From: Eshel Yaron via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
To: Eli Zaretskii <eliz@gnu.org>
Cc: sbaugh@janestreet.com, 63825@debbugs.gnu.org
Subject: bug#63825: 29.0.90; The header line should be hidden when empty
Date: Sat, 03 Jun 2023 10:28:20 +0300 [thread overview]
Message-ID: <m1pm6duhrf.fsf@eshelyaron.com> (raw)
In-Reply-To: <83jzwl9k1h.fsf@gnu.org> (Eli Zaretskii's message of "Sat, 03 Jun 2023 08:44:42 +0300")
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Eli Zaretskii <eliz@gnu.org> writes:
>> For example, @code{(format-mode-line header-line-format)} returns the
>> -text that would appear in the selected window's header line (@code{""}
>> -if it has no header line). @code{(format-mode-line header-line-format
>> -'header-line)} returns the same text, with each character
>> -carrying the face that it will have in the header line itself, and also
>> -redraws the header line.
>> +text that would appear in the selected window's header line.
>> +@code{(format-mode-line header-line-format 'header-line)} returns the
>> +same text, with each character carrying the face that it will have in
>> +the header line itself, and also redraws the header line.
>
> I'm not sure why you removed the part about an empty string. There's
> no change in format-mode-line to justify that, AFAICT, and neither
> should there be.
Indeed, my patch doesn't change `format-mode-line`. I removed this part
because AFAICT it's wrong: it suggests that if `format-mode-line`
returns the empty string with some argument, then using that argument as
the value of `header-line-format` will result in no header line at all.
But that's not the case (and it wasn't before my patch), because
`(format-mode-line header-line-format)` returning an empty string means
that the header line is either absent or empty, not necessarily absent.
>> + if (CONSP (fmt))
>> + {
>> + car = XCAR (fmt);
>> + if (SYMBOLP (car))
>> + {
>> + if (EQ (car, QCeval)
>> + && NILP (Feval (XCAR (XCDR (fmt)), Qnil)))
>> + return true;
>
> This should use safe__eval (or something similar), not Feval, because
> it is called as part of redisplay, where we cannot allow any errors to
> throw to top-level.
Got it, here's an updated patch:
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From bb6004521faefdd8936dafe7a64f24b3525fdaff Mon Sep 17 00:00:00 2001
From: Eshel Yaron <me@eshelyaron.com>
Date: Fri, 2 Jun 2023 20:09:43 +0300
Subject: [PATCH v2] Avoid header line with some empty non-nil formats
Allow the value of 'header-line-format' to indicate that no header
line should be displayed when it trivially yields 'nil', even if it is
not plain 'nil'. Previously, any non-nil 'header-line-format'
resulted in a (possibly empty) header line. This change adds some
flexibility by also taking a non-nil value of 'header-line-format' to
mean that no header line should be displayed if it's a list whose
'car' is a symbol and either that symbol is ':eval' and the second
list element evaluates to 'nil', or the symbol's value as a variable
is 'nil' or void.
(Bug#63825)
* src/xdisp.c (safe_eval_inhibit_quit): New function.
(display_mode_element): Use it.
* src/lisp.h (safe_eval_inhibit_quit): Declare it.
* src/window.c (null_header_line_format): New function.
(window_wants_header_line): Use it.
* doc/lispref/modes.texi (Header Line): Update to reflect new
conditions for displaying a window's header line.
(Emulating Mode Line): Don't falsely suggest that if
'format-mode-line' yields the empty string then there is no header
line, as there may be an empty header line instead.
* etc/NEWS: Announce updated treatment of 'header-line-format'.
---
doc/lispref/modes.texi | 18 ++++++++++++-----
etc/NEWS | 8 ++++++++
src/lisp.h | 1 +
src/window.c | 44 ++++++++++++++++++++++++++++++++++++++++--
src/xdisp.c | 8 +++++++-
5 files changed, 71 insertions(+), 8 deletions(-)
diff --git a/doc/lispref/modes.texi b/doc/lispref/modes.texi
index c2698da6d99..c94ad229250 100644
--- a/doc/lispref/modes.texi
+++ b/doc/lispref/modes.texi
@@ -2597,6 +2597,15 @@ Header Lines
line.
@end defvar
+Emacs displays the header line for a window unless
+@code{header-line-format} is either @code{nil}, or it's a list whose
+@sc{car} is a symbol, and either that symbol is @code{:eval} and the
+second list element evaluates to @code{nil} or the symbol's value as a
+variable is @code{nil} or void. Note that there are other possible
+values @code{header-line-format} that result in an empty header line
+(for example, @code{""}), but all other values tell Emacs to display a
+header line, whether or not it is empty.
+
If @code{display-line-numbers-mode} is turned on in a buffer
(@pxref{Display Custom, display-line-numbers-mode,, emacs, The GNU
Emacs Manual}), the buffer text is indented on display by the amount
@@ -2707,11 +2716,10 @@ Emulating Mode Line
(Other faces do not cause redisplay.)
For example, @code{(format-mode-line header-line-format)} returns the
-text that would appear in the selected window's header line (@code{""}
-if it has no header line). @code{(format-mode-line header-line-format
-'header-line)} returns the same text, with each character
-carrying the face that it will have in the header line itself, and also
-redraws the header line.
+text that would appear in the selected window's header line.
+@code{(format-mode-line header-line-format 'header-line)} returns the
+same text, with each character carrying the face that it will have in
+the header line itself, and also redraws the header line.
@end defun
@node Imenu
diff --git a/etc/NEWS b/etc/NEWS
index 9529282f047..f09e8972bc6 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -451,6 +451,14 @@ hooks named after the feature name, like 'esh-mode-unload-hook'.
+++
** 'copy-tree' now copies records when its optional 2nd argument is non-nil.
++++
+** Certain values of 'header-line-format' now inhibit empty header line.
+Emacs now avoids displaying a header line, instead of displaying an
+empty one, when 'header-line-format' is a list whose 'car' is a
+symbol, and either that symbol is ':eval' and the second element of
+the list evaluates to 'nil' or the symbol's value as a variable is
+'nil' or void.
+
\f
* Lisp Changes in Emacs 30.1
diff --git a/src/lisp.h b/src/lisp.h
index 2bfcd1a1983..2978de962d9 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -4174,6 +4174,7 @@ verify (FLT_RADIX == 2 || FLT_RADIX == 16);
extern void syms_of_xdisp (void);
extern void init_xdisp (void);
extern Lisp_Object safe_eval (Lisp_Object);
+extern Lisp_Object safe_eval_inhibit_quit (Lisp_Object);
extern bool pos_visible_p (struct window *, ptrdiff_t, int *,
int *, int *, int *, int *, int *);
diff --git a/src/window.c b/src/window.c
index f4e09f49eae..fd9d7cbd9d3 100644
--- a/src/window.c
+++ b/src/window.c
@@ -5471,6 +5471,45 @@ window_wants_mode_line (struct window *w)
}
+/**
+ * null_header_line_format:
+ *
+ * Return non-zero when header line format FMT indicates that the
+ * header line should not be displayed at all.
+ *
+ * This is when FMT is nil, or if FMT is a cons cell and either its
+ * car is a symbol whose value as a variable is nil or void, or its
+ * car is the symbol ':eval' and its cadr evaluates to nil.
+ */
+static bool
+null_header_line_format (Lisp_Object fmt)
+{
+ Lisp_Object car;
+ Lisp_Object val;
+
+ if (NILP (fmt))
+ return true;
+
+ if (CONSP (fmt))
+ {
+ car = XCAR (fmt);
+ if (SYMBOLP (car))
+ {
+ if (EQ (car, QCeval)
+ && NILP (safe_eval_inhibit_quit (XCAR (XCDR (fmt)))))
+ return true;
+
+ val = find_symbol_value (car);
+ return (SYMBOLP (car)
+ && (EQ (val, Qunbound)
+ || NILP (val)));
+ }
+ }
+
+ return false;
+}
+
+
/**
* window_wants_header_line:
*
@@ -5495,8 +5534,9 @@ window_wants_header_line (struct window *w)
&& !MINI_WINDOW_P (w)
&& !WINDOW_PSEUDO_P (w)
&& !EQ (window_header_line_format, Qnone)
- && (!NILP (window_header_line_format)
- || !NILP (BVAR (XBUFFER (WINDOW_BUFFER (w)), header_line_format)))
+ && (!null_header_line_format (window_header_line_format)
+ || !null_header_line_format (BVAR (XBUFFER (WINDOW_BUFFER (w)),
+ header_line_format)))
&& (WINDOW_PIXEL_HEIGHT (w)
> (window_wants_mode_line (w)
? 2 * WINDOW_FRAME_LINE_HEIGHT (w)
diff --git a/src/xdisp.c b/src/xdisp.c
index a6ec966ea3c..fc7de149d2b 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -3074,6 +3074,12 @@ safe__eval (bool inhibit_quit, Lisp_Object sexpr)
return safe__call1 (inhibit_quit, Qeval, sexpr);
}
+Lisp_Object
+safe_eval_inhibit_quit (Lisp_Object sexpr)
+{
+ return safe__eval (true, sexpr);
+}
+
/* Call function FN with two arguments ARG1 and ARG2.
Return the result, or nil if something went wrong. */
@@ -27408,7 +27414,7 @@ display_mode_element (struct it *it, int depth, int field_width, int precision,
if (CONSP (XCDR (elt)))
{
Lisp_Object spec;
- spec = safe__eval (true, XCAR (XCDR (elt)));
+ spec = safe_eval_inhibit_quit (XCAR (XCDR (elt)));
/* The :eval form could delete the frame stored in the
iterator, which will cause a crash if we try to
access faces and other fields (e.g., FRAME_KBOARD)
--
2.40.1
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--
Best,
Eshel
next prev parent reply other threads:[~2023-06-03 7:28 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-01 13:37 bug#63825: 29.0.90; The header line should be hidden when empty Spencer Baugh
2023-06-01 16:14 ` Eli Zaretskii
2023-06-01 16:45 ` Eshel Yaron via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-06-01 17:37 ` Spencer Baugh
2023-06-01 18:46 ` Eli Zaretskii
2023-06-01 20:22 ` Spencer Baugh
2023-06-02 6:19 ` Eshel Yaron via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-06-02 11:36 ` Eli Zaretskii
2023-06-02 18:53 ` Eshel Yaron via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-06-03 5:44 ` Eli Zaretskii
2023-06-03 7:28 ` Eshel Yaron via Bug reports for GNU Emacs, the Swiss army knife of text editors [this message]
2023-06-04 7:03 ` Eli Zaretskii
2023-06-04 16:45 ` Eshel Yaron via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-06-06 12:18 ` Eli Zaretskii
2023-06-06 12:28 ` Eshel Yaron via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-06-02 6:23 ` Eli Zaretskii
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