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.

3 files changed, 32 insertions, 12 deletions

diff --git a/lisp/emacs-lisp/tabulated-list.el b/lisp/emacs-lisp/tabulated-list.el
index d1d7c0a8042..73ddadfb805 100644
--- a/lisp/emacs-lisp/tabulated-list.el
+++ b/lisp/emacs-lisp/tabulated-list.el
@@ -193,10 +193,10 @@ Populated by `tabulated-list-init-header'.")
   ;; is displayed.
   (if (not display-line-numbers)
            0
-    (let ((cbuf-window (get-buffer-window (current-buffer))))
+    (let ((cbuf-window (get-buffer-window (current-buffer) t)))
       (if (window-live-p cbuf-window)
           (with-selected-window cbuf-window
-            (+ (line-number-display-width) 2))
+            (line-number-display-width 'columns))
         4))))
 
 (defun tabulated-list-init-header ()
@@ -329,8 +329,6 @@ Check the current row, the previous one and the next row."
                            (string-width (if (stringp nt) nt (car nt)))))
                        tabulated-list--near-rows)))
 
-(defvar tabulated-list-entry-lnum-width nil)
-
 (defun tabulated-list-print (&optional remember-pos update)
   "Populate the current Tabulated List mode buffer.
 This sorts the `tabulated-list-entries' list if sorting is
@@ -373,7 +371,6 @@ changing `tabulated-list-sort-key'."
       (unless tabulated-list-use-header-line
         (tabulated-list-print-fake-header)))
     ;; Finally, print the resulting list.
-    (setq tabulated-list-entry-lnum-width (tabulated-list-line-number-width))
     (while entries
       (let* ((elt (car entries))
              (tabulated-list--near-rows
@@ -428,9 +425,8 @@ of column descriptors."
         (x     (max tabulated-list-padding 0))
         (ncols (length tabulated-list-format))
         (inhibit-read-only t))
-    (setq x (+ x tabulated-list-entry-lnum-width))
     (if (> tabulated-list-padding 0)
-        (insert (make-string (- x tabulated-list-entry-lnum-width) ?\s)))
+        (insert (make-string x ?\s)))
     (let ((tabulated-list--near-rows ; Bind it if not bound yet (Bug#25506).
            (or (bound-and-true-p tabulated-list--near-rows)
                (list (or (tabulated-list-get-entry (point-at-bol 0))
@@ -601,6 +597,14 @@ With a numeric prefix argument N, sort the Nth column."
     (tabulated-list-init-header)
     (tabulated-list-print t)))
 
+(defvar tabulated-list--current-lnum-width nil)
+(defun tabulated-list-watch-line-number-width (_window)
+  (if display-line-numbers
+      (let ((lnum-width (tabulated-list-line-number-width)))
+        (when (not (= tabulated-list--current-lnum-width lnum-width))
+          (setq-local tabulated-list--current-lnum-width lnum-width)
+          (tabulated-list-revert)))))
+
 ;;; The mode definition:
 
 (define-derived-mode tabulated-list-mode special-mode "Tabulated"
@@ -645,7 +649,12 @@ as the ewoc pretty-printer."
   ;; column of the first entry happens to begin with a R2L letter.
   (setq bidi-paragraph-direction 'left-to-right)
   ;; This is for if/when they turn on display-line-numbers
-  (add-hook 'display-line-numbers-mode-hook #'tabulated-list-revert nil t))
+  (add-hook 'display-line-numbers-mode-hook #'tabulated-list-revert nil t)
+  ;; This is for if/when they customize the line-number face or when
+  ;; the line-number width needs to change due to scrolling.
+  (setq-local tabulated-list--current-lnum-width 0)
+  (add-hook 'pre-redisplay-functions
+            #'tabulated-list-watch-line-number-width nil t))
 
 (put 'tabulated-list-mode 'mode-class 'special)
 
diff --git a/lisp/proced.el b/lisp/proced.el
index c9e851b7e05..aec54b59211 100644
--- a/lisp/proced.el
+++ b/lisp/proced.el
@@ -604,7 +604,8 @@ Important: the match ends just after the marker.")
   "Return header line for Proced buffer."
   (list (propertize " "
                     'display
-                    (list 'space :align-to (+ 2 (line-number-display-width))))
+                    (list 'space :align-to
+                          (line-number-display-width 'columns)))
         (if (<= (window-hscroll) (length proced-header-line))
             (replace-regexp-in-string ;; preserve text properties
              "\\(%\\)" "\\1\\1"
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)))