GTK+ 2.0 Tutorial
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Functions

Setting up the source widget

The function gtk_drag_source_set() specifies a set of target types for a drag operation on a widget.

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

The parameters signify the following:

widget specifies the drag source widget
start_button_mask specifies a bitmask of buttons that can start the drag (e.g. GDK_BUTTON1_MASK)
targets specifies a table of target data types the drag will support
n_targets specifies the number of targets above
actions specifies a bitmask of possible actions for a drag from this window

The targets parameter is an array of the following structure:

struct GtkTargetEntry {
   gchar *target;
   guint  flags;
   guint  info;
 };

The fields specify a string representing the drag type, optional flags and application assigned integer identifier.

If a widget is no longer required to act as a source for drag-and-drop operations, the function gtk_drag_source_unset() can be used to remove a set of drag-and-drop target types.

void gtk_drag_source_unset( GtkWidget *widget );

Signals on the source widget:

The source widget is sent the following signals during a drag-and-drop operation.

Table 1. Source widget signals

drag_begin	`void (drag_begin)(GtkWidget widget, GdkDragContext *dc, gpointer data)`
drag_motion	`gboolean (drag_motion)(GtkWidget widget, GdkDragContext *dc, gint x, gint y, guint t, gpointer data)`
drag_data_get	`void (drag_data_get)(GtkWidget widget, GdkDragContext dc, GtkSelectionData selection_data, guint info, guint t, gpointer data)`
drag_data_delete	`void (drag_data_delete)(GtkWidget widget, GdkDragContext *dc, gpointer data)`
drag_drop	`gboolean (drag_drop)(GtkWidget widget, GdkDragContext *dc, gint x, gint y, guint t, gpointer data)`
drag_end	`void (drag_end)(GtkWidget widget, GdkDragContext *dc, gpointer data)`

Setting up a destination widget:

gtk_drag_dest_set() specifies that this widget can receive drops and specifies what types of drops it can receive.

gtk_drag_dest_unset() specifies that the widget can no longer receive drops.

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

void gtk_drag_dest_unset( GtkWidget *widget );

Signals on the destination widget:

The destination widget is sent the following signals during a drag-and-drop operation.

Table 2. Destination widget signals

drag_data_received void (*drag_data_received)(GtkWidget *widget, GdkDragContext *dc, gint x, gint y, GtkSelectionData *selection_data, guint info, guint t, gpointer data)

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