DragSource

class DragSource(**properties: Any)

Superclasses: GestureSingle, Gesture, EventController, Object

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

GtkDragSource 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 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 add_controller.

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, GtkDragSource 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.

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 GdkDrag object has been created, and can be used to set up the drag icon.

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, GtkDragSource 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_ACTION_MOVE, you need to listen for the drag_end signal and delete the data after it has been transferred.

Constructors

class DragSource

classmethod new() → DragSource: Creates a new GtkDragSource object.

Methods

class DragSource

drag_cancel() → None: Cancels a currently ongoing drag operation.

get_actions() → DragAction: Gets the actions that are currently set on the GtkDragSource.

get_content() → ContentProvider | None: Gets the current content provider of a GtkDragSource.

get_drag() → Drag | None: Returns the underlying GdkDrag object for an ongoing drag.

set_actions(actions: DragAction) → None

Sets the actions on the GtkDragSource.

During a DND operation, the actions are offered to potential drop targets. If actions include %GDK_ACTION_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.

Parameters:: actions – the actions to offer

set_content(content: ContentProvider | None = None) → None

Sets a content provider on a GtkDragSource.

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.

Parameters:: content – a GdkContentProvider

set_icon(paintable: Paintable | None, hot_x: int, hot_y: int) → None

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.

Parameters:

paintable – the GdkPaintable to use as icon
hot_x – the hotspot X coordinate on the icon
hot_y – the hotspot Y coordinate on the icon

Properties

class DragSource

props.actions: DragAction

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_ACTION_MOVE.

props.content: ContentProvider: The data that is offered by drag operations from this source.

Signals

class DragSource.signals

drag_begin(drag: Drag) → None

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.

Parameters:: drag – the GdkDrag object

drag_cancel(drag: Drag, reason: DragCancelReason) → bool

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.

Parameters:

drag – the GdkDrag object
reason – information on why the drag failed

drag_end(drag: Drag, delete_data: bool) → None

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.

Parameters:

drag – the GdkDrag object
delete_data – True if the drag was performing %GDK_ACTION_MOVE, and the data should be deleted

prepare(x: float, y: float) → ContentProvider | None

Emitted when a drag is about to be initiated.

It returns the GdkContentProvider 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.

Parameters:

x – the X coordinate of the drag starting point
y – the Y coordinate of the drag starting point