This is a huge reorganization of GtkDropTarget. I did not know how to
split this up, so it's unfortunately all one commit.
Highlights:
- Split GtkDropTarget into GtkDropTarget and GtkDropTargetAsync
GtkDropTarget is the simple one that only works with GTypes and offers
a synchronous interface.
GtkDropTargetAsync retains the full old functionality and allows
handling mime types.
- Drop events are handled differently
Instead of picking a single drop target and sending all DND events to
it, every event is sent to every drop target. The first one to handle
the event gets to call gdk_drop_status(), further handlers do not
interact with the GdkDrop.
Of course, for the ultimate GDK_DROP_STARTING event, only the first
one to accept the drop gets to handle it.
This allows stacking DND event controllers that aren't necessarily
interested in handling the event or that might decide later to drop
it.
- Port all widgets to either of those
Both have a somewhat changed API due to the new event handling.
For the ones who should use the sync version, lots of cleanup was
involved to operate on a sync API.
It is enough to just set the parent (and make the parent
call gtk_native_check_resize in size_allocate).
This commit removes the relative_to argument to the
constructors of GtkPopover and GtkPopoverMenu, and
updates all callers.
Actually use GValues for the DND operation instead of sending GBytes of
pointer addresses through pipes.
This is a bit complicated because we need to special-case rootwindow
drops, because they're handled on the source side, so we need a custom
ContentProvider.
When we dismantle our children in dispose, we
trigger a11y children-changed signals which end
up calling back into the notebook. Handle this
without critical warnings.
Don't make the whole notebook a drop target
for tab dnd, but just the tab bar. This will
help with drag highlighting, and it arguably
more correct anyway.
Remove arguments from the constructor.
For actions, we now default to COPY, which is the most common one
that we should enable by default (MOVE requires handling deletion
on the the source side, and ASK only makes sense if we have
multiple actions).
For the content provider, we add a new ::prepare signal where
it should be provided just-in-time.
We don't need to cover every case with a va_marshaller, but there are a
number of them that are useful because they will often only be connected
to by a single signal handler.
Generally speaking, if I opened into a file to add a va_marshaller, I just
set all of them.
