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, 33 insertions, 16 deletions

diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index fbdd810247d..17126ce72b9 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -2050,14 +2050,17 @@ calculations.
 
 @defun line-number-display-width &optional pixelwise
 This function returns the width used for displaying the line numbers
-in the selected window.  Optional argument @var{pixelwise}, if
-non-@code{nil}, means return the value in pixels; otherwise the value
-is returned in column units of the font defined for the
+in the selected window.  If the optional argument @var{pixelwise} is
+the symbol @code{columns}, the return value is a float number of the
+frame's canonical columns; if @var{pixelwise} is @code{t} or any other
+non-@code{nil} value, the value is an integer and is measured in
+pixels.  If @var{pixelwise} is omitted or @code{nil}, the value is the
+integer number of columns of the font defined for the
 @code{line-number} face, and doesn't include the 2 columns used to pad
-the numbers.  If line numbers are not displayed in the selected
-window, the value is zero.  Use @code{with-selected-window}
-(@pxref{Selecting Windows}) if you need this information about another
-window.
+the numbers on display.  If line numbers are not displayed in the
+selected window, the value is zero regardless of the value of
+@var{pixelwise}.  Use @code{with-selected-window} (@pxref{Selecting
+Windows}) if you need this information about another window.
 @end defun
 
 
@@ -4636,7 +4639,7 @@ as an absolute number of pixels.
 
 @smallexample
 @group
-  @var{expr} ::= @var{num} | (@var{num}) | @var{unit} | @var{elem} | @var{pos} | @var{image} | @var{form}
+  @var{expr} ::= @var{num} | (@var{num}) | @var{unit} | @var{elem} | @var{pos} | @var{image} | @var{xwidget} | @var{form}
   @var{num}  ::= @var{integer} | @var{float} | @var{symbol}
   @var{unit} ::= in | mm | cm | width | height
 @end group
@@ -4652,22 +4655,34 @@ as an absolute number of pixels.
   The form @var{num} specifies a fraction of the default frame font
 height or width.  The form @code{(@var{num})} specifies an absolute
 number of pixels.  If @var{num} is a symbol, @var{symbol}, its
-buffer-local variable binding is used.
+buffer-local variable binding is used; that binding can be either a
+number or a cons cell of the forms shown above (including yet another
+cons cell whose @code{car} is a symbol that has a buffer-local
+binding).
 
   The @code{in}, @code{mm}, and @code{cm} units specify the number of
 pixels per inch, millimeter, and centimeter, respectively.  The
 @code{width} and @code{height} units correspond to the default width
-and height of the current face.  An image specification @code{image}
-corresponds to the width or height of the image.
+and height of the current face.  An image specification of the form
+@w{@code{(image . @var{props})}} (@pxref{Image Descriptors})
+corresponds to the width or height of the specified image.  Similarly,
+an xwidget specification of the form @w{@code{(xwidget . @var{props})}}
+stands for the width or height of the specified xwidget.
+@xref{Xwidgets}.
 
   The elements @code{left-fringe}, @code{right-fringe},
 @code{left-margin}, @code{right-margin}, @code{scroll-bar}, and
-@code{text} specify to the width of the corresponding area of the
-window.
+@code{text} specify the width of the corresponding area of the window.
+When the window displays line numbers (@pxref{Size of Displayed
+Text}), the width of the @code{text} area is decreased by the screen
+space taken by the line-number display.
 
   The @code{left}, @code{center}, and @code{right} positions can be
 used with @code{:align-to} to specify a position relative to the left
-edge, center, or right edge of the text area.
+edge, center, or right edge of the text area.  When the window
+displays line numbers, the @code{left} and the @code{center} positions
+are offset to account for the screen space taken by the line-number
+display.
 
   Any of the above window elements (except @code{text}) can also be
 used with @code{:align-to} to specify that the position is relative to
@@ -4683,13 +4698,15 @@ the left-margin, use
 
   If no specific base offset is set for alignment, it is always relative
 to the left edge of the text area.  For example, @samp{:align-to 0} in a
-header-line aligns with the first text column in the text area.
+header-line aligns with the first text column in the text area.  When
+the window displays line numbers, the text is considered to start where
+the space used for line-number display ends.
 
   A value of the form @code{(@var{num} . @var{expr})} stands for the
 product of the values of @var{num} and @var{expr}.  For example,
 @code{(2 . in)} specifies a width of 2 inches, while @code{(0.5 .
 @var{image})} specifies half the width (or height) of the specified
-image.
+@var{image} (which should be given by its image spec).
 
   The form @code{(+ @var{expr} ...)} adds up the value of the
 expressions.  The form @code{(- @var{expr} ...)} negates or subtracts