If a "Protection from" effect negates damage, is it still considered "damage dealt"?

Question

If I have a Justice ("Whenever a red creature or spell deals damage, Justice deals that much damage to that creature's or spell's controller.") and a Thermal Glider (which has "protection from red") in play, and my opponent attacks with some red creature (say, a Goblin Chariot; 2/2).

I can choose to block with my Thermal Glider, and its protection from red will prevent the damage and it will survive the encounter.

But will Justice's ability trigger? Did the red creature "deal damage" even though all the damage was reduced to zero?

Answer 1

No, damage which is prevented is not dealt at all.

615.1a Effects that use the word “prevent” are prevention effects. Prevention effects use “prevent” to indicate what damage will not be dealt.

615.6. If damage that would be dealt is prevented, it never happens. [...]

Answer 2

No damage is dealt if it all gets prevented, so anything that triggers on damage being dealt will not occur.

119.8. If a source would deal 0 damage, it does not deal damage at all. That means abilities that trigger on damage being dealt won’t trigger. It also means that replacement effects that would increase the damage dealt by that source, or would have that source deal that damage to a different object or player, have no event to replace, so they have no effect.