[Mischback]

Originally Posted by Coldkil I have a similar problem with druids. (i hate they multiple forms) I have made the combobar as a simple frame with 5 text strings, that stay at .2 alpha when not up, then go at alpha 1 when the combo builds up. The fact is that i want to register the shapeshift events for make them disappear completely when the druid isn't in cat form. Same would be good for eclipse bar, displaying it only when in moonkin form. Is it possible or it's something that i canot achieve? thanks.

No, I didn't want to suggest an altering of oUF's core! At least not on parts, that are working perfectly.
On the other hand, the cpoints-module doesn't include a PostUpdate (hint at haste!), so you'll have to put some effort into it!

Go and style your CPoints in your layout as you want them to be. Don't include any conditions to them, though.

The oUF-module DOES include the possibility to override the original update-function, and this would be the way to go!

You can merely use, what you already got and put it into a function inside of your layout

local function CPointsOverride(self, event, unit)
        if (unit == 'pet') then return end
    local cp = nil
    if(UnitHasVehicleUI'player') then
        cp = GetComboPoints('vehicle', 'target')
    else
        cp = GetComboPoints('player', 'target')
    end
 
        local cpoints = self.CPoints
        if (cp) then
                cpoints:Show()
            for i=1, MAX_COMBO_POINTS do
                if(i <= cp) then
                    cpoints[i]:SetAlpha(1)
                else
                    cpoints[i]:SetAlpha(0.2)
                end
            end
        else
                cpoints:Hide()
        end
end

This way, you're getting your CPoints shown everytime, when CPoints are on the target, regardless of your class. If there is at least one combo point, the whole element is shown and updated as you want it with the alpha settings.

Note: You don't have to include those cpoints:Show() / :Hide() stuff, it would be my approach.
If you want your CPoints always visible if you're in cat-form or on an rogue, just show them all the time (rogue) or if you're in cat (drood).

Create a frame and register the "UPDATE_SHAPESHIFT_FORM"-event and apply a script to this event

local function ShapeshiftControl()
    if (currentform == CAT) then
        ShowCPoints()
    else
        HideCPoints()
    end
end

This is of course pseudo-code, you will have to fill it with life.

edit: Second approach is easily modified to handle eclipse-bar, too!