Configuring Drag-n-Drop in GTK 4.12

, ,

I had a question regarding GdkContentProvider, specifically the function gdk_content_provider_new_union as I’m trying to implement drag-n-drop using GtkDragSource and GtkDropTarget. My question is, is it possible to wrap two (or more) different types in a GdkContentProvider array and then have access to them in the drop site?
For example, in the following snippet, I set the drag content in prepare_drag_content() function using two objects of different types:

static void
on_drop (GtkDropTarget *target,
         GValue        *value,
         gdouble        x,
         gdouble        y,
         GtkWidget     *button)
    // Use @value to access the drag content set earlier

static GdkContentProvider *
prepare_drag_content (CustomWidget *self,
                      GtkWidget    *button)
   * Setting content for drag-n-drop:
   * How to access these two objects in `on_drop` callback above?
  GdkContentProvider *content[2] = {
    gdk_content_provider_new_typed (CUSTOM_TYPE_WIDGET, self),
    gdk_content_provider_new_typed (GTK_TYPE_WIDGET, button)

  return gdk_content_provider_new_union (content, 2);

static void
add_drag_source (CustomWidget *self,
                 GtkWidget    *button)
  GtkDragSource *source = gtk_drag_source_new ();
  gtk_drag_source_set_content (source, prepare_drag_content (self, button)); // set the content for dnd
  gtk_widget_add_controller (GTK_WIDGET (button), GTK_EVENT_CONTROLLER (source));

Currently, I have created a custom type that wraps the two objects and then I’m unpacking it using g_value_get_object on the drop site (i have set the drop site to accept this custom type only for now). The issue with this is having to create a new custom type just for this operation.
Additionally, I am not clear on how GdkContentProvider gets converted to GValue mid-event.

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