Is “ne” expletive in “elle n’en avait encore presque pas un que je ne lui eusse vu inventer”?

Question

The question is on ne as highlighted in this passage from chapter 5 of La porte étroite by André Gide. Jerome is the narrator of the whole passage and is quoting (in italics) a letter from Alissa.

La lettre suivante ne parlait que de la naissance de sa nièce, dont elle devait être marraine, de la joie de Juliette, de celle de mon oncle… mais de ses sentiments à elle, il n’était plus question.
      Puis ce furent des lettres datées de Fongueusemare de nouveau, où Juliette vint la rejoindre en juillet…

      Édouard et Juliette nous ont quittés ce matin. C’est ma petite filleule surtout que je regrette ; quand je la reverrai, dans six mois, je ne reconnaîtrai plus tous ses gestes ; elle n’en avait encore presque pas un que je ne lui eusse vu inventer. Les formations sont toujours si mystérieuses et surprenantes ! c’est par défaut d’attention que nous ne nous étonnons pas plus souvent. Que d’heures j’ai passées, penchée sur ce petit berceau plein d’espérance. Par quel égoïsme, quelle suffisance, quelle inappétence du mieux, le développement s’arrête-t-il si vite, et toute créature se fixe-t-elle encore si distante de Dieu ? Oh ! si pourtant nous pouvions, nous voulions nous rapprocher de Lui davantage… quelle émulation ce serait !

QUESTION

1. Is ne here a negation or expletive?

For a definition of ne as an expletive, I quote from Wiktionery (although I don't believe the element of doubt is relevant to our sentence):

Used in a subordinate clause before a subjunctive verb (especially when the main verb expresses doubt or fear), to provide extra overtones of doubt or uncertainty (but not negating its verb); the so-called "pleonastic" or "expletive" ne.

2. If your answer is that it is a negation, please see the "How I Want to Read It" segment of the BACKGROUND below and give me an idea of how to make sense of the passage in keeping with your answer. I don't mean just grammatical sense, but what's going on in the fictional situation.

3. Suppose there was no context, and all we had was this sentence:

elle n’en avait encore presque pas un que je ne lui eusse vu inventer

From purely grammatical principles, can we determine whether this ne is negative or expletive? If so, which is it?

BACKGROUND

The Way I Want to Read It:

I want to read this ne as an expletive. (Last night, however, I asked this other question while thinking it was a negation.)

You may need some filling in. There are four points in time at play in the passage.

• Remote Past: Alissa visits her sister Juliette. Juliette gives birth to a daughter, i.e. niece to Alissa.

• Near Past: Juliette and her daughter visit Alissa.

• Present: Alissa writes Jerome.

• Future: Six months hence, at which time Alissa fears she may no longer recognize her niece's gestures.

Now this fear is expressed by:

quand je la reverrai, dans six mois, je ne reconnaîtrai plus tous ses gestes

The very next sentence, it would appear, is adduced in support of this fear by noting that the gestures which Alissa had witnessed in their invention (at Remote Past) were already almost all gone (by Near Past):

elle n’en avait encore presque pas un que je ne (expletive) lui eusse vu inventer

In English:

she had now (Near Past) almost none of them which I had seen (Remote Past) her invent.

The overall idea would be that the rapid loss of gestures between Remote Past and Near Past would be repeated between Present and Future.

Translations

However, all three translations I have seem to read ne as a negation.

Dorothy Bussy:

she had scarcely one which I hadn't seen her invent.

Felix Paul Greve:

sie hatte fast noch keine einzige, die ich sie nicht hätte erfinden sehen.

Maria Honeit:

sie hatte kaum eine, die ich nicht von dem Augenblick an miterlebt hätte, als sie sie erfand.

Answer 1

No, it's not expletive.

The sentence could translate as :

There was almost none of them that I hadn't see her invent

"There was none that she didn't invent" is an elaborate (and confusing, I agree) way to say she invented all of them.

As you may already know, an expletive ne doesn't make the sentence negative, it goes like:

Je crains de n'avoir oublié de prévenir nos invités = j'ai oublié de prévenir nos invités

Even out of context, this sentence wouldn't be read as using an expletive ne. It's actually pretty rare, you can't fit in anywhere. Your definition says it's often with fear or doubt, but it has to be expressed more clearly and in the same sentence (like in the example I gave). There are other uses, but the "fear or doubt" isn't applicable here.

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Maybe you'll understand better from an article in French than from a mere definition from the Wiktionary. Feel free to ask about clarifications about it of you need, in comments or in another question depending on what you're missing.