Add --form-feed option.

Related to #496.

forwback.c

@@ -35,6 +35,7 @@ extern int ignore_eoi;
 extern int header_lines;
 extern int header_cols;
 extern int full_screen;
+extern int stop_on_form_feed;
 extern POSITION header_start_pos;
 #if HILITE_SEARCH
 extern size_t size_linebuf;
@@ -345,6 +346,8 @@ public void forw(int n, POSITION pos, lbool force, lbool only_last, int nblank)
 			continue;
 		}
 		put_line();
+		if (stop_on_form_feed && !do_repaint && line_is_ff() && position(TOP) != NULL_POSITION)
+			break;
 #if 0
 		/* {{ 
 		 * Can't call clear_eol here.  The cursor might be at end of line
@@ -431,6 +434,8 @@ public void back(int n, POSITION pos, lbool force, lbool only_last)
 			home();
 			add_line();
 			put_line();
+			if (stop_on_form_feed && line_is_ff())
+				break;
 		}
 	}
 	if (nlines == 0)

less.hlp

@@ -221,6 +221,8 @@
                   Automatically determine the size of the input file.
                 --follow-name
                   The F command changes files if the input file is renamed.
+                --form-feed
+                  Stop scrolling when a form feed character is reached.
                 --header=[_L[,_C[,_N]]]
                   Use _L lines (starting at line _N) and _C columns as headers.
                 --incsearch

less.nro.VER

@@ -1330,6 +1330,10 @@ If the reopen succeeds and the file is a different file from the original
 with the same name as the original (now renamed) file),
 .B less
 will display the contents of that new file.
+.IP "\-\-form-feed"
+When scrolling forward or backward in the file,
+stop if a line beginning with a form feed character (\(haL) is reached.
+This can be useful when viewing a file which uses form feeds between pages.
 .IP "\-\-header=\fIL\fP,\fIC\fP,\fIN\fP"
 .RS
 Sets the number of header lines and columns displayed on the screen.

line.c

@@ -53,6 +53,7 @@ static int curr_last_ansi;
 public size_t size_linebuf = 0; /* Size of line buffer (and attr buffer) */
 static struct ansi_state *line_ansi = NULL;
 static lbool ansi_in_line;
+static int ff_starts_line;
 static int hlink_in_line;
 static int line_mark_attr;
 static int cshift;   /* Current left-shift of output line buffer */
@@ -252,6 +253,7 @@ public void prewind(void)
 	pendc = '\0';
 	in_hilite = 0;
 	ansi_in_line = FALSE;
+	ff_starts_line = -1;
 	hlink_in_line = 0;
 	line_mark_attr = 0;
 	line_pos = NULL_POSITION;
@@ -1038,9 +1040,16 @@ public int pappend_b(char c, POSITION pos, lbool before_pendc)
 
 public int pappend(char c, POSITION pos)
 {
+	if (ff_starts_line < 0)
+		ff_starts_line = (c == CONTROL('L'));
 	return pappend_b(c, pos, FALSE);
 }
 
+public lbool line_is_ff(void)
+{
+	return (ff_starts_line == 1);
+}
+
 static int store_control_char(LWCHAR ch, constant char *rep, POSITION pos)
 {
 	if (ctldisp == OPT_ON)

opttbl.c

@@ -82,6 +82,7 @@ public int proc_tab;            /* Special handling of tab */
 public int proc_return;         /* Special handling of carriage return */
 public int match_shift;         /* Extra horizontal shift on search match */
 public int no_paste;            /* Don't accept pasted input */
+public int stop_on_form_feed;   /* Stop scrolling on a line starting with form feed */
 public long match_shift_fraction = NUM_FRAC_DENOM/2; /* 1/2 of screen width */
 public char intr_char = CONTROL('X'); /* Char to interrupt reads */
 #if HILITE_SEARCH
@@ -163,6 +164,7 @@ static struct optname want_filesize_optname = { "file-size",     NULL };
 static struct optname status_line_optname = { "status-line",     NULL };
 static struct optname header_optname = { "header",               NULL };
 static struct optname no_paste_optname = { "no-paste",           NULL };
+static struct optname form_feed_optname = { "form-feed",         NULL };
 static struct optname nonum_headers_optname = { "no-number-headers", NULL };
 static struct optname nosearch_headers_optname = { "no-search-headers", NULL };
 static struct optname nosearch_header_lines_optname = { "no-search-header-lines", NULL };
@@ -621,6 +623,14 @@ static struct loption option[] =
 			NULL
 		}
 	},
+	{ OLETTER_NONE, &form_feed_optname,
+		BOOL, OPT_OFF, &stop_on_form_feed, NULL,
+		{
+			"Don't stop on form feed",
+			"Stop on form feed",
+			NULL
+		}
+	},
 	{ OLETTER_NONE, &nonum_headers_optname,
 		BOOL|REPAINT, 0, &nonum_headers, NULL,
 		{