How do Damage Calculations account for Damage Buffs and DoT Effects?

On damage modifiers, such as the Kog'Maw's Bio-Arcane Barrage or Kayle's Righteous Fury can the damage given by AP/AD be changed mid-effect? For example:

Say I'm playing Kayle and I have 100 AP. I trigger Righteous Fury which does 60 plus an additional 40 damage from my AP. I had Guinsoo's Rageblade and attacked someone 4 times causing my AP to go up 20. Righteous Fury is still in affect, so will the next attack with it have that extra 20 AP applied to it?

Basically, if I trigger a damage modifier ability, will any respective damage buffs (AP/AD), given mid-ability, affect the damage bonus from said ability?

Will it happen for DoT effects (poisons, Malzahar's Malefic Visions, etc.) and/or channels (Supresses, Kat's Ultimate, Fiddle's Drain, etc.) as well?

P.S. This is even written confusingly for me, I'd appreciate if someone could edit it to make it sound more logical.

Solution 1:

As I touch briefly on in this question, damage is calculated the moment it is applied, and no sooner.

This means, among other things, with projectile skills you can:

• Level up a projectile skill while it is in midair to increase its damage
• Gain spellvamp if an ally with Will of the Ancients wanders in range (or Rageblade triggers)
• Gain a damage boost if armor/mr shred gets placed on the target before your skill hits.

DoTs and channeled abilities are a special case, because their damage is calculated once, when the ability is first cast. (Though debuffs can still apply, which reduces the amount the damage is lowered, so you get more bang for the same, pre-calculated buck).

To answer your specific question, Righteous Fury would gain in power with each successive swing.