Make :align-to account for display-line-numbers

These changes also update the various bundled packages to use
new feature, and better support customizations of the line-number
face.
* src/xdisp.c (calc_pixel_width_or_height): Improve commentary.
Make :align-to count from the end of the line-number display when
the offset or the width form reference that of the text area.
(Bug#28855)

* src/indent.c (Fline_number_display_width): Implement support for
the PIXELWISE argument being 'columns'.  Update the doc string.
(syms_of_indent): New symbol 'columns'.

* lisp/ruler-mode.el (ruler-mode-window-col, ruler-mode-ruler):
Call line-number-display-width with last argument 'columns'.

* lisp/proced.el (proced-header-line): Call
line-number-display-width with 2nd arg 'columns', which also fixes
a problem when display-line-numbers is nil.

* lisp/emacs-lisp/tabulated-list.el
(tabulated-list-line-number-width): Call line-number-display-width
with 2nd arg 'columns.
(tabulated-list-entry-lnum-width): Remove unneeded defvar.
(tabulated-list-print, tabulated-list-print-entry): No need to
account for the value of tabulated-list-entry-lnum-width.
(tabulated-list--current-lnum-width): New defvar.
(tabulated-list-watch-line-number-width): New function.
(tabulated-list-mode): Bind tabulated-list--current-lnum-width
locally, and set up tabulated-list-watch-line-number-width as
pre-redisplay-functions hook.

* doc/lispref/display.texi (Size of Displayed Text): Document the
'columns' value of the PIXELWISE argument.
(Pixel Specification): Update and improve the documentation of the
supported forms.

1 files changed, 13 insertions, 3 deletions

diff --git a/lisp/ruler-mode.el b/lisp/ruler-mode.el
index 7a23f4d03c0..3d27858d0fe 100644
--- a/lisp/ruler-mode.el
+++ b/lisp/ruler-mode.el
@@ -307,7 +307,12 @@ or remove a tab stop.  \\[ruler-mode-toggle-show-tab-stops] or
 N is a column number relative to selected frame.
 If required, account for screen estate taken by `display-line-numbers'."
   (if display-line-numbers
-      (setq n (- n (line-number-display-width) 2)))
+      ;; FIXME: ruler-mode relies on N being an integer, so if the
+      ;; 'line-number' face is customized to use a font that is larger
+      ;; or smaller than that of the default face, the alignment might
+      ;; be off by up to half a column, unless the font width is an
+      ;; integral multiple or divisor of the default face's font.
+      (setq n (- n (round (line-number-display-width 'columns)))))
   (- n
      (or (car (window-margins)) 0)
      (fringe-columns 'left)
@@ -668,7 +673,12 @@ Optional argument PROPS specifies other text properties to apply."
   (let* ((w (ruler-mode-text-scaled-window-width))
          (m (window-margins))
          (f (window-fringes))
-         (i (if display-line-numbers (+ (line-number-display-width) 2) 0))
+         (i (if display-line-numbers
+                ;; FIXME: ruler-mode relies on I being an integer, so
+                ;; the column numbers might be slightly off if the
+                ;; line-number face is customized.
+                (round (line-number-display-width 'columns))
+              0))
          (j (ruler-mode-text-scaled-window-hscroll))
          ;; Setup the scrollbar, fringes, and margins areas.
          (lf (ruler-mode-space
@@ -708,7 +718,7 @@ Optional argument PROPS specifies other text properties to apply."
             ;; line-number display be blank, not filled with
             ;; ruler-mode-basic-graduation-char.
             (if display-line-numbers
-                (let* ((lndw (+ (line-number-display-width) 2))
+                (let* ((lndw (round (line-number-display-width 'columns)))
                        (s (make-string lndw ?\s)))
                   (concat s (make-string (- w lndw)
                                          ruler-mode-basic-graduation-char)))