  Direct CP violation in the hadronic charm decays provides a good testing
ground for the Kobayashi-Maskawa mechanism in the Standard Model. Any
significant deviations from the expectation would be indirect evidence of
physics beyond the Standard Model. In view of improved measurements from LHCb
and BESIII experiments, we re-analyze the Cabibbo-favored $D \to P\!P$ and
$V\!P$ decays in the topological diagram approach. By assuming certain
SU(3)-breaking effects in the tree-type amplitudes, we make predictions for
both branching fractions and CP asymmetries of the singly Cabibbo-suppressed
decay modes. While the color-allowed and -suppressed amplitudes are preferred
to scale by the factor dictated by factorization in the $P\!P$ modes, no such
scaling is required in the $V\!P$ modes. The $W$-exchange amplitudes are found
to change by 10\% to 50\% and depend on whether $d\overline{d}$ or
$s\overline{s}$ pair directly emerges from $W$-exchange. The predictions of
branching fractions are generally improved after these SU(3) symmetry breaking
effects are taken into account. We show in detail how the tree-type,
QCD-penguin, and weak penguin-annihilation diagrams contribute and modify CP
asymmetry predictions. Future measurements of sufficiently many direct CP
asymmetries will be very useful in removing a discrete ambiguity in the strong
phases as well as discriminating among different theory approaches. In
particular, we predict $a_{CP}(K^+K^-)-a_{CP}(\pi^+\pi^-) = (-1.14 \pm 0.26)
\times 10^{-3}$ or $(-1.25 \pm 0.25) \times 10^{-3}$, consistent with the
latest data, and $a_{CP}(K^+K^{*-})-a_{CP}(\pi^+\rho^-) = (-1.52 \pm 0.43)
\times 10^{-3}$, an attractive and measurable observable in the near future.
Moreover, we observe that such CP asymmetry differences are dominated by
long-distance penguin-exchange through final-state rescattering.
