Refs #98
This refactor overhauls the reactive system to move all the reactive
methods to traits. The side effect of this change is that now
DynamicReader's API is the same as Dynamic's API, but because it only
implements Source<T>, DynamicReader does not offer any mutation
functions.
While it's unfortunate to have more traits to include to use Cushy, this
seems like the best option, and it offers a path to try to integrate
this into the tuple ForEach/MapEach traits. Unfortunately, my attempt at
doing those in this set of changes led to issues specifying generic
associated lifetimes for the DynamicGuard. But, I was also in the middle
of this larger refactoring, so it might be that a fresh attempt will
succeed.
- On Linux, `fm-match` is used to query for the default fonts.
- DynamicComponents now have their own trait and can now be specified
with a constant or dynamic.
- Roboto Flex is now always loaded when the feature is enabled.
Overriding the default sans serif font prefers the overridden value,
then roboto, then the result of fc-match/fontdb's default.
- Button now supports background colors being set on a transparent
button.
measure() now is layout(). LayoutContext can either persist layout
information or be used temporarily for measurement. While this caching
is constantly thrown out currently, this is a step towards being able to
only re-layout widgets if they've been invalidated.
