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.

1 files changed, 7 insertions, 1 deletions

diff --git a/src/term.c b/src/term.c
index 3d7f4ada0b9..87a412666d0 100644
--- a/src/term.c
+++ b/src/term.c
@@ -1585,10 +1585,16 @@ produce_glyphs (struct it *it)
     {
       int absolute_x = (it->current_x
                         + it->continuation_lines_width);
+      int x0 = absolute_x;
+      /* Adjust for line numbers.  */
+      if (!NILP (Vdisplay_line_numbers))
+        absolute_x -= it->lnum_pixel_width;
       int next_tab_x
         = (((1 + absolute_x + it->tab_width - 1)
             / it->tab_width)
            * it->tab_width);
+      if (!NILP (Vdisplay_line_numbers))
+        next_tab_x += it->lnum_pixel_width;
       int nspaces;
 
       /* If part of the TAB has been displayed on the previous line
@@ -1596,7 +1602,7 @@ produce_glyphs (struct it *it)
          been incremented already by the part that fitted on the
          continued line.  So, we will get the right number of spaces
          here.  */
-      nspaces = next_tab_x - absolute_x;
+      nspaces = next_tab_x - x0;
 
       if (it->glyph_row)
         {