mouse-1-click-in-non-selected-windows

mouse-1-click-in-non-selected-windows is a variable defined in `mouse.el'.
Its value is

t

Documentation:
If non-nil, a Mouse-1 click also follows links in non-selected windows.

If nil, a Mouse-1 click on a link in a non-selected window performs
the normal mouse-1 binding, typically selects the window and sets
point at the click position.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 22.1 of Emacs.