ma;hshar : 'A place of assembly or congregation; — ... the day of the place of congregation, the day of judgment'. (Platts p.1009)
Usually aa))inah-e ma;hshar refers to the sun of Doomsday, but here the literal meaning of the words is enough. Majnun's dust wanders around in the form of a whirlwind; so to speak, it is the mirror of the devastation/'Doomsday' that has fallen upon Majnun. This whirlwind has lifted up within me a very restless heart. yak-bayaabaa;N dil-e betaab = It manifests the intensity of the restless heart. Having seen the 'Doomsday' of Majnun, restlessness will have come over him-- that since this Doomsday came over Majnun, he himself too would have the same fate.
Or, again: out of sympathy for Majnun, the whole wilderness/jungle rose up.
SETS == LIST
DESERT: {3,1}
DOOMSDAY: {10,11}
MIRROR: {8,3}
For more on Ghalib's unpublished verses, see the discussion in {4,8x}. See also the overview index.
Formally speaking, this is an 'A,B' verse of the 'list' kind. The first line is verb-free and consists of a noun ('whirlwind'), followed by a noun ('mirror') with adjectives. The second line consists of a noun ('heart') with adjectives, followed by a ne verb ('has lifted up') but without a grammatical subject. So we're really left to arrange the clauses for ourselves.
The most persuasive way to do this is surely to take seriously the verb. Something, the speaker says, 'has lifted me up'. And what could do this lifting more appropriately than the 'whirlwind' in the first line? This whirlwind could then quite well be called a 'mirror of the ma;hshar of Majnun's dust'-- with an enjoyably double meaning, because the whirlwind is as devastating as 'Doomsday', and also because the whirlwind is a 'place of assembly' of Majnun's dust (see the definition above).
Thus it's also very plausible that this whirlwind would be called a 'whole-desertful restless heart'. (On Persianized expressions compounded with yak , see {11,1}.) After all, the whirlwind is composed of the dust of Majnun, who roamed endlessly in the desert and was nothing if not a 'restless heart'.
Still, the verse is not very well constructed.
Zamin:
He says, the Maker has made me the embodiment of a restless heart, and my restlessness is the mirror of my madness-- the way the wildness and confusion of a whirlwind shows that its origin/essence is the dust of Majnun. That is, the whirlwind is originally the dust of Majnun, that in the ebullition of madness has flown high and is becoming confused/wandering.... To use u;Thaayaa hai in the sense of banaayaa hai is far from idiomatic usage.
== Zamin, p. 439