This will give a nicer API to expose to .60. If the struct weren't
repr(C) then the booleans would be nicely packed, but alas that's not
happening. On the other hand we're not keeping many instances of them
around.
Fold CharacterInput into KeyPressed/KeyReleased and store the "key" as a string.
Also, instead of exposing the KeyCode we're encoding special characters
into the string.
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.
In the future the TextInput will request focus on mouse click,for
example.
Pass the outer-most component through to ItemVTable's input_event.
For the purpose of disambiguating this component from any nested
component instantiated by a repeater or so, it's called the
app_component.
The ComponentVTable takes a reference to a ComponentRefPin instead of a
ComponentRefPin by value, as the vtable macro gets confused otherwise
and thinks it's a self argument.
When selecting to the left, the anchor remains to the right of the cursor.
When deleting such a selection, we fetch the cursor and anchor using a helper
method, which ensures that the anchor is to the left of the cursor.
Finally when setting the cursor then to the anchor, we need to also
set the anchor, since both were swapped.
This also add an automated test for this scenario.
