clarify doc for compute_nonzero_normal_flux_constraints

diff --git a/include/deal.II/numerics/vector_tools.h b/include/deal.II/numerics/vector_tools.h
index 24c1fe87eaf589cedb8305a271532c629ae2fa2e..7e22e5e1c518ee69d5108d923ea4fbbc24d56d06 100644 (file)
--- a/include/deal.II/numerics/vector_tools.h
+++ b/include/deal.II/numerics/vector_tools.h
@@ -1686,8 +1686,11 @@ namespace VectorTools
    * function multiple times with only one boundary indicator, or whether we
    * call the function once with the whole set of boundary indicators at once.
    *
-   * The fourth parameter describes the boundary function that is used for
-   * computing these constraints.
+   * Argument four (@p function_map) describes the boundary function $\vec u_\Gamma$
+   * for each boundary id. The function <code>function_map[id]</code>
+   * is used on boundary with id @p id taken from the set @p boundary_ids.
+   * Each function in @p function_map is expected to have @p dim
+   * components, which are used independent of @p first_vector_component.
    *
    * The mapping argument is used to compute the boundary points at which the
    * function needs to request the normal vector $\vec n$ from the boundary