Support display of line numbers natively

This merges branch 'line-numbers'.
* src/buffer.c (disable_line_numbers_overlay_at_eob): New
function.
* src/lisp.h (disable_line_numbers_overlay_at_eob): Add prototype.
* src/dispextern.h (struct it): New members pt_lnum, lnum,
lnum_bytepos, lnum_width, and lnum_pixel_width.
* src/indent.c (line_number_display_width): New function,
refactored from line-number width calculations in vertical-motion.
(Fvertical_motion): Call line_number_display_width when the width
of line-number display is needed.
(Fline_number_display_width): New defun.
(syms_of_indent): Defsubr it.
* src/indent.c (Fvertical_motion): Help C-n/C-p estimate correctly
the width used up by line numbers by looking near the window-start
point.  If window-start is outside of the accessible portion,
temporarily widen the buffer.
* src/term.c (produce_glyphs): Adjust tab stops for the horizontal
space taken by the line-number display.
* src/xdisp.c (display_count_lines_logically)
(display_count_lines_visually, maybe_produce_line_number)
(should_produce_line_number, row_text_area_empty): New functions.
(try_window_reusing_current_matrix): Don't use this method when
display-line-numbers is in effect.
(try_window_id, try_cursor_movement): Disable these optimizations
when the line-number-current-line face is different from
line-number face and for relative line numbers.
(try_window_id, redisplay_window, try_cursor_movement): For
visual line-number display, disable the same redisplay
optimizations as for relative.
(x_produce_glyphs): Adjust tab stops for the horizontal
space taken by the line-number display.
(hscroll_window_tree): Adjust hscroll calculations to line-number
display.
(DISP_INFINITY): Renamed from INFINITY to avoid clashes with
math.h; all users changed.
(set_cursor_from_row): Fix calculation of cursor X coordinate in
R2L rows with display-produced glyphs at the beginning.
(display_line): Use should_produce_line_number to determine
whether a line number should be produced for each glyph row, and
maybe_produce_line_number to produce line numbers.
Don't display line numbers in the minibuffer and in tooltip
frames.
Call row_text_area_empty to verify that a glyph
row's text area is devoid of any glyphs that came from a buffer or
a string.  This fixes a bug with empty-lines indication
disappearing when line numbers or line-prefix are displayed.
(syms_of_xdisp) <display-line-numbers, display-line-numbers-widen>
<display-line-number-width>: New buffer-local variables.
<display-line-numbers-current-absolute>: New variable.

* lisp/cus-start.el (standard): Provide customization forms for
display-line-numbers and its sub-features.
* lisp/faces.el (line-number, line-number-current-line): New faces.
* lisp/frame.el: Add display-line-numbers, display-line-numbers-widen,
display-line-numbers-current-absolute, and
display-line-number-width to the list of variables that should
trigger redisplay of the current buffer.
* lisp/menu-bar.el (menu-bar-showhide-menu): Add menu-bar item to
turn display-line-numbers on and off.
(toggle-display-line-numbers): New function.
* lisp/simple.el (last--line-number-width): New internal variable.
(line-move-visual): Use it to adjust temporary-goal-column when
line-number display changes its width.

* doc/emacs/basic.texi (Position Info): Add cross-reference to
"Display Custom", for line-number display.
* doc/emacs/custom.texi (Init Rebinding):
* doc/emacs/modes.texi (Minor Modes): Remove references to
linum-mode.
* doc/emacs/display.texi (Display Custom): Describe the
line-number display.
* doc/lispref/display.texi (Size of Displayed Text): Document
line-number-display-width.

* etc/NEWS: Document display-line-numbers and its customizations.

5 files changed, 80 insertions, 8 deletions

diff --git a/doc/emacs/basic.texi b/doc/emacs/basic.texi
index 6b66c18016b..5878e7da256 100644
--- a/doc/emacs/basic.texi
+++ b/doc/emacs/basic.texi
@@ -630,7 +630,8 @@ Display the line number of point.
 @item M-x line-number-mode
 @itemx M-x column-number-mode
 Toggle automatic display of the current line number or column number.
-@xref{Optional Mode Line}.
+@xref{Optional Mode Line}.  If you want to have a line number
+displayed before each line, see @ref{Display Custom}.
 
 @item M-=
 Display the number of lines, words, and characters that are present in
diff --git a/doc/emacs/custom.texi b/doc/emacs/custom.texi
index c84f4a975d8..a756a89e3f8 100644
--- a/doc/emacs/custom.texi
+++ b/doc/emacs/custom.texi
@@ -1701,7 +1701,6 @@ and mouse events:
 (global-set-key (kbd "C-c y") 'clipboard-yank)
 (global-set-key (kbd "C-M-q") 'query-replace)
 (global-set-key (kbd "<f5>") 'flyspell-mode)
-(global-set-key (kbd "C-<f5>") 'linum-mode)
 (global-set-key (kbd "C-<right>") 'forward-sentence)
 (global-set-key (kbd "<mouse-2>") 'mouse-save-then-kill)
 @end example
diff --git a/doc/emacs/display.texi b/doc/emacs/display.texi
index c4554eb3187..083fcdf97a6 100644
--- a/doc/emacs/display.texi
+++ b/doc/emacs/display.texi
@@ -1333,7 +1333,7 @@ characters in the buffer, which means that @samp{k} for 10^3, @samp{M}
 for 10^6, @samp{G} for 10^9, etc., are used to abbreviate.
 
 @cindex line number display
-@cindex display of line number
+@cindex display of current line number
 @findex line-number-mode
   The current line number of point appears in the mode line when Line
 Number mode is enabled.  Use the command @kbd{M-x line-number-mode} to
@@ -1710,6 +1710,66 @@ variable @code{visual-line-fringe-indicators}.
   This section describes variables that control miscellaneous aspects
 of the appearance of the Emacs screen.  Beginning users can skip it.
 
+@vindex display-line-numbers
+@cindex number lines in a buffer
+@cindex display line numbers
+  If you want to have Emacs display line numbers for every line in the
+buffer, customize the buffer-local variable
+@code{display-line-numbers}; it is @code{nil} by default.  This
+variable can have several different values to support various modes of
+line-number display:
+
+@table @asis
+@item @code{t}
+Display (an absolute) line number before each non-continuation screen
+line that displays buffer text.  If the line is a continuation line,
+or if the entire screen line displays a display or an overlay string,
+that line will not be numbered.
+
+@item @code{relative}
+Display relative line numbers before non-continuation lines which show
+buffer text.  The line numbers are relative to the line showing point,
+so the numbers grow both up and down as lines become farther from the
+current line.
+
+@item @code{visual}
+This value causes Emacs to count lines visually: only lines actually
+shown on the display will be counted (disregarding any lines in
+invisible parts of text), and lines which wrap to consume more than
+one screen line will be numbered that many times.  The displayed
+numbers are relative, as with @code{relative} value above.  This is
+handy in modes that fold text, such as Outline mode (@pxref{Outline
+Mode}), and need to move by exact number of screen lines.
+
+@item anything else
+Any other non-@code{nil} value is treated as @code{t}.
+@end table
+
+@vindex display-line-numbers-current-absolute
+When Emacs displays relative line numbers, you can control the number
+displayed before the current line, the line showing point.  By
+default, Emacs displays the absolute number of the current line there,
+even though all the other line numbers are relative.  If you customize
+the variable @code{display-line-numbers-current-absolute} to a
+@code{nil} value, the number displayed for the current line will be
+zero.  This is handy if you don't care about the number of the current
+line, and want to leave more horizontal space for text in large
+buffers.
+
+@vindex display-line-numbers-widen
+In a narrowed buffer (@pxref{Narrowing}) lines are normally numbered
+starting at the beginning of the narrowing.  However, if you customize
+the variable @code{display-line-numbers-widen} to a non-@code{nil}
+value, line numbers will disregard any narrowing and will start at the
+first character of the buffer.
+
+@cindex line-number face
+The line numbers are displayed in a special face @code{line-number}.
+The current line number is displayed in a different face,
+@code{line-number-current-line}, so you can make the current line's
+number have a distinct appearance, which will help locating the line
+showing point.
+
 @vindex visible-bell
   If the variable @code{visible-bell} is non-@code{nil}, Emacs attempts
 to make the whole screen blink when it would normally make an audible bell
diff --git a/doc/emacs/modes.texi b/doc/emacs/modes.texi
index be893403012..eb0c88b2901 100644
--- a/doc/emacs/modes.texi
+++ b/doc/emacs/modes.texi
@@ -225,11 +225,6 @@ Font-Lock mode automatically highlights certain textual units found in
 programs.  It is enabled globally by default, but you can disable it
 in individual buffers.  @xref{Faces}.
 
-@findex linum-mode
-@cindex Linum mode
-@item
-Linum mode displays each line's line number in the window's left margin.
-
 @item
 Outline minor mode provides similar facilities to the major mode
 called Outline mode.  @xref{Outline Mode}.
diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index 2ebe872c362..005d31af05a 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -2045,6 +2045,23 @@ selected window.  The value includes the line spacing of the line
 (@pxref{Line Height}).
 @end defun
 
+When a buffer is displayed with line numbers (@pxref{Display Custom,,,
+emacs, The GNU Emacs Manual}), it is sometimes useful to know the
+width taken for displaying the line numbers.  The following function
+is for Lisp programs which need this information for layout
+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
+@code{line-number} face.  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.
+@end defun
+
 
 @node Line Height
 @section Line Height