  The elastic $I=1$ $p$-wave $\pi\pi$ scattering amplitude is calculated
together with the isovector timelike pion form factor using lattice QCD with
$N_{\rm f}=2+1$ dynamical quark flavors. Wilson clover ensembles generated by
the Coordinated Lattice Simulations (CLS) initiative are employed at four
lattice spacings down to $a = 0.05\,\mathrm{fm}$, several pion masses down to
$m_{\pi} = 200\,\mathrm{MeV}$, and spatial volumes of extent $L =
3.1-5.5\,\mathrm{fm}$. The set of measurements on these ensembles, which is
publicly available, enables an investigation of systematic errors due to the
finite lattice spacing and spatial volume. The $\pi\pi$ scattering amplitude is
fit on each ensemble by a Breit-Wigner resonance lineshape, while the form
factor is described better by a thrice-subtracted dispersion relation than the
Gounaris-Sakurai parametrization.
