[Spec] Implement Effects

[PureWeen]

Effects

Currently Effects don't get wired into Handlers. The need for effects in XF came from the need to be able to register something that was smaller than a renderer. The usefulness of an effect inside MAUI is debatable because inside MAUI users can just subscribe to AttachedHandler/DetachedHandler and achieve basically the same thing. You could even just use a behavior at this point. Should we deprecate effects and just tell people to use Behaviors?

Parts we need

• AppHostingExtension method that lets users specify the xplat effect and the native effect type
• Ensure that assembly scanning works.

Implementation

Effects should be fairly trivial to implement from a functional stand point. We should be able to just subscribe to the AttachedHandler/DetachedHandler events on a view. If that view has an effect then we new up the native effect and call OnAttached

We need to also figure out where to register effects outside of the registrar?

API

Registering an effect

An effect has the native part, resolution group, and the xplat part. I'm pretty sure the resolution group only really mattered for assembly scanning purposes so that effects wouldn't collide.

Should Effects be apart of Configure Handlers? Or should it be its own Configure Effects with its own _effectsCollection?

builder.ConfigureEffects(effectsCollection =>
{
    effectsCollection.RegisterEffect<XplatEffect, NativeEffectPart>();
});

Migration Notes

Once this has been implemented please update the WIKI about how users should migrate their app to handle effects

Backward Compatibility

if users enable assembly scanning then whatever custom effects they have made should still register

Difficulty : [low]