk::Device::get_surface_at_position | ( |  | ) |

Obtains the surface underneath the device.

Returns an empty RefPtr if the surface tree under the device is not known to GDK (for example, belongs to another application).

Since gtkmm 3.0:

Returns
  The Gdk::Surface under the device position.

## ◆ get_surface_at_position() [2/4]

Glib::RefPtr< const Surface > Gdk::Device::get_surface_at_position | ( |  | ) | const

Obtains the surface underneath the device.

Returns an empty RefPtr if the surface tree under the device is not known to GDK (for example, belongs to another application).

Since gtkmm 3.0:

Returns
  The Gdk::Surface under the device position.

## ◆ get_surface_at_position() [3/4]

Glib::RefPtr< Surface > Gdk::Device::get_surface_at_position | ( | double & | win_x,
|  | double & | win_y
| ) |  |

Obtains the surface underneath device, returning the location of the device in win_x and win_y.

Parameters

  win_x | Return location for the X coordinate of the device location relative to the surface origin.
  win_y | Return location for the Y coordinate of the device location relative to the surface origin.

Returns
  The `Gdk::Surface` under the device position.

## ◆ get_surface_at_position() [4/4]

Glib::RefPtr< const Surface > Gdk::Device::get_surface_at_position | ( | double & | win_x,
|  | double & | win_y
| ) |  | const

Obtains the surface underneath device, returning the location of the device in win_x and win_y.

Parameters

  win_x | Return location for the X coordinate of the device location relative to the surface origin.
  win_y | Return location for the Y coordinate of the device location relative to the surface origin.

Returns
  The `Gdk::Surface` under the device position.

## ◆ get_timestamp()

guint32 Gdk::Device::get_timestamp | ( |  | ) | const

Returns the timestamp of the last activity for this device.

In practice, this means the timestamp of the last event that was received from the OS for this device. (GTK may occasionally produce events for a device that are not received from the OS, and will not update the timestamp).

Since gtkmm 4.2:

Returns
  The timestamp of the last activity for this device.

## ◆ get_type()

static GType Gdk::Device::get_type | ( |  | ) |
| static

Get the GType for this class, for use with the underlying GObject type system.

## ◆ get_vendor_id()

Glib::ustring Gdk::Device::get_vendor_id | ( |  | ) | const

Returns the vendor ID of this device.

This ID is retrieved from the device, and does not change.

This function, together with get_product_id(), can be used to eg. compose `Gio::Settings` paths to store settings for this device.

[C example ellipted]

Returns
  The vendor ID.

## ◆ gobj() [1/2]

GdkDevice * Gdk::Device::gobj | ( |  | ) |
| inline

Provides access to the underlying C GObject.

## ◆ gobj() [2/2]

const GdkDevice * Gdk::Device::gobj | ( |  | ) | const
| inline

Provides access to the underlying C GObject.

## ◆ gobj_copy()

GdkDevice * Gdk::Device::gobj_copy | ( |  | ) |

Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs.

## ◆ has_bidi_layouts()

bool Gdk::Device::has_bidi_layouts | ( |  | ) | const

Determines if layouts for both right-to-left and left-to-right languages are in use on the keyboard.

This is only relevant for keyboard devices.

Returns
  `true` if there are layouts with both directions, `false` otherwise.

## ◆ has_device_pad()

bool Gdk::Device::has_device_pad | ( |  | ) | const

Checks if this Device instance is a DeviceWithPad.

The underlying C object is usually a subclass of GdkDevice. If that subclass implements the GdkDevicePad interface, this C++ Gdk::Device instance is a Gdk::DeviceWithPad instance, and can be cast to a Gdk::DeviceWithPad by device_with_pad_cast().

Returns
  `true` if this instance is a DeviceWithPad.

Since gtkmm 3.96:

## ◆ operator=()

Device & Gdk::Device::operator= | ( | Device && | src | ) |
| noexcept

## ◆ property_caps_lock_state()

Glib::PropertyProxy_ReadOnly< bool > Gdk::Device::property_caps_lock_state | ( |  | ) | const

Whether Caps Lock is on.

This is only relevant for keyboard devices.

Default value: `false`

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ property_direction()

Glib::PropertyProxy_ReadOnly< Pango::Direction > Gdk::Device::property_direction | ( |  | ) | const

The direction of the current layout.

This is only relevant for keyboard devices.

Default value: Pango::Direction::NEUTRAL

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ property_display()

Glib::PropertyProxy_ReadOnly< Glib::RefPtr< Display > > Gdk::Device::property_display | ( |  | ) | const

The `Gdk::Display` the `Gdk::Device` pertains to.

Since gtkmm 3.22:

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ property_has_bidi_layouts()

Glib::PropertyProxy_ReadOnly< bool > Gdk::Device::property_has_bidi_layouts | ( |  | ) | const

Whether the device has both right-to-left and left-to-right layouts.

This is only relevant for keyboard devices.

Default value: `false`

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ property_has_cursor()

Glib::PropertyProxy_ReadOnly< bool > Gdk::Device::property_has_cursor | ( |  | ) | const

Whether the device is represented by a cursor on the screen.

Since gtkmm 3.22:

Default value: `false`

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ property_modifier_state()

Glib::PropertyProxy_ReadOnly< ModifierType > Gdk::Device::property_modifier_state | ( |  | ) | const

The current modifier state of the device.

This is only relevant for keyboard devices.

Default value: 0

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ property_n_axes()

Glib::PropertyProxy_ReadOnly< guint > Gdk::Device::property_n_axes | ( |  | ) | const

Number of axes in the device.

Since gtkmm 3.22:

Default value: 0

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ property_name()

Glib::PropertyProxy_ReadOnly< Glib::ustring > Gdk::Device::property_name | ( |  | ) | const

The device name.

Since gtkmm 3.22:

Default value: ""

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ property_num_lock_state()

Glib::PropertyProxy_ReadOnly< bool > Gdk::Device::property_num_lock_state | ( |  | ) | const

Whether Num Lock is on.

This is only relevant for keyboard devices.

Default value: `false`

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ property_num_touches()

Glib::PropertyProxy_ReadOnly< guint > Gdk::Device::property_num_touches | ( |  | ) | const

The maximal number of concurrent touches on a touch device.

Will be 0 if the device is not a touch device or if the number of touches is unknown.

Since gtkmm 3.22:

Default value: 0

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ property_product_id()

Glib::PropertyProxy_ReadOnly< Glib::ustring > Gdk::Device::property_product_id | ( |  | ) | const

Product ID of this device.

See Gdk::Device::get_product_id().

Since gtkmm 3.22:

Default value: ""

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ property_scroll_lock_state()

Glib::PropertyProxy_ReadOnly< bool > Gdk::Device::property_scroll_lock_state | ( |  | ) | const

Whether Scroll Lock is on.

This is only relevant for keyboard devices.

Default value: `false`

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ property_seat() [1/2]

Glib::PropertyProxy< Glib::RefPtr< Seat > > Gdk::Device::property_seat | ( |  | ) |

`Gdk::Seat` of this device.

Since gtkmm 3.22:

Returns
  A PropertyProxy that allows you to get or set the value of the property, or receive notification when the value of the property changes.

## ◆ property_seat() [2/2]

Glib::PropertyProxy_ReadOnly< Glib::RefPtr< Seat > > Gdk::Device::property_seat | ( |  | ) | const

`Gdk::Seat` of this device.

Since gtkmm 3.22:

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ property_source()

Glib::PropertyProxy_ReadOnly< InputSource > Gdk::Device::property_source | ( |  | ) | const

Source type for the device.

Since gtkmm 3.22:

Default value: Gdk::InputSource::MOUSE

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ property_tool()

Glib::PropertyProxy_ReadOnly< Glib::RefPtr< DeviceTool > > Gdk::Device::property_tool | ( |  | ) | const

The `Gdk::DeviceTool` that is currently used with this device.

Since gtkmm 3.94:

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ property_vendor_id()

Glib::PropertyProxy_ReadOnly< Glib::ustring > Gdk::Device::property_vendor_id | ( |  | ) | const

Vendor ID of this device.

See Gdk::Device::get_vendor_id().

Since gtkmm 3.22:

Default value: ""

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

## ◆ signal_changed()

Glib::SignalProxy< void()> Gdk::Device::signal_changed | ( |  | ) |

Slot Prototype:
  `void on_my_changed()`

Flags: Run Last

Emitted either when the number of either axes or keys changes.

On X11 this will normally happen when the physical device routing events through the logical device changes (for example, user switches from the USB mouse to a tablet); in that case the logical device will change to reflect the axes and keys on the new physical device.

Since gtkmm 3.22:

## ◆ signal_tool_changed()

Glib::SignalProxy< void(const Glib::RefPtr< DeviceTool > &)> Gdk::Device::signal_tool_changed | ( |  | ) |

Slot Prototype:
  `void on_my_tool_changed(const Glib::RefPtr<DeviceTool>& tool)`

Flags: Run Last

Emitted on pen/eraser devices whenever tools enter or leave proximity.

Since gtkmm 3.94:

Parameters

  tool | The new current tool.

## Friends And Related Function Documentation

## ◆ wrap()

Glib::RefPtr< Gdk::Device > wrap | ( | GdkDevice * | object,
|  | bool | take_copy = `false`
| ) |  |
| related

A Glib::wrap() method for this object.

Parameters

  object | The C instance.
  take_copy | False if the result should take ownership of the C instance. True if it should take a new copy or ref.

Returns
  A C++ instance that wraps this C instance.