  The contribution to the spin of the proton from the gluon helicity is
starting to come into focus: for gluons carrying a large fraction $x$ of the
proton momentum, evidence of positive gluon polarization has been observed, via
measurements of the longitudinal double-spin asymmetry $A_{LL}$ for inclusive
jet and dijet production. $A_{LL}$ is sensitive to the polarized gluon
distribution function, $\Delta g(x)$, and while it is positive at high $x$, it
is not well constrained for $x<0.05$. Recent measurements at STAR of
observables originating dominantly from quark-gluon and gluon-gluon
subprocesses aim to improve the precision of $\Delta g(x)$ at high $x$, as well
as for the first time provide insight into the low-$x$ contribution. $A_{LL}$
measurements of inclusive jets and dijets at midrapidity $(|\eta|<1)$ and
intermediate rapidity $(0.8<\eta<2)$ at STAR at $\sqrt{s}=200$ and $510$ GeV
will be shown, along with the statuses of ongoing analyses; these measurements
will help improve the $\Delta g(x)$ precision for $x\gtrsim 0.01$. Recent
$\pi^0$ $A_{LL}$ measurements in the forward region $(2.65<\eta<3.9)$ at
$\sqrt{s}=510$ GeV will also be presented, which probe $\Delta g(x)$ down to
$x{\sim}10^{-3}$. Comparisons of these results to recent global analyses and
extrapolations will be discussed.
