Minor copyedits of completion-at-point-functions documentation

* lisp/minibuffer.el (completion-at-point-functions):
* doc/lispref/minibuf.texi (Completion in Buffers): Fix wording
and filling.

doc/lispref/minibuf.texi

@@ -1877,10 +1877,11 @@ are used to compute a completion table for completing the text at
 point.  It can be used by major modes to provide mode-specific
 completion tables (@pxref{Major Mode Conventions}).
 
-When the command @code{completion-at-point} runs, it calls the functions in the
-list one by one, without any argument.  Each function should return @code{nil}
-unless it can and wants to take responsibility for the completion data for the
-text at point.  Otherwise it should return a list of the form
+When the command @code{completion-at-point} runs, it calls the
+functions in the list one by one, without any argument.  Each function
+should return @code{nil} unless it can and wants to take
+responsibility for the completion data for the text at point.
+Otherwise it should return a list of the following form:
 
 @example
 (@var{start} @var{end} @var{collection} . @var{props})
@@ -1910,8 +1911,8 @@ next function in @code{completion-at-point-functions} instead of
 reporting a completion failure.
 @end table
 
-The functions on this hook should generally return quickly, since they may be
-called very often (e.g., from @code{post-command-hook}).
+The functions on this hook should generally return quickly, since they
+may be called very often (e.g., from @code{post-command-hook}).
 Supplying a function for @var{collection} is strongly recommended if
 generating the list of completions is an expensive operation.  Emacs
 may internally call functions in @code{completion-at-point-functions}
@@ -1934,10 +1935,11 @@ can defer generating completions until necessary.  You can use
             (my-make-completions)))))
 @end smallexample
 
-Additionally, the @var{collection} should generally not be pre-filtered based
-on the current text between @var{start} and @var{end}, because that is the
-responsibility of the caller of @code{completion-at-point-functions} to do that
-according to the completion styles it decides to use.
+Additionally, the @var{collection} should generally not be
+pre-filtered based on the current text between @var{start} and
+@var{end}, because that is the responsibility of the caller of
+@code{completion-at-point-functions} to do that according to the
+completion styles it decides to use.
 
 A function in @code{completion-at-point-functions} may also return a
 function instead of a list as described above.  In that case, that

lisp/minibuffer.el

@@ -2074,10 +2074,11 @@ Currently supported properties are all the properties that can appear in
 As is the case with most hooks, the functions are responsible for
 preserving things like point and current buffer.
 
-NOTE: These functions should be cheap to run since they're sometimes run from
-`post-command-hook' and they should ideally only choose which kind of
-completion table to use and not pre-filter it based on the current text between
-START and END (e.g. that would not obey `completion-styles').")
+NOTE: These functions should be cheap to run since they're sometimes
+run from `post-command-hook'; and they should ideally only choose
+which kind of completion table to use, and not pre-filter it based
+on the current text between START and END (e.g., they should not
+obey `completion-styles').")
 
 (defvar completion--capf-misbehave-funs nil
   "List of functions found on `completion-at-point-functions' that misbehave.