GtkDropTargetAsync

GtkDropTargetAsync — Event controller to receive DND drops

Properties

GdkDragAction actions Read / Write
GdkContentFormats * formats Read / Write

Signals

gboolean accept Run Last
GdkDragAction drag-enter Run Last
void drag-leave Run Last
GdkDragAction drag-motion Run Last
gboolean drop Run Last

Types and Values

Object Hierarchy

    GObject
    ╰── GtkEventController
        ╰── GtkDropTargetAsync

Includes

#include <gtk/gtk.h>

Description

GtkDropTargetAsync is an auxiliary object that can be used to receive Drag-and-Drop operations. It is the more complete but also more complex method of handling drop operations compared to GtkDropTarget and you should only use it if GtkDropTarget doesn't provide all the features you need.

To use a GtkDropTargetAsync to receive drops on a widget, you create a GtkDropTargetAsync object, configure which data formats and actions you support, connect to its signals, and then attach it to the widget with gtk_widget_add_controller().

During a drag operation, the first signal that a GtkDropTargetAsync emits is “accept”, which is meant to determine whether the target is a possible drop site for the ongoing drop. The default handler for the ::accept signal accepts the drop if it finds a compatible data format and an action that is supported on both sides.

If it is, and the widget becomes a target, you will receive a “drag-enter” signal, followed by “drag-motion” signals as the pointer moves, optionally a “drop” signal when a drop happens, and finally a “drag-leave” signal when the pointer moves off the widget.

The ::drag-enter and ::drag-motion handler return a GdkDragAction to update the status of the ongoing operation. The ::drop handler should decide if it ultimately accepts the drop and if it does, it should initiate the data transfer and finish the operation by calling gdk_drop_finish().

Between the ::drag-enter and ::drag-leave signals the widget is a current drop target, and will receive the GTK_STATE_FLAG_DROP_ACTIVE state, which can be used by themes to style the widget as a drop target.

Functions

gtk_drop_target_async_new ()

GtkDropTargetAsync *
gtk_drop_target_async_new (GdkContentFormats *formats,
                           GdkDragAction actions);

Creates a new GtkDropTargetAsync object.

Parameters

formats

the supported data formats.

[nullable][transfer full]

actions

the supported actions

 

Returns

the new GtkDropTargetAsync


gtk_drop_target_async_set_formats ()

void
gtk_drop_target_async_set_formats (GtkDropTargetAsync *self,
                                   GdkContentFormats *formats);

Sets the data formats that this drop target will accept.

Parameters

self

a GtkDropTargetAsync

 

formats

the supported data formats or NULL for any format.

[nullable]

gtk_drop_target_async_get_formats ()

GdkContentFormats *
gtk_drop_target_async_get_formats (GtkDropTargetAsync *self);

Gets the data formats that this drop target accepts.

If the result is NULL, all formats are expected to be supported.

Parameters

self

a GtkDropTargetAsync

 

Returns

the supported data formats.

[nullable]


gtk_drop_target_async_set_actions ()

void
gtk_drop_target_async_set_actions (GtkDropTargetAsync *self,
                                   GdkDragAction actions);

Sets the actions that this drop target supports.

Parameters

self

a GtkDropTargetAsync

 

actions

the supported actions

 

gtk_drop_target_async_get_actions ()

GdkDragAction
gtk_drop_target_async_get_actions (GtkDropTargetAsync *self);

Gets the actions that this drop target supports.

Parameters

self

a GtkDropTargetAsync

 

Returns

the actions that this drop target supports


gtk_drop_target_async_reject_drop ()

void
gtk_drop_target_async_reject_drop (GtkDropTargetAsync *self,
                                   GdkDrop *drop);

Sets the drop as not accepted on this drag site.

This function should be used when delaying the decision on whether to accept a drag or not until after reading the data.

Parameters

self

a GtkDropTargetAsync

 

drop

the GdkDrop of an ongoing drag operation

 

Types and Values

GtkDropTargetAsync

typedef struct _GtkDropTargetAsync GtkDropTargetAsync;

Property Details

The “actions” property

  “actions”                  GdkDragAction

The GdkDragActions that this drop target supports

Owner: GtkDropTargetAsync

Flags: Read / Write


The “formats” property

  “formats”                  GdkContentFormats *

The GdkContentFormats that determines the supported data formats

Owner: GtkDropTargetAsync

Flags: Read / Write

Signal Details

The “accept” signal

gboolean
user_function (GtkDropTargetAsync *self,
               GdkDrop            *drop,
               gpointer            user_data)

The ::accept signal is 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 gtk_drop_target_reject() or ultimately by returning FALSE from GtkDropTarget::drop

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 needs further procesing, such as inspecting the data, this function should return TRUE and proceed as is drop was accepted and if it decides to reject the drop later, it should call gtk_drop_target_reject_drop().

Parameters

self

the GtkDropTargetAsync

 

drop

the GdkDrop

 

user_data

user data set when the signal handler was connected.

 

Returns

TRUE if drop is accepted

Flags: Run Last


The “drag-enter” signal

GdkDragAction
user_function (GtkDropTargetAsync *self,
               GdkDrop            *drop,
               gdouble             x,
               gdouble             y,
               gpointer            user_data)

The ::drag-enter signal is emitted on the drop site when the pointer enters the widget. It can be used to set up custom highlighting.

Parameters

self

the GtkDropTargetAsync

 

drop

the GdkDrop

 

x

the x coordinate of the current pointer position

 

y

the y coordinate of the current pointer position

 

user_data

user data set when the signal handler was connected.

 

Returns

Preferred action for this drag operation.

Flags: Run Last


The “drag-leave” signal

void
user_function (GtkDropTargetAsync *self,
               GdkDrop            *drop,
               gpointer            user_data)

The ::drag-leave signal is emitted on the drop site when the pointer leaves the widget. Its main purpose it to undo things done in “drag-enter”.

Parameters

self

the GtkDropTargetAsync

 

drop

the GdkDrop

 

user_data

user data set when the signal handler was connected.

 

Flags: Run Last


The “drag-motion” signal

GdkDragAction
user_function (GtkDropTargetAsync *self,
               GdkDrop            *drop,
               gdouble             x,
               gdouble             y,
               gpointer            user_data)

The ::drag-motion signal is emitted while the pointer is moving over the drop target.

Parameters

self

the GtkDropTargetAsync

 

drop

the GdkDrop

 

x

the x coordinate of the current pointer position

 

y

the y coordinate of the current pointer position

 

user_data

user data set when the signal handler was connected.

 

Returns

Preferred action for this drag operation.

Flags: Run Last


The “drop” signal

gboolean
user_function (GtkDropTargetAsync *self,
               GdkDrop            *drop,
               gdouble             x,
               gdouble             y,
               gpointer            user_data)

The ::drop signal is 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 must ensure that gdk_drop_finish() is called to let the source know that the drop is done. The call to gtk_drag_finish() must only be done when all data has been received.

To receive the data, use one of the read functions provides by GdkDrop such as gdk_drop_read_async() or gdk_drop_read_value_async().

Parameters

self

the GtkDropTargetAsync

 

drop

the GdkDrop

 

x

the x coordinate of the current pointer position

 

y

the y coordinate of the current pointer position

 

user_data

user data set when the signal handler was connected.

 

Returns

whether the drop is accepted at the given pointer position

Flags: Run Last

See Also

GtkDropTarget