Struct gtk4::DropTarget

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

DropTarget is an event controller to receive Drag-and-Drop operations.

The most basic way to use a DropTarget to receive drops on a widget is to create it via new(), passing in the GType of the data you want to receive and connect to the drop signal to receive the data:

⚠️ The following code is in c ⚠️

static gboolean
on_drop (GtkDropTarget *target,
         const GValue  *value,
         double         x,
         double         y,
         gpointer       data)
{
  MyWidget *self = data;

  // Call the appropriate setter depending on the type of data
  // that we received
  if (G_VALUE_HOLDS (value, G_TYPE_FILE))
    my_widget_set_file (self, g_value_get_object (value));
  else if (G_VALUE_HOLDS (value, GDK_TYPE_PIXBUF))
    my_widget_set_pixbuf (self, g_value_get_object (value));
  else
    return FALSE;

  return TRUE;
}

static void
my_widget_init (MyWidget *self)
{
  GtkDropTarget *target =
    gtk_drop_target_new (G_TYPE_INVALID, GDK_ACTION_COPY);

  // This widget accepts two types of drop types: GFile objects
  // and GdkPixbuf objects
  gtk_drop_target_set_gtypes (target, (GTypes [2]) {
    G_TYPE_FILE,
    GDK_TYPE_PIXBUF,
  }, 2);

  g_signal_connect (target, "drop", G_CALLBACK (on_drop), self);
  gtk_widget_add_controller (GTK_WIDGET (self), GTK_EVENT_CONTROLLER (target));
}

DropTarget supports more options, such as:

• rejecting potential drops via the accept signal and the reject() function to let other drop targets handle the drop
• tracking an ongoing drag operation before the drop via the enter, motion and leave signals
• configuring how to receive data by setting the preload property and listening for its availability via the value property

However, DropTarget is ultimately modeled in a synchronous way and only supports data transferred via GType. If you want full control over an ongoing drop, the DropTargetAsync object gives you this ability.

While a pointer is dragged over the drop target’s widget and the drop has not been rejected, that widget will receive the StateFlags::DROP_ACTIVE state, which can be used to style the widget.

If you are not interested in receiving the drop, but just want to update UI state during a Drag-and-Drop operation (e.g. switching tabs), you can use DropControllerMotion.

Properties

actions

The GdkDragActions that this drop target supports.

Readable | Writeable

current-drop

The gdk::Drop that is currently being performed.

Readable

drop

The gdk::Drop that is currently being performed.

Readable

formats

The gdk::ContentFormats that determine the supported data formats.

Readable | Writeable | Construct Only

preload

Whether the drop data should be preloaded when the pointer is only hovering over the widget but has not been released.

Setting this property allows finer grained reaction to an ongoing drop at the cost of loading more data.

The default value for this property is false to avoid downloading huge amounts of data by accident.

For example, if somebody drags a full document of gigabytes of text from a text editor across a widget with a preloading drop target, this data will be downloaded, even if the data is ultimately dropped elsewhere.

For a lot of data formats, the amount of data is very small (like GDK_TYPE_RGBA), so enabling this property does not hurt at all. And for local-only Drag-and-Drop operations, no data transfer is done, so enabling it there is free.

Readable | Writeable

value

The value for this drop operation.

This is None if the data has not been loaded yet or no drop operation is going on.

Data may be available before the drop signal gets emitted - for example when the preload property is set. You can use the ::notify signal to be notified of available data.

Readable

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

accept

Emitted on the drop site when a drop operation is about to begin.

If the drop is not accepted, false will be returned and the drop target will ignore the drop. If true is returned, the drop is accepted for now but may be rejected later via a call to DropTarget::reject() or ultimately by returning false from a drop handler.

The default handler for this signal decides whether to accept the drop based on the formats provided by the @drop.

If the decision whether the drop will be accepted or rejected depends on the data, this function should return true, the preload property should be set and the value should be inspected via the ::notify:value signal, calling DropTarget::reject() if required.

drop

Emitted on the drop site when the user drops the data onto the widget.

The signal handler must determine whether the pointer position is in a drop zone or not. If it is not in a drop zone, it returns false and no further processing is necessary.

Otherwise, the handler returns true. In this case, this handler will accept the drop. The handler is responsible for using the given @value and performing the drop operation.

enter

Emitted on the drop site when the pointer enters the widget.

It can be used to set up custom highlighting.

leave

Emitted on the drop site when the pointer leaves the widget.

Its main purpose it to undo things done in enter.

motion

Emitted while the pointer is moving over the drop target.

Implements

EventControllerExt, glib::ObjectExt

Implementations

impl DropTarget

pub fn new(type_: Type, actions: DragAction) -> DropTarget

Creates a new DropTarget object.

If the drop target should support more than 1 type, pass G_TYPE_INVALID for @type_ and then call set_types().

type_

The supported type or G_TYPE_INVALID

actions

the supported actions

Returns

the new DropTarget

pub fn builder() -> DropTargetBuilder

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

This method returns an instance of DropTargetBuilder which can be used to create DropTarget objects.

pub fn actions(&self) -> DragAction

Gets the actions that this drop target supports.

Returns

the actions that this drop target supports

pub fn current_drop(&self) -> Option<Drop>

Available on crate feature v4_4 only.

Gets the currently handled drop operation.

If no drop operation is going on, None is returned.

Returns

The current drop

pub fn drop(&self) -> Option<Drop>

Gets the currently handled drop operation.

If no drop operation is going on, None is returned.

Deprecated since 4.4

Use current_drop() instead

Returns

The current drop

pub fn formats(&self) -> Option<ContentFormats>

Gets the data formats that this drop target accepts.

If the result is None, all formats are expected to be supported.

Returns

the supported data formats

pub fn is_preload(&self) -> bool

Gets whether data should be preloaded on hover.

Returns

true if drop data should be preloaded

pub fn value(&self) -> Option<Value>

Gets the current drop data, as a GValue.

Returns

The current drop data

pub fn reject(&self)

Rejects the ongoing drop operation.

If no drop operation is ongoing, i.e when current-drop is None, this function does nothing.

This function should be used when delaying the decision on whether to accept a drag or not until after reading the data.

pub fn set_actions(&self, actions: DragAction)

Sets the actions that this drop target supports.

actions

the supported actions

pub fn set_preload(&self, preload: bool)

Sets whether data should be preloaded on hover.

preload

true to preload drop data

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

Emitted on the drop site when a drop operation is about to begin.

If the drop is not accepted, false will be returned and the drop target will ignore the drop. If true is returned, the drop is accepted for now but may be rejected later via a call to reject() or ultimately by returning false from a drop handler.

The default handler for this signal decides whether to accept the drop based on the formats provided by the @drop.

If the decision whether the drop will be accepted or rejected depends on the data, this function should return true, the preload property should be set and the value should be inspected via the ::notify:value signal, calling reject() if required.

drop

the gdk::Drop

Returns

true if @drop is accepted

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

Emitted on the drop site when the pointer enters the widget.

It can be used to set up custom highlighting.

x

the x coordinate of the current pointer position

y

the y coordinate of the current pointer position

Returns

Preferred action for this drag operation or 0 if dropping is not supported at the current @x,@y location.

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

Emitted on the drop site when the pointer leaves the widget.

Its main purpose it to undo things done in enter.

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

Emitted while the pointer is moving over the drop target.

x

the x coordinate of the current pointer position

y

the y coordinate of the current pointer position

Returns

Preferred action for this drag operation or 0 if dropping is not supported at the current @x,@y location.

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

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

Available on crate feature v4_4 only.

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

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

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

impl DropTarget

pub fn set_types(&self, types: &[Type])

Sets the supported GTypes for this drop target.

types

all supported GTypes that can be dropped on the target

pub fn value_as<V: for<'b> FromValue<'b> + 'static>(&self) -> Option<V>

Similar to Self::value but panics if the value is of a different type.

pub fn types(&self) -> Slice<Type>

Gets the list of supported GTypes that can be dropped on the target.

If no types have been set, NULL will be returned.

Returns

the G_TYPE_INVALID-terminated array of types included in formats

pub fn connect_drop<F: Fn(&DropTarget, &Value, f64, f64) -> bool + 'static>( &self, f: F ) -> SignalHandlerId

Emitted on the drop site when the user drops the data onto the widget.

The signal handler must determine whether the pointer position is in a drop zone or not. If it is not in a drop zone, it returns false and no further processing is necessary.

Otherwise, the handler returns true. In this case, this handler will accept the drop. The handler is responsible for using the given @value and performing the drop operation.

value

the GValue being dropped

x

the x coordinate of the current pointer position

y

the y coordinate of the current pointer position

Returns

whether the drop was accepted at the given pointer position

Trait Implementations

impl Clone for DropTarget

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 DropTarget

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

Formats the value using the given formatter.

impl Default for DropTarget

fn default() -> Self

Returns the “default value” for a type.

impl Display for DropTarget

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

Formats the value using the given formatter.

impl HasParamSpec for DropTarget

type ParamSpec = ParamSpecObject

type SetValue = DropTarget

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

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

fn param_spec_builder() -> Self::BuilderFn

impl Hash for DropTarget

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 DropTarget

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 DropTarget

type Parent = EventController

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

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 DropTarget

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 DropTarget

fn static_type() -> Type

Returns the type identifier of Self.

impl Eq for DropTarget

impl IsA<EventController> for DropTarget