GtkDropTarget

GtkDropTarget — Event controller to receive DND drops

Properties

GdkDragAction actions Read / Write
GdkDrop * drop Read
GdkContentFormats * formats Read
gboolean preload Read / Write
GValue * value Read

Signals

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

Types and Values

Object Hierarchy

    GObject
    ╰── GtkEventController
        ╰── GtkDropTarget

Includes

#include <gtk/gtk.h>

Description

GtkDropTarget is an event controller implementing a simple way 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 gtk_drop_target_new() passing in the GType of the data you want to receive and connect to the GtkDropTarget::drop signal to receive the data.

GtkDropTarget supports more options, such as:

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 GtkDropTargetAsync 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 GTK_STATE_FLAG_DROP_ACTIVE state, which can be used to style the widget.

Functions

gtk_drop_target_new ()

GtkDropTarget *
gtk_drop_target_new (GType type,
                     GdkDragAction actions);

Creates a new GtkDropTarget object.

If the drop target should support more than 1 type, pass G_TYPE_INVALID for type and then call gtk_drop_target_set_gtypes().

Parameters

type

The supported type or G_TYPE_INVALID

 

actions

the supported actions

 

Returns

the new GtkDropTarget


gtk_drop_target_set_gtypes ()

void
gtk_drop_target_set_gtypes (GtkDropTarget *self,
                            GType *types,
                            gsize n_types);

Sets the supported GTypes for this drop target.

The GtkDropTarget::drop signal will

Parameters

self

a GtkDropTarget

 

types

all supported GTypes that can be dropped.

[nullable][transfer none][array length=n_types]

n_types

number of types

 

gtk_drop_target_get_gtypes ()

const GType *
gtk_drop_target_get_gtypes (GtkDropTarget *self,
                            gsize *n_types);

Gets the list of supported GTypes for self . If no type have been set, NULL will be returned.

Parameters

self

a GtkDropTarget

 

n_types

optional pointer to take the number of GTypes contained in the return value.

[out][optional]

Returns

G_TYPE_INVALID-terminated array of types included in formats or NULL if none.

[transfer none][nullable][array length=n_types]


gtk_drop_target_get_formats ()

GdkContentFormats *
gtk_drop_target_get_formats (GtkDropTarget *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 GtkDropTarget

 

Returns

the supported data formats.

[nullable]


gtk_drop_target_set_actions ()

void
gtk_drop_target_set_actions (GtkDropTarget *self,
                             GdkDragAction actions);

Sets the actions that this drop target supports.

Parameters

self

a GtkDropTarget

 

actions

the supported actions

 

gtk_drop_target_get_actions ()

GdkDragAction
gtk_drop_target_get_actions (GtkDropTarget *self);

Gets the actions that this drop target supports.

Parameters

self

a GtkDropTarget

 

Returns

the actions that this drop target supports


gtk_drop_target_set_preload ()

void
gtk_drop_target_set_preload (GtkDropTarget *self,
                             gboolean preload);

Sets the GtkDropTarget:preload property.

Parameters

self

a GtkDropTarget

 

preload

TRUE to preload drop data

 

gtk_drop_target_get_preload ()

gboolean
gtk_drop_target_get_preload (GtkDropTarget *self);

Gets the value of the GtkDropTarget:preload property.

Parameters

self

a GtkDropTarget

 

Returns

TRUE if drop data should be preloaded


gtk_drop_target_get_drop ()

GdkDrop *
gtk_drop_target_get_drop (GtkDropTarget *self);

Gets the currently handled drop operation.

If no drop operation is going on, NULL is returned.

Parameters

self

a GtkDropTarget

 

Returns

The current drop.

[nullable][transfer none]


gtk_drop_target_get_value ()

const GValue *
gtk_drop_target_get_value (GtkDropTarget *self);

Gets the value of the GtkDropTarget:value porperty.

Parameters

self

a GtkDropTarget

 

Returns

The current drop data.

[nullable][transfer none]


gtk_drop_target_reject ()

void
gtk_drop_target_reject (GtkDropTarget *self);

Rejects the ongoing drop operation.

If no drop operation is ongoing - when GdkDropTarget:drop returns NULL - 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.

Parameters

self

a GtkDropTarget

 

Types and Values

GtkDropTarget

typedef struct _GtkDropTarget GtkDropTarget;

Property Details

The “actions” property

  “actions”                  GdkDragAction

The GdkDragActions that this drop target supports

Owner: GtkDropTarget

Flags: Read / Write


The “drop” property

  “drop”                     GdkDrop *

The GdkDrop that is currently being performed

Owner: GtkDropTarget

Flags: Read


The “formats” property

  “formats”                  GdkContentFormats *

The GdkContentFormats that determine the supported data formats

Owner: GtkDropTarget

Flags: Read


The “preload” property

  “preload”                  gboolean

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'n'drop operations, no data transfer is done, so enabling it there is free.

Owner: GtkDropTarget

Flags: Read / Write

Default value: FALSE


The “value” property

  “value”                    GValue *

The value for this drop operation or NULL if the data has not been loaded yet or no drop operation is going on.

Data may be available before the GtkDropTarget::drop signal gets emitted - for example when the GtkDropTarget:preload property is set. You can use the GObject::notify signal to be notified of available data.

Owner: GtkDropTarget

Flags: Read

Signal Details

The “accept” signal

gboolean
user_function (GtkDropTarget *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 inspecting the data, this function should return TRUE, the GtkDropTarget:preload property should be set and the value should be inspected via the GObject::notify:value signal and then call gtk_drop_target_reject().

Parameters

self

the GtkDropTarget

 

drop

the GdkDrop

 

user_data

user data set when the signal handler was connected.

 

Returns

TRUE if drop is accepted

Flags: Run Last


The “drop” signal

gboolean
user_function (GtkDropTarget *self,
               GValue        *value,
               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 is responsible for rading the given value and performing the drop operation.

Parameters

self

the GtkDropTarget

 

value

the GValue being dropped

 

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 was accepted at the given pointer position

Flags: Run Last


The “enter” signal

GdkDragAction
user_function (GtkDropTarget *self,
               gdouble        x,
               gdouble        y,
               gpointer       user_data)

The ::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 GtkDropTarget

 

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 or 0 if dropping is not supported at the current x ,y location.

Flags: Run Last


The “leave” signal

void
user_function (GtkDropTarget *self,
               gpointer       user_data)

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

Parameters

self

the GtkDropTarget

 

user_data

user data set when the signal handler was connected.

 

Flags: Run Last


The “motion” signal

GdkDragAction
user_function (GtkDropTarget *self,
               gdouble        x,
               gdouble        y,
               gpointer       user_data)

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

Parameters

self

the GtkDropTarget

 

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 or 0 if dropping is not supported at the current x ,y location.

Flags: Run Last