As of now, the only way to add an app icon to a folder is
by dragging it to the folder icon itself. Even though we
allow opening the folder popup when hovering the icon,
dropping an app icon there wouldn't work.
Make the folder view add the app icon to it's GSettings
key (which will trigger _redisplay() and will show the
new icon) when dropping to a specific position.
Right now, only AppIcon supports being dragged. In the future,
however, both app and folder icons will be reorderable, and to
avoid copying the same code between FolderIcon and AppIcon,
add a new base class BaseViewIcon that contains the shared code
between them.
Adding this new base class also has the side effect that it
already allows for folder icons to be dragged, although full
support for that will come in next commits.
Because the Dash icons are not drop targets themselves, add a
tiny DashIcon class, which is an AppDisplay.AppIcon subclass,
and disable all DND drop code from it.
Moving an app icon to other positions is semantically different
to dragging an actor to the dash; the act of moving should itself
be semantic, in that we should feel like we are moving the actual
icon.
Currently, AppIcon gives the DnD code a simplified version of itself,
with just its icon, instead of a complete copy with the label.
Make AppIcon create a new IconGrid.BaseIcon and use it as the drag
actor.
As per design direction, scale and fade the app icon
when starting dragging it, and show it again if the
drop is accepted. Clutter takes care of animating the
rest of icon positions through implicit animations.
Scale and fade the dragged icon while it's being dragged.
