TL;DR: Is it possible to make emacs use single-column completion?
When using emacs' completion mechanisms and there are multiple possibilities, then completions are displayed in a separate window, e.g.
Possible completions are: i i-search i1 i18n i2 i3 iar ibm ibm1047 ibm1047-dos ibm1047-mac ibm1047-unix ibm437 ibm437-dos ibm437-mac ibm437-unix ibm775 ibm775-dos ibm775-mac ibm775-unix ibm850 ibm850-dos ibm850-mac ibm850-unix ibm851 ibm851-dos ibm851-mac ibm851-unix ibm852 ibm852-dos ibm852-mac ibm852-unix ibm855 ibm855-dos ibm855-mac ibm855-unix ibm857 ibm857-dos
While this format is perfectly fine for a few items, when the list is long having successive completions on the same line, i.e. ordered as
1 2 3 4 5 6
is rather distracting. Ideally I'd prefer an ordering
1 4 2 5 3 6
but I fear this is not possible, since it wouldn't be able to handle completions, that are wider than each column. Emacs in this case uses a format
111 222 33333333 444 5555
which works only because of the "horizontal first" ordering; Also my preferred ordering would require adjustig the completion-buffer contents depending on window height (likewise unpracticable).
So as an alternative I'd like completion to use only one column, i.e.
Possible completions are: i i-search i1 i18n i2 i3 iar ibm ibm1047 ibm1047-dos ibm1047-mac ibm1047-unix ibm437 ibm437-dos ibm437-mac ibm437-unix
which I'd find easier to scan visually.
Is this possible?