With this paper we present an overview of mean-field density-functional models for the study of the line tension and boundary tension at wetting. The system under consideration is the three-phase equilibrium with two components. The investigation of the critical behavior of the line tension can be implemented by mean-field models, derived as extensions of the van der Waals theory. First-order and second-order wetting transitions are described by suitable choices of the free-energy density functional. Recently a new model was proposed and its wetting phase diagram has been explored. Within the same framework wetting transitions of first order, higher than first order and infinite order are described. The order of the wetting transition depends sensitively on the parameters of the model. A criterion for the characterization of the transition is given.