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Drag and Drop

Drag and Drop — Functions for controlling drag and drop handling

Types and Values

Includes

#include <gtk/gtk.h>

Description

GTK+ has a rich set of functions for doing inter-process communication via the drag-and-drop metaphor. GTK+ can do drag-and-drop (DND) via multiple protocols. The currently supported protocols are the Xdnd and Motif protocols. As well as the functions listed here, applications may need to use some facilities provided for Selections. Also, the Drag and Drop API makes use of signals in the GtkWidget class.

Functions

gtk_drag_dest_set ()

void
gtk_drag_dest_set (GtkWidget *widget,
                   GtkDestDefaults flags,
                   const GtkTargetEntry *targets,
                   gint n_targets,
                   GdkDragAction actions);

Sets a widget as a potential drop destination, and adds default behaviors.

The default behaviors listed in flags have an effect similar to installing default handlers for the widget's drag-and-drop signals (“drag-motion”, “drag-drop”, ...). They all exist for convenience. When passing GTK_DEST_DEFAULT_ALL for instance it is sufficient to connect to the widget's “drag-data-received” signal to get primitive, but consistent drag-and-drop support.

Things become more complicated when you try to preview the dragged data, as described in the documentation for “drag-motion”. The default behaviors described by flags make some assumptions, that can conflict with your own signal handlers. For instance GTK_DEST_DEFAULT_DROP causes invokations of gdk_drag_status() in the context of “drag-motion”, and invokations of gtk_drag_finish() in “drag-data-received”. Especially the later is dramatic, when your own “drag-motion” handler calls gtk_drag_get_data() to inspect the dragged data.

There's no way to set a default action here, you can use the “drag-motion” callback for that. Here's an example which selects the action to use depending on whether the control key is pressed or not:

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static void
drag_motion (GtkWidget *widget,
             GdkDragContext *context,
             gint x,
             gint y,
             guint time)
{
  GdkModifierType mask;

  gdk_window_get_pointer (gtk_widget_get_window (widget),
                          NULL, NULL, &mask);
  if (mask & GDK_CONTROL_MASK)
    gdk_drag_status (context, GDK_ACTION_COPY, time);
  else
    gdk_drag_status (context, GDK_ACTION_MOVE, time);
}

Parameters

widget

a GtkWidget

 

flags

which types of default drag behavior to use

 

targets

a pointer to an array of GtkTargetEntrys indicating the drop types that this widget will accept, or NULL. Later you can access the list with gtk_drag_dest_get_target_list() and gtk_drag_dest_find_target().

[allow-none][array length=n_targets]

n_targets

the number of entries in targets

 

actions

a bitmask of possible actions for a drop onto this widget .

 

gtk_drag_dest_set_proxy ()

void
gtk_drag_dest_set_proxy (GtkWidget *widget,
                         GdkWindow *proxy_window,
                         GdkDragProtocol protocol,
                         gboolean use_coordinates);

Sets this widget as a proxy for drops to another window.

Parameters

widget

a GtkWidget

 

proxy_window

the window to which to forward drag events

 

protocol

the drag protocol which the proxy_window accepts (You can use gdk_drag_get_protocol() to determine this)

 

use_coordinates

If TRUE, send the same coordinates to the destination, because it is an embedded subwindow.

 

gtk_drag_dest_unset ()

void
gtk_drag_dest_unset (GtkWidget *widget);

Clears information about a drop destination set with gtk_drag_dest_set(). The widget will no longer receive notification of drags.

Parameters

widget

a GtkWidget

 

gtk_drag_dest_find_target ()

GdkAtom
gtk_drag_dest_find_target (GtkWidget *widget,
                           GdkDragContext *context,
                           GtkTargetList *target_list);

Parameters

widget

drag destination widget

 

context

drag context

 

target_list

list of droppable targets, or NULL to use gtk_drag_dest_get_target_list (widget ). Looks for a match between the supported targets of context and the dest_target_list , returning the first matching target, otherwise returning GDK_NONE. dest_target_list should usually be the return value from gtk_drag_dest_get_target_list(), but some widgets may have different valid targets for different parts of the widget; in that case, they will have to implement a drag_motion handler that passes the correct target list to this function.

[allow-none]

Returns

first target that the source offers and the dest can accept, or GDK_NONE.

[transfer none]


gtk_drag_dest_get_target_list ()

GtkTargetList *
gtk_drag_dest_get_target_list (GtkWidget *widget);

Returns the list of targets this widget can accept from drag-and-drop.

Parameters

widget

a GtkWidget

 

Returns

the GtkTargetList, or NULL if none.

[transfer none]


gtk_drag_dest_set_target_list ()

void
gtk_drag_dest_set_target_list (GtkWidget *widget,
                               GtkTargetList *target_list);

Sets the target types that this widget can accept from drag-and-drop. The widget must first be made into a drag destination with gtk_drag_dest_set().

Parameters

widget

a GtkWidget that's a drag destination

 

target_list

list of droppable targets, or NULL for none.

[allow-none]

gtk_drag_dest_add_text_targets ()

void
gtk_drag_dest_add_text_targets (GtkWidget *widget);

Add the text targets supported by GtkSelection to the target list of the drag destination. The targets are added with info = 0. If you need another value, use gtk_target_list_add_text_targets() and gtk_drag_dest_set_target_list().

Parameters

widget

a GtkWidget that's a drag destination

 

Since: 2.6


gtk_drag_dest_add_image_targets ()

void
gtk_drag_dest_add_image_targets (GtkWidget *widget);

Add the image targets supported by GtkSelection to the target list of the drag destination. The targets are added with info = 0. If you need another value, use gtk_target_list_add_image_targets() and gtk_drag_dest_set_target_list().

Parameters

widget

a GtkWidget that's a drag destination

 

Since: 2.6


gtk_drag_dest_add_uri_targets ()

void
gtk_drag_dest_add_uri_targets (GtkWidget *widget);

Add the URI targets supported by GtkSelection to the target list of the drag destination. The targets are added with info = 0. If you need another value, use gtk_target_list_add_uri_targets() and gtk_drag_dest_set_target_list().

Parameters

widget

a GtkWidget that's a drag destination

 

Since: 2.6


gtk_drag_dest_set_track_motion ()

void
gtk_drag_dest_set_track_motion (GtkWidget *widget,
                                gboolean track_motion);

Tells the widget to emit ::drag-motion and ::drag-leave events regardless of the targets and the GTK_DEST_DEFAULT_MOTION flag.

This may be used when a widget wants to do generic actions regardless of the targets that the source offers.

Parameters

widget

a GtkWidget that's a drag destination

 

track_motion

whether to accept all targets

 

Since: 2.10


gtk_drag_dest_get_track_motion ()

gboolean
gtk_drag_dest_get_track_motion (GtkWidget *widget);

Returns whether the widget has been configured to always emit ::drag-motion signals.

Parameters

widget

a GtkWidget that's a drag destination

 

Returns

TRUE if the widget always emits ::drag-motion events

Since: 2.10


gtk_drag_finish ()

void
gtk_drag_finish (GdkDragContext *context,
                 gboolean success,
                 gboolean del,
                 guint32 time_);

Informs the drag source that the drop is finished, and that the data of the drag will no longer be required.

Parameters

context

the drag context.

 

success

a flag indicating whether the drop was successful

 

del

a flag indicating whether the source should delete the original data. (This should be TRUE for a move)

 

time_

the timestamp from the "drag_data_drop" signal.

 

gtk_drag_get_data ()

void
gtk_drag_get_data (GtkWidget *widget,
                   GdkDragContext *context,
                   GdkAtom target,
                   guint32 time_);

Gets the data associated with a drag. When the data is received or the retrieval fails, GTK+ will emit a "drag_data_received" signal. Failure of the retrieval is indicated by the length field of the selection_data signal parameter being negative. However, when gtk_drag_get_data() is called implicitely because the GTK_DEST_DEFAULT_DROP was set, then the widget will not receive notification of failed drops.

Parameters

widget

the widget that will receive the "drag_data_received" signal.

 

context

the drag context

 

target

the target (form of the data) to retrieve.

 

time_

a timestamp for retrieving the data. This will generally be the time received in a "drag_data_motion" or "drag_data_drop" signal.

 

gtk_drag_get_source_widget ()

GtkWidget *
gtk_drag_get_source_widget (GdkDragContext *context);

Determines the source widget for a drag.

Determines the source widget for a drag.

Parameters

context

a (destination side) drag context

 

Returns

if the drag is occurring within a single application, a pointer to the source widget. Otherwise, NULL.

[transfer none]


gtk_drag_highlight ()

void
gtk_drag_highlight (GtkWidget *widget);

Draws a highlight around a widget. This will attach handlers to "expose_event" and "draw", so the highlight will continue to be displayed until gtk_drag_unhighlight() is called.

Parameters

widget

a widget to highlight

 

gtk_drag_unhighlight ()

void
gtk_drag_unhighlight (GtkWidget *widget);

Removes a highlight set by gtk_drag_highlight() from a widget.

Parameters

widget

a widget to remove the highlight from.

 

gtk_drag_begin ()

GdkDragContext *
gtk_drag_begin (GtkWidget *widget,
                GtkTargetList *targets,
                GdkDragAction actions,
                gint button,
                GdkEvent *event);

Initiates a drag on the source side. The function only needs to be used when the application is starting drags itself, and is not needed when gtk_drag_source_set() is used.

The event is used to retrieve the timestamp that will be used internally to grab the pointer. If event is NULL, then GDK_CURRENT_TIME will be used. However, you should try to pass a real event in all cases, since that can be used by GTK+ to get information about the start position of the drag, for example if the event is a GDK_MOTION_NOTIFY.

Generally there are three cases when you want to start a drag by hand by calling this function:

  1. During a button-press-event handler, if you want to start a drag immediately when the user presses the mouse button. Pass the event that you have in your button-press-event handler.

  2. During a motion-notify-event handler, if you want to start a drag when the mouse moves past a certain threshold distance after a button-press. Pass the event that you have in your motion-notify-event handler.

  3. During a timeout handler, if you want to start a drag after the mouse button is held down for some time. Try to save the last event that you got from the mouse, using gdk_event_copy(), and pass it to this function (remember to free the event with gdk_event_free() when you are done). If you can really not pass a real event, pass NULL instead.

Parameters

widget

the source widget.

 

targets

The targets (data formats) in which the source can provide the data.

 

actions

A bitmask of the allowed drag actions for this drag.

 

button

The button the user clicked to start the drag.

 

event

The event that triggered the start of the drag.

 

Returns

the context for this drag.

[transfer none]


gtk_drag_set_icon_widget ()

void
gtk_drag_set_icon_widget (GdkDragContext *context,
                          GtkWidget *widget,
                          gint hot_x,
                          gint hot_y);

Changes the icon for a widget to a given widget. GTK+ will not destroy the icon, so if you don't want it to persist, you should connect to the "drag-end" signal and destroy it yourself.

Parameters

context

the context for a drag. (This must be called with a context for the source side of a drag)

 

widget

a toplevel window to use as an icon.

 

hot_x

the X offset within widget of the hotspot.

 

hot_y

the Y offset within widget of the hotspot.

 

gtk_drag_set_icon_pixmap ()

void
gtk_drag_set_icon_pixmap (GdkDragContext *context,
                          GdkColormap *colormap,
                          GdkPixmap *pixmap,
                          GdkBitmap *mask,
                          gint hot_x,
                          gint hot_y);

Sets pixmap as the icon for a given drag. GTK+ retains references for the arguments, and will release them when they are no longer needed. In general, gtk_drag_set_icon_pixbuf() will be more convenient to use.

Parameters

context

the context for a drag. (This must be called with a context for the source side of a drag)

 

colormap

the colormap of the icon

 

pixmap

the image data for the icon

 

mask

the transparency mask for the icon

 

hot_x

the X offset within pixmap of the hotspot.

 

hot_y

the Y offset within pixmap of the hotspot.

 

gtk_drag_set_icon_pixbuf ()

void
gtk_drag_set_icon_pixbuf (GdkDragContext *context,
                          GdkPixbuf *pixbuf,
                          gint hot_x,
                          gint hot_y);

Sets pixbuf as the icon for a given drag.

Parameters

context

the context for a drag. (This must be called with a context for the source side of a drag)

 

pixbuf

the GdkPixbuf to use as the drag icon.

 

hot_x

the X offset within widget of the hotspot.

 

hot_y

the Y offset within widget of the hotspot.

 

gtk_drag_set_icon_stock ()

void
gtk_drag_set_icon_stock (GdkDragContext *context,
                         const gchar *stock_id,
                         gint hot_x,
                         gint hot_y);

Sets the icon for a given drag from a stock ID.

Parameters

context

the context for a drag. (This must be called with a context for the source side of a drag)

 

stock_id

the ID of the stock icon to use for the drag.

 

hot_x

the X offset within the icon of the hotspot.

 

hot_y

the Y offset within the icon of the hotspot.

 

gtk_drag_set_icon_name ()

void
gtk_drag_set_icon_name (GdkDragContext *context,
                        const gchar *icon_name,
                        gint hot_x,
                        gint hot_y);

Sets the icon for a given drag from a named themed icon. See the docs for GtkIconTheme for more details. Note that the size of the icon depends on the icon theme (the icon is loaded at the symbolic size GTK_ICON_SIZE_DND), thus hot_x and hot_y have to be used with care.

Parameters

context

the context for a drag. (This must be called with a context for the source side of a drag)

 

icon_name

name of icon to use

 

hot_x

the X offset of the hotspot within the icon

 

hot_y

the Y offset of the hotspot within the icon

 

Since: 2.8


gtk_drag_set_icon_default ()

void
gtk_drag_set_icon_default (GdkDragContext *context);

Sets the icon for a particular drag to the default icon.

Parameters

context

the context for a drag. (This must be called with a context for the source side of a drag)

 

gtk_drag_set_default_icon ()

void
gtk_drag_set_default_icon (GdkColormap *colormap,
                           GdkPixmap *pixmap,
                           GdkBitmap *mask,
                           gint hot_x,
                           gint hot_y);

gtk_drag_set_default_icon is deprecated and should not be used in newly-written code.

Change the default drag icon via the stock system by changing the stock pixbuf for GTK_STOCK_DND instead.

Changes the default drag icon. GTK+ retains references for the arguments, and will release them when they are no longer needed.

Parameters

colormap

the colormap of the icon

 

pixmap

the image data for the icon

 

mask

the transparency mask for an image, or NULL.

[allow-none]

hot_x

The X offset within widget of the hotspot.

 

hot_y

The Y offset within widget of the hotspot.

 

gtk_drag_check_threshold ()

gboolean
gtk_drag_check_threshold (GtkWidget *widget,
                          gint start_x,
                          gint start_y,
                          gint current_x,
                          gint current_y);

Checks to see if a mouse drag starting at (start_x , start_y ) and ending at (current_x , current_y ) has passed the GTK+ drag threshold, and thus should trigger the beginning of a drag-and-drop operation.

Parameters

widget

a GtkWidget

 

start_x

X coordinate of start of drag

 

start_y

Y coordinate of start of drag

 

current_x

current X coordinate

 

current_y

current Y coordinate

 

Returns

TRUE if the drag threshold has been passed.


gtk_drag_source_set ()

void
gtk_drag_source_set (GtkWidget *widget,
                     GdkModifierType start_button_mask,
                     const GtkTargetEntry *targets,
                     gint n_targets,
                     GdkDragAction actions);

Sets up a widget so that GTK+ will start a drag operation when the user clicks and drags on the widget. The widget must have a window.

Parameters

widget

a GtkWidget

 

start_button_mask

the bitmask of buttons that can start the drag

 

targets

the table of targets that the drag will support, may be NULL.

[allow-none][array length=n_targets]

n_targets

the number of items in targets

 

actions

the bitmask of possible actions for a drag from this widget

 

gtk_drag_source_set_icon ()

void
gtk_drag_source_set_icon (GtkWidget *widget,
                          GdkColormap *colormap,
                          GdkPixmap *pixmap,
                          GdkBitmap *mask);

Sets the icon that will be used for drags from a particular widget from a pixmap/mask. GTK+ retains references for the arguments, and will release them when they are no longer needed. Use gtk_drag_source_set_icon_pixbuf() instead.

Parameters

widget

a GtkWidget

 

colormap

the colormap of the icon

 

pixmap

the image data for the icon

 

mask

the transparency mask for an image.

[allow-none]

gtk_drag_source_set_icon_pixbuf ()

void
gtk_drag_source_set_icon_pixbuf (GtkWidget *widget,
                                 GdkPixbuf *pixbuf);

Sets the icon that will be used for drags from a particular widget from a GdkPixbuf. GTK+ retains a reference for pixbuf and will release it when it is no longer needed.

Parameters

widget

a GtkWidget

 

pixbuf

the GdkPixbuf for the drag icon

 

gtk_drag_source_set_icon_stock ()

void
gtk_drag_source_set_icon_stock (GtkWidget *widget,
                                const gchar *stock_id);

Sets the icon that will be used for drags from a particular source to a stock icon.

Parameters

widget

a GtkWidget

 

stock_id

the ID of the stock icon to use

 

gtk_drag_source_set_icon_name ()

void
gtk_drag_source_set_icon_name (GtkWidget *widget,
                               const gchar *icon_name);

Sets the icon that will be used for drags from a particular source to a themed icon. See the docs for GtkIconTheme for more details.

Parameters

widget

a GtkWidget

 

icon_name

name of icon to use

 

Since: 2.8


gtk_drag_source_unset ()

void
gtk_drag_source_unset (GtkWidget *widget);

Undoes the effects of gtk_drag_source_set().

Parameters

widget

a GtkWidget

 

gtk_drag_source_set_target_list ()

void
gtk_drag_source_set_target_list (GtkWidget *widget,
                                 GtkTargetList *target_list);

Changes the target types that this widget offers for drag-and-drop. The widget must first be made into a drag source with gtk_drag_source_set().

Parameters

widget

a GtkWidget that's a drag source

 

target_list

list of draggable targets, or NULL for none.

[allow-none]

Since: 2.4


gtk_drag_source_get_target_list ()

GtkTargetList *
gtk_drag_source_get_target_list (GtkWidget *widget);

Gets the list of targets this widget can provide for drag-and-drop.

Parameters

widget

a GtkWidget

 

Returns

the GtkTargetList, or NULL if none.

[transfer none]

Since: 2.4


gtk_drag_source_add_text_targets ()

void
gtk_drag_source_add_text_targets (GtkWidget *widget);

Add the text targets supported by GtkSelection to the target list of the drag source. The targets are added with info = 0. If you need another value, use gtk_target_list_add_text_targets() and gtk_drag_source_set_target_list().

Parameters

widget

a GtkWidget that's is a drag source

 

Since: 2.6


gtk_drag_source_add_image_targets ()

void
gtk_drag_source_add_image_targets (GtkWidget *widget);

Add the writable image targets supported by GtkSelection to the target list of the drag source. The targets are added with info = 0. If you need another value, use gtk_target_list_add_image_targets() and gtk_drag_source_set_target_list().

Parameters

widget

a GtkWidget that's is a drag source

 

Since: 2.6


gtk_drag_source_add_uri_targets ()

void
gtk_drag_source_add_uri_targets (GtkWidget *widget);

Add the URI targets supported by GtkSelection to the target list of the drag source. The targets are added with info = 0. If you need another value, use gtk_target_list_add_uri_targets() and gtk_drag_source_set_target_list().

Parameters

widget

a GtkWidget that's is a drag source

 

Since: 2.6

Types and Values

enum GtkDestDefaults

The GtkDestDefaults enumeration specifies the various types of action that will be taken on behalf of the user for a drag destination site.

Members

GTK_DEST_DEFAULT_MOTION

If set for a widget, GTK+, during a drag over this widget will check if the drag matches this widget's list of possible targets and actions. GTK+ will then call gdk_drag_status() as appropriate.

 

GTK_DEST_DEFAULT_HIGHLIGHT

If set for a widget, GTK+ will draw a highlight on this widget as long as a drag is over this widget and the widget drag format and action are acceptable.

 

GTK_DEST_DEFAULT_DROP

If set for a widget, when a drop occurs, GTK+ will will check if the drag matches this widget's list of possible targets and actions. If so, GTK+ will call gtk_drag_get_data() on behalf of the widget. Whether or not the drop is successful, GTK+ will call gtk_drag_finish(). If the action was a move, then if the drag was successful, then TRUE will be passed for the delete parameter to gtk_drag_finish().

 

GTK_DEST_DEFAULT_ALL

If set, specifies that all default actions should be taken.

 

enum GtkTargetFlags

The GtkTargetFlags enumeration is used to specify constraints on an entry in a GtkTargetTable.

Members

GTK_TARGET_SAME_APP

If this is set, the target will only be selected for drags within a single application.

 

GTK_TARGET_SAME_WIDGET

If this is set, the target will only be selected for drags within a single widget.

 

GTK_TARGET_OTHER_APP

If this is set, the target will not be selected for drags within a single application. Since 2.12

 

GTK_TARGET_OTHER_WIDGET

If this is set, the target will not be selected for drags withing a single widget. Since 2.12

 
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