Each widget can have an input focus highlight, which is a border that is drawn in color when the widget has the input focus. This border is outside the border used to draw the 3D relief for widgets. It has the pleasant visual effect of providing a little bit of space around widgets, even when they do not have the input focus. The addition of the input focus highlight does not break anything, but it changes the appearance of your interfaces a little. In particular, the highlight on a canvas obscures objects that are at its edge. See page 531 for a description of the generic widget attributes related to the input focus highlight.