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docs: Add examples of GtkDragSource use

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The description is a bit terse; we should help out application
developers some more.
This commit is contained in:
Emmanuele Bassi
2020-12-21 17:03:59 +00:00
parent 6c31ed53f4
commit b9bcdbbfdc
1 changed files with 51 additions and 3 deletions
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54
gtk/gtkdragsource.c
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@@ -55,15 +55,63 @@
* source must be added to a widget as an event controller, using
* gtk_widget_add_controller().
*
* |[<!-- language="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, #GtkDragSource
* has #GtkDragSource::prepare and #GtkDragSource::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 ::drag-begin signal is emitted
* after the #GdkDrag object has been created, and can be used
* to set up the drag icon.
* drag should be started with.
*
* |[<!-- language="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 #GdkDrag object has
* been created, and can be used to set up the drag icon.
*
* |[<!-- language="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, GtkDragSource emits signals that
* can be used to obtain updates about the status of the operation,