  Many exotic charmonium resonances have been identified recently in
experiment, however their nature and properties are mostly unknown. Algorithmic
and theoretical progress in lattice calculations has enabled reliable numerical
investigation of the spectrum below the strong decay threshold, while the study
of charmonium resonances remains an open challenge. The main difficulty to
overcome is the presence of many open decay channels which are coupled
together, resulting in a complex finite volume quantization condition. We
report on our recent progress towards the determination of single-channel and
coupled-channel scattering matrices in the scalar and vector channels on CLS
ensembles. We also present an update concerning the study of the charmonium
spectrum in moving frames.
