Those property features don't seem to be in use anywhere.
They are redundant since the docs cover the same information
and more. They also created unnecessary translation work.

Closes #4904

We need to disable the DND support in
GtkColorSwatch completely for this to work
in X11.

Provide default icons for paintables and files.
This is easy to do, and makes sense.

fixup drag icon

We run into trouble on X11 if the widgets
in the drag icon have drop targets attached.
Prevent this by suppressing event delivery
to drag icons outright.

Adding a random member to it resulted in a lot of header surgery as a
side effect.

Somebody should make this default drag icon machinery pluggable.

Instead of drag'n'drop, say drag-and-drop. That is easier
to read, and less unclear on the markdown syntax implications.

Remove a boatload of "or %NULL" from nullable parameters
and return values. gi-docgen generates suitable text from
the annotation that we don't need to duplicate.

This adds a few missing nullable annotations too.

This is now handle by the corresponding implemenatations using per
non-gobject-type API.

It didn't even use GtkNative, just the vfunc it set to the interface
sturct.

This changes allocation of the widget trees to happen as a side effect
to the GdkSurface::layout signal, which first passes the GtkNative
instance where it is then forwarded to the implementations of the
GtkNative interface.

The implementations of GtkNative are the ones doing the actual
gtk_widget_allocate(), and they do so in their GtkNativeClass::layout
function.

Showing before the child would result in bogus
gdk_drag_surface_present() with an "empty" (1x1) size. This can easily
be avoided by postponing showing until there is anything to show.

Mark gtk_drag_icon_create_widget_for_value with
GDK_AVAILABLE_IN_ALL, since it is meant to be public.
Also, clarify the documentation a bit.

Fixes: #3325

gtkcssnodeprivate.h was mainly used for repositioning CSS nodes in
gadgets, and gadgets are gone now.

We are not sure yet if allowing out-of-tree
implementations of GtkNative are a good idea.

No need to ship empty headers.

Change gtk_widget_translate_coordinates and
gtk_native_get_surface_transform to operate
on doubles. Update all callers.

In many cases, the default widget vfuncs work just fine,
combined with setting focusable.

This wasn't meant to derive from GtkContainer.

After the :can-focus change in the previous commit, widgets
need to set suitable focus and grab_focus implementations
to implement the desired focus behavior.

This commit does that for all widgets.

Make :focus-widget a GtkWindow property and add vfuncs
to the GtkRoot interface instead of the property.

... and use it to set a drag icon.

Before, gtk_drag_icon_new_for_drag() allowed creating new drag icons.
This could cause multiple drag icons to exist for a single drag.

Now, gtk_drag_icon_get_for_drag() makes sure that only one drag icon is
created.

FIXME: Is this necessary?

Could the surfaces just clamp to 1x1 themselves?
We recently declared that surfaces can decide on whatever size they want
so natives need to inspect the size they requested anyway.

Replace uses of gtk_css_style_get_value with direct access,
throughout the tree. We don't replace all uses, just those
where we are dealing with a fixed property. Be careful to
handle the currentColor special case for color properties.

Just go to the css node directly.

This is needed if we want to use gdk_drag_begin
for one-off drags, without a GtkDragSource.

This is a GtkRoot implemntation for drag icons,
using the surface provided by GdkDrag. This lets
us avoid GTK_WINDOW_POPUP and
gtk_window_set_hardcoded_surface.