bug#17809: 24.4.50; Completions display

[Juri Linkov]

Severity: wishlist
Tags: patch

This is a follow-up to bug#17554.  There are two existing
display actions that could help to better display *Completions*:

- display-buffer-at-bottom for minibuffer-completion-help
  to display *Completions* near the active minibuffer
  where it would be easier to find them;

- display-buffer-below-selected for completion-at-point
  that could work like displaying *Marking Files* in Dired
  to display *Completions* near the point of completion
  in the current buffer.

=== modified file 'lisp/minibuffer.el'
--- lisp/minibuffer.el  2014-06-02 00:18:22 +0000
+++ lisp/minibuffer.el  2014-06-19 06:55:32 +0000
@@ -1796,7 +1796,25 @@ (defun minibuffer-completion-help (&opti
              ;; window, mark it as softly-dedicated, so bury-buffer in
              ;; minibuffer-hide-completions will know whether to
              ;; delete the window or not.
-             (display-buffer-mark-dedicated 'soft))
+             (display-buffer-mark-dedicated 'soft)
+             ;; Disable `pop-up-windows' temporarily to allow
+             ;; `display-buffer--maybe-pop-up-frame-or-window'
+             ;; in the overridden actions below to pop up a frame
+             ;; if `pop-up-frames' is non-nil, but not to pop up a window.
+             (pop-up-windows nil)
+             (display-buffer-base-action
+              ;; First check for defined `display-buffer-base-action'
+              ;; that might be already bound by `completion-at-point'.
+              (or (and (car-safe display-buffer-base-action)
+                       display-buffer-base-action)
+                  ;; This is a copy of `display-buffer-fallback-action'
+                  ;; where `display-buffer-use-some-window' is replaced
+                  ;; with `display-buffer-at-bottom'.
+                  '((display-buffer--maybe-same-window
+                     display-buffer-reuse-window
+                     display-buffer--maybe-pop-up-frame-or-window
+                     display-buffer-at-bottom)
+                    (window-height . fit-window-to-buffer)))))
         (with-output-to-temp-buffer "*Completions*"
           ;; Remove the base-size tail because `sort' requires a properly
           ;; nil-terminated list.
@@ -2073,7 +2091,17 @@ (defun completion-at-point ()
 The completion method is determined by `completion-at-point-functions'."
   (interactive)
   (let ((res (run-hook-wrapped 'completion-at-point-functions
-                               #'completion--capf-wrapper 'all)))
+                               #'completion--capf-wrapper 'all))
+        ;; Display buffer like in `minibuffer-completion-help',
+        ;; but instead of `display-buffer-at-bottom'
+        ;; use `display-buffer-below-selected'.
+        (pop-up-windows nil)
+        (display-buffer-base-action
+         '((display-buffer--maybe-same-window
+            display-buffer-reuse-window
+            display-buffer--maybe-pop-up-frame-or-window
+            display-buffer-below-selected)
+           (window-height . shrink-window-if-larger-than-buffer))))
     (pcase res
       (`(,_ . ,(and (pred functionp) f)) (funcall f))
       (`(,hookfun . (,start ,end ,collection . ,plist))