Closes#60
Stepping in sliders is a compromise due to the flexibility of the
current slider implementation. I don't want to force types to implement
Add, and I don't like forcing types to require a Step (ie, what's the
appropriate value for f32 to specify as its next value?). Using a
percentage combined with lerp keeps the implementation fairly
straightfoward, although I remember experiencing this type of
configuration in another UI framework a long time ago and thinking it
was a little annoying to work with.
Ultimately, setting actual step boundaries can be done by customizing
the type that the slider is operating over. I feel like that's a much
more powerful design than I've experienced in previous frameworks, so
I'm hoping this percent step behavior is a reasonable compromise.
The issue was that my last set of changes were causing the animations to
restart, causing the animation to keep being extended to another 150ms.
I think the only way for this to work is to switch to an event
mechanism to notify widgets once they've been invalidated. This event
could include a parameter stating whether it was a direct invalidation
or an invalidation due to another widget in the hierarchy. Button
doesn't really care about the rest of the hierarchy, it only cares about
its own state, and the cache key was including too many changes.
Scroll was previously taking the graphics region as its control size as
opposed to the constraints. This was due to this code originally living
in redraw. This fixes scroll areas being able to scroll their contents
fully when sharing window space with other widgts.
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.
