Cellular bases of generalized q-Schur algebras

We show that cellular bases of generalized $q$-Schur algebras can be constructed by gluing arbitrary bases of the cell modules and their dual basis (with respect to the anti-involution giving the cell structure) along defining idempotents. For the rational form, over the field $\mathbb{Q}(v)$ of rational functions in an indeterminate $v$, our proof of this fact is self-contained and independent of the theory of quantum groups. In the general case, over a commutative ring $\mathbb{k}$ regarded as a $\mathbb{Z}[v,v^{-1}]$-algebra via specialization $v\mapsto q$ for some chosen invertible $q\in \mathbb{k}$, our argument depends on the existence of the canonical basis.