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.
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.
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.
