Adding the `linetabs' request. If set, tab distances are not

computed relative to the input line but relative to the output line.

* src/roff/troff/env.h (environment): New member `line_tabs'.
* src/roff/troff/env.cc (line_tabs_request): Implement request.
(environment::environment, environment::copy): Updated.
(environment::distance_to_next_tab): Use `line_tabs'.
(init_env_requests): Register request.
* src/roff/troff/troff.man, man/groff.man, NEWS: Document it.  Other
fixes.

1 files changed, 53 insertions, 43 deletions

diff --git a/man/groff.man b/man/groff.man
index 1d12afc6..03b794aa 100644
--- a/man/groff.man
+++ b/man/groff.man
@@ -1282,6 +1282,15 @@ Write the length of the string
 in
 .argument register .
 .
+.REQ .linetabs
+Enable line-tabs mode (i.e., calculate tab positions relative to output
+line).
+.
+.REQ .linetabs n
+If
+.argument n
+is zero, disable line-tabs mode, otherwise enable it.
+.
 .REQ .lf N file
 Set input line number to
 .argument N
@@ -2298,6 +2307,9 @@ from request calls.
 .LP
 .PD 0
 .REG .$ Number of arguments in the current macro.
+.REG .a
+Post-line extra line-space most recently utilized using
+.escarg x 'N' .
 .REG .A
 Set to
 .number 1
@@ -2309,19 +2321,8 @@ is used; always
 .number 1
 in
 .BR nroff .
-.REG .H Available horizontal resolution in basic units.
-.REG .T
-Set to
-.number 1
-if option
-.B \-T
-is used.
-.REG .V Available vertical resolution in basic units.
-.REG .a
-Post-line extra line-space most recently utilized using
-.escarg x 'N' .
-.REG .C 1 if compatibility mode is in effect, 0 otherwise.
 .REG .c Current input line number.
+.REG .C 1 if compatibility mode is in effect, 0 otherwise.
 .REG .cdp
 The depth of the last character added to the current environment.
 It is positive if the character extends below the baseline.
@@ -2347,6 +2348,7 @@ Current vertical place in current diversion; equal to register
 Always 1 in GNU troff.
 Macros should use it to test if running under groff.
 .REG .h Text base-line high-water mark on current page or diversion.
+.REG .H Available horizontal resolution in basic units.
 .REG .hla
 The current hyphenation language as set by the
 .B .hla
@@ -2412,6 +2414,12 @@ The number of lines to be right-justified as set by the rj request.
 The last requested pointsize in points as a decimal fraction
 (string-valued).
 .REG .t Distance to the next trap.
+.REG .T
+Set to
+.number 1
+if option
+.B \-T
+is used.
 .REG .tabs
 A string representation of the current tab settings suitable for use as
 an argument to the
@@ -2440,6 +2448,7 @@ The value of the parameters set by the second argument of the
 request.
 .REG .u Equal to 1 bin fill mode and 0 in nofill mode.
 .REG .v Current vertical line spacing.
+.REG .V Available vertical resolution in basic units.
 .REG .vpt
 .number 1
 if vertical position traps are enabled,
@@ -2452,6 +2461,25 @@ The sum of the number codes of the currently enabled warnings.
 .REG .y The minor version number.
 .REG .Y The revision number of groff.
 .REG .z Name of current diversion.
+.PD
+.
+.\" --------------------------------------------------------------------
+.SS "WRITABLE REGISTERS"
+.\" --------------------------------------------------------------------
+The following registers can be read and written by the user.
+They have predefined default values, but these can be modified for
+customizing a document.
+.LP
+.PD 0
+.REG % Current page number.
+.REG c. Current input line number.
+.REG ct Character type (set by width function
+.esc w ).
+.REG dl Maximal width of last completed diversion.
+.REG dn Height of last completed diversion.
+.REG dw Current day of week (1-7).
+.REG dy Current day of month (1-31).
+.REG hp Current horizontal position at input line.
 .REG llx
 Lower left x-coordinate (in PostScript units) of a given PostScript
 image (set by
@@ -2460,6 +2488,9 @@ image (set by
 Lower left y-coordinate (in PostScript units) of a given PostScript
 image (set by
 .request .psbb ).
+.REG ln Output line number.
+.REG mo Current month (1-12).
+.REG nl Vertical position of last printed text base-line.
 .REG rsb Like
 .register sb ,
 but takes account of the heights and depths of characters.
@@ -2474,6 +2505,10 @@ Depth of string below base line (generated by width function
 Right skip width from the center of the last character in the
 .esc w
 argument.
+.REG slimit
+If greater than 0, the maximum number of objects on the input stack.
+If \(<=0 there is no limit, i.e., recursion can continue until virtual
+memory is exhausted.
 .REG ssc
 The amount of horizontal space (possibly negative) that should be added
 to the last character before a subscript (generated by width function
@@ -2481,6 +2516,12 @@ to the last character before a subscript (generated by width function
 .REG st
 Height of string above base line (generated by width function
 .esc w ).
+.REG systat
+The return value of the
+.I system()
+function executed by the last
+.request .sy
+request.
 .REG urx
 Upper right x-coordinate (in PostScript units) of a given PostScript
 image (set by
@@ -2489,37 +2530,6 @@ image (set by
 Upper right y-coordinate (in PostScript units) of a given PostScript
 image (set by
 .request .psbb ).
-.PD
-.
-.\" --------------------------------------------------------------------
-.SS "WRITABLE REGISTERS"
-.\" --------------------------------------------------------------------
-The following registers can be read and written by the user.
-They have predefined default values, but these can be modified for
-customizing a document.
-.LP
-.PD 0
-.REG % Current page number.
-.REG c. Current input line number.
-.REG ct Character type (set by width function
-.esc w ).
-.REG dl Maximal width of last completed diversion.
-.REG dw Current day of week (1-7).
-.REG dy Current day of month (1-31).
-.REG hp Current horizontal position at input line.
-.REG ln Output line number.
-.REG mo Current month (1-12).
-.REG nl Vertical position of last printed text base-line.
-.REG slimit
-If greater than 0, the maximum number of objects on the input stack.
-If \(<=0 there is no limit, i.e., recursion can continue until virtual
-memory is exhausted.
-.REG systat
-The return value of the
-.I system()
-function executed by the last
-.request .sy
-request.
 .REG year The current year (year 2000 compliant).
 .REG yr
 Current year minus 1900.  For Y2K compliance use register