DropTarget

class DropTarget(**properties: Any)

Superclasses: EventController, Object

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 new, passing in the GType of the data you want to receive and connect to the drop signal to receive the data:

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, (GType [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 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, 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 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.

Constructors

class DropTarget

classmethod new(type: type, actions: DragAction) → DropTarget

Creates a new GtkDropTarget object.

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

Parameters:

type – The supported type or Invalid
actions – the supported actions

Methods

class DropTarget

get_actions() → DragAction: Gets the actions that this drop target supports.

get_current_drop() → Drop | None

Gets the currently handled drop operation.

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

Added in version 4.4.

get_drop() → Drop | None

Gets the currently handled drop operation.

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

Deprecated since version 4.4: Use get_current_drop instead

get_formats() → ContentFormats | None

Gets the data formats that this drop target accepts.

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

get_gtypes() → list[type] | None

Gets the list of supported GType’s that can be dropped on the target.

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

get_preload() → bool: Gets whether data should be preloaded on hover.

get_value() → Any | None: Gets the current drop data, as a GValue.

reject() → None

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.

set_actions(actions: DragAction) → None

Sets the actions that this drop target supports.

Parameters:: actions – the supported actions

set_gtypes(types: Sequence[type] | None = None) → None

Sets the supported GType’s for this drop target.

Parameters:: types – all supported GType’s that can be dropped on the target

set_preload(preload: bool) → None

Sets whether data should be preloaded on hover.

Parameters:: preload – True to preload drop data

Properties

class DropTarget

props.actions: DragAction: The GdkDragActions that this drop target supports.

props.current_drop: Drop: The GdkDrop that is currently being performed.

Added in version 4.4.

props.formats: ContentFormats: The GdkContentFormats that determine the supported data formats.

props.preload: bool

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.

props.value: Any

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.

Signals

class DropTarget.signals

accept(drop: Drop) → bool

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.

Parameters:: drop – the GdkDrop

drop(value: Any, x: float, y: float) → bool

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.

Parameters:

value – the GValue being dropped
x – the x coordinate of the current pointer position
y – the y coordinate of the current pointer position

enter(x: float, y: float) → DragAction

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

It can be used to set up custom highlighting.

Parameters:

x – the x coordinate of the current pointer position
y – the y coordinate of the current pointer position

leave() → None

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

Its main purpose it to undo things done in enter.

motion(x: float, y: float) → DragAction

Emitted while the pointer is moving over the drop target.

Parameters:

x – the x coordinate of the current pointer position
y – the y coordinate of the current pointer position