Remove all the old 2.x and 3.x version annotations.
GTK+ 4 is a new start, and from the perspective of a
GTK+ 4 developer all these APIs have been around since
the beginning.
This API allows specifying a GType and va_args of a value of that type
to set the clipboard contents. This massively simplifies setting weird
object types into the clipboard.
2 example patches included in this patch are the GtkTextBuffer and the
file list in the file chooser.
Using gobject-introspection, this should work without specifying the
type, so that you can literlally say
clipboard.set ("Hello World")
or
clipboard.set (pixbuf)
which is why I've also marked all other setters as (skip). They just
exist in C as wrappers for type safety reasons.
This is in preparation of using input streams to show that these
coordinates aren't needed most of the time and can otherwise be saved
during GtkWidget::drag-drop.
Also make clipboard_claim() a vfunc so backends can override it.
Because the whole operation a vfunc, backends have the option of adding
code before the actual claim is done and potentially even fail or do
something after the successful claim.
GdkContentProvider is the object that represents local data in the
clipboard.
This patch only introduces the object and adds the clipboard properties,
it does not yet provide a way for the actual implementations to access
it.
The only access that is implemented is the local shortcut GValue access.
This allows us not just to pass any mime type to the read function, but
it also makes it possible to pass multiple mime types and the clipboard
can then try them in order until it finds a supported one.
This is so far not implemented though.
