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, 21 insertions, 1 deletions

diff --git a/src/dispextern.h b/src/dispextern.h
index 8644ce26d13..1df769a8f99 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -384,6 +384,7 @@ struct glyph
       glyph standing for newline at end of line    0
       empty space after the end of the line       -1
       overlay arrow on a TTY                      -1
+      glyph displaying line number                -1
       glyph at EOB that ends in a newline         -1
       left truncation glyphs:                     -1
       right truncation/continuation glyphs        next buffer position
@@ -2537,7 +2538,12 @@ struct it
      Do NOT use !BUFFERP (it.object) as a test whether we are
      iterating over a string; use STRINGP (it.string) instead.
 
-     Position is the current iterator position in object.  */
+     Position is the current iterator position in object.
+
+     The 'position's CHARPOS is copied to glyph->charpos of the glyph
+     produced by PRODUCE_GLYPHS, so any artificial value documented
+     under 'struct glyph's 'charpos' member can also be found in the
+     'position' member here.  */
   Lisp_Object object;
   struct text_pos position;
 
@@ -2621,6 +2627,20 @@ struct it
      coordinate is past first_visible_x.  */
   int hpos;
 
+  /* Current line number, zero-based.  */
+  ptrdiff_t lnum;
+
+  /* The byte position corresponding to lnum.  */
+  ptrdiff_t lnum_bytepos;
+
+  /* The width, in columns and in pixels, needed for display of the
+     line numbers, or zero if not computed.  */
+  int lnum_width;
+  int lnum_pixel_width;
+
+  /* The line number of point's line, or zero if not computed yet.  */
+  ptrdiff_t pt_lnum;
+
   /* Left fringe bitmap number (enum fringe_bitmap_type).  */
   unsigned left_user_fringe_bitmap : FRINGE_ID_BITS;