Just curious
Gaining a level Happiness 0-99 +5 Happiness 100-199 +3 Happiness 200-MAX +2 Using an item Happiness 0-99 +5 Happiness 100-199 +3 Happiness 200-MAX +2 Challenging a gym leader Happiness 0-99 +3 Happiness 100-199 +2 Happiness 200-MAX +1 Fainting Happiness 0-99 -1 Happiness 100-199 -1 Happiness 200-MAX -1 -Dr.f
so that explains it mid way through to bottom, max happiness is 255 obviously.
Fainting
Using EnergyPowder
Using Heal Powder
Using Energy Root
Using Revival Herb
Trading