How to get callbacks for the changes made to effects added to AEGP plugins?

what effect are you applying?

according to your code you're applying the first effect installed on AE arbitrarily.

GetNumInstalledEffects and GetNextInstalledEffect both refer to the effects loaded by AE ion startup, and not the effects on the a layer.

if you already knew that, then forget what i just wrote....

the technique is dependant of a few things:

1. what changes are you trying to monitor?

changes made by the user, or changes that happen over time, like keyframed values.

2. is the effect you're monitoring an effect you've written, or is it a random effect?

in an effect you've written you can apply param supervision.

this way whenever the user changes a value you get a call from AE telling you what param has changed,

and then the effect could report back to your AEGP.

this will only work if the user makes the change. not so for keyframes and expressions.

if the effect you're monitoring was not written by you or you wish to monitor non user triggered changes,

you could use PF_GetCurrentState and PF_HasParamChanged to look for changes in that effect.

if you need continuous monitoring, and not just during specific times, you could setup an idle_hook in your AEGP.

that would result in AE giving you a call every time it's not rendering something. that happens more that 20 times per second whenver AE is idle.

you could use that time to look for changes in these effects.

maybe there are more methods of working around this problem,

but there's no way of making AE report you automatically of changes made in a random effect.