Instead of determining the focus item through item tree traversal and
pointer comparison and storing the intermediate indices in the
components in the tree, remember the focus item by a pair of
VWeak<ComponentVTable, Dyn> and item_index: usize.
This speeds up determining the focus item as well as delivering events,
which can now be done directly after retrieving an ItemRef with
get_item_ref.
This also fixes the duplicate line edit focus in the 7gui cells
test case.
This is in preparation for allowing the run-time / items to clone VRc's
of the component.
ComponentVTable functions like visit_children_item contine to take a
ComponentRefPin as "self" parameter type, as a VRc would not be
supported by rust right now. That means the implementation then uses
self_weak to obtain a strong self-reference.
Centralize the self_weak setup to be emitted only once, in the create()
function. create() is now always emitted and equipped with a parent
parameter, for non-root components. This allows slightly simplifying the
generic repeater code.
Avoid empty lines in stderr from the compiler, and make sure
the description from the compile line mention the output target
instead of not the source tomake it consistant with other outputs
Move the layout constraint tracker into the window where we can apply
the constraints right before drawing, instead of doing that from within
the event loop. This allows to remove the component parameter from the
run function.
When converting a Weak<VT, T> into Weak<VT, Dyn>, we were ignoring that
while T inside VRcInner may be at a certain offset to satisfy alignment,
the empty Dyn field may not and thus be at a different offset.
On wasm32 for example the compiler generated component struct has a
16-byte alignment, while the Dyn has none. So converting the Weak<VT,
Dyn> to a VRc<VT, Dyn> and then calling borrow() would use the wrong
instance pointer.
To fix this, this patch introduces an extra offset field that's
preserved during the casting and that's used for borrow() as well as
drop().
