Implement two new conditional operators `F <name>' and `S <name>'

which check whether <name> is a valid font or style, respectively.

* src/libs/libgroff/font.cpp (text_file): Add `silent' member.
(text_file::text_file): Updated.
(text_file::error): Don't emit message if `silent' is set.
(font::load_font): Add optional third argument (which is directly
passed to `load'.
(font::load): Add optional second argument to check the header of
a font only, without emitting warning or error messages.
* src/include/font.h (font): Updated.

* src/roff/troff/input.cpp (do_if_request): Implement `S' and `F'
conditionals.
* src/roff/troff/node.cpp (mount_font_no_translate): Add optional
fourth argument to check a font without mounting.
(check_font, check_style): New functions.
* src/roff/troff/node.h: Updated.

* man/groff_diff.man, man/groff.man, NEWS, doc/groff.texinfo:
Updated.

1 files changed, 28 insertions, 9 deletions

diff --git a/man/groff_diff.man b/man/groff_diff.man
index b3ebc940..19e9a600 100644
--- a/man/groff_diff.man
+++ b/man/groff_diff.man
@@ -3,7 +3,7 @@
 .ig
 groff_diff.man
 
-Last update : 27 Jun 2004
+Last update : 29 Jun 2004
 
 This file is part of groff, the GNU roff type-setting system.
 It is the source of the man-page groff_diff(7).
@@ -1440,7 +1440,11 @@ Whenever a font named
 .I f
 is referred to in an
 .B \[rs]f
-escape sequence, or in the
+escape sequence, in the
+.B F
+and
+.B S
+conditional operators, or in the
 .BR ft ,
 .BR ul ,
 .BR bd ,
@@ -3079,6 +3083,26 @@ has been defined by the
 .B char
 request.
 .
+.TP
+.BI .if\ F f
+True if font
+.I f
+exists.
+.
+.B f
+is handled as if it was opened with the
+.B ft
+request (this is, font translation and styles are applied), without
+actually mounting it.
+.
+.TP
+.BI .if\ S s
+True if style
+.I s
+has been registered.
+.
+Font translation is applied.
+.
 .P
 The
 .B tr
@@ -3095,16 +3119,11 @@ Example:
 .ne 6v+\n(.Vu
 .ft CB
 .nf
-.Text .de foo
-.Text .  nop Hello, I'm `foo'.
-.Text .  nop I will now define `bar'.
+.Text .if t \[rs]{\[rs]
 .Text .  de bar
 .Text .    nop Hello, I'm `bar'.
 .Text .  .
-.Text .  nop Done.
-.Text ..
-.Text .foo
-.Text .bar
+.Text .\[rs]}
 .fi
 .
 .