Much of St is undocumented, aside from input/output arguments. This is
no doubt because a lot of it parallels Gtk closely, but is worth
improving since many new programmers are not familiar with Gtk.
closes https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2983
On the one hand, this is a bit of a stretch: StImageContent is what
we create from GIcons.
But on the other hand, there's some justification: StImageContent does
represent an image (and likely icon) after all, and there's some
precedent with GdkPixbuf.
In the end as we don't care about serialization or loading from other
API, we can go with a very crude implementation that allows us to
pass out a content as GIcon and use it directly when "loading" it.
We will use that soon to represent X11 window icons as GIcons, which
in turn will allow us to unify app icon handling.
https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1342
In `st`, we can do this by using `ST_PARAM_*`. In the other code files,
just use `G_PARAM_STATIC_STRINGS` directly.
This is just a minor convenience to prevent a few unnecessary string
copies.
https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/646
Create StImageContent as a simple ClutterImage with preferred width/height
properties in order to be able to use explicit sizing when creating clutter
contents that will be applied to actors whose size depends on the content itself.
https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/5
