[_Max_Cavalera_]

ok, yeah that seems like a good idea, it's not like I'm using the Frame specifically for anything other than to define a space/anchor for everything else, right? So making it a button would allow me to use the OnClick and continue to do everything I'm already using it for.

edit:. ok..... i'm stupid..... damn....

After trying a million things before and after Lombra's post and not getting any results I realized it was actually working, what wasn't working was what I made it do, I made it open the artifact weapon window and that wasn't working, but the click was being registered and working, I just added a chat message to test (yes I should have done this in the first place xD) and the chat message shows.

edit:. ok, making the frame a button like Lombra first suggested and then doing

frame:SetScript("OnMouseUp", function(self, button)
    if button == "LeftButton" then
        ArtifactFrame_LoadUI()
        if (ArtifactFrame:IsVisible()) then
            HideUIPanel(ArtifactFrame)
        else
            SocketInventoryItem(16);
        end
    end
end);

Seems to be enough, didn't even need the registerforclicks, tries with and without, seems to be the same.

Here's my full code so far.

local akMulti = {
    25, 50, 90, 140, 200,
    275, 375, 500, 650, 850,
    1100, 1400, 1775, 2250, 2850,
    3600, 4550, 5700, 7200, 9000,
    11300, 14200, 17800, 22300, 24900
};
 
local frame = CreateFrame("Button", "m4xArtifactFrame", UIParent);
local text = frame:CreateFontString(nil, "ARTWORK");
text:SetFont("Fonts\\FRIZQT__.TTF", 15, "OUTLINE");
text:SetJustifyH("LEFT");
text:SetTextColor(1, 0.82, 0);
text:SetPoint("TOPLEFT", UIParent, "TOPLEFT");
 
frame:SetAllPoints(text);
 
frame:RegisterEvent("PLAYER_LOGIN");
frame:RegisterEvent("PLAYER_ENTERING_WORLD");
frame:RegisterEvent("PLAYER_EQUIPMENT_CHANGED");
frame:RegisterEvent("ARTIFACT_CLOSE");
frame:RegisterEvent("ARTIFACT_RESPEC_PROMPT");
frame:RegisterEvent("ARTIFACT_XP_UPDATE");
 
frame:SetScript("OnEvent", function(self, event, ...)
    local itemID, _, _, _, totalXP, pointsSpent = C_ArtifactUI.GetEquippedArtifactInfo()
    
    if itemID then
        local pointsFree, xpToNextPoint = 0, C_ArtifactUI.GetCostForPointAtRank(pointsSpent);
        
        while totalXP >= xpToNextPoint do
            totalXP, pointsSpent, pointsFree, xpToNextPoint = totalXP - xpToNextPoint, pointsSpent + 1, pointsFree + 1, C_ArtifactUI.GetCostForPointAtRank(pointsSpent + 1);
        end
 
        text:SetFormattedText("AP |cff00ff00%d/%d (%.1f%%)|r" .. (pointsFree > 0 and " (+%d)" or ""), totalXP, xpToNextPoint, 100 * totalXP / xpToNextPoint, pointsFree);
    end
 
    frame:SetShown(itemID and true or false);
end);
 
local function OnEnter(self)
    local _, akLevel = GetCurrencyInfo(1171);
    local _, _, itemName, itemIcon, _, pointsSpent = C_ArtifactUI.GetEquippedArtifactInfo()
    local _, effectiveStat = UnitStat("player", 3);
 
    GameTooltip:SetOwner(self, "ANCHOR_BOTTOM");
    GameTooltip:SetText(string.format("|T%d:0|t %s", itemIcon, itemName));
    GameTooltip:AddLine(" ");
    GameTooltip:AddLine(string.format("Artifact Knowledge Level: |cff00ff00%d (+%d%%)|r", akLevel, akMulti[akLevel] or 0));
    GameTooltip:AddLine(string.format("Next Artifact Knowledge: |cff00ff00%d (+%d%%)|r", akLevel + 1, akMulti[akLevel + 1]));
    GameTooltip:AddLine(" ");
    GameTooltip:AddLine(string.format("Stamina from points: |cff00ff00+%g%% (+%d)|r", pointsSpent * 0.75, effectiveStat - (effectiveStat / ((pointsSpent * 0.75 / 100) + 1))));
    GameTooltip:Show();
end
 
local function OnLeave(self)
    GameTooltip:Hide();
end
 
frame:SetScript("OnMouseUp", function(self, button)
    if button == "LeftButton" then
        if ArtifactFrame and ArtifactFrame:IsVisible() then
            HideUIPanel(ArtifactFrame);
        else
            SocketInventoryItem(16);
        end
    end
end);
 
frame:SetScript("OnEnter", OnEnter);
frame:SetScript("OnLeave", OnLeave);

I'm still trying out events for the initial load, because I have a few times that the text wasn't becoming visible with PLAYER_ENTERING_WORLD, we talked about this, I think it was SDPhantom that said the addon didn't have the artifact info available at that point.
I donno, is there any other events that happen once at start bu after that one? The PLAYER_LOGIN one is probably not doing anything tbh.
I just need to get this to load at start every time and for some reason, some times it doesn't, it IS rare but it happens.