GI.Gtk.Objects.DropTarget

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

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

c code

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));
}

GtkDropTarget supports more options, such as:

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

However, GtkDropTarget 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 StateFlagsDropActive 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.

Exported types

newtype DropTarget

Memory-managed wrapper type.

Constructors

DropTarget (ManagedPtr DropTarget)

Instances

Eq DropTarget

Defined in GI.Gtk.Objects.DropTarget

Methods

(==) :: DropTarget -> DropTarget -> Bool

(/=) :: DropTarget -> DropTarget -> Bool

GObject DropTarget

Defined in GI.Gtk.Objects.DropTarget

ManagedPtrNewtype DropTarget

Defined in GI.Gtk.Objects.DropTarget

Methods

toManagedPtr :: DropTarget -> ManagedPtr DropTarget

TypedObject DropTarget

Defined in GI.Gtk.Objects.DropTarget

Methods

glibType :: IO GType

HasParentTypes DropTarget

Defined in GI.Gtk.Objects.DropTarget

IsGValue (Maybe DropTarget)

Convert DropTarget to and from GValue. See toGValue and fromGValue.

Defined in GI.Gtk.Objects.DropTarget

Methods

gvalueGType_ :: IO GType

gvalueSet_ :: Ptr GValue -> Maybe DropTarget -> IO ()

gvalueGet_ :: Ptr GValue -> IO (Maybe DropTarget)

type ParentTypes DropTarget

Defined in GI.Gtk.Objects.DropTarget

type ParentTypes DropTarget = '[EventController, Object]

class (GObject o, IsDescendantOf DropTarget o) => IsDropTarget o

Type class for types which can be safely cast to DropTarget, for instance with toDropTarget.

Instances

(GObject o, IsDescendantOf DropTarget o) => IsDropTarget o

Defined in GI.Gtk.Objects.DropTarget

toDropTarget :: (MonadIO m, IsDropTarget o) => o -> m DropTarget

Cast to DropTarget, for types for which this is known to be safe. For general casts, use castTo.

Methods

Click to display all available methods, including inherited ones

Methods

bindProperty, bindPropertyFull, forceFloating, freezeNotify, getv, isFloating, notify, notifyByPspec, ref, refSink, reject, reset, runDispose, stealData, stealQdata, thawNotify, unref, watchClosure.

Getters

getActions, getCurrentDrop, getCurrentEvent, getCurrentEventDevice, getCurrentEventState, getCurrentEventTime, getData, getDrop, getFormats, getGtypes, getName, getPreload, getPropagationLimit, getPropagationPhase, getProperty, getQdata, getValue, getWidget.

Setters

setActions, setData, setDataFull, setGtypes, setName, setPreload, setPropagationLimit, setPropagationPhase, setProperty, setStaticName.

getActions

dropTargetGetActions

Arguments

:: (HasCallStack, MonadIO m, IsDropTarget a)

=> a

self: a GtkDropTarget

-> m [DragAction]

Returns: the actions that this drop target supports

Gets the actions that this drop target supports.

getCurrentDrop

dropTargetGetCurrentDrop

Arguments

:: (HasCallStack, MonadIO m, IsDropTarget a)

=> a

self: a GtkDropTarget

-> m (Maybe Drop)

Returns: The current drop

Gets the currently handled drop operation.

If no drop operation is going on, Nothing is returned.

Since: 4.4

getDrop

dropTargetGetDrop

Arguments

:: (HasCallStack, MonadIO m, IsDropTarget a)

=> a

self: a GtkDropTarget

-> m (Maybe Drop)

Returns: The current drop

Deprecated: (Since version 4.4)Use dropTargetGetCurrentDrop instead

Gets the currently handled drop operation.

If no drop operation is going on, Nothing is returned.

getFormats

dropTargetGetFormats

Arguments

:: (HasCallStack, MonadIO m, IsDropTarget a)

=> a

self: a GtkDropTarget

-> m (Maybe ContentFormats)

Returns: the supported data formats

Gets the data formats that this drop target accepts.

If the result is Nothing, all formats are expected to be supported.

getGtypes

dropTargetGetGtypes

Arguments

:: (HasCallStack, MonadIO m, IsDropTarget a)

=> a

self: a GtkDropTarget

-> m (Maybe [GType])

Returns: the G_TYPE_INVALID-terminated array of types included in formats

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

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

getPreload

dropTargetGetPreload

Arguments

:: (HasCallStack, MonadIO m, IsDropTarget a)

=> a

self: a GtkDropTarget

-> m Bool

Returns: True if drop data should be preloaded

Gets whether data should be preloaded on hover.

getValue

dropTargetGetValue

Arguments

:: (HasCallStack, MonadIO m, IsDropTarget a)

=> a

self: a GtkDropTarget

-> m (Maybe GValue)

Returns: The current drop data

Gets the current drop data, as a GValue.

new

dropTargetNew

Arguments

:: (HasCallStack, MonadIO m)

=> GType

type: The supported type or G_TYPE_INVALID

-> [DragAction]

actions: the supported actions

-> m DropTarget

Returns: the new GtkDropTarget

Creates a new GtkDropTarget object.

If the drop target should support more than 1 type, pass G_TYPE_INVALID for type and then call dropTargetSetGtypes.

reject

dropTargetReject

Arguments

:: (HasCallStack, MonadIO m, IsDropTarget a)

=> a

self: a GtkDropTarget

-> m ()

Rejects the ongoing drop operation.

If no drop operation is ongoing, i.e when DropTarget:currentDrop is Nothing, 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.

setActions

dropTargetSetActions

Arguments

:: (HasCallStack, MonadIO m, IsDropTarget a)

=> a

self: a GtkDropTarget

-> [DragAction]

actions: the supported actions

-> m ()

Sets the actions that this drop target supports.

setGtypes

dropTargetSetGtypes

Arguments

:: (HasCallStack, MonadIO m, IsDropTarget a)

=> a

self: a GtkDropTarget

-> Maybe [GType]

types: all supported GTypes that can be dropped on the target

-> m ()

Sets the supported GTypes for this drop target.

setPreload

dropTargetSetPreload

Arguments

:: (HasCallStack, MonadIO m, IsDropTarget a)

=> a

self: a GtkDropTarget

-> Bool

preload: True to preload drop data

-> m ()

Sets whether data should be preloaded on hover.

Properties

actions

The GdkDragActions that this drop target supports.

constructDropTargetActions :: (IsDropTarget o, MonadIO m) => [DragAction] -> m (GValueConstruct o)

Construct a GValueConstruct with valid value for the “actions” property. This is rarely needed directly, but it is used by new.

getDropTargetActions :: (MonadIO m, IsDropTarget o) => o -> m [DragAction]

Get the value of the “actions” property. When overloading is enabled, this is equivalent to

get dropTarget #actions

setDropTargetActions :: (MonadIO m, IsDropTarget o) => o -> [DragAction] -> m ()

Set the value of the “actions” property. When overloading is enabled, this is equivalent to

set dropTarget [ #actions := value ]

currentDrop

The GdkDrop that is currently being performed.

Since: 4.4

getDropTargetCurrentDrop :: (MonadIO m, IsDropTarget o) => o -> m (Maybe Drop)

Get the value of the “current-drop” property. When overloading is enabled, this is equivalent to

get dropTarget #currentDrop

formats

The GdkContentFormats that determine the supported data formats.

constructDropTargetFormats :: (IsDropTarget o, MonadIO m) => ContentFormats -> m (GValueConstruct o)

Construct a GValueConstruct with valid value for the “formats” property. This is rarely needed directly, but it is used by new.

getDropTargetFormats :: (MonadIO m, IsDropTarget o) => o -> m (Maybe ContentFormats)

Get the value of the “formats” property. When overloading is enabled, this is equivalent to

get dropTarget #formats

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.

constructDropTargetPreload :: (IsDropTarget o, MonadIO m) => Bool -> m (GValueConstruct o)

Construct a GValueConstruct with valid value for the “preload” property. This is rarely needed directly, but it is used by new.

getDropTargetPreload :: (MonadIO m, IsDropTarget o) => o -> m Bool

Get the value of the “preload” property. When overloading is enabled, this is equivalent to

get dropTarget #preload

setDropTargetPreload :: (MonadIO m, IsDropTarget o) => o -> Bool -> m ()

Set the value of the “preload” property. When overloading is enabled, this is equivalent to

set dropTarget [ #preload := value ]

value

The value for this drop operation.

This is Nothing if the data has not been loaded yet or no drop operation is going on.

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

getDropTargetValue :: (MonadIO m, IsDropTarget o) => o -> m (Maybe GValue)

Get the value of the “value” property. When overloading is enabled, this is equivalent to

get dropTarget #value

Signals

accept

type DropTargetAcceptCallback

Arguments

 = Drop

drop: the GdkDrop

-> IO Bool

Returns: True if drop is accepted

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 dropTargetReject or ultimately by returning False from a DropTarget::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 DropTarget:preload property should be set and the value should be inspected via the notify:value signal, calling dropTargetReject if required.

afterDropTargetAccept :: (IsDropTarget a, MonadIO m) => a -> ((?self :: a) => DropTargetAcceptCallback) -> m SignalHandlerId

Connect a signal handler for the accept signal, to be run after the default handler. When overloading is enabled, this is equivalent to

after dropTarget #accept callback

By default the object invoking the signal is not passed to the callback. If you need to access it, you can use the implit ?self parameter. Note that this requires activating the ImplicitParams GHC extension.

onDropTargetAccept :: (IsDropTarget a, MonadIO m) => a -> ((?self :: a) => DropTargetAcceptCallback) -> m SignalHandlerId

Connect a signal handler for the accept signal, to be run before the default handler. When overloading is enabled, this is equivalent to

on dropTarget #accept callback

drop

type DropTargetDropCallback

Arguments

 = GValue

value: the GValue being dropped

-> Double

x: the x coordinate of the current pointer position

-> Double

y: the y coordinate of the current pointer position

-> IO Bool

Returns: whether the drop was accepted at the given pointer position

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.

afterDropTargetDrop :: (IsDropTarget a, MonadIO m) => a -> ((?self :: a) => DropTargetDropCallback) -> m SignalHandlerId

Connect a signal handler for the drop signal, to be run after the default handler. When overloading is enabled, this is equivalent to

after dropTarget #drop callback

By default the object invoking the signal is not passed to the callback. If you need to access it, you can use the implit ?self parameter. Note that this requires activating the ImplicitParams GHC extension.

onDropTargetDrop :: (IsDropTarget a, MonadIO m) => a -> ((?self :: a) => DropTargetDropCallback) -> m SignalHandlerId

Connect a signal handler for the drop signal, to be run before the default handler. When overloading is enabled, this is equivalent to

on dropTarget #drop callback

enter

type DropTargetEnterCallback

Arguments

 = Double

x: the x coordinate of the current pointer position

-> Double

y: the y coordinate of the current pointer position

-> IO [DragAction]

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

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

It can be used to set up custom highlighting.

afterDropTargetEnter :: (IsDropTarget a, MonadIO m) => a -> ((?self :: a) => DropTargetEnterCallback) -> m SignalHandlerId

Connect a signal handler for the enter signal, to be run after the default handler. When overloading is enabled, this is equivalent to

after dropTarget #enter callback

By default the object invoking the signal is not passed to the callback. If you need to access it, you can use the implit ?self parameter. Note that this requires activating the ImplicitParams GHC extension.

onDropTargetEnter :: (IsDropTarget a, MonadIO m) => a -> ((?self :: a) => DropTargetEnterCallback) -> m SignalHandlerId

Connect a signal handler for the enter signal, to be run before the default handler. When overloading is enabled, this is equivalent to

on dropTarget #enter callback

leave

type DropTargetLeaveCallback = IO ()

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

Its main purpose it to undo things done in DropTarget::enter.

afterDropTargetLeave :: (IsDropTarget a, MonadIO m) => a -> ((?self :: a) => DropTargetLeaveCallback) -> m SignalHandlerId

Connect a signal handler for the leave signal, to be run after the default handler. When overloading is enabled, this is equivalent to

after dropTarget #leave callback

By default the object invoking the signal is not passed to the callback. If you need to access it, you can use the implit ?self parameter. Note that this requires activating the ImplicitParams GHC extension.

onDropTargetLeave :: (IsDropTarget a, MonadIO m) => a -> ((?self :: a) => DropTargetLeaveCallback) -> m SignalHandlerId

Connect a signal handler for the leave signal, to be run before the default handler. When overloading is enabled, this is equivalent to

on dropTarget #leave callback

motion

type DropTargetMotionCallback

Arguments

 = Double

x: the x coordinate of the current pointer position

-> Double

y: the y coordinate of the current pointer position

-> IO [DragAction]

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

Emitted while the pointer is moving over the drop target.

afterDropTargetMotion :: (IsDropTarget a, MonadIO m) => a -> ((?self :: a) => DropTargetMotionCallback) -> m SignalHandlerId

Connect a signal handler for the motion signal, to be run after the default handler. When overloading is enabled, this is equivalent to

after dropTarget #motion callback

By default the object invoking the signal is not passed to the callback. If you need to access it, you can use the implit ?self parameter. Note that this requires activating the ImplicitParams GHC extension.

onDropTargetMotion :: (IsDropTarget a, MonadIO m) => a -> ((?self :: a) => DropTargetMotionCallback) -> m SignalHandlerId

Connect a signal handler for the motion signal, to be run before the default handler. When overloading is enabled, this is equivalent to

on dropTarget #motion callback