  Very recently, the LHCb Collaboration observed the $CP$ violation (CPV) in
the charm sector for the first time, with $\Delta A_{CP}^{\rm dir}\equiv
A_{CP}(D^0\to K^+K^-)-A_{CP}(D^0\to \pi^+\pi^-)=(-1.54\pm0.29)\times10^{-3}$.
This result is consistent with our prediction of $\Delta A_{CP}^{\rm
SM}=(-0.57\sim -1.87)\times 10^{-3}$ obtained in the factorization-assisted
topological-amplitude (FAT) approach in [PRD86,036012(2012)]. It implies that
the current understanding of the penguin dynamics in charm decays in the
Standard Model is reasonable. Motivated by the success of the FAT approach, we
further suggest to measure the $D^+\to K^+K^-\pi^+$ decay, which is the next
potential mode to reveal the CPV of the same order as $10^{-3}$.
