  The problem of describing the analytic functions $g$ on the unit disc such
that the integral operator $T_g(f)(z)=\int_0^zf(\zeta)g'(\zeta)\,d\zeta$ is
bounded (or compact) from a Banach space (or complete metric space) $X$ of
analytic functions to the Hardy space $H^\infty$ is a tough problem and remains
unsettled in many cases. For analytic functions $g$ with non-negative Maclaurin
coefficients, we describe the boundedness and compactness of $T_g$ acting from
a weighted Dirichlet space $D^p_\omega$, induced by an upper doubling weight
$\omega$, to $H^\infty$. We also characterize, in terms of neat conditions on
$\omega$, the upper doubling weights for which $T_g: D^p_\omega\to H^\infty$ is
bounded (or compact) only if $g$ is constant.
