I have wondered why here pop-to-buffer does not split the unsplitted window in
my frame. Then i have tested the following (The value of `pop-up-windows' is
t!):
(pop-to-buffer (get-buffer-create "*BlaBlaBla*"))
which splits an unsplitted window in 2 windows - well!
(pop-to-buffer (get-buffer-create "*Customization*"))
which does not split an unsplitted windows in 2 - very bad and ugly!
Conclusion: pop-up-buffer must have somewhere in the c-code - or maybe
display-buffer) but anyway - some logic which decides dependent on the
buffer-name if the window should be splitted or not?! I write this not to the
bug-list because it is not really a bug but it is a strong violation of one
of the most important design-principles: "Separation of concerns".