Struct gtk4::DragSource[][src]

pub struct DragSource(_);
Expand description

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

DragSource 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 WidgetExt::add_controller().

⚠️ The following code is in c ⚠️

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, DragSource has signal::DragSource::prepare and signal::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.

⚠️ The following code is in c ⚠️

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

⚠️ The following code is in c ⚠️

static void
on_drag_begin (GtkDragSource *source,
               GtkDrag       *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, DragSource 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 signal::DragSource::drag-end signal and delete the data after it has been transferred.

Implements

GestureSingleExt, GestureExt, EventControllerExt, glib::ObjectExt

Implementations

Creates a new DragSource object.

Returns

the new DragSource

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

This method returns an instance of DragSourceBuilder which can be used to create DragSource objects.

Cancels a currently ongoing drag operation.

Gets the actions that are currently set on the DragSource.

Returns

the actions set on self

Gets the current content provider of a DragSource.

Returns

the gdk::ContentProvider of self

Returns the underlying gdk::Drag object for an ongoing drag.

Returns

the gdk::Drag of the current drag operation, or None

Sets the actions on the DragSource.

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

actions

the actions to offer

Sets a content provider on a DragSource.

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 signal::DragSource::prepare signal.

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

content

a gdk::ContentProvider, or 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 signal::DragSource::prepare or signal::DragSource::drag-begin signal handler.

paintable

the gdk::Paintable to use as icon, or None

hot_x

the hotspot X coordinate on the icon

hot_y

the hotspot Y coordinate on the icon

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().

drag

the gdk::Drag object

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

the gdk::Drag object

reason

information on why the drag failed

Returns

true if the failed drag operation has been already handled

Emitted on the drag source when a drag is finished.

A typical reason to connect to this signal is to undo things done in signal::DragSource::prepare or signal::DragSource::drag-begin handlers.

drag

the gdk::Drag object

delete_data

true if the drag was performing gdk::DragAction::MOVE, and the data should be deleted

Emitted when a drag is about to be initiated.

It returns the gdk::ContentProvider to use for the drag that is about to start. The default handler for this signal returns the value of the property::DragSource::content property, so if you set up that property ahead of time, you don’t need to connect to this signal.

x

the X coordinate of the drag starting point

y

the Y coordinate fo the drag starting point

Returns

a gdk::ContentProvider, or None

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