Gtk.DragSource¶

class — extends GestureSingle

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 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 Widget.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 DragSource.prepare and DragSource.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.DragAction.MOVE, you need to listen for the DragSource.drag-end signal and delete the data after it has been transferred.

Constructors¶

new¶

@classmethod
def new(cls) -> DragSource

Creates a new GtkDragSource object.

Methods¶

drag_cancel¶

def drag_cancel(self) -> None

Cancels a currently ongoing drag operation.

get_actions¶

def get_actions(self) -> Gdk.DragAction

Gets the actions that are currently set on the GtkDragSource.

get_content¶

def get_content(self) -> Gdk.ContentProvider | None

Gets the current content provider of a GtkDragSource.

get_drag¶

def get_drag(self) -> Gdk.Drag | None

Returns the underlying GdkDrag object for an ongoing drag.

set_actions¶

def set_actions(self, actions: Gdk.DragAction | int) -> None

Sets the actions on the GtkDragSource.

During a DND operation, the actions are offered to potential drop targets. If actions include Gdk.DragAction.MOVE, you need to listen to the DragSource.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 DragSource.prepare signal.

Parameters:

actions — the actions to offer

set_content¶

def set_content(self, content: Gdk.ContentProvider | 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 DragSource.prepare signal.

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

Parameters:

content — a GdkContentProvider

set_icon¶

def set_icon(self, paintable: Gdk.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 DragSource.prepare or DragSource.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¶

actions¶

actions: Gdk.DragAction | int  # read/write

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

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

content¶

content: Gdk.ContentProvider  # read/write

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

Signals¶

drag-begin¶

def on_drag_begin(self, drag: Gdk.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 DragSource.set_icon.

drag-cancel¶

def on_drag_cancel(self, drag: Gdk.Drag, reason: Gdk.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.

drag-end¶

def on_drag_end(self, drag: Gdk.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 DragSource.prepare or DragSource.drag-begin handlers.

prepare¶

def on_prepare(self, x: float, y: float) -> Gdk.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 DragSource.content property, so if you set up that property ahead of time, you don't need to connect to this signal.