PaneContainer is responsible for all pane-related logic. Laying them
out, switching focus between them, etc. This should help make RootView
simpler and keep pane-layout related tests in their own focused area.
Since this is the more external method, having a shorter name
is more convenient. The former `buildEditSession` method took a
Buffer, and is now called `buildEditSessionForBuffer`.
In additional, rename `registerViewClass(es)` to `registerDeserializer(s)`.
This moves us to a situation where any kind of object may want to be
deserialized, not just views.
Allowing root view to be focused was stealing focus away from the
editor whenever a click event made it to the root view. This unnecessary
switching of focus was interfering with the ability to drag tabs.
But if RootView can't be focused, focus ends up being returned to the
document body when there are no focusable elements. This would be fine,
except for the fact that we frequently bind global events on root view,
and so they aren't triggered when events are triggered on the body. We
could just bind all global events on the body, but this would require
us to always attach elements to the DOM during specs, which is a serious
performance killer in specs.
The workaround is in the keymap. When the keymap handles a key event
that was triggered on the body, it triggers the corresponding semantic
event on the root view anyway, so from the event perspective, it's as
if the root view actually had focus. The only place this might fall
down is if someone wants to capture raw key events. But that's the
keymap's job anyway, and we maybe add a hook on the keymap if such a
need ever arises.
Previously if the tree-view was open and was focused and no
editors were open and tab was pressed the document body would
become focused which would not allow events bound to root view
to be triggerable.
This ensures that the root-view always gets focus back when
another view is tabbed away from.
This is because RootView listens to some of its own events. It needs
to be first in line to handle its own events because package event
handlers might rely on tree view's event handlers having been run.
This also brings behavior more in line with what we'll experience in
specs.
Previously we were relying on the package module itself to have a
`name` field. But now that we're using `atom.loadPackage` to load up
packages, we can infer the name of the module from the name of the
package directory.
This problem was when the focus element is detached
when navigating away from the window and when
the window is then given focus again nothing has
focus.
The solution is to use RootView's focus handler
on the window to bring focus to the editor or
other view when the document's active element
is the body meaning nothing inside the RootView
currently has focus.
