Some internally created emulated/instantiated events didn't have a
device id. This PR sets for these cases a device id.
Also rename `DEVICE_ID_TOUCH_MOUSE` to the more generic
`DEVICE_ID_EMULATION`.
`Viewport.to_screen_rect` is used only in a single location to compare it
to `Rect2i()`.
When called from `SubViewport`, `to_screen_rect` is always equal to `Rect2i()`.
When called from `Window`, `to_screen_rect` is always different from `Rect2i()`.
So the comparison `to_screen_rect != Rect2i()` can be replaced by
`Object::cast_to<Window>(this)`.
This allows the removal of `Viewport.to_screen_rect` and the simplification of
`Viewport::_set_size`.
CanvasItem::get_screen_transform returns a transform from the CanvasItem
to the coordinate system, where a Popup - created as a child of the
CanvasItem - should be opened.
get_screen_transform makes some simplifications, that work well, when used
in the editor, but not in general cases.
Since Popups like Tooltips are now used more commonly in projects,
it becomes necessary to correct these simplifications.
This solution introduces Viewport::get_popup_base_transform, which makes
the necessary calculations.
As many open source projects have started doing it, we're removing the
current year from the copyright notice, so that we don't need to bump
it every year.
It seems like only the first year of publication is technically
relevant for copyright notices, and even that seems to be something
that many companies stopped listing altogether (in a version controlled
codebase, the commits are a much better source of date of publication
than a hardcoded copyright statement).
We also now list Godot Engine contributors first as we're collectively
the current maintainers of the project, and we clarify that the
"exclusive" copyright of the co-founders covers the timespan before
opensourcing (their further contributions are included as part of Godot
Engine contributors).
Also fixed "cf." Frenchism - it's meant as "refer to / see".
