 Line adjustment ratio

The line adjustment ratio measures the stretch or shrink required to make a candidate line fit. In the finite-glue model, let $N$ be its natural line width, $W$ its target typesetting line width, and $S$ and $T$ the total stretch and shrink coefficients of its typesetting glue. DefineIt is a dimensionless quantity: numerator and denominator are widths measured in the same units. Each glue item uses the same $r$, scaled by its own appropriate coefficient.^[ref]

For $N=30$, $S=4$ and $T=2$, targets 32 and 28 give $r=1/2$ and $r=-1$ respectively. If a nonzero width difference requires a coefficient total of zero, this model cannot make the adjustment. With ordinary bounded shrinkage, $r<-1$ asks the glue to shrink beyond its total allowance and is infeasible. Positive stretch is usually limited by an acceptable-quality threshold rather than by treating $r=1$ as an absolute geometric limit.

The typesetting badness scores spacing quality from the required adjustment, while a line-breaking fitness class records a coarser category for comparison with neighbouring lines. Neither measure alone incorporates every typesetting penalty.