:)

i can see the point of that.
however, we already have Plasma::SvgWidget that does exactly what that is.

recommendation: drop StandardCustomWidget. use Plasma::SvgWidget.

Didn't know! My mistake.
Or did I know?!

there is ManageWidgetsPushButton, which subclass StandardCustomWidget. just
use Plasma::PushButton instead. it can do everything you need and will fit
into the rest of plasma much better.

Yeah, I did that cause I wanted the button to have the same svg background as everybody else - so I did this ManageWidgetsPushButton that subclasses StandardCustomWidget and put a KPushButton in there. I tried to make the button transparent, but didn't succeed... =/
Does the Plasma::PushButton uses the svg background or is it just going to look a bit different from everyone else? That's ok! But we actually still don't know where to put this tricky button, right?!

AppletsListSearch should just be a Plasma::LineEdit.

Should _be_ or should _have_? Cause now AppletsListSearch has a AppletsList and a KLineEdit. Did you see that?! It comes all together: the search box and the list...
I'll change the K for a Plasma:: on the KLineEdit then :)

FilteringList should probably be a Plasma::TreeView. it takes a model, too :)

Well, it isn't but it has one!  It subclasses StandardCustomWidget, to have the svg background, and inside it, it has a Plasma::TreeView, taking the model and everything (pretty useful, btw :).

AppletsList (no Widget at the end of that name? :)

I don't know why, actually. :P
I'll put that :)