Struct gtk4::DragSource

#[repr(transparent)]
pub struct DragSource { /* private fields */ }

DragSource is an event controller to initiate Drag-And-Drop operations.

DragSource can be set up with the necessary ingredients for a DND operation ahead of time. This includes the source for the data that is being transferred, in the form of a gdk::ContentProvider, the desired action, and the icon to use during the drag operation. After setting it up, the drag source must be added to a widget as an event controller, using WidgetExt::add_controller().

⚠️ The following code is in c ⚠️

static void
my_widget_init (MyWidget *self)
{
  GtkDragSource *drag_source = gtk_drag_source_new ();

  g_signal_connect (drag_source, "prepare", G_CALLBACK (on_drag_prepare), self);
  g_signal_connect (drag_source, "drag-begin", G_CALLBACK (on_drag_begin), self);

  gtk_widget_add_controller (GTK_WIDGET (self), GTK_EVENT_CONTROLLER (drag_source));
}

Setting up the content provider and icon ahead of time only makes sense when the data does not change. More commonly, you will want to set them up just in time. To do so, DragSource has prepare and drag-begin signals.

The ::prepare signal is emitted before a drag is started, and can be used to set the content provider and actions that the drag should be started with.

⚠️ The following code is in c ⚠️

static GdkContentProvider *
on_drag_prepare (GtkDragSource *source,
                 double         x,
                 double         y,
                 MyWidget      *self)
{
  // This widget supports two types of content: GFile objects
  // and GdkPixbuf objects; GTK will handle the serialization
  // of these types automatically
  GFile *file = my_widget_get_file (self);
  GdkPixbuf *pixbuf = my_widget_get_pixbuf (self);

  return gdk_content_provider_new_union ((GdkContentProvider *[2]) {
      gdk_content_provider_new_typed (G_TYPE_FILE, file),
      gdk_content_provider_new_typed (GDK_TYPE_PIXBUF, pixbuf),
    }, 2);
}

The ::drag-begin signal is emitted after the gdk::Drag object has been created, and can be used to set up the drag icon.

⚠️ The following code is in c ⚠️

static void
on_drag_begin (GtkDragSource *source,
               GdkDrag       *drag,
               MyWidget      *self)
{
  // Set the widget as the drag icon
  GdkPaintable *paintable = gtk_widget_paintable_new (GTK_WIDGET (self));
  gtk_drag_source_set_icon (source, paintable, 0, 0);
  g_object_unref (paintable);
}

During the DND operation, DragSource emits signals that can be used to obtain updates about the status of the operation, but it is not normally necessary to connect to any signals, except for one case: when the supported actions include gdk::DragAction::MOVE, you need to listen for the drag-end signal and delete the data after it has been transferred.

Properties

actions

The actions that are supported by drag operations from the source.

Note that you must handle the drag-end signal if the actions include gdk::DragAction::MOVE.

Readable | Writeable

content

The data that is offered by drag operations from this source.

Readable | Writeable

GestureSingle

button

Mouse button number to listen to, or 0 to listen for any button.

Readable | Writeable

exclusive

Whether the gesture is exclusive.

Exclusive gestures only listen to pointer and pointer emulated events.

Readable | Writeable

touch-only

Whether the gesture handles only touch events.

Readable | Writeable

Gesture

n-points

The number of touch points that trigger recognition on this gesture.

Readable | Writeable | Construct Only

EventController

name

The name for this controller, typically used for debugging purposes.

Readable | Writeable

propagation-limit

The limit for which events this controller will handle.

Readable | Writeable

propagation-phase

The propagation phase at which this controller will handle events.

Readable | Writeable

widget

The widget receiving the GdkEvents that the controller will handle.

Readable

Signals

drag-begin

Emitted on the drag source when a drag is started.

It can be used to e.g. set a custom drag icon with DragSource::set_icon().

drag-cancel

Emitted on the drag source when a drag has failed.

The signal handler may handle a failed drag operation based on the type of error. It should return true if the failure has been handled and the default “drag operation failed” animation should not be shown.

drag-end

Emitted on the drag source when a drag is finished.

A typical reason to connect to this signal is to undo things done in prepare or drag-begin handlers.

prepare

Emitted when a drag is about to be initiated.

It returns the gdk::ContentProvider to use for the drag that is about to start. The default handler for this signal returns the value of the content property, so if you set up that property ahead of time, you don’t need to connect to this signal.

Gesture

begin

Emitted when the gesture is recognized.

This means the number of touch sequences matches n-points.

Note: These conditions may also happen when an extra touch (eg. a third touch on a 2-touches gesture) is lifted, in that situation @sequence won’t pertain to the current set of active touches, so don’t rely on this being true.

cancel

Emitted whenever a sequence is cancelled.

This usually happens on active touches when EventControllerExt::reset() is called on @gesture (manually, due to grabs…), or the individual @sequence was claimed by parent widgets’ controllers (see GestureExt::set_sequence_state()).

@gesture must forget everything about @sequence as in response to this signal.

end

Emitted when @gesture either stopped recognizing the event sequences as something to be handled, or the number of touch sequences became higher or lower than n-points.

Note: @sequence might not pertain to the group of sequences that were previously triggering recognition on @gesture (ie. a just pressed touch sequence that exceeds n-points). This situation may be detected by checking through GestureExt::handles_sequence().

sequence-state-changed

Emitted whenever a sequence state changes.

See GestureExt::set_sequence_state() to know more about the expectable sequence lifetimes.

update

Emitted whenever an event is handled while the gesture is recognized.

@sequence is guaranteed to pertain to the set of active touches.

Implements

GestureSingleExt, GestureExt, EventControllerExt, glib::ObjectExt

Implementations

impl DragSource

pub fn new() -> DragSource

Creates a new DragSource object.

Returns

the new DragSource

pub fn builder() -> DragSourceBuilder

Creates a new builder-pattern struct instance to construct DragSource objects.

This method returns an instance of DragSourceBuilder which can be used to create DragSource objects.

pub fn drag_cancel(&self)

Cancels a currently ongoing drag operation.

pub fn actions(&self) -> DragAction

Gets the actions that are currently set on the DragSource.

Returns

the actions set on @self

pub fn content(&self) -> Option<ContentProvider>

Gets the current content provider of a DragSource.

Returns

the gdk::ContentProvider of @self

pub fn drag(&self) -> Option<Drag>

Returns the underlying gdk::Drag object for an ongoing drag.

Returns

the gdk::Drag of the current drag operation

pub fn set_actions(&self, actions: DragAction)

Sets the actions on the DragSource.

During a DND operation, the actions are offered to potential drop targets. If @actions include gdk::DragAction::MOVE, you need to listen to the drag-end signal and handle @delete_data being true.

This function can be called before a drag is started, or in a handler for the prepare signal.

actions

the actions to offer

pub fn set_content(&self, content: Option<&impl IsA<ContentProvider>>)

Sets a content provider on a DragSource.

When the data is requested in the cause of a DND operation, it will be obtained from the content provider.

This function can be called before a drag is started, or in a handler for the prepare signal.

You may consider setting the content provider back to None in a drag-end signal handler.

content

a gdk::ContentProvider

pub fn set_icon( &self, paintable: Option<&impl IsA<Paintable>>, hot_x: i32, hot_y: i32 )

Sets a paintable to use as icon during DND operations.

The hotspot coordinates determine the point on the icon that gets aligned with the hotspot of the cursor.

If @paintable is None, a default icon is used.

This function can be called before a drag is started, or in a prepare or drag-begin signal handler.

paintable

the gdk::Paintable to use as icon

hot_x

the hotspot X coordinate on the icon

hot_y

the hotspot Y coordinate on the icon

pub fn connect_drag_begin<F: Fn(&Self, &Drag) + 'static>( &self, f: F ) -> SignalHandlerId

Emitted on the drag source when a drag is started.

It can be used to e.g. set a custom drag icon with set_icon().

drag

the gdk::Drag object

pub fn connect_drag_cancel<F: Fn(&Self, &Drag, DragCancelReason) -> bool + 'static>( &self, f: F ) -> SignalHandlerId

Emitted on the drag source when a drag has failed.

The signal handler may handle a failed drag operation based on the type of error. It should return true if the failure has been handled and the default “drag operation failed” animation should not be shown.

drag

the gdk::Drag object

reason

information on why the drag failed

Returns

true if the failed drag operation has been already handled

pub fn connect_drag_end<F: Fn(&Self, &Drag, bool) + 'static>( &self, f: F ) -> SignalHandlerId

Emitted on the drag source when a drag is finished.

A typical reason to connect to this signal is to undo things done in prepare or drag-begin handlers.

drag

the gdk::Drag object

delete_data

true if the drag was performing gdk::DragAction::MOVE, and the data should be deleted

pub fn connect_prepare<F: Fn(&Self, f64, f64) -> Option<ContentProvider> + 'static>( &self, f: F ) -> SignalHandlerId

Emitted when a drag is about to be initiated.

It returns the gdk::ContentProvider to use for the drag that is about to start. The default handler for this signal returns the value of the content property, so if you set up that property ahead of time, you don’t need to connect to this signal.

x

the X coordinate of the drag starting point

y

the Y coordinate of the drag starting point

Returns

a gdk::ContentProvider

pub fn connect_actions_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_content_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

Trait Implementations

impl Clone for DragSource

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for DragSource

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for DragSource

fn default() -> Self

Returns the “default value” for a type.

impl Display for DragSource

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl HasParamSpec for DragSource

type ParamSpec = ParamSpecObject

type SetValue = DragSource

Preferred value to be used as setter for the associated ParamSpec.

type BuilderFn = fn(_: &str) -> ParamSpecObjectBuilder<'_, DragSource>

fn param_spec_builder() -> Self::BuilderFn

impl Hash for DragSource

fn hash<H>(&self, state: &mut H)where H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for DragSource

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Selfwhere Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Selfwhere Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Selfwhere Self: Sized + PartialOrd<Self>,

Restrict a value to a certain interval.

impl ParentClassIs for DragSource

type Parent = GestureSingle

impl<OT: ObjectType> PartialEq<OT> for DragSource

fn eq(&self, other: &OT) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<OT: ObjectType> PartialOrd<OT> for DragSource

fn partial_cmp(&self, other: &OT) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl StaticType for DragSource

fn static_type() -> Type

Returns the type identifier of Self.

impl Eq for DragSource

impl IsA<EventController> for DragSource

impl IsA<Gesture> for DragSource

impl IsA<GestureSingle> for DragSource