That explains how "burst"-type Charge mechanics work (Berserker / Embermage), but what about "scaling"-type Charge mechanics (like the Outlander)?
It depends on the event being monitored. In the case of the Arbiter, the event MAXEDCHARGE is either true or false (a burst as u put it). For the Wanderer, the event is the state of the affix "WANDERER_PASSIVES.DAT" (in MEDIA/AFFIXES/PLAYER/).
If u look inside that affix it is modified by the state of the STAT "Player Charge Percent"
Which says something like "on update self, use 100% of the value of Player Charge Percent, multiply it by 0.1 and use that value to adjust EFFECT TYPE".
The STAT "Player Charge Percent" is predefined; I'm not sure how, but all it does is read what percentage of maximum charge youre at. So it "slides" up and down and thus produces a scaling impact on the above affix.
…Of course, I only noticed your reply after I had already spent the day implementing a Charge-mechanic based on the wiki page I finally noticed the existence of. ;}
I ended up copying over the base Charge Affix from the "Nethermancer" class. The Nether is ultimately the original source of Ember Blight, after all—and Blighted madness was going to be the theme for my Charge system anyway. :P
The Charge-bar graphic I chose, is from the "Dragonborn" class. That one seems to be the best visual fit for the style of my class.
And of course, I went ahead and used a Passive Skill to attach the Affix to the Emberdrake class ("friendly charge-bar passives"). I even gave the Skill some flavor text and an appropriate icon. After all, why not go all the way? ;}
Next session will be to actually build and test the mod in-game (to make sure I did not break something significant).
The ported Charge-system code is fully functional. It may need some tweaks to the tooltip size and alignment (for readability), but it definitely works, and will be included in the next build.
I will, of course, be tweaking the balance of the Charge Affix, now that I understand what it does in-game.
For a more technical explanation of what I have found, see below.
If you would like, I can also write a proper step-by-step tutorial on how to use Nethermancer-like Charge scaling. ;}