Okay, I've spent a whole day on this now, and it finally kinda works!
With this patch, CObject and all of its derived classes are reference
counted instead of tree-owned.
The previous, Qt-like model was nice and familiar, but ultimately also
outdated and difficult to reason about.
CObject-derived types should now be stored in RefPtr/NonnullRefPtr and
each class can be constructed using the forwarding construct() helper:
auto widget = GWidget::construct(parent_widget);
Note that construct() simply forwards all arguments to an existing
constructor. It is inserted into each class by the C_OBJECT macro,
see CObject.h to understand how that works.
CObject::delete_later() disappears in this patch, as there is no longer
a single logical owner of a CObject.
Since we're moving to a world of ref-counting, we can't have weird
behaviors like "windows delete themselves when you close them."
The "close app when there are no more windows" mechanism is moved
to GWindow::hide(). Now, we close the app when it has no more
windows on screen.
We were only deleting the pointee when the ObjectPtr was destroyed.
If the ObjectPtr is cleared before that, we should also delete the
pointee. This is not the most important class to get right, since
it will go away as soon as we're able to switch to RefPtr.
It's pretty confusing when a CObject is owned both by its parent-child
relationship, but also by an ObjectPtr member in the parent.
In those cases, we have to make sure we both unparent the child *and*
reove it from the ObjectPtr.
This will become a bit less confusing when ObjectPtr becomes RefPtr,
although still not crystal clear. I'm not sure what the solution is.
Subclasses of CNetworkJob handle this by overriding shutdown().
This patch implements it for CHttpJob by simply tearing down the
underlying socket.
We also automatically call shutdown() after the job finishes,
regardless of success or failure. :^)
The C_OBJECT macro now also inserts a static construct(...) helper into
the class. Now we can make the constructor(s) private and instead call:
auto socket = CTCPSocket::construct(arguments);
construct() returns an ObjectPtr<T>, which we'll later switch to being
a NonnullRefPtr<T>, once everything else in in place for ref-counting.
